Industrial and laboratory alkylations

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

0.1

0.3

0.2

MOLE % 2-METHYL-l-BUTENE

Figure 14. The trityl ion controls olefin-initiated isomerization of 3methylpentane

70 Air/Acid 50

•

C

1

6

H

3

3

N

(CH ) 3

3

40 i C

30

13 27 H

( C H

3 2 )

Films contain 1

N

C H

2

C

6

H

5

ion/130A^

20

C /Acid 6

10

-6

-5

-4

-3 log C

Figure 15.

Unsymmetrical quaternary ammonium ions—active at air-acid and oilr-acid surfaces

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

18

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

content and t i t r a t a b l e a c i d i t y . In t h i s study the e f f e c t s of s t i r r i n g , o l e f i n space v e l o c i t y , o l e f i n type and modifier type were examined. In preliminary experiments i t was found that alkylate quality was e s s e n t i a l l y independent of s t i r r i n g speeds above 1000 rpm. Accordingly a l l runs were made at 1200 rpm except when s t i r r i n g was being investigated. One series was made with an isobutane - 2-butene feed, 6.6% o l e f i n , at 10°C and o l e f i n space v e l o c i t i e s of 0.077 to 0.7 V/Hr/V. The additives studied are l i s t e d i n Table IV. Table IV Concentration, wt %

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

Alkylation Additives Tet rame thy lammonium Chloride (TMAC) Dimethyltridecylbenzylammonium chloride (DMTDB) FC-95 FX-161 Cetyltrimethylammonium bromide (CTMAB) Cetylamine Octylamine

1.1 0.7 0.01 0.01 0.01 0.01 0.01

The long chain ammonium s a l t and amine surfactants showed better s e l e c t i v i t y and calculated MON's. The improvement i n MON ranged from about 0.4 at an OSV of 0.08 V/Hr/V to more than 2 at 0.7 V/Hr/V. The space v e l o c i t y was normally 0.077 and was cycled during the course of a run between t h i s value and higher rates which were held u n t i l the product quality was steady. A comparison of s e l e c t i v i t y to Cg's i n the C^ f r a c t i o n i s shown i n Figure 16. Octylamine was intermediate i n i t s a b i l i t y to improve s e l e c t i v i t y while two of the surfactants which were anionic (FC-95 and FX-161), showed no improvement under well mixed conditions. In addition the tetramethylammonium ion which i s not surface active was also an i n e f f e c t i v e additive. Under poorly mixed conditions the surface active cations show much more noticeable improvements, Figure 17. Typical data obtained at 400 to 600 rpm are i l l u s t r a t e d i n Figure 17 and suggest that the surfactants might be useful i n overcoming mixing l i m i t a t i o n s , i f they e x i s t , i n commercial units. The surface active cations also improve product quality when a l k y l a t i n g with a t y p i c a l r e f i n e r y feed. Table V contains a l i s t of additives studied with a feed containing 94 percent isobutane and 6 percent butènes. The butènes contained 42 percent i s o butylene and an equilibrium mixture of 1- and 2-butene. +

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

1. KRAMER

Alkylation Studies

Figure 16.

Cationic surfactants improve selectivity with 2-butene

Figure 17. Cationic surfactant improves alkylate in poorly mixed reactor

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19

20

INDUSTRIAL

A N DL A B O R A T O R Y A L K Y L A T I O N S

Table V Test Conditions With Refinery Olefins 10°C, 0.077 to 0.28 V/Hr/V, OSV Additive

Concentration, wt %

Cetylamine

0.01

CTMAB

0.005, 0.01, 0.05

Aromax 18/12, C H ( C H 0 H ) N 0

0.01

Deriphat 151C, N-Coco 3-aminopropionic acid

0.01

Armeen HT, RNH 60% C , 30% C

0.01

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

18

2

37

2

4

1 8

Armeen 12D, RNH , 97% C 2

2

1 6

0.01

1 2

In a l l cases some improvement i n s e l e c t i v i t y and octane quality was obtained. Cetylamine and CTMAB showed the best results with t y p i c a l improvements of about 0.5 MON and 1.5% i n s e l e c t i v i t y throughout the range of o l e f i n space v e l o c i t i e s . Figure 18 shows the improvements obtained with the C-j^ amine. In commercial a l k y l a t i o n one generally finds that improved reaction conditions lead to more selective and higher octane product, less acid consumption and higher y i e l d s based on o l e f i n fed to the unit. Analyses of the spent acid obtained i n the p i l o t plant also indicate that acid consumption i s strongly reduced when the cationic surfactants are used. Table VI Acid Consumption Reduced With Cationic Surfactants 10°C, 80 psig, 87 Vol % i C 2-Butene Acidity V/v(a) wt % Blank 0.01% C H N H 16

33

0.01% CTMAB(b)

2

4

i n HC Phase, 98% H S 0 2

% C

4

Mixed Olefins Acidity wt % % C vM > a

18.0

89.0

3.6

14.4

91.5

3.3

19.2

93.3

2.8

10.6

94.9

2.2

19.1

92.7

2.2

13.3

93.3

2.9

(a) Cumulative volume of o l e f i n fed per volume of acid. (b) In the run with mixed o l e f i n s , 0.05% was used.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Alkylation Studies

KRAMER

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

100,

0

0.10

0.20

OLEFIN

Figure 18.

SPACE

0.30 VELOCITY

V/HR/V

Alkylation selectivity improved with refinery olefins

2500

B/O REACTOR 8

400

G/HR

75% Acid-Emulsion 7 5 % i C4 in Product .08 SV 50°F H

2

S

0

4

98%

2500

B/D REACTOR 7

400

Figure 19.

G/HR

Plant test conditions

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

22

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

Table VI shows that the t i t r a t a b l e a c i d i t y of used acid i s higher and the carbon content lower i n the runs containing additives with a 2-butene feed. The difference i s somewhat less but s t i l l substantial i n the experiments with the mixed o l e f i n feed. For comparison one can estimate the a c i d i t y of the blank a f t e r feeding 10.6 volumes of olefin/volume acid as 93.2 percent. The reactions involved i n consuming acid are not well under­ stood at t h i s time and the simplest r a t i o n a l i z a t i o n of the data i s to note that as a l k y l a t i o n conditions improve, less of the feed has the opportunity of entering side reactions that deplete the acid.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

Commercial Test One of the c a t i o n i c surfactants was evaluated i n a commercial a l k y l a t i o n unit at the Baytown r e f i n e r y . A p a r a l l e l test was conducted i n which two reactors received the same feed and fresh acid, Figure 19. The modifier was injected into an acid recycle l i n e on reactor 8, to rapidly bring i t s concentration to working strength and then the rate was lowered to maintain the concentra­ t i o n . After 11 days the additive concentration was doubled and a f t e r 19 days i t s addition was switched from reactor 8 to reactor 7. The additive concentration i n reactors 7 and 8 i s shown i n Figure 20· Note that a f t e r the switch the concentration i n reactor 8 depletes i n accord with the acid replacement rate of the unit and so this reactor w i l l continue to receive the benefit of the additive u n t i l the concentration drops to a l e v e l estimated as about 0.005 wt percent. After this time a l l improvements due to the additive should be seen as changes developing i n reactor 7. The difference i n t i t r a t a b l e a c i d i t y of the recycle acid from the reactors was taken as the best parameter for measuring the effectiveness of the additive i n the t e s t . I t can be shown that the t i t r a t a b l e a c i d i t y , C, (wt % H2SO4) w i l l respond according to equation 7. c

C

- A " (C -C )eA

k t

(7)

0

Here k i s a constant, t i s the time, C i s the steady state a c i d i t y i n the presence of the additive and C i s the steady state a c i d i t y i n the absence of additive. The rate constant k i s determined by the acid make up rate and the acid inventory i n the system and has a value of 0.12 per day i n this study. The difference i n t i t r a t a b l e a c i d i t y , Δ, between reactors 7 and 8 should follow equations 8, 9 and 10. A

0

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Alkylation Studies

KRAMER

1 .02

1

-

Reactor 8

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

1

/

Reactor

1 0

7

10

ι

ι

ι

20

30

40

TIME

Figure 20.

τ

_l

Ο

DAYS

Additive concentration in commercial test

1

I

10

1

I

20

1

I

30

r

ί-

40

TIME, DAYS

Figure 21.

Additive is effective

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24

INDUSTRIAL

A N DLABORATORY

ALKYLATIONS

Δ

=

(c

A

- cJQ. - e" t], 0-20 days

(8)

Δ

=

[c

A

- cJËe-^t-

(9)

Δ

=

k

2 0

)^- ^),

20-31 days

1

(?A - c J ^ - k C t ^ D - e - k i t ^ O ) - ^ ,

31-43 days

During the f i r s t twenty days the additive was i n reactor 8 and not reactor 7 and the difference i n t i t r a t a b l e a c i d i t y should follow equation 8. During the next eleven days the additive i s in both reactors and the Δ decreases according to equation 9. On the 3 1 day the additive i s below i t s e f f e c t i v e concentration l e v e l , (^0.005 wt % ) , and the difference i n a c i d i t y decreases at a faster rate. The s o l i d curve i n Figure 21 was calculated from these equations using a value of C - C of 0.7. The c i r c l e s i n Figure 21 are experimental points, each representing a minimum of 36 t i t r a t i o n s . The t i t r a t a b l e a c i d i t y of each reactor was measured i n t r i p l i c a t e every eight hours and the points average two-day periods. These data show an uncorrected decrease of 14 percent i n acid consumption (derived from Δ developed a f t e r 18 to 20 dayg). However the average temperature i n reactor 8 was 4 to 5 F higher than i n reactor 7 during the entire test and we estimate that the difference i n acid consumption i s closer to 20 percent at constant temperature. The plant test was unfortunately terminated before the f u l l Δ i n the opposite d i r e c t i o n could be obtained but the data c l e a r l y shows the additive to be strongly b e n e f i c i a l i n a l k y l a t i o n . In addition to saving acid the additive appeared to improve the octane number by more than 0.1 MON as was indicated by a few spot checks of alkylate during the run. The improvements generally arose from a s l i g h t increase i n the C3 f r a c t i o n , a r i s e i n the trimethylpentane concentration and changes of the t r i ­ methylpentane d i s t r i b u t i o n . The octane analyses are not nearly as extensive as the t i t r a t a b l e a c i d i t y determinations and the improvements are noted as being consistent with what would be estimated from plant correlations and the observed reduction i n acid composition. The additive used i n the commercial test i s being used i n nearly a l l of Exxon's a l k y l a t i o n units. No operating problems have been encountered and i t generally has been found to reduce acid consumption by 15 to 20 percent and to generate s l i g h t l y higher octane number product. The cost of the additive i s small r e l a t i v e to the acid savings alone and i t i s available f o r license. The a l k y l a t i o n model developed i n this work i s one i n which the reaction i s viewed as occurring i n the acid phase and at the acid-hydrocarbon interface. The formation of Cg s and trimethyl­ pentanes occurs p r e f e r e n t i a l l y at the interface. Adding c a t i o n i c surfactants reduces the s t a b i l i t y of the carbonium ion s t

A

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

(10)

Q

r

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

1.

Alkyfotion Studies

KRAMER

C

25

Feed

4

C4 Feed

hC -Cglc -C i-C ^

K -N-C 1N-C -N^

Acid

Acid

4

4

4

4

4

8

4

Figure 22. An alkyhtion model. Cationic surfactants should block sur­ face reactions and destabilize reaction intermediates.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

intermediates and causes them to abstract hydride ions more rapidly from isobutane or any other p o t e n t i a l donor. Increased hydride transfer converts more of the carbonium ions at the acid interface to saturates faster, y i e l d i n g product while minimizing polymerization and side reactions. I t i s also l i k e l y that the surfactants p h y s i c a l l y block a l k y l ions from one another i n the surface f i l m and thus impede ion + o l e f i n polymerization. In such a f i l m the carbonium ion concentration must also be lower than i n the absence of surfactant and mass law e f f e c t s w i l l therefore also lead to less polymerization and cracking. The fact that steady state hydride transfer rates i n H S0 are subject to control through the use of acid modifiers which act i n the bulk acid and at the acid-hydrocarbon interface i s the key to the control of s u l f u r i c acid a l k y l a t i o n . 2

4

Literature Cited 1. 2. 3.

4. 5. 6. J. 7. 8. 9. J.

Kennedy, R. M. i n "Catalysis," V I , ed. P. H. Emmett, Chapter 1, 1, Reinhold (1958). Condon, F . E . i n "Catalysis," V I , ed. P. H. Emmett, Chapter 2, 43, Reinhold (1958). Schmerling, L . i n "The Chemistry of Petroleum Hydrocarbons," I I I , ed. Β. T. Brooks, S. S. Kurtz, Jr., C. E . Board, L . Schmerling, Chapter 34, 363, Reinhold (1955). Burwell, R. L . and Gordon, G. S., III, J. Am. Chem. Soc. (1948) 70, 3128. Burwell, R. L . Jr., Maury, L . G. and Scott, R. B . , J. Am. Chem. Soc. (1954) 76, 5828. Burwell, R. L., Scott, R. B., Maury, L . G. and Hussey, A. S . , Am. Chem. Soc. (1954) 76, 5822. Gordon, G. S . , III and Burwell, R. L., J. Am. Chem. Soc. (1949) 71, 2355. Ingold, C. K., R a i s i n , C. G. and Wilson, C. L., J. Am. Chem. Soc. (1936) 58, 1643. Otvos, J. W., Stevenson, D. P., Wagner, C. D. and Beeck, O., Am. Chem. Soc. (1951) 73, 5741.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26

INDUSTRIAL AND LABORATORY ALKYLATIONS

10.

J.

J.

Stekina, V. N., Jursanov, D. Ν., Sterligov, O. D. and Liberaan, A. L., Doklady Akad. Nauk. S.S.S.R. (1952) 85, 1045. 11. Stevenson, D. P., Wagner, C. D . , Beeck, O. and Otvos, J. W., Am. Chem. Soc. (1952) 74, 3269. 12a. Thomas, C. L., "Catalytic Processes and Proven Catalysts," Chapter 9, 87 Acad. Press (1970). 12b. Doshi, B. and A l b r i g h t , L . F., Ind. Eng. Chem., Proc. Des. Dev. (1976) 15, 53. 13. Unpublished results of G. M. Kramer. Mentioned i n Hoffmann, E . and Schriesheim, Α . , J. Am. Chem. Soc. (1962) 84, 953. 14. Kramer, G. M., J. Org. Chem. (1965) 30, 2671. Kramer, G. M., J. Org. Chem. (1967) 32, 920. Kramer, G. M., J. Org. Chem. (1967) 32, 1916. Hoffmann, J. E . and Schriesheim, Α . , J. Am. Chem. Soc., (1962) 84, 957.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch001

15. 16. 17.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2

Reaction

Mechanisms for

Hydrofluoric

Acid

Alkylation

T. HUTSON, JR. and G. E. HAYS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Phillips Petroleum Company, Bartlesville, OK 74004

I.

Conclusions

1. A l l four butene isomers are believed to be capable of undergoing isomerization and polymerization under alkylation conditions. These ionic reactions are extremely rapid and precede or accompany isobutane alkyla­ tion. 2. Since alkylate compositions from the four butene isomers are basically similar, the butenes are thought to isomerize considerably, approaching equilibrium composition prior to isobutane alkylation. Such a postulation is at variance with previously published alkylation mecha­ nisms. The isomerization step yields predominantly isobutene which then polymerizes and forms a 2, 2, 4-trimethylpentyl carbonium ion, a precursor of 2, 2, 4-trimethylpentane, the principal end product. The 2, 2, 4-tri­ methylpentyl ion is also capable of isomerization to other trimethylpentyl ions and thus yields other trimethylpentanes, principally 2, 3, 4-trimethyl­ pentane and 2, 3, 3-trimethylpentane. 3. Dimethylhexanes are believed to result mainly from codimerization of butene-l and isobutene, followed by abstraction of a hydride ion from isobutane. This mechanism differs significantly from previously published theory. Thus, high initial concentrations of butene-l favor dimethylhex­ ane formation. Some isomerization of dimethylhexyl carbonium ions occurs. 4. 2,2,3-Trimethylpentane and its ionic form are not primary reaction products or intermediates of isobutane and 2-butene alkylation. Found in alkylation product in very small concentrations, 2, 2,3-trimethylpentane probably results mainly from isomerization of 2, 2,4-trimethylpentyl carbonium ions. 5. Excessive olefin polymerization followed by hydride ion abstraction from isobutane probably accounts for the formation of saturated residue. I-Butene, propylene, the catalysts's low water content, and low isobutaneto-olefin ratio favor the production of residue. 6. In the case of propylene-isobutane alkylation, primary alkylation, 27

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

28

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

hydrogen transfer (chain initiation), and polymerization reactions predominate — î n that relative order of importance. Product analysis indicates concentrations of about 52, 28, and 12 weight percent of Cy, Cg, and residue, respectively. 7. Disproportionate of primary Cy alkylate (from propylene) with isobutane under alkylation conditions probably accounts for the near-equal amounts of isopentane and isohexanes found in propylene alkylate. 8. The effect of water in HF alkylation catalyst is an important one; it appears to be that of slowing polymerization. The production of lowoctane-number residue can be reduced by 50 percent when catalyst water content is optimized. 9. In studies with propylene, increasing isobutane-to-olefin ratio suppressed the formation of high-molecular-weight residue, indicating a substantial reduction in the role of olefin polymerization to large ions. At the same time, the concentration of the Cy fraction (primary product) decreased, and the Cg fraction (from chain initiation and subsequent hydrogen transfer) increased markedly. 10. HF alkylate shows a significant composition advantage over that made with conventional H 2 S O 4 catalyst. This is believed to be due to a lesser amount of polymerization occurring with HF catalyst. Also, higher octane-fraction content, lower dimethylhexane content, and lower heptane content in HF alkylate indicate that HF catalyst favors a greater amount of hydrogen transfer from propylene. 11. Good hydrocarbon dispersion in hydrofluoric acid is an important factor in producing alkylate rich in trimethylpentanes and thus favors olefin isomerization (to isobutene), isobutene dimerization, and maximizes hydrogen transfer and primary alkylation reactions. Excess olefin polymerization to form residue is suppressed by good dispersion. M.

Introduction

Our purposes in studying HF alkylation reaction mechanisms are several fold. The works of Qapetta (1945) and Schmerling (1946,1955), although classic in the field of alkylation in their time, were limited by the then available analytical tools. Today, by using greatly improved analytical procedures, the product makeup can be much better defined. Elucidation and better understanding of these mechanisms will make current experimental work more effective, facilitating the development of improved HF catalysts, process conditions, mass transfer, etc. Fundamentally, the proposed mechanisms for HF-catalyzed alkylation explain the production of alkylates of better quality than those obtained from H 2 S O 4 catalyzed alkylation. A large number of investigators have offered theories on reaction mechanisms in HF- or H2SO4-catalyzed isobutane-olefin alkylation.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

2.

HUTSON

AND

HAYS

Hydrofluoric Acid Alkylation

29

All of these theories were based on a carbonium-ion, chain mechanism. Previous investigators have ignored the possibility of olefin isomerization and polymerization as substantial reaction steps in the overall alkylation mechanism. In separate articles Schmerling (1955) and Cupitjet a L (1961) summarized the most generally accepted theories similarly. Reliance was heavy on "methyl shift" and "hydride ion shift" to explain the many isomers typically present in various alkylates. High-boiling by-products were postulated to result from polymerization reactions requiring more than one olefin molecule per molecule of isoparaffin. Ciapetta (1945) and Schmerling (1955) attributed dimethylhexanes to isobutane alkylation with Ibutene, involving formation of the dimethylhexyl ion which underwent rearrangement before being converted to octane molecules. Hofmann and Schriesheim (1962) using tagged molecules in isobutane-butene alkylation, attributed the formation of all products other than octanes to the formation of a C|2 carbonium ion intermediate. III.

Types of Reactions

Chain Initiation. The theory postulated by a number of investigators ( C u p î t et a l . , 1961, Schmerling, 1955) is that carbonium ions are generated by addition of a proton (H+) to an olefin molecule in the presence of HF. Albright and L i , 1970, and Hofmann and Schriesheim, 1962, indicate that initiation steps with H2 SO4 catalyst may involve red oil hydrocarbons. However, only the tertiary butyl carbonium ion performs the chain carrying function in isobutane alkylation. Reactions follow:

CD

?

C=C

+

H

—>

+

c (2)

C=C-C-C

C-C+

c +

H+

—>

C-C-C-C -ί-

Ο (2-A)

C-C-C-C

c

4- C-C-H — >

C-C-C-C

c (3)

C=»C-C

+

H+

+ C-C+ c

— > C-C-C

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

30

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

c (3-A)

I

c-c-c +

I"

C-C-H

c-c+ I

c

H

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Thus, the most direct route to chain-carrying, tertiary butyl carbonium ions is offered in isobutene-isobutane alkylation (Equation I). When initiating with either a linear butene or propylene, a second step is necessary to form the tertiary butyl carbonium ion, i . e . , abstraction of a hydride ion from an isobutane molecule while forming a molecule of normal alkane. (Equation 2, 2 - A , 3, 3-A). Reaction sequences in these equations are often referred to as hydrogen- or hydride transfer reactions and will be discussed subsequently. Chain Propagation. In the chain propagation step, an olefin molecule reacts with a tertiary butyl carbonium ion as postulated by Whitmore (1934). This addition reaction produces a larger carbonium ion which then either undergoes isomerization or abstracts a hydride from an isobutane molecule. (Under some circumstances, the larger carbonium ion may add a second molecule of olefin; this reaction will be discussed under "Polymerization".) Hydride abstraction regenerates a chain-carrying, tertiary butyl carbonium ion and also forms a molecule of isoparaffin. Reactions follow: c

c I c-c-c-c-c

C

I

I

(4)

C-C+ I

c

c=c I c

I

+

c

Chain Termination. Chain termination in isobutane alkylation is any reaction sequence which results in the elimination of a tertiary butyl carbonium ion. Specifically, two tertiary butyl carbonium ions are consumed and only one is regenerated. Reactions follow: C (5)

C-C+

C —>

C=C

+

H

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

AND

HAYS

I

C-C+

c=c

I

c

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

—>

I

c

c

i

'

+

c I

4- C-C

C-C-C-Ç-C 2 ± '+

I

c

c

( 5 - B ) C-C-C-C-C

t

31

c

C (5-A)

Hydrofluoric Acid Alkylation

C — ^

\

c-c-c

c I

C-C+ I

c

c

l

When alkylating isobutane, chain termination forms primarily, but not entirely, 2,2,4-trimethylpentane; the alkylate from chain termination very closely resembles isobutene alkylate. The similarity of alkylate compositions, particularly their Cg fractions, originating from various olefins and the distance from thermodynamic equilibrium composition indicates that alkylate molecules, once formed, are relatively stable under alkylation conditions and undergo little isomerization. Undesirable side products, e . g . , dimethylhexanes and residue, are probably formed by butene isomerization and polymerization (rather than by isomerization of alkylate or by isomerization of the C3 carbonium ion which subsequently becomes alkylate). Olefin Isomerization. Olefin isomerization plays an important role in butene-isobutane alkylation reaction mechanisms. Normal butènes are largely isomerized to isobutene before alkylation. This is believed to take place in ionic form, i . e . , immediately following olefin protonation, since a number of olefins have been found to add HF across their double bonds quite readily at room temperature (Grosse and Linn, 1938). Thus, the likelihood of olefin molecules being present for very long under alkylation conditions is not great. The following facts are the basis for butene isomerization: (I) There is a basic similarity in the composition of alkylates produced from all four butene isomers. (2) Alkylate molecules, once formed, are relatively stable under alkylation conditions and do not isomerize to any appreciable extent; alkylate fractions having the same carbon number are not equilibrated (see Table I). (3) Thermodynamic equilibrium between the butene olefins highly favors isobutene formation at alkylation temperatures. (4) Normal butènes produce only small and variable amounts of normal butane, thus indicating only a small and variable amount of chain initiation from normal b u t è n e s . Yet the alkylate composition shows a high concentration of trimethylpentanes and a low concentration of dimethylhexanes. (5) A few of the octane isomers can be explained only by isomerization of the eight-carbon skeletal structure; this isomerization occurs while isobutene dimer is in ionic form. For example, 2 , 3 , 3 - and 2,3,4-trimethylpentanes

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

32

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

are postulated to be formed by isomerization of the 2,2,4-trimethylpentyl carbonium ion. Similarly, 2,3-dimethylhexane is probably formed by isomerization of isobutene-normaI butene codimer, the 2,4-dimethylhexane structure, while in the ionic form; Scharfe (1973) reports finding these d i methylhexenes, along with trimethylpentenes, in a codimer not made in an alkylation unit. It is obvious that any isobutane formed by isomerization of normal butènes to isobutene, followed by a hydride transfer to the isobutene, cannot be distinguished from the isobutane charge unless a tracer technique is used. Hofmann and Schriesheim (1962) found, in alkylation studies with C - labeled l-butene and isobutene, that C'4 did indeed appear in the isobutane fraction as well as in the pentane and heavier fractions at what they called "steady-state". (They did not distinguish whether normal butane with C'4 was present in the isobutane fraction.) The percentage of total radioactivity appearing in the isobutane fraction was 23 percent for l-butene and 38 percent for isobutene. Neither this laboratory nor others (Albright and L i , 1970) has found normal butane production during normal butènes alkylation to be more than a tenth of that 23 percent value. Clearly this order of magnitude discrepancy suggests olefin isomerization of normal butènes to isobutene. Schmerling (1946) suggested such isomerization of sec-butyl cation to tert-butyl cation before hydride transfer and cited other authors who had made the same assumption; until the C'4 tracer work was done, this isomerization remained an unverified assumption. Hofmann and Schriesheim's reasoning and conclusion about the importance of the C|2 carbonium ion are not supported by their data, unless one assumes that labeled normal butènes do not isomerize and that labeled isobutane does not react. The 38 percent value cited in isobutene akylation confirms hydride transfer back and forth between labeled isobutene and isobutane. Olefin Dimerization. Other investigators (Schaad, 1955, Sparks et a l . , 1939) have reported that the catalytic polymerization of isobutene produced a liquid polymer consisting mainly of isooctenes. H y d r o g é n a t i o n of these isooctenes gave isooctanes consisting of 70 to 90 percent 2,2,4tri me thy I pentane; the remainder was reported as mainly 2,3,4-trimethylpentane. That earlier work used analytical techniques inferior to those now available. Typically, it is now found that the Cg fraction of isobutene-isobutane alkylate catalyzed by HF contains about 62.6 percent 2,2,4-trimethylpentane, 13.4 percent 2,3,4-trimethylpentane, 11.7 percent 2 , 3 , 3 - t r î m e t h y l p e n t a n e , 1.3 percent 2,2,3-trimethylpentane, and II percent dimethylhexanes (see normalized data column for isobutene feed in Table VII). Thus it appears that, under alkylation conditions, isobutene dimerization followed by hydride abstraction from isobutane is another reaction route to the large amount of 2,2,4-trimethylpentane.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

AND

Hydrofluoric Acid Alkylation

HAYS

33

The lesser amounts of other trimethylpentanes are formed mainly by isomer­ ization of trimethylpentyl carbonium ions followed by hydride abstraction. These reactions are illustrated as follows: Isobutene Dimerization C II 2 C-C

(6)

C c t I C-C-C-C-C

H+

I

c

+

c

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Hydride Abstraction

(6-A)

C

C

I

I

c I

c-c-c-cI

—>

C-C I

+

c

C

Carbonium Ion

c I

C-C+ I C

Isomerization

C

c

C C C

C-k-C-C-C L +

(7)

cc c (7-A)

c c c-c-c-c-c c

I I

I

c-c-c-c-c +

C-C

I

c

ι ι » c-c-c-c-c + cc c ι ι ι c-c-c-c-c

c C-C+ I

c

Reaction sequence I, 4, and 4 - A , and sequence 6 and 6-A shown above are believed to represent the predominant ones involved in isobutane-butene alkylation, since the greater portion (80 to 90 percent) of C8 fractions from all four butènes is made up of trimethylpentanes which are predominantly 2,2,4-trimethylpentane . Hofmann and Schriesheim (1962) in alkylation studies with radio-labeled butènes, concluded that a majority of trimethylpentanes does not arise as a result of expected isobutane-isobutene alkylation, but that rapid isobutene polymerization followed by hydride transfer predominates. These investigators also found about the same levels of radioactivity in all of the trimethylpentanes, which is consistent with the isobutene dimerization and C 3 carbonium ion isomerization route rather than the postulation that some trimethylpentanes are formed by other routes. Both of the above reaction sequence groups

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

34

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

(6 and 7) give the same overall net reaction, i . e . , one mole of isobutene combined with one mole of isobutane to yield one mole of alkylate. Thus, one mole of isobutane reacts to produce each mole of product; such yields are substantiated in pilot plant and commercial plant operation (Hutson and Logan, 1975). The following reasons do not support the early postulation (Ciapetta, 1945, Schmerling, 1955) that the 2,2,3-trimethylpentane configuration is a primary reaction product of isobutane and butene-2 and that it isomerizes readily: (I) In degradation reactions using sulfuric acid catalyst, 2, 2,3-trimethylpentane showed very great stability, i . e . , considerably less reactivity than the other three trimethylpentanes (Doshi and Albright, 1976). (2) Based on thermodynamic equilibrium composition, the 2 , 2 , 3 isomer would be substantially favored over the 2,3,4- and 2,3,3-isomers (Table I). (3) The 2, 2,3-trimethylpentane isomer appears in very small amounts in the alkylation product from isobutane and 2-butene; these concentrations are much lower than those for 2 , 3 , 4 - and 2,3,3-trimethylpentane . Schmerling (1955) observed that normal butene polymers when alkylated gave products similar to those obtained by alkylation of the monomers with H 2 S O 4 . Based on the yields of trimethylpentanes, he concluded that with trimers depolyalkylation predominated, rather than hydrogen transfer (and subsequent chain terminations). He concluded that trîmers depolymerized to butylènes prior to alkylation with isobutane. He rationalized that, since the yield of trimethylpentanes was about 50 percent greater than the theoretical (stoichiometric) based on hydrogen transfer alone, the reason had to be de polymerization of the trimers. With trimers, he observed that 75-83 percent of the trimer depolyalkylated. He rationalized further that dimers could behave similarly; this is a moot point, because yields of alkylate from butene monomers and dimers are identical when the alkylate formed during chain termination is considered. It was observed (Phillips Petroleum Company, 1946) that isobutene-butene copolymer yielded alkylate identical to that from the monomers. Hydrogen Transfer. Hydrogen transfer (sometimes called self alkylation of isobutane) occurs with propylene-isobutane mixtures using HF catalyst. This is a chain initiative reaction in that tertiary butyl carbonium ions are formed. End products are (I) propane and (2) 2 , 2 , 4 trimethylpentane. Reactions follow:

(8)

C H 3

6

+

H+

^ ±

C H+ 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

(8-A)

Hydrofluoric Acid Alkylation

A N D HAYS

C H 3

+

+

?

iC H 4

—

1 Q

i C

(8-B)

(8-C)

iC H

(8-D)

iC H +

4

+

g

g

1 7

H

4 9

+

~ ^

iC H + 4

+

9

iC H 4

1 { )

C H

f

3

i C

35 +

8

H

4 8

+

H

^

1C H +

_>

IC H

->

C H

8

iC H + 4

9

+

17

g

1 8

+

+

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Overall Reaction: (9)

C H 3

+

6

2iC H 4

1 0

3

8

+

iC H 8

1 8

Similarly, hydrogen transfer reactions occur when isobutane is alkylated with n-butenes or with amylenes. There is no chain termination taking place in hydrogen transfer; hydrogen transfer represents either chain initiation or chain transfer. Excess Polymerization. A small amount of high-boiling heavy "tail" or residue is formed in isobutane alkylation, even under the most favorable reaction conditions. The polymer molecule is in reality an isoparaffin formed from two or more molecules of olefin plus one molecule of isobutane. Polymer is formed because of the inherent tendency of larger carbonium ions, e . g . , Cj or Cg ions, to complete with tertiary butyl carbonium ions for addition of olefin molecules before abstracting hydride ions and becoming isoparaffin molecules. Reactions follow:

(10)

2C H

8

+

iC H +

->

iC H +

1C H +

+

1C H

->

iC

4

(10-A)

12

25

4

4

9

1 0

1 2

1 2

H

2 5

2 6

+ IC.H^

Polymer or residue formation is minimized by maintaining proper reaction conditions, i . e . , good mass transfer, high isobutane-to-olefin ratio, proper catalyst activity, and minimum concentration of alkylate in the reaction zone. The other important reaction of the polymer ion is that of cracking or scission to form a lower-molecular-weight carbonium ion plus an

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

36

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

olefin molecule. For example: i2 25 7 15 5 l(T Both of these products are subject to further reaction under alkylation conditions and can account for many isoparaffins commonly found in alkylates in minor amounts. Similar equations may be written for i Q o H 3 3 ions. i C

H

+ =

i C

H

+

+

i C

H

+

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Disproportionation. Disproportionate on is believed to play only a minor role in the formation of alkylate components. What does occur is probably via a carbonium ion mechanism, i . e . , when the precursor is in ionic form. Disproportionation reactions could account for the for­ mation of the small concentrations of isopentane, isohexanes, and isoheptanes which are usually found in butene-isobutane alkylates. An example follows:

(11)

C

C

C

C

ι

ι

I

I

c-c c

+

c-c-c-c-c c

—>

C-C-C-C

C

C I

+

I

c-c-c-c-c

Conjunct Polymers. Conjunct polymers (frequently called acidsoluble oils in HF alkylation, red oils in sulfuric acid alkylation) are an exceedingly complex mixture of highly unsaturated, cyclic hydrocarbons. These polymers are by-products of tertiary butyl carbonium ions, and their formation undoubtedly involves a complexity of reactions. Miron and Lee (1963) found the bulk of an HF conjunct polymer to be made up of molecules containing 2-4 rings with an average ring size of 5-6 carbon atoms. They estimated the number of double bonds per molecule of poly­ mer at about 2.5 to 3. Thus, these polymers are hydrogen-deficient. The hydrogen lost during their formation apparently goes into chain term­ ination, i . e . , the formation of isobutane most probably and possibly some propane when propylene is present in alkylation feed. HF alkylation has found no benefit from having acid-soluble oils present in the catalyst. When they are present in amounts greater than about one weight percent, they have a detrimental effect on alkylate quality and yield. IV.

Experimental

Normal Butene Reactions. Under alkylation conditions, all four butene isomers are believed to undergo isomerization, dimerization, and co-dimerization when first coming in contact with HF catalyst, i . e . , immediately following protonation. These are very rapid, ionic reactions and take place competitively along with isobutane alkylation. Alkylate compositions from the four butènes are basically similar (see Table VI1). However, l-butene produces a CQ fraction containing nearly two times

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

A N D HAYS

Hydrofluoric Acid Alkyhtion

37

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

the amount of dimethylhexanes produced from the other three butènes (21.77 vs about 10.5 percent; see normalized data columns in Table VII). The remaining Cg material, largely trimethylpentanes, is of a composition similar to that produced from the other three b u t è n e s . Since thermodynamic equilibrium at alkylation temperature (about 77F) highly favors isobutene formation (the following thermodynamic equilibrium composition was calculated from API Project 44 data at 77F: Isobutene =84.5 percent, trans-2-butene = 11.6 percent, c î s - 2 - b u t e n e = 3.6 percent, and l-butene = 0.3 percent), it is postulated that the similarity of Cg compositions results from either (I) the rapid rate of olefin isomerization and then isobutane alkylation of isobutene — both of these reactions take place in ionic form — or (2) olefin isomerization followed by olefin dimerization and hydride abstraction from isobutane. Isoparaffin and Carbonium Ion Isomerization. It is well known that 2,2,4-trimethylpentane is relatively stable when contacted with HF; reaction conditions must be quite severe (high temperatures and long contact times) to obtain any appreciable conversion of this isoparaffin. Therefore, isoparaffin isomerization is believed to be of small significance in the overall reaction scheme. Isomerization of trimethylpentyl carbonium ions is believed to account for the production of minor amounts of the other three trimethylpentanes. However, the approach to equilibrium composition within the Cg fraction is very poor as shown in Table I. TABLE I,

OCTANES FRACTION FROM ISOBUTENE ALKYLATE

Isobutene Alkylate (3) (1)

Equilibrium Composition (20°C) (3) (2)

2,2,4-Trimethylpentane

62.63

70.37

8.0

69.77

2,3,4-Trimethylpentane

13.35

15.00

1.1

9.58

2,3,3-Trimethylpentane

11.67

13.12

0.77

6.71

2,2,3-Trimethylpentane

1.34

1.51

1.6

13.94

11.01

-

84.06

—

Dimethylhexanes + Methylheptanes Other

4.47

-

(1) Data for isobutene, Table VII. (2) Prosen, E. J . , Pitzer, K. S . , Rossini, F. D . , J . Res. Nat. Bur. . Stand., 34, 255 (1945). (3) Trimethylpentanes only, normalized to 100 percent.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

38

A N DLABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

As shown m Table I, the equilibrium composition for dimethylhexanes is nearly eight times as great as actually found in isobutene alkylate; whereas, the trimethylpentane concentration of isobutene alkylate exceeds the equilibrium concentration by about eight times. When considering only the trimethylpentanes, the 2,2,4 content of isobutene alkylate is very near that for equilibrium (70.37 percent vs 69.77 percent). Agreement for the other three trimethylpentanes on this basis is poor. The conclusion is that the alkylation reactions are quite specific, and that isomerization of alkylation products is minor. Dimethylhexane Formation. Dimethylhexane formation is believed to result largely from reactions of butene-l. This includes (I) codimerization of butene-l and isobutene, (2) dimerization of butene-l, and (3) dimeriza­ tion of isobutene, and (4) isomerization of dimethylhexyl carbonium ions; each of these reactions is followed by abstraction of a hydride ion from isobutane. Reactions follow: Codimerization C ι

C 11 C-C-C

(12)

C I

(12-A)

+

C=C-C

C I

c-c-c-c-c-c +

+ H+

c

c

C

I

c-c-c-c-c-c + +

I C-C

—>

C-C-C-C-C-C

I

(8.04%,) + C-c+ I

c

I

c Dimerization C (13)

C-C-C

C

C +

C-C-C +

1Γ

—>

C

C-C-C-C-C-C

+

(13-A)

C

c

c

I

/

ι

C-C-C-C-C-C + C-C +

cc I

c

I

I ,

C-C-C-C-C-C (1.25%) + C-C+ I

I

C

c

(14)

C II C-C-C

c II c-c-c

H+

— Ï

c I

c I

c-c-c-c-c-c +

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

C (14-A)

Hydrofluoric Acid Alkylation

A N D HAYS

C

C

C

C-C-C-C-C-C + C-t —>

39

C

C

C-C-C-C-C-C (4.94%) + C-C

C

+

fc

Carbonium Ion Isomerization C (15)

CC

C-C-C-C-C-C

C C Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

C

(15-A)

—>

C

C-C-C-C-C-C

+

C-C-C-C-C-C

C C

C

— ^ c-C-C-C-C-C (8.87%) + C-C+

C-C

+ (The above percentage values in parentheses denote concentrations in normalized Cg fractions as shown in Table VII for butene-l.) Propylene Reactions. The following reaction mechanisms are gener­ ally recognized as the principal ones occurring in propylene-isobutane alkylation with hydrofluoric acid catalyst (Ciapetta, 1945). In parenthe­ ses are shown amounts of products from each mechanism; these are from Table VII for propylene: Primary Alkylation (56.18%) C

C C

I

(16)

C=C-C

+

C-C+ I

| i

c-c-c-c-c

jr?

C

C I

I

= c-c-c-c-c

+

+

cc

c

c cc

c

II

(16-A)

ι

C-C-C-C-C

+

C-C

+

I

I I

—>

C-C-C-C-C

+

C-C+

ι

I

c

c

(A reaction similar to 16-A could take place with the 2,4-dimethylpenlyl ion.) The overall reaction for primary alkylation may be written: (16-B)

C H 3

6

+

iC H, 4

0

=

fC H| 7

6

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

40

INDUSTRIAL

A N DLABORATORY

ALKYLATIONS

Hydrogen Transfer (24.50%) (17)

C=C-C

+

2Z> C-C-C

H+

+

c (17-A)

C-C-C +

c

C-C

+

— >

C-C-C + C-C+

ι

ι

c

C

c

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

(17-B)

c

C-C+ C C-C

(17-C)

+

I c c

(17-D)

C C C-C+

C-C

^ ±

C C C C-C-C-C-C

«

I

c

c

c

+

+

c

C-C

+

C

H

— >

+

+

c

C-C-C-C-C I

^ >

c

c

C-C-C-C-C

+ C-C+

I

I

»

C

C

c

The overall reaction for hydrogen transfer may be written: (17-E)

C H 3

+

6

2lC H|o

=

C-fc+ C

£±

4

C H 3

+

8

îC H| 8

8

P o l y m e r l z a t î o n (6.92%) (18)

2 C=C-C

+

i C

H

io 21

C (18-A)

1C

1 0

H

2 1 +

+

Ç

+ C-i:

1C H 1 0

2 2

+ C-C+ r

1

c

C

The o v e r a l l polymerization reaction may be written: (18-B)

2C H 3

6

+

iC H 4

1 0

=

iC

1 Q

H

2 2

Thus, the polymer molecule Is made up of two (or more) molecules of propylene plus one molecule of Isobutane. Cracking or scission of C J Q

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

AND

41

Hydrofluoric Acid Alkyfotion

HAYS

or larger carbonium Ions, producing an olefin plus a smaller carbonium Ion, can account for many additional compounds commonly seen In propylene alkylates In small amounts. DIsproportIonatlon

f C-C

(19)

(Isopentane =6.11%) (Only one example Is shown.)

? ? C-C-C-C-C

+

-

Ç C-C-C-C

C

+

c-i-c-c-c

c

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Although this reaction Is shown In summary form, It Is believed to occur via a carbonium Ion mechanism. Dimerization (Isohexanes = 4.38%)

(20)

2C H

(20-A)

C H +

3

6

6

13

+

H+

+

iC Hi

(20-B)

^ >

A

0

iC H + 4

(20-C)

iC H^"

(20-D)

C H +

+

4

8

+

17

C H 4

9

—>

C

H

6 13 C H

1 4

+

iC H

8

+

H+

6

^ ± C H 4

+

4

+ 9

+ ± C H +

8

8

1C H 4

->

1 0

1?

C H 8

+

1 8

i

C

^

The o v e r a l l reaction for propylene dimerization may be written:

(20-E)

2 C H 3

6

+

2 iC H 4

+ CgH^

1 Q

Thus, propylene dimerization could result In the formation of both Isohexanes and Isooctanes. However, little propylene dimerization Is thought to take place since It should result In the formation of mainly 2,3-dImethylbutane; a small amount of this Isohexane Is found In propylene alkylate. Cracking (21)

2C H 3

6

+

iC H 4

+ 9

j ±

1C H + 10

21

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

42

INDUSTRIAL

(21-A)

1C

1 0

H

2 1 +

1C H 5

1 0

+

A N D LABORATORY

ALKYLATIONS

iC H + 5

n

Cracking or scission of large ions is believed to be of minor significance. Both of the products (there are others) are subject to further reaction under alkylation conditions and can account for a number of isoparaffins commonly formed in propylene alkylate in minor amounts. Examination of Cg fractions from propylene and isobutene alkylates (see Table I) shows a great degree of similarity. Data are summarized in Table II.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

TABLE I I .

SIMILARITY OF C

FRACTIONS IN ISOBUTENE

g

AND PROPYLENE ALKYLATES In Isobutene

In Propylene

Alkylate

Alkylate

62.63

64.94

2,5 DMH

4.07

2.88

2,4 DMH

4.45

3.16

2,2,3 TMP

1.34

1.08

2,3,4 TMP

13.35

16.54

2,3,3 TMP

11.67

11.04

2.22

0.18

-

0.04

0.26

0.11

2,2,4 TMP

2,3 DMH 2 M Heptane 3,4 DMH

-

3 M Heptane

100.00

0.04 100.00

The similarity of these Cg fractions îs strong evidence that (I) propylenederlved octanes come largely from hydrogen transfer reactions (self alkylation of isobutane)and (2) isobutene dimerization is probably an Intermediate reaction step for production of 2 5-dImethylhexane In both propylene and butene alkylation. A small quantity of isooctane could also be /

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

Hydrofluoric Acid Alkylation

A N D HAYS

43

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

formed In the hydrogen transfer reactions associated with propylene dimerization. (see the reaction 20 group.) Effects of Water In HF Catalyst. A number of Investigators have pointed out that water has an important role In alkylation catalysts. Schmerling (1955) stated that the use of HF catalyst with one percent water produced a favorable result In propylene-isobutane alkylation, whereas, with a catalyst containing ten percent water, isopropyl fluoride was the principal product and no alkylate was formed. (Both reactions were at 25C.) Albright et a l . (1972) found the water content of sulfuric acid to be "highly important" in affecting the quality and yield of butene-Isobutane alkylate. They postulated that the water content of sulfuric acid controlled the level of ionization and hydride transfer rate In the catalyst phase. It appears that dissolved water affects HF alkylation catalyst similarly and also exerts further physical influence on the catalyst phase such as reducing viscosity, interfacial tension, and Isobutane solubility. Alkylation tests were conducted in the pilot plant with a cat cracker mixed olefin feed. As the water in HF was Increased from 0.25 to about 2.8 percent, the alkylate composition changed dramatically. These changes are summarized In Table III; detailed alkylate compositions are given In Table VIII. (a)

TABLE I I I . EFFECT OF WATER ON ALKYLATE COMPOSITION

'

Alkylate Composition, weight per cent Residue +

Water i n HF, wt %

C

5

C

6

C

7

C

8

C

9

0.25

10.39

4.94

17.76

48.75

18.16

0.43

5.51

3.83

19.43

58.30

12.87

0.6

4.57

2.89

19.16

60.60

12.79

0.9

3.62

2.63

24.29

60.39

9.07

1.4

2.89

2.35

23.29

62.83

8.63

2.0

3.51

2.54

26.35

60.10

7.50

2.8

3.72

2.88

25.48

61.43

6.49

4.4

4.28

3.44

28.40

56.56

7.32

(a) Feed composition, liquid % (paraffin-free basis): propylene 42.5, butènes 57.2, pentanes 0.3.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

44

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Referring to Table III, the Cg's appear to have peaked when catalyst contained near 1.4 percent water. However, residue, which has an octane number of only about 60 (RON + 3) exerted a strong influence on alkylate quality, and the best quality alkylate resulted when catalyst water content was about 2.8 percent. As discussed previously, residue is be lieved to result from excessive olefin polymerization prior to hydride abstraction. Earlier work characterized residue as having a molecular weight of about 178-196; it could therefore be considered a trimer or cotrimer when alkylating isobutane and propyl e ne-bute ne mixtures. Typically, an overall reaction as described in an earlier paragraph would be: 2C4Hg + 1C4H|Q = iC 1 2 ^ 2 6 · Thus, the effect of water in HF alkylation catalyst appears to be that of slowing polymerization (trimerization) and reducing residue; proper water control should be given serious consideration in order to maximize alkylate quality and yield. Isobutane-to-Olefin Ratio with Propylene Feed. The isobutane-toolefin ratio has long been recognized as an important process variable in the alkylation of isobutane with either butènes or propylene (Phillips Petroleum Company, 1946). By maintaining a sufficiently high concentration of isobutane in the reaction zone, the abstraction of hydride ions from isobutane is favored over abstraction from product isoparaffins. Even with propylene feed, a high isobutane-to-olefin ratio influences the product toward predominantly Cg hydrocarbons which have the highest octane number and also improves yields. Thus, both alkylate quality and yield are found to improve with increasing ratio and olefin dilution. In Table IX, detailed propylene-isobutane alkylate composition data are shown, where the volume ratio was increased from 4.6 to 126. For quick reference, composition data are summarized in Table IV. The Cj -fraction (direct propylene-isobutane alkylation product) decreased from 55.11 to 40.49 percent, while the Cg-fraction (hydrogen transfer product) Increased from 19.52 to 54.1 percent. At the same time, the concentration of residue decreased from 15.69 to only 2.06 percent, Indicating a substantial reduction in the role of olefin polymerization as olefin dilution with isobutane was increased. Considering the normalized Cg-fractions (Table IX), the trimethylpentane content of the product Increased from 86.5 to 95.9 percent as the ratio was Increased. Higher isobutane ratios suppressed the formation of isopentane and isohexanes, which are believed to result from disproportionation or scission of large polymer Ions and (to some extent) propylene dimerization.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

A N D HAYS

Hydrofluoric Acid Alkylation

45

TABLE IV. EFFECT OF ISOBUTANE--TO-OLEFIN RATIO ON ALKYLATE COMPOSITION Composition, wt % Ratio

C

55.11

8 19.52

9 15.69

2.95

48.78

32.23

11.95

4.82

2.90

45.79

34.01

10.99

22

3.69

2.63

48.84

36.22

8.47

52

2.22

2.08

45.50

45.13

3.57

109

2.24

2.02

42.58

49.54

3.32

126

1.36

1.72

40.49

54.19

2.06

C

5.09

6 4.55

13

3.56

16

4.6

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Residue +

C

5

C

7

C

Propylene-isobutane Alkylation with Propane Added. The principal effect of adding a straight-chajn paraffin to alkylation feed appears to be a decrease in the percentage of the olefin going into chain initiation. This, in turn, decreases the percentage of the alkylate formed via chain termination, thereby reducing the amount of trimethylpentanes formed. Specifically, when the feed concentration of isobutane is lowered by propane dilution, the addition of propylene to tertiary butyl carbonium Ions to produce Cy carbonium Ions (precursors of isoheptanes) Is favored over hydrogen transfer reactions. The experimental studies reported here in Tables VII—XI indicate that as the propane-to-propylene ratio in alkylation feed was increased from 0 to 3 . 6 / 1 , alkylate yield and isobutane consumption decreased significantly. The main effect on alkylate composition was an increase in the isoheptanes at the expense of the trimethylpentanes. Since, with propylene feed, trimethylpentane formation is a result mainly of hydrogen transfer reactions, the synthetic propane would be expected to decrease. This decrease was observed. A similar result occurred when normal butane was used as a diluent in alkylation feed. HF versus H 9 S O 4 Alkylates. The quality and yield advantages of HF alkylate over H2^0 ^ alkylate made from mixed olefin are attested in the literature (NPRA, 1973). HF alkylates typically contain higher concentrations of high-octane C Q * S and lesser amounts of low-octane C ç + material. Volumetric yields based on olefin feed are generally higher for HF alkylates because of their lower density.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

46

A N D LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Marked differences are observed î n component distribution of isobutane-mixed olefin alkylates prepared with HF and H2SO4 catalysts. The alkylate samples in Table V were prepared under typical operating conditions for the respective processes from similar feedstocks. Significant composition advantages which HF alkylate shows over alkylate are: (I) Lower residue (C9+) content (6.49 vs 12.85 percent). This is believed to be due to a lesser amount of polymerization occurring with HF catalyst. (2) Higher Cg-fraction content (61.43 vs 45.32 percent) and lower heptane content (25.48 vs 30.84 percent). HF catalyst favors a greater amount of hydrogen transfer reaction from propylene, resulting in high yields of isooctanes and a lesser amount of direct propylene-isobutane alkylate. (3) Lesser amounts of C 5 and material (6.60 vs 10.99 percent). Examination of the normalized Cg-fraction (see Table IV) shows the HF and the ^ S C ^ - c a t a l y z e d products to contain about the same amounts of total trimethylpentanes (88.30 vs 86.40 percent). (4) Lesser amounts of dimethylhexanes (11.61 vs 13.88 percent). The octane advantage in favor of HF alkylate was approximately 1.5 R O N . TABLE V.

COMPARISON OF HF- AND

^4-CATALYZED ALKYLATES

O l e f i n Feed Composition ( l i q u i d volume %) HF

H S0

H

42.5

43.5

H

57.2

54.9

H

0.3

1.6

100.0

100.0

Olefin C

3 6

C

4 8

C

5 10

Composition Fraction

(a)

C

5

C

6

C

7

C

8

C

9

+

(weight % )

(

a

2

4

)

HF

H S0 2

4

3.72

5.34

2.88

5.65

25.48

30.84

61.43

45.32

6.49

12.85

100.00 100.00 Detailed alkylate analyses are shown in Table X; compositions are summarized.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

A N D HAYS

Hydrofluoric Acid Alkylation

47

Hydrocarbon Disperson. Hydrocarbon dispersion (in HF catalyst) was found to be an important factor in producing alkylates of different composition and quality from the same olefin under the same reaction conditions. As the degree of dispersion was changed from poor to excellent by improving mass transfer, alkylate composition underwent drastic changes. These changes are summarized in Table VI. (Detailed alkylate compositions are in Table XI). TABLE VI.

EFFECT OF DISPERSION ON ALKYLATE COMPOSITION

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Alkylate Composition Excellent

Dispersion

Poor

Isopentane

14.04%

Isohexanes

7.65

3.61

Isoheptanes

22.30

22.15

4.65

0.69

Trimethylpentanes

27.17

50.74

Residue

14.79

5.87

2,2,5-Trimethylhexane

7.31%

Thus, good dispersion or mass transfer favors olefin isomerization (to isobutene), isobutene dimerization, and maximizes hydrogen transfer and primary alkylation reactions, i . e . , yielding the greatest amount of highoctane-number trimethylpentanes, and minimizing low-octane-number byproducts from secondary reactions such as excess polymerization. There seems a strong possibility that olefin isomerization and dimerization could take place in the catalyst phase and that alkylation could take place in the hydrocarbon phase. When hydrocarbon dispersion is poor, i . e . , droplets are large, a mass transfer limitation exists, and olefin isomerization and dimerization are reduced. This results in a product containing large amounts of residue, which may be due to secondary alkylation of, say, an isobutene molecule with an isooctyl carbonium Ion to produce a dodecyl carbonium ion which can then undergo hydride transferor scission. Under conditions of good hydrocarbon dispersion (small droplets with large amount of surface area), the reactions yield less heavies and scission products and more of the desirable trimethylpentanes.

American Chemical Society Library 1155 16th St., N.W. In IndustrialWashington, and Laboratory Alkylations; Albright, L., el al.; D.C. 20036 ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

TABLE VII EFFECT OF OLEFIN FEED

Butene-l

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Isobutene

Normalized

Wt %

Mol %

99.09 0.91 0.0 64.95 27.65

2.67 0.02 0.0 1.07 0.48

4.25 0.03 0.0 1.43 0.64

99.26 0.74 0.0 62.94 28.24

0.30 0.0 0.0 2.67 0.0

7.40 0.0 0.0 62.40 0.0

0.15 0.0 0.0 1.60 0.0

0.20 0.0 0.0 1.83 0.0

8.82 0.0 0.0 58.39 0.0

0.0 0.13 1.18 0.13 50.12

0.0 0.15 1.32 0.15 49.18

0.0 3.39 30.81 3.39 62.63

0.0 0.14 0.80 0.20 39.67

0.0 0.16 0.92 0.23 39.86

0.0 5.11 29.20 7.30 46.34

2,5-DMH 2,4-DMH 2,2,3-TMP 2,3,4-TMP 2,3,3-TMP

3.26 3.56 1.07 10.68 9.34

3.20 3.49 1.05 10.48 9.16

4.07 4.45 1.34 13.35 11.67

4.23 6.88 1.26 13.33 11.37

4.25 6.91 1.27 13.39 11.42

4.94 8.04 1.47 15.57 13.28

2,3-DMH 2MHeptane 3,4-DMH 3MHeptane 2,2,5-TMH

1.78 0.0 0.21 0.0 1.31

1.75 0.0 0.21 0.0 1.14

2.22 0.0 0.26 0.0 100.00

7.59 0.20 1.07 0.0 0.40

7.63 0.20 1.08 0.0 0.36

8.87 0.23 1.25 0.0 100.00

Residue

6.25

3.50

100.00

6.88

3.95

100.00

Wt %

Mol %

Isopentane n-Pentane 2,2-DMB 2,3-DMB 2MPentane

5.43 0.05 0.0 2.02 0.86

8.43 0.08 0.0 2.63 1.12

3MPentane n-Hexane 2,2-DMP 2,4-DMP Triptane

0.23 0.0 0.0 2.39 0.0

3,3-DMP 2MHexane 2,3-DMP 3MHexane 2,2,4-TMP

Normalized

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

A N D HAYS

Hydrofluoric Acid Alkylation

Table VII

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

cis-Butene-2 Wt %

Mol %

2.21 0.04 0.0 1.15 0.52

3.46 0.06 0.0 1.51 0.68

0.15 0.0 0.0 1.59 0.0

Normalized

49

(Cont.)

P r o p y l ene

trans-Butene-2 Normalized

Wt %

Mol % Normalized

Wt %

Mol %

98.22 1.78 0.0 63.19 28.57

2.52 0.11 0.0 1.18 0.48

3.95 0.17 0.0 1.55 0.63

95.82 4.18 0.0 65.19 26.52

4.10 0.0 0.0 2.31 0.99

6.11 0.0 0.0 2.88 1.24

100.00 0.0 0.0 65.81 28.21

0.20 0.0 0.0 1.79 0.0

8.24 0.0 0.0 57.61 0.0

0.15 0.0 0.0 1.58 0.0

0.20 0.0 0.0 1.78 0.0

8.29 0.0 0.0 56.03 0.0

0.21 0.0 0.02 14.78 0.0

0.26 0.0 0.02 15.86 0.0

5.98 0.0 0.04 28.23 0.0

0.0 0.17 0.83 0.17 49.03

0.0 0.19 0.94 0.19 48.51

0.0 6.16 30.07 6.16 54.28

0.0 0.20 0.84 0.20 48.60

0.0 0.23 0.95 0.23 48.07

0.0 7.09 29.79 7.09 54.36

0.0 0.20 36.70 0.66 18.06

0.0 0.21 39.38 0.71 17.00

0.0 0.38 70.09 1.26 64.94

2.87 3.53 1.27 18.39 12.47

2.84 3.49 1.26 18.19 12.34

3.18 3.91 1.41 20.36 13.80

2.91 3.52 1.27 18.08 12.38

2.88 3.48 1.26 17.88 12.24

3.25 3.94 1.42 20.22 13.85

0.80 0.88 0.30 4.60 3.07

0.75 0.83 0.28 4.33 2.89

2.88 3.16 1.08 16.54 11.04

2.50 0.0 0.27 0.0 0.17

2.47 0.0 0.27 0.0 0.15

2.77 0.0 0.30 0.0 100.00

2.41 0.0 0.24 0.0 0.24

2.38 0.0 0.24 0.0 0.21

2.70 0.0 0.27 0.0 100.00

0.05 0.01 0.03 0.01 0.28

0.05 0.01 0.03 0.01 0.23

0.18 0.04 0.11 0.04 100.00

2.66

1.46

100.00

3.09

1.69

100.00

11.95

6.92

100.00

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

50

INDUSTRIAL

A N DLABORATORY ALKYLATIONS

TABLE VIII EFFECT OF WATER IN HF CATALYST Mixed C~-C, Olefins Water in HF, Wt X

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Wt X

OJ25 Mol % Normalized

Wt__%

0,43 Mol X Normalized

Wt it

0^6 Mol % Normalized

Wt X

OJL Mol X Normalized

Isopentane n-Pentane 2,2-DMB 2,3-DMB 2MPentane

10.35 0.04 0.04 2.42 1.74

15.70 0.06 0.05 3.07 2.21

99..62 0,,38 0,.81 48..99 35..22

5.51 0.06 0.02 1.92 1.30

8.50 0.09 0.03 2.48 1.68

98.92 1.08 0.52 50.13 33.94

4.56 0.01 0.01 1.47 1.00

7,.10 0..02 0,.01 1..92 1,.30

99.78 0.22 0.35 50.87 34 .60

3..60 0.02 0,.01 1.60 0.73

5.54 0.03 0.01 2,.06 0,.94

99.45 0.55 0.38 60.84 27.76

3MPentane n-Hexane 2,2-DMP 2,4-DMP Triptane

0.67 0.07 0.01 6.52 0.12

0.85 0.09 0.01 7.12 0.13

13..56 1,.42 0..06 36..71 0..68

0.51 0,.08 0.01 7,.53 0,.09

0.66 0.10 0.01 8.36 0.10

13.32 2.09 0.05 38.75 0.46

0.37 0.04 0.01 7.58 0.10

0..48 0,.05 0..01 8,.50 0,.11

12,.80 1.38 0,.05 39 .56 0,.52

0,.28 0,.01 0,.01 8..08 0..10

0,.36 0,.01 0,.01 8,.96 0,.11

10.65 0.38 0.04 33.26 0.41

3,3-DMP 2MHexane 2,3-DMP 3MHexane 2,2,4-TMP

0.02 0.73 9.66 0.70 2S.00

0.02 0.80 10.55 0.76 23.96

0..11 4,.11 54,.39 3,.94 51..28

0.03 0,.62 10,.45 0,.70 32,.43

0.03 0.69 11.61 0.78 31.60

0.15 3.19 53.78 3.60 55.63

0.01 0.49 10.39 0.58 35.80

0,.01 0..55 11,.65 0..65 35,.20

0.05 2,.56 54 .23 3.03 59 .06

0,.01 0..35 15,.21 0,.53 35,.77

0,.01 0,.39 16,.86 0,.59 34,.78

0.04 1.44 62.62 2.18 59.23

2,5-DMH 2,4-DMH 2,2,3-TMP 2,3,4-TMP 2,3,3-TMP

3.51 3.88 2.05 4.67 5.86

3.36 3.72 1.96 4.47 5.62

7..20 7..96 4.,21 9..58 12..02

3,.26 3,.82 1,.93 5.,92 7,,21

3.18 3.72 1.88 5.77 7.03

5.59 6.55 3.31 10.15 12.37

2.51 3.14 1.49 6.97 7.42

2,.47 3..09 1,.47 6. .85 7..30

4,.14 5,.18 2.46 11,.50 12,.24

1,.89 2,.67 1..14 8..44 7..22

1,.84 2,.60 1,.11 8,.21 7,,02

3.13 4.42 1.89 13.98 11.96

2,3-DMH 2MHeptane 3,4-DMH 3MHeptane 2,2,5-TMH

2.86 0.25 0.44 0'.23 2.81

2.74 0.24 0.42 0.22 2.40

5..87 0.,51 0.,90 0.,47 100.00

2,.95 0,,16 0..44 0.,18 1..35

2.87 0.16 0.43 0.18 1.17

5.06 0.27 0.75 0.31 100.00

2.57 0.15 0.44 0.13 1.11

2..53 0..15 0..43 0.,13 0..97

4,.24 0,.25 0,.73 0.,21 100,.00

2,.70 0,.08 0,.42 0,.06 0,.68

2,.63 0,.08 0,.41 0,,06 0,.59

4.47 0.13 0.70 0.10 100.00

15.35

9.45

100.00

11.,52

6.90

100.00

11.68

7.,06

100,.00

8.,39

4,,81

100.00

Residue

2.29 0.05 0.25 0.02 0.59

4.24 0.09 0.46 0.04 100.00

3.66

100.00

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

Hydrofluoric Acid Alkylation

A N D HAYS

51

TABLE IX EFFECT OF ISOBUTANE TO OLEFIN RATIO ON ALKYLATE COMPOSITION Propylene Feed Ratio

4_Jj Wt %

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Isopentane n-Pentane 2,2-DMB 2,3-DMB 2MPentane

Mol %

13

Normalized

Wt %

Mol %

16_ Normalized

Wt %

Mol %

Normalized

5.09 0.0 0.0 3 .06 1,.12

7.56 0.0 0.0 3.81 1 .39

100.00 0.0 0.0 67.25 24.62

4.10 0.0 0.0 2.31 0.99

6.11 0.0 0.0 2.88 1.24

100 .00 0,.0 0,.0 65,.81 28,.21

4.82 0.0 0.0 2.67 0.90

7.19 0.0 0.0 3.33 1 .12

100.00 0.0 0.0 68.46 23.08

3MPentane n-Hexane 2,2-DMP 2,4-DMP Triptane

0,.36 0,.01 0,.01 14,.26 0,.0

0.45 0.01 0.01 15 .25 0 .0

7.91 0.22 0.02 25.88 0.0

0.21 0.0 0.02 14.78 0.0

0.26 0.0 0.02 15.86 0.0

5,.98 0,.0 0,,04 28..23 0..0

0.33 0.0 0.01 15.98 0.20

0.41 0.0 0.01 17 .16 0,.21

8.46 0.0 0.02 34.90 0.44

3,3-DMP 2MHexane 2,3-DMP 3MHexane 2,2,4-TMP

0,,01 0,,45 39.,74 0.,64 12. 43

0,.01 0..48 42,.50 0,,68 11.,66

0.02 0.82 72.11 1.16 63.68

0.0 0.20 36.70 0.66 18.06

0.0 0.21 39.38 0.71 17.00

0.,0 0.,38 70. 09 1.26 64. 94

0.0 0.50 28.40 0.70 21.73

0,.0 0,.54 30,,49 0,.75 20,.46

0.0 1.09 62.02 1.53 63.89

2,5-DMH 2,4-DMH 2,2,3-TMP 2,3,4-TMP 2,3,3-TMP

0.76 0.99 0.25 2.34 1.86

0,,71 0.,93 0.23 2.,20 1.,74

3.89 5.07 1.28 11.99 9.53

0.80 0.88 0.30 4.60 3.07

0.75 0.83 0.28 4.33 2.89

2.88 3.16 1.08 16. 54 11. 04

1.16 1.20 0.27 5.33 3.22

1,.09 1,.13 0..25 5.,02 3.,03

3.41 3.53 0.79 15.67 9.47

2,3-DMH 2MHeptane 3,4-DMH 3MHeptane 2,2,5-TMH

0.69 0.03 0.13 0.04 0.04

0.65 0.03 0.12 0.04 0.03

3.53 0.15 0.67 0.20 100.00

0.05 0.01 0.03 0.01 0.28

0.05 0.01 0.03 0.01 0.23

0.18 0.04 0.11 0.04 100.00

0.80 0.10 0.20 0.0 0.49

0.,75 0.,09 0.,19 0.0 0.41

2.35 0.29 0.59 0.0 100.00

15.69

9.50

100.00

11.95

6.92

100.00

10.99

6.35

100.00

Residue

22

126

109

52

Wt %

Mol %

Normalized

Wt %

Mol %

3.69 0.0 0.0 1.71 0.70

5.49 0.0 0.0 2.13 0.87

100 .00 0.0 0,.0 65,.02 26,.62

3 .33 0.0 0.01 1 .06 0.61

4,.91 0,.0 0.01 1 .31 0,.75

100 .00 0,.0 0.48 50,.96 29,.33

0.22 0.0 0.02 14.09 0.10

0.27 0.0 0.02 15.10 0.11

8,.37 0,.0 0..04 28,.85 0,,20

0.22 0,.18 0.03 9,.74 0,.08

0.27 0,.22 0,.03 10 .34 0,.08

0.0 0.40 33.53 0.70 23.71

0.0 0.43 35.94 0.75 22.29

0..0 0.,82 68.,65 1.,43 65.,46

0,.01 0,.27 34,.84 0..53 31,.52

0.93 0.90 0.15 6.47 3.16

0.87 0.85 0.14 6.08 2.97

2.,57 2.,48 0,,41 17..86 8.,72

0.80 0.0 0.10 0.0 0.15

0.75 0.0 0.09 0.0 0.13

8.47

4.69

Ζ

Mol %

Normalized

Wt %

Mol %

2..24 0,.0 0,,01 0,,89 0,,54

3.33 0.0 0.01 1.11 0.67

100,.00 0,.0 0,.50 44,.06 26,.73

1.,36 0,,0 0,,04 0,,68 0.,38

2,.03 0,.0 0,.05 0,.85 0,.47

100,.00 0,.0 2,.33 39..53 22,.09

10,.58 8,.65 0,.07 21,.41 0,.18

0..22 0,.36 0..04 7..70 0..08

0.27 0.45 0.04 8.25 0.09

10,.89 17..82 0.,09 18. 08 0.,19

0.,16 0.,46 0.,04 7.,24 0.,06

0,.20 0,.57 0,.04 7..78 0..06

9..30 26.,74 0,,10 17.,88 0,,15

0,.01 0,.29 37,.00 0,.56 29..36

0,.02 0..59 76.,57 1,.16 69.,84

0..01 0..30 33,,96 0..49 33,,97

0.01 0.32 36.38 0.52 31.92

0,,02 0.,70 79,.76 1,,15 68,.57

0.,01 0.,28 32.,40 0.,46 37.,15

0,.01 0,.30 34.,82 0,.49 35,.02

0..02 0.,69 80..02 1,,14 68..56

0,.57 0,.66 0,.48 6,,85 4,,20

0,.53 0..61 0,,45 6..38 3..91

1..26 1.,46 1..06 15..18 9..31

0..62 0..70 0,.60 8,.11 4,.65

0.58 0.66 0.56 7.62 4.37

1,.25 1,.41 1,.21 16,.37 9.39

0..63 0,.70 0,.63 9..08 5..08

0,.59 0,.66 0.59 8.56 4.79

1..16 1,.29 1,.16 16,.76 9,.37

2.,21 0.,0 0.,28 0.,0 100.,00

0..69 0..05 0..10 0.,01 0..39

0.,64 0..05 0.,09 0..01 0.,32

1..53 0..11 0.,22 0.02 100.,00

0,.73 0,.05 0,.09 0,.02 0,.30

0.69 0.05 0.08 0.02 0.25

1,.47 0,.10 0.18 0.04 100,.00

0,,78 0,.05 0,.07 0,.02 0,,18

0,.74 0.05 0.07 0.02 0.15

1 .44 0 .09 0 .13 0 .04 100,.00

100.00

3.,57

1.,84

100.,00

3,.32

1.73

100,.00

2,.06

1 .08

100 .00

Normalized

Wt

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Normalized

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

TABLE X ALKYLATE COMPOSITIONS - MIXED OLEFIN FEED

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

HF Catalyst Wt %

Mol %

Normalized

Isopentane n-Pentane 2,2-DMB 2,3-DMB 2MPentane

3.61 0.04 0.0 1.50 0.52

5.56 0.06 0.0 1.93 0.67

98.90 1.10 0.0 67.57 23.42

3MPentane n-Hexane 2,2-DMP 2,4-DMP Triptane

0.20 0.0 0.0 6.21 0.04

0.26 0.0 0.0 6.89 0.04

9.01 0.0 0.0 25.60 0.16

3,3-DMP 2MHexane 2,3-DMP 3MHexane 2,2,4-TMP

0.01 0.19 17.52 0.29 37.85

0.01 0.21 19.43 0.32 36.81

0.04 0.78 72.22 1.20 61.88

2,5-DMH 2,4-DMH 2,2,3-TMP 2,3,4-TMP 2,3,3-TMP

1.20 1.80 0.77 10.41 6.91

1.17 1.75 0.75 10.13 6.72

1.96 2.94 1.26 17.02 11.30

2,3-DMH 2MHeptane 3,4-DMH 3MHeptane 2,2,5-TMH

2.00 0.01 0.20 0.02 0.57

1.95 0.01 0.19 0.02 0.49

3.27 0.02 0.33 0.03 100.00

Residue

8.11

4.63

100.00

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

A N D HAYS

Hydrofluoric Acid Alkyhtion

Table X (Cont.)

H S1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

2

Catalyst Normalized

Wt %

Mol %

5.34 0.0 0.0 4.42 0.82

8.07 0.0 0.0 5.59 1.04

100.00 0.0 0.0 78.23 14.51

0.41 0.0 0.20 10.17 0.0

0.52 0.0 0.22 11.06 0.0

7.26 0.0 0.65 32.98 0.0

0.0 0.31 19.65 0.51 19.23

0.0 0.34 21.37 0.55 18.35

0.0 1.01 63.72 1.65 42.43

1.85 1.64 1.23 8.94 9.76

1.77 1.56 1.17 8.53 9.31

4.08 3.62 2.71 19.73 21.54

2.16 0.10 0.41 0.0 1.75

2.06 0.10 0.39 0.0 1.49

4.77 0.22 0.90 0.0 100.00

11.10

6.51

100.00

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

53

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

TABLE XI EFFECTS OF DISPERSION Mixed O l e f i n Feed

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Wt %

Excellent Mol % Normalized

Isopentane n-Pentane 2,2-DMB 2,3-DMB 2MPentane

7.31 0.0 0.0 2.36 0.91

10.92 0.0 0.0 2.95 1.14

100.00 0.0 0.0 65.37 25.21

3MPentane n-Hexane 2,2-DMP 2,4-DMP Triptane

0.34 0.0 0.02 9.26 0.10

0.43 0.0 0.02 9.96 0.11

9.42 0.0 0.09 41.81 0.45

3,3-DMP 2MHexane 2,3-DMP 3MHexane 2,2,4-TMP

0.0 0.48 11.81 0.48 32.32

0.0 0.52 12.71 0.52 30.51

0.0 2.17 53.32 2.17 53.54

2,5-DMH 2,4-DMH 2,2,3-TMP 2,3,4-TMP 2,3,3-TMP

3.42 3.42 0.90 8.63 8.89

3.23 3.23 0.85 8.15 8.39

5.67 5.67 1.49 14.30 14.73

2,3-DMH 2MHeptane 3,4-DMH 3MHeptane 2,2,5-TMH

2.31 0.0 0.48 0.0 0.69

2.18 0.0 0.45 0.0 0.58

3.83 0.0 0.80 0.0 100.00

Residue

5.87

3.16

100.00

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2.

HUTSON

A N D HAYS

Hydrofluoric Acid Alkyhtion

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

Table XI (Cont.)

Wt %

Poor Mol %

14.04 0.21 0.0 5.23 1.74

20.58 0.31 0.0 6.42 2.13

98.53 1.47 0.0 68.37 22.75

0.68 0.0 0.03 8.90 0.10

0.83 0.0 0.03 9.39 0.11

8.89 0.0 0.13 39.91 0.45

0.0 0.48 12.31 0.48 15.66

0.0 0.51 12.99 0.51 14.50

0.0 2.15 55.20 2.15 43.09

3.19 3.19 0.64 5.45 5.42

2.95 2.95 0.59 5.04 5.02

8.78 8.78 1.76 15.00 14.91

2.31 0.0 0.48 0.0 4.65

2.14 0.0 0.44 0.0 3.83

6.36 0.0 1.32 0.0 100.00

14.79

8.73

100.00

Normalized

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

55

INDUSTRIAL

56

A N D LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch002

References Albright, L . F., Houle, L., Sumatka, A . M., Eckert, R. E.,"lnd. Eng. Chem. Process Des. Develop.", II, 446 (1972). Albright, L . F., Li, K . W . , "Ind. Eng. Chem. Process Des. Develop.," 9, 447 (1970). Ciaipetta, F . G., "Ind. Eng. Chem.", 37, 1210 (1945). Cupit, C . R., Gwyn, J. E., Jernigan, E. C., "Petro/Chem. Eng.", 33 (13), 203 (1961). Doshi, B . , Albright, L . F., "Ind. Eng. Chem. Process Des. Develop.", 15, 53 (1976). Grosse, A V., and Linn, C . B . , "J. O r g . Chem., 3, 26 (1938). Hofmann, J. E., Schriesheim, Α., "J. Amer. Chem. Soc.," 84, 957 (1962). Hutson, J r . , T., Logan, R. S., "Hydrocarbon Processing, 54" (9), 107 (1975). Miron, S., Lee, R. J., "J. Chem. Eng. Data," 8, 150 (1963). NPRA's 72 Panel, "Hydrocarbon Processing, 52" (4), 143 (1973). Phillips Petroleum Company (1946), Hydrofluoric Acid Alkylation, Bartlesville, O k , Phillips, pp. 5, 117, 126, 170, 305-7, 343. Schaad, R Ε (1955) in The Chemistry of Petroleum Hydrocarbons V o l . III, Brooks, B. T., Kurtz, S. S., Boord, C . E., Schmerling, L., Ed. New York, N.Y., Reinhold, Chapter 48. Scharfe, G., "Hydrocarbon Processing", 52 (4), 171 (1973). Schmerling, L., "J. Amer. Chem. Soc.," 68, 275 (1946). Schmerling, L . (1955) in The Chemistry of Petroleum Hydrocarbons V o l . III, Brooks, B. T., Kurtz, S. S., Boord, C . E., Schmerling, L., Ed.,New York, N.Y., Reinhold, Chapter 54. Sparks, W. J., Rosen, R., Frolich, P. K., "Trans. Faraday Soc.", 35 1040 (1939). Whitmore, F . C., "Ind. Eng. Chem.", 26, 94 (1934).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3

Fluorosulfonic

Acid

Promoters

in

HF

Alkylation

ROBERT A. INNES

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

Gulf Research and Development Co., P. O. Drawer 2038, Pittsburgh, PA 15230

High octane blending stock for gasoline i s produced by the strong acid catalyzed a l k y l a t i o n of C to C o l e f i n s with i s o ­ butane. Alkylate t y p i c a l l y comprises 10 to 15 percent of the gasoline pool. Although a l k y l a t i o n has been an important r e ­ finery process for more than t h i r t y years, substantial improve­ ments can still be made. In p a r t i c u l a r , refiners would l i k e to increase the octane ratings of t h e i r alkylate to help compensate for the removal of lead from gasoline. This can be accomplished by c o n t r o l l i n g the many side reactions which accompany a l k y l a ­ t i o n . For example, a t y p i c a l refinery produces 92 RON alkylate from a C3-C5 feedstock. It i s t h e o r e t i c a l l y possible to produce 95 RON alkylate from the same feedstock by eliminating those side reactions which are detrimental to alkylate quality and encouraging those which are b e n e f i c i a l . Such fine tuning of the a l k y l a t i o n process requires modification of the acid c a t a l y s t . This paper describes how the c a t a l y t i c properties of HF may be enhanced by the addition of minor amounts of trifluoromethane­ sulfonic acid (CF SO H) or fluorosulfonic acid (FSO H). (1,2) 3

3

3

5

3

Experimental Methods Apparatus and Procedure. Blends of C P . Grade isobutane with various o i e f i n i e feedstocks were reacted i n the continuous flow apparatus shown i n Figure 1. The reactor was a small stainless s t e e l autoclave equipped with a magnetically driven s t i r r e r . A polyethylene-lined sight glass was employed as a s e t t l i n g vessel for the separation of acid catalyst from hydrocarbon product. Acid blends were stored i n a s t a i n l e s s s t e e l bomb. The system was pressurized to 50 psig with nitrogen p r i o r to the s t a r t of each run. A portion of the acid blend was then transferred to the reactor using the sight glass to gauge the amount. The acid l e v e l was adjusted so that the autoclave would hold approximately equal volumes of acid and hydrocarbon under reaction conditions.

57

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

58

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

3.

Fluorosulfonic Acid Promoters

INNÉS

59

The reactor was then pressurized to 200 psig and the run begun, Isobutane-olefin feed was pumped into the autoclave. The reactor was s t i r r e d at 1600 RPM, intimately mixing the acid and hydrocarbon phases. Contact times (half the reactor volume divided by the hydrocarbon feed rate) ranged from 0.3 to 3.0 minutes. The temperature inside the reactor was controlled by passing water or antifreeze solution from a controlled temperature reservoir through the jacket of the autoclave. The r e action temperature was monitored by a sheathed thermocouple i n serted into the autoclave just below the s t i r r e r . A stream of acid-hydrocarbon emulsion passed continuously from the autoclave to the s e t t l e r . The acid catalyst settled to the bottom and returned to the reactor by gravity flow. The hydrocarbon product passed out the top of the s e t t l e r through a pressure cont r o l valve which maintained the reactor at 200 psig. After passage through a bed of Ascarite and alumina beads to remove dissolved HF, the a l k y l a t i o n product was collected at -78°C. The c o l l e c t i o n of the products reported herein was not begun u n t i l the volume of feed pumped equaled 15 times the reactor volume. At t h i s point the product composition was changing very slowly, i f at a l l . The duration of a run was three hours. A n a l y t i c a l Methods. Liquefied samples of the feed and r e actor effluent were analyzed by gas chromatography. A l l gas chromatographs were t i e d to a chromatographic data processing system which determined peak areas and calculated sample compositions. Sample components were i d e n t i f i e d on the basis of their retention times. Response factors were determined experimentally, using synthetic blends resembling actual a l k y l a tion feeds and products. Except i n those cases where RON was to be determined on a test engine, n-hexane was added to the samples as an i n t e r n a l standard. A l l samples were analyzed using a gas chromatograph equipped with a flame i o n i z a t i o n detector and a 200' χ 0.01" squalane-coated c a p i l l a r y column. Analyses were also made on conventional packed columns i n chromatographs equipped with thermal conductivity detectors. Feeds were analyzed on a s i l v e r nitrate-benzyl cyanide column. Products were analyzed on a 10 χ 1/4" column packed with 25% hexatriacontane on Chromosorb R. After the Ce's had been eluted, the h e x a t r i ­ acontane column was backflushed through the detector to deter­ mine the heavies content of the sample. 1

Determination of Octane Numbers. In some cases Research and Motor octane numbers were estimated from alkylate com­ positions, using the formula,

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

60

INDUSTRIAL

Ν

est

A N D LABORATORY

ALKYLATIONS

Σ .W.N. - u i Z.W. ι

ι

where Wi i s the weight of component i and Ni i s the ASTM (clear) octane number (3,4) of component i i n i t s pure form. The octane ratings of the "heavies" portion of the alkylate were taken as 87 RON and 84 MON. Otherwise, RON was determined experimentally on a test engine. The reactor effluent was d i s t i l l e d to remove isobutane then submitted to our Product Evaluation D i v i s i o n for deter­ mination of RON by the standard ASTM method.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

Results and Discussion Refiners normally charge a mixture of o l e f i n s to t h e i r a l k y l a t i o n units. However, i n studying a l k y l a t i o n , i t i s often i n s t r u c t i v e to alkylate individual o l e f i n s . Accordingly, to demonstrate the e f f e c t of temperature on alkylate composition, we ran the HF a l k y l a t i o n of various pure o l e f i n feeds at 4°C and 45°C. The results are shown i n Tables I and I I . The con­ tact time was 3.0 minutes for the runs at 4°C and 1.0 minute for those at 45°C. The isobutane-olefin molar r a t i o was 24 when a l k y l a t i n g diisobutene and 12 when a l k y l a t i n g other o l e f i n s . The product names are abbreviated: IP for isopentane, 23DMB for 2,3-dimethylbutane, 224TMP for 2,2,4-trimethylpentane, 23DMH for 2,3-dimethylhexane, and so on. If a l k y l a t i o n were a s e l e c t i v e process, one would expect to obtain 23DMP from propylene, 23DMH from l-butene, 224TMP from isobutene and diisobutene, and a mixture of TMP s from c i s - or trans-2-butene. (5,6,, 7) These are the products which predominated at 4 C. The many other products l i s t e d i n Tables I and II are the result of the various side reactions which accompany a l k y l a t i o n . At 45°C, the y i e l d of primary a l k y l a t i o n products was greatly reduced. A l k y l a t i o n yielded increased amounts of 24DMP and 224TMP from propylene, mixed TMP's from l-butene, DMH s from the other C4 o l e f i n s , and heavy and l i g h t ends from a l l feedstocks. Thus, as the reaction temperature was increased, side reactions became increasingly important. From an octane number standpoint TMP s are the most de­ sirable a l k y l a t i o n product, while the formation of DMH's and heavy and l i g h t ends should be avoided. When a l k y l a t i n g pro­ pylene, i t i s important to note that 23DMP has a higher octane rating than 24DMP. Accordingly, most side reactions are detrimental to alkylate quality. Two exceptions to t h i s rule are the hydrogen transfer and butene isomerization reactions. Hydrogen transfer converts propylene and isobutane to propane and isobutylene, 1

e

1

1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 3

0.8 4.2 98.4 95.6

3.0 1.9 1.0 0.6 0.4 3.2 98.6 95.9

37.7 5.9 1.1 2.7 0.2 13.3 84.3 85.8

0.4 0.5 0.4 0.1

0.6 13.6

91.3 89.0

225 TMH Heavies

Est. RON Est. MON

DMH DMH DMH DMH

23 24 25 34

1.5 45.0 13.8 25.2

0.9 18.7 5.5 10.2

0.2 11.5 1.6 2.0

TMP TMP TMP TMP

223 224 233 234

2.4 2.0 1.1 0.4

1.4 42.6 13.5 25.6

0.5 1.0 0.2

0.5 0.9 0.2

0.2 0.5 0.3

56.5 5.4 0.1

23 DMP 24 DMP Other C7

1.0 0.3 0.2

0.8 0.3 0.2

trans C4H8-2

0.5 0.7 0.1

1.7 0.9 0.2

8

2.7

4

cis C H -2

1.7

23 DMB 2 MP 3 MP

C4H8-I

1.0

6

3.9

C H

IP

Component, Wt %

Olefin

ALKYLATE PRODUCED FROM PURE OLEFIN FEEDS AT 4°C

Table I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

8

0.8 59.7 6.4 10.7

1.2 54.7 6.5 9.6

96.1 94.6

1.8 9.7

96.9 95.4

1.5 6.8

1.1 2.5 1.7 0.2

0.9 1.5 0.2

1.2 1.7 0.3

1.3 2.7 1.7 0.2

1.5 0.5 0.2

3.7

244-TM1

1.7 0.6 0.3

4.7

4

iso C H

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

0.5 20.9 2.8 3.6

TMP TMP TMP TMP

DMH DMH DMH DMH

223 224 233 234

23 24 25 34 0.7 3.6

90.6 89.1

225 TMH Heavies

Est. RON Est. MON

0.8 1.2 1.0 0.2

33.6 19.7 1.9

2.5 1.2 0.4

23 DMP 24 DMP Other C7

5.0

IP

C3H6

23 DMB 2 MP 3 MP

Component, Wt %

Olefin

88.4 88.4

0.8 11.3

11.8 9.7 5.0 1.4

1.2 35.4 6.0 7.2

1.0 2.1 0.6

1.2 0.9 0.3

4.1

C4H8-I

94.6 92.6

1.6 5.8

2.9 4.4 3.7 0.6

2.1 42.3 10.7 12.5

1.2 2.3 0.5

1.9 0.1 0.3

5.6

cis C4H8-:

2.0 5.4 94.6 92.9

9.8 2.4 4.1 3.5 0.5

12.1 3.1 4.6 3.6 0.6 1.4 4.6 94.8 92.9

1.8 46.4 9.1

1.3 2.5 0.5

2.2 0.9 0.3

6.6

iso C4H8

2.3 44.3 11.0

1.2 2.3 0.5

1.8 0.8 0.3

5.1

trans C4H8-2

ALKYLATE PRODUCED FROM PURE OLEFIN FEEDS AT 45°C

Table I I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

1.8 5.7 94.6 92.9

10.6 2.5 4.1 3.5 0.5

1.8 46.3 8.9

1.3 2.4 0.5

2.1 0.9 0.3

6.6

244-TMP-l

£ d

3 Ά Ζ g

f

g

ζ,

g

>

>

Ι

g

g

3.

Fluorosulfonic Acid Promoters

INNÉS

C-C=C + H

C-C-C +

C-Ç-C

63

-> C-C-C

Ç-C c-ç-c

> C-C-C + C-£:-c

> C-Ç=C + H

+

while butene isomerization converts l-butene to 2-butene.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

+ C-C-C=C + H

C-C-C-C

+

> C-C-C-C

> C-C=C-C + H

The product o l e f i n s y i e l d TMP's when alkylated rather than the lower octane 23DMP or 23DMH, expected from the s t a r t i n g o l e f i n s . A comparison of Tables I and I I demonstrates the importance of side reactions i n determining alkylate quality. The quality of the alkylates produced from isobutene, diisobutene, c i s - 2 butene, and trans-2-butene was greatly improved when side r e actions were reduced by lowering the reaction temperature to 4°C At 45°C, the alkylates obtained from these o l e f i n s were remarkably s i m i l a r i n composition. The estimated RON s ranged from 94.6 to 94.8. Reducing the reaction temperature to 4°C inhibited the formation of DMH's and increased the y i e l d of TMP's, boosting octane ratings 1.5 to 4.0 RON. Reducing side reactions does not always mean greatly improved octane ratings. Propylene alkylate was only s l i g h t l y improved at the low temperature, because the hydrogen transfer reaction was i n h i b i t e d along with undesirable side reactions. A decrease i n the y i e l d of 24DMP and other undesirable products was o f f s e t by a decrease i n the y i e l d of 224TMP. The quality l-butene alkylate at low temperatures was very poor because the desirable butene-l isomerization reaction was i n h i b i t e d . At 45°C most l-butene isomerized to 2-butene p r i o r to a l k y l a t i o n and TMP s were the major product; but, at 4°C, less than half the l-butene isomerized and 23DMH predominated. The same e f f e c t s were seen with mixed o l e f i n feeds. The refinery stream described i n Table I I I was blended with C P . Grade isobutane to obtain a 9.0-to-1.0 isobutane-to-olefin molar r a t i o . This feed was alkylated at temperatures ranging from 4°C to 45°C The contact time was held constant at 1.0 minutes. The results are shown i n Table IV. The alkylate compositions include pentanes derived from the feed, but only 1

1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

Table I I I C3-C5 REFINERY STREAM

Component

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

Ethane

Vol % 0.06

Propane

13.26

Propene

27.34

Isobutane

19.55

N-butane

4.71

Butene-l

4.44

Isobutene

4.64

Trans-butene-2

5.20

Cis-butene-2

3.40

Isopentane

12.28

N-pentane

0.61

Pentene-1

0.60

Cis and trans pentene-2

1.26

2-methylbutene-l

1.35

2-methylbutene-2

0.90

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 15

2.8 10.1

2.7 10.6

225 TMH Heavies

2.5 9.5

3.9 1.6 0.7 0.5 0.1

4.6 1.5 0.7 0.5 0.1

4.6 1.6 0.7 0.5 0.1

4.9 1.3 0.6 0.5 0.1

23 DMH 24 DMH 25 DMH 34 DMH Other C8 2.9 11.0

0.5 20.1 3.7 6.9

0.5 16.3 3.4 6.7

0.4 15.4 3.2 6.7

0.3 14.7 3.2 6.3

25.9 3.0 0.2

27.7 2.7 0.2

28.4 2.5 0.2

223 224 233 234

1.8 0.6 0.2

2.0 0.7 0.2

2.2 0.7 0.2

2.0 0.6 0.2

17.3 0.9

198 92.6

18.2 0.8

30.5 2.3 0.1

TMP TMP TMP TMP

12 185 92.4

18.3 0.9

179 92.4

10

18.3 0.8

172 92.3

23 DMP 24 DMP Other C7

23 DMB 2 MP 3 MP

IP Ρ

Alkylate Composition, Wt %

Y i e l d , Wt % RON

Temperature, °C

2.8 9.2

4.1 1.8 0.8 0.5 0.2

0.5 20.0 3.9 7.1

24.9 3.8 0.2

1.8 0.6 0.2

16.9 0.8

193 92.6

20

45

2.3 1.0 0.4 16.6 9.8 1.0 0.6 19.9 3.9 5.4 2.2 2.7 1.7 0.4 0.3 3.3 9.6

2.0 0.8 0.3 17.5 8.1 0.8 0.5 21.0 4.1 6.8 2.0 2.4 1.6 0.4 0.2 3.0 10.2

18.0 6.4 0.5 0.5 22.0 4.1 6.5 3.0 2.3 1.2 0.4 0.2 3.1 10.2

18.9 5.1 0.4 0.5 22.5 4.0 6.5 3.4 2.4 1.1 0.4 0.2 3.0 10.1

1.8 0.7 0.3

1.9 0.7 0.3

204 91.8

18.2 0.8 18.0 0.8

38 208 92.

32 207 92.4

18.1 0.8

18.0 0.8

206 92.5

27

HF ALKYLATION OF C3-C5 REFINERY FEED WITHOUT PROMOTER

Table IV

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

INDUSTRIAL

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

INNÉS

Fluorosulfonic Acid Promoters

67

the net increase i n these materials was considered i n c a l c u l a t i n g the y i e l d of a l k y l a t e . As with the pure o l e f i n feeds, lowering the reaction temperature i n h i b i t e d side reactions. The y i e l d of primary alkyl a t i o n products such as 23DMH and 23DMP increased, as the formation of other DMH isomers and 24DMP was i n h i b i t e d . TMP s are both a primary product and a byproduct. Thus, TMP s from i s o butene and 2-butene increased as TMP's from propylene and 1butene decreased. The t o t a l TMP y i e l d was optimized at 27°C. The net e f f e c t on alkylate quality was that RON increased from 91.8 to 92.6, then f e l l back to 92.3. The t h e o r e t i c a l y i e l d of alkylate based on o l e f i n i n the feed was 220 wt %. Below 27°C, o l e f i n conversion was incomplete. Unreacted o l e f i n s were detected i n the reactor effluent and alkylate y i e l d s were considerably below the t h e o r e t i c a l value. From 27°C to 45°C, the o l e f i n feed was completely reacted. In this temperature range the o l e f i n y i e l d averaged 206 wt %. Small amounts of added CF3SO3H dramatically changed the c a t a l y t i c properties of the HF phase. Tables V, VI, and VII show the e f f e c t at low temperatures with propylene, l-butene, and mixed-olefin feeds, respectively. The f i r s t two feeds contained 95 wt % isobutane and 5 wt % o l e f i n . The t h i r d feed, prepared from C P . Grade isobutane and the C3-C5 refinery stream shown i n Table I I I , had an isobutane-olefin molar r a t i o of 12. With HF alone, the y i e l d of primary a l k y l a t i o n products was very high. The addition of CF3SO3H s e l e c t i v e l y restored the hydrogen transfer and butene isomerization reactions. TMP y i e l d s were enhanced at the expense of 23DMP and 23DMH without unduly i n creasing undesirable byproducts such as 24DMP. As a r e s u l t , substantial increases i n alkylate quality were recorded for a l l three feedstocks. Most importantly, the octane rating of the alkylate produced from the C3-C5 refinery stream was boosted from 92.1 to 93.9 RON. Furthermore, reaction rates i n the presence of CF3SO3H were several times those obtained with HF alone. The increased alkylate y i e l d s r e s u l t i n g from CF3SO3H were due i n part to i n creased o l e f i n conversions. In an extension of the experiments i n Table VII, contact time was varied at several temperatures and promoter l e v e l s . The alkylate y i e l d s were plotted against contact time as i n Figure 2. An estimate of the r e l a t i v e r e action rates was made by comparing the contact times required to achieve a 195 wt % y i e l d of a l k y l a t e . The Figure shows that the enhancement of reaction rate by CF3SO3H was more than enough to compensate for a reduction i n temperature from 38°C to 4°C. The e f f e c t of FSO3H on HF a l k y l a t i o n was very much l i k e that of CF3SO3H. The 9-to-l blend of isobutane with refinery o l e f i n s , alkylated e a r l i e r with HF alone (Table IV), was used to study the c a t a l y t i c properties of HF-FSO3H blends. Table VIII gives the r e s u l t s of runs made at 4°C and 1.0 minute 1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

Table V EFFECT OF CF3SO3H ON PROPYLENE ALKYLATION

Wt % CF3SO3H

0

3.8

6.6

Contact Time, Minutes

3.0

3.0

3.0

Temperature, °C

2

3

4

176

199

230

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

Wt % Y i e l d Est. RON

90.8

92.8

93.5

1.7

2.5

2.5

1.3

2.2

2.4

23 DMP

77.0

51.8

41.6

24 DMP

3.9

9.9

12.2

TMP's

9.5

30.3

37.5

DMH's

0.8

1.5

1.8

225 TMH

0.1

0.1

0.2

Heavies

6.2

2.0

1.8

Alkylate Composition, Wt % C

5

C6

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3.

INNÉS

Fluorosulfonic Acid Promoters

69

Table VI

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

EFFECT OF CF3SO3H ON BUTENE-1 ALKYLATION

Wt % CF3SO3H

0

3.6

7.0

Contact Time, Minutes

3.0

3.0

3.0

Temperature, °C

2

3

4

188

198

203

Wt % Y i e l d Est. RON

83.8

90.8

94.5

C5

0.9

1.6

1.6

C

1.2

1.5

2.2

0.9

1.2

1.2

40.2

62.3

75.0

48.9

31.1

18.2

Other Ce

0.3

0.2

0.3

225 TMH

0.1

0.5

0.5

Heavies

7.5

1.2

1.2

Alkylate Composition, Wt %

6

C7 TMP's 1

DMH s

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

70

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

Table VII EFFECT OF CF3SO3H WHEN ALKYLATING A C3-C5 REFINERY STREAM AT 4°C

Wt % CF3SO3H

0

2.7.

6.5

8.6

Contact Time, Minutes

1.5

1.5

1.5

1.5

182

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

Wt % Y i e l d

205

211

217

92.1

92.9

93.9

93.7

19.1

18.8

18.9

17.1

2.3

2.4

2.3

2.0

23 DMP

28.5

23.7

21.5

16.8

24 DMP

2.3

2.9

3.1

4.4

Other C7

0.1

0.1

0.2

0.2

24.3

32.5

36.8

38.7

DMH s

7.3

5.5

4.5

4.4

Other Cg

0.2

0.2

0.1

0.1

225 TMH

2.7

3.0

3.0

3.0

Heavies

13.1

11.0

9.6

13.3

RON

Alkylate Composition, Wt % C5

c

6

TMP's 1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 0.3 14.7 3.2 6.3

223 224 233 234 4.9 1.3 0.6 0.5 0.1 2.7 10.6

23 DMH 24 DMH 25 DMH 34 DMH Other CQ

225 TMH Heavies

TMP TMP TMP TMP

30.5 2.3 0.1

2.0 0.6 0.2

23 DMP 24 DMP Other C7

23 DMB 2 MP 3 MP

IP Ρ 18.3 0.8

172 92.3

Y i e l d , Wt % RON

Alkylate Composition, Wt %

— 100.0

FSO3H HF

Catalyst Composition, Wt %

2.8 9.6

4.0 1.1 0.5 0.4 0.1

0.3 21.1 4.1 6.3

24.9 3.3 0.1

1.9 0.6 0.2

18.0 0.8

191 93.0

3.3 96.7

3.1 8.2

2.9 0.8 0.5 0.4 0.0

0.2 25.1 4.8 6.0

21.2 4.1 0.1

1.9 0.6 0.2

18.8 0.8

206 93.6

6.6 93.4

3.0 9.9

2.3 1.0 0.4 0.3 0.0

0.5 24.0 5.6 6.6

21.3 4.2 0.3

1.6 0.6 0.2

17.2 0.8

208 93.9

9.7 90.3

3.8 11.6

1.9 1.7 1.2 0.3 0.1

1.4 28.6 6.3 4.7

10.5 5.8 0.7

1.4 0.8 0.3

17.8 0.9

215 93.6

15.7 84.3

4.6 13.1

2.0 1.8 1.5 0.4 0.2

1.7 26.6 5.9 4.2

8.6 5.8 0.6

1.7 1.1 0.5

18.7 0.9

210 93.2

21.8 78.2

5.4 12.0

1.9 2.2 1.9 0.4 0.2

2.4 24.7 6.0 3.7

8.2 6.3 0.9

2.1 1.2 0.4

19.0 0.9

213 92.6

32.4 67.6

EFFECT OF ADDED FSO3H ON THE ALKYLATION OF C3-C5 REFINERY FEED AT 4°C

Table VIII

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

6.0 13.6

1.8 2.3 2.0 0.4 0.2

2.3 21.0 6.1 3.5

7.4 6.9 1.3

2.2 1.4 0.5

20.1 1.0

204 91.9

50.0 50.0

8.7 15.4

1.4 2.7 2.6 0.4 0.6

2.8 14.2 3.7 2.3

5.8 5.2 1.9

2.7 2.4 0.9

25.5 1.0

204 90.1

100

s:

Ci

I

2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

72

INDUSTRIAL

A N DLABORATORY

ALKYLATIONS

contact time. The percentage of FSO3H i n the catalyst blend was varied from 0 to 100 wt %. The highest quality alkylate (93.9 RON) was obtained with a catalyst blend containing 9.7 wt % FSO3H. Once again the promoter s e l e c t i v e l y restored the hydrogen transfer and butene isomerization reactions, boosting TMP y i e l d s at the expense of 23DMP and 23DMH. Above the o p t i mum promoter l e v e l , alkylate quality deteriorated because DMH's, 24DMP, and heavy and l i g h t ends were increasingly formed. With 50% or 100% FSO3H, alkylate octane ratings f e l l below those obtained with HF alone. Reaction i n the absence of promoter was r e l a t i v e l y slow, so o l e f i n conversion was incomplete. The addition of FSO3H markedly increased reaction rates, and alkylate y i e l d s approached the t h e o r e t i c a l value of 220 wt %. Only 6.6 wt % FSO3H was required to achieve complete conversion, so the enhancement of reaction rates was of the same magnitude achieved with CF3SO3H. In Table IX a l k y l a t i o n was carried out at various temperatures with a catalyst blend containing 9.7 wt % FSO3H. As the reaction temperature was raised, undesirable side reactions increased. A comparison of Tables IX and IV shows that above 25°C the addition of 9.7 wt % FSO3H was detrimental to alkylate quality. Conclusion A commercial HF a l k y l a t i o n unit operating at 45°C produces 92.1 RON alkylate from the C3-C5 r e f i n e r y stream used i n these experiments. We have shown that 93.9 RON alkylate can be obtained from the same feedstock by lowering the reaction temperature to 4°C and adding an optimum amount of CF3SO3H or FSO3H promoter. Reducing the reaction temperature increases the s e l e c t i v i t y for primary a l k y l a t i o n products, but i n the absence of promoter this has only a small e f f e c t on RON because both desirable and undesirable side reactions are i n h i b i t e d . The addition of promoter restores hydrogen transfer and butene isomerization without markedly increasing undesirable side reactions. Consequently, alkylate quality i s improved. The addition of CF3SO3H or FSO3H also greatly accelerates the rate of alkylate production. This means that throughputs for a modif i e d HF a l k y l a t i o n process employing one of these promoters would be at least as high as i n conventional HF a l k y l a t i o n , despite the lower reaction temperature. The u t i l i z a t i o n of CF3SO3H or FSO3H as promoters i n HF a l kylation w i l l depend on the value assigned by r e f i n e r s to an incremental octane number. The added value of the alkylate must be high enough to j u s t i f y the i n s t a l l a t i o n and operation of the required r e f r i g e r a t i o n equipment. At present most refiners are s t i l l able to increase the quality of their gasoline pool by less costly methods such as by operating t h e i r reforming units at higher severity. However, i f the demand for high-octane

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 0.5 24.0 5.6 6.6

223 224 233 234 2.3 1.0 0.4 0.3 0.0 3.0 9.9

23 DMH 24 DMH 25 DMH 34 DMH Other CQ

225 TMH Heavies

TMP TMP TMP TMP

21.3 4.2 0.3

1.6 0.6 0.2

17.2 0.8

208 93.9

23 DMP 24 DMP Other C7

23 DMB 2 MP 3 MP

IP Ρ

Alkylate Composition, Wt %

Y i e l d , Wt % RON

Temperature, °C

3.4 9.1

2.2 1.6 1.1 0.4 0.2

2.1 1.5 1.0 0.4 0.1 3.3 9.2

1.1 27.0 5.9 5.1

15.3 6.4 0.7

1.8 0.7 0.3

16.9 0.8

3.7 9.2

2.1 1.9 1.3 0.4 0.1

1.3 26.6 6.0 4.9

13.1 7.3 0.8

1.9 0.9 0.4

17.1 0.8

210 93.2

222 93.5

1.0 27.7 6.0 5.2

15.4 6.2 0.6

1.7 0.7 0.2

16.6 0.8

205 93.7

16

10

4.1 9.4

2.2 2.1 1.5 0.4 0.2

1.5 25.1 5.8 4.6

12.0 7.7 1.1

2.2 1.2 0.4

17.4 0.8

210 92.8

20

3.7 10.4

2.5 2.2 1.7 0.4 0.2

1.4 25.0 5.8 4.7

10.9 7.5 1.0

2.3 1.2 0.4

17.8 0.9

213 92.5

25

3.9 11.9

2.6 2.3 2.0 0.5 0.3

1.5 23.3 5.3 4.0

10.1 7.9 1.2

2.3 1.4 0.4

18.2 0.9

212 92.1

32

HF ALKYLATION OF C3-C5 REFINERY FEED PROMOTED BY 9.7 WT % FSO3H

Table IX

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

4.2 12.3

2.8 2.6 2.3 0.6 0.3

1.5 22.4 5.0 3.8

9.1 8.3 1.3

2.2 1.4 0.5

18.5 0.9

207 91.7

38

4.5 13.0

3.1 2.9 2.5 0.7 0.4

1.5 19.9 4.9 3.7

8.5 8.7 1.5

2.2 1.5 0.5

19.1 0.9

203 91.3

45

3

3 ο S?

&

Ci

3

i

74

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

unleaded gasoline increases s i g n i f i c a n t l y , the use of these promoters could be j u s t i f i e d .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch003

Literature Cited (1) Innes, R. Α., U.S. Patent Application S e r i a l No. 501, 664, August 29, 1974. (2) McCaulay, D. Α., U.S. Patent 3, 928, 487 (December 23, 1975). (3) "Knocking Characteristics of Pure Hydrocarbons", ASTM Special Publication No. 225, American Society for Testing Materials, Philadelphia (1958). (4) ASTM Manual for Rating Motor, Diesel, and Aviation Fuels, pp 16 & 37, American Society for Testing Materials, Philadelphia (1971). (5) Schmerling, L., J. Amer. Chem. Soc., 67, 1778 (1945). (6) Schmerling, L., "Alkylation of Saturated Hydrocarbons", Chemistry of Petroleum Hydrocarbons, I I I , 363, Reinhold, New York (1955). (7) Schmerling, L., "Alkylation of Saturated Hydrocarbons", F r i e d e l Crafts and Related Reactions, 2, 1075, Interscience, New York (1964).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4 Isoparaffin/Olefin Trifluoride

Alkylation

over

Resin/Boron

Catalysts

T. J. HUANG Mobil Research and Development Corporation, P. O. Box 1025, Princeton, NJ 08540

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

S. YURCHAK Mobil Research and Development Corporation, Paulsboro Laboratory, Paulsboro, NJ 08066

Conventional s u l f u r i c a c i d and HF a l k y l a t i o n processes (1,2,3) employ l i q u i d - l i q u i d c a t a l y t i c systems which are expensive and troublesome because o f such problems as maintaining an acid/hydrocarbon emulsion, product s e p a r a t i o n and waste d i s p o s a l (H2SO4 process o n l y ) . A s o l i d c a t a l y s t should e l i m i n a t e many o f these problems. I n view o f t h e i r h i g h a c t i v i t y , z e o l i t e s have been used by a number o f workers (4 _5,6,2) catal y z e i s o p a r a f f i n / o l e f i n a l k y l a t i o n w i t h v a r y i n g degrees of success. Z e o l i t e s appear t o have l i m i t e d a t t r a c t i v e n e s s because they age r a p i d l y and cannot perform e f f e c t i v e l y a t h i g h o l e f i n space v e l o c i t i e s . M a c r o r e t i c u l a r a c i d i c i o n exchange r e s i n s represent a c l a s s o f m a t e r i a l s a v a i l a b l e w i t h a r i g i d pore structure. While they have shown good low-temperature a c t i v i t y f o r a number o f a c i d - c a t a l y z e d r e a c t i o n s , they are i n e f f e c t i v e f o r i s o p a r a f f i n / o l e f i n a l k y l a t i o n since they lack hydride t r a n s f e r c a p a b i l i t y . I t may, however, be p o s s i b l e t o i n c r e a s e the a c i d i t y o f i o n exchange r e s i n s by forming a complex between the a c i d groups o f the r e s i n and a Lewis a c i d . T h i s approach was taken by K e l l y (8) who found t h a t i s o p a r a f f i n / o l e f i n a l k y l a t i o n could be c a t a l y z e d by a gel-type a c i d i c ion exchange r e s i n i n the presence o f BF3. The e f f i c i e n c y o f t h i s c a t a l y s t system seems t o have been impaired by the non-swelling nature o f g e l - t y p e r e s i n s i n hydrocarbons. Such l i m i t a t i o n s are not imposed on m a c r o r e t i c u l a r ion exchange r e s i n s . In t h i s paper, we present some o f our data on the use o f m a c r o r e t i c u l a r ion exchange r e s i n s t o c a t a l y z e the a l k y l a t i o n o f isobutane with butene i n the presence o f BF3. t

o

#

75

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

76

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

Experimental

In conducting i s o p a r a f f i n / o l e f i n a l k y l a t i o n , part i c u l a r a t t e n t i o n must be given to minimizing the c h i e f s i d e r e a c t i o n — o l e f i n p o l y m e r i z a t i o n . In the l a b o r atory, t h i s can be c o n v e n i e n t l y done by u s i n g a semibatch r e a c t o r with o l e f i n being charged c o n t i n u o u s l y to a pool of isobutane, c a t a l y s t and product. The o l e f i n feed r a t e i s kept low enough so t h a t i t does not accumulate i n the r e a c t o r . In t h i s manner, the b i m o l e c u l a r p o l y m e r i z a t i o n r e a c t i o n r a t e i s minimized. The e x p e r i ment i s continued f o r a time s u f f i c i e n t t o g i v e the desired external i s o p a r a f f i n / o l e f i n r a t i o . This r a t i o bears some s i m i l a r i t y t o the i s o p a r a f f i n / o l e f i n feed r a t i o t o a continuous r e a c t o r employed i n commercial a l k y l a t i o n systems. In accordance w i t h the above, most runs were performed i n a 300 ml, Type 316 s t a i n l e s s s t e e l s t i r r e d autoclave equipped f o r semi-batch o p e r a t i o n with o l e fin. Reactor pressure was s u f f i c i e n t to maintain the r e a c t a n t s i n the l i q u i d phase. In the standard procedure, 7 grams of dry r e s i n (Rohm and Haas, see Table I) was placed i n the r e a c t o r and 93 grams o f isobutane (Instrument Grade, Matheson) was charged i n t o the react o r by N2 pressure. Then about 6-7 grams of BF3 ( P f a u l t y and Bauer) was charged and the contents s t i r red at 1800 rpm. A f t e r the d e s i r e d temperature was reached, butene ( C P . , Matheson) was fed i n slowly f o r the d u r a t i o n o f the run. An o n - l i n e chromatograph, which was equipped w i t h a f l a m e - i o n i z a t i o n d e t e c t o r and a d i g i t a l i n t e g r a t e r , was used t o monitor the course o f a l k y l a t i o n . D e t a i l s on o p e r a t i n g c o n d i t i o n s are given i n the t a b l e s . At the end o f the run, the product was discharged under N2 flow i n t o a metal bomb which was kept at -73 °C. The product was warmed t o room temperature and t r a n s f e r r e d t o the atmospheric pressure weathering system which c o n s i s t e d of two BF3-scrubbers, a s o l e n o i d v a l v e and a t e n - l i t e r gas c o l l e c t o r which was equipped w i t h an automatic pressure c o n t r o l l e r . Both the weathered l i q u i d and the weathered gas were anal y z e d on a Scot Pak column. Resins were p r e t r e a t e d i n the f o l l o w i n g manner: e l u t i o n w i t h methanol; d i s t i l l e d water wash; exchange w i t h 4 percent NaOH, d i s t i l l e d water wash; exchange w i t h 15 percent H2S04# d i s t i l l e d water wash u n t i l a c i d f r e e . Treated runs were s t o r e d i n d i s t i l l e d water. The p r e t r e a t e d r e s i n was d r i e d i n vacuo f o r three hours at 120°C p r i o r t o use. A l l r e s i n s were ground t o pass through 100 mesh unless otherwise s p e c i f i e d .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2

Surface Area, m /g dry

Cross-linkage % d1vinyl benzene

40-50

-20

150

100-120

550-600

-150

-150

f

40-50

80-90

200-600

Avg. pore diameter, Â

28

-150

24

47

42

32

Porosity, %

Maximum Temperature, °C

4.2

3.3

3

3.4

AmberlystXN-1011

4.9

AmberlystXN-1010

Hydrogen i o n concentration meq/g d r y

AmberlystXN-1005

RS0 H

Styrene-DVB

Amberlyst15

Ionic functionality

Skeletal structure

Resin

30-40

-150

400-800

4.5

AmberlystXN-1008

PHYSICAL PROPERTIES OF VARIOUS MACRORETICULAR RESINS

TABLE I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

40-50

-20

150

4.3

Amberlite 200

δδ*

3

•3»

4

78

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Results and D i s c u s s i o n The C5+ hydrocarbon y i e l d together with chromatographic data and bromine number has been used t o assess the e f f e c t i v e n e s s o f a c a t a l y s t f o r c a t a l y z i n g i s o paraf f i n / o l e f i n a l k y l a t i o n . T h i s y i e l d i s d e f i n e d as the grams o f C5+ hydrocarbon produced per gram o f o l e f i n converted. For butene feed, i f only a l k y l a t i o n occurs, the C5+ y i e l d would be 2.04 g Cs+/g C4 converted; however, i f only p o l y m e r i z a t i o n occurs, the C5 y i e l d would be 1.0 g C$ /g C4 converted. The 04= WHSV i s defined as g C4=/g c a t a l y s t / h o u r . =

+

=

+

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

I.

Amberlyst-15 Resin

P r e l i m i n a r y experiments were performed using Amberlyst-15 resin/BF3 c a t a l y s t t o explore the s t o i c h i o metric requirements necessary t o o b t a i n a good a l k y l a t i o n c a t a l y s t . As the r e s u l t s i n Table I I show, BF3 alone, Amberlyst-15 alone and Amberlyst-I5/BF3 c a t a l y s t with a 1:1 e q u i v a l e n t r a t i o o f BF3 t o -SO3H groups i n the r e s i n are not e f f e c t i v e a l k y l a t i o n c a t a l y s t s . However, i n the presence o f a l a r g e excess o f BF3 (BF3/ -SO3H > 2 e q u i v a l e n t / e q u i v a l e n t ) , the c a t a l y s t i s a c t i v e f o r a l k y l a t i o n as i n d i c a t e d by the C5 y i e l d being equal t o 1.92 g C s / g 04= converted (Run 4, Table I I ) , o r 1.95 g C5+/ ; C4= converted (Run 6, Table I I ) . Amberlyst-15 i n the Na+ form (prepared by exchange with NaOH) was used t o determine i f the H on the -SO3H group p a r t i c i p a t e s i n the a l k y l a t i o n . _The r e s u l t s are shown below ( c o n d i t i o n s : 40°C, 2.6 C4" WHSV, and i - C 4 / C = 5): +

+

0

+

=

4

Cation i n r e s i n

H

O l e f i n conversion % C+ 5

yield, 9 C / g C4

100 1.95

=

+

5

+

Na

+

91 0.93

converted

The d i f f e r e n c e i n 05+ y i e l d c l e a r l y demonstrates t h a t the s u l f o n i c a c i d group i s e s s e n t i a l f o r isobutane alkylation. A l s o shown i n Table I I i s the e f f e c t o f o l e f i n space v e l o c i t y . Comparison o f Runs 4 and 6 shows t h a t the Amberlyst-I5/BF3 c a t a l y s t can a l k y l a t e isobutane w i t h butene i n good y i e l d a t an o l e f i n WHSV o f 2.6 g o l e f i n / g r e s i n - h o u r . The a l k y l a t e y i e l d s are s l i g h t l y lower than the t h e o r e t i c a l v a l u e o f 2.04 due t o removal of some o f the r e a c t o r contents v i a the o n - l i n e sampli n g system. The y i e l d s shown are based on the l i q u i d

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 5

+

Amberlyst15/BF

=

i - •c4/c4=

100.0

=

2.4

99.2

*Operating c o n d i t i o n s : i -•c4/c4=

3

1.7

5.1 and C

7.5 and C

1.95

1.02

4

4

=

=

< 0.1

—

Alkylation

P r i m a r i l y polymerization

Alkylation

P r i m a r i l y polymerization

P r i m a r i l y polymerization

No r e a c t i o n but trace o f o l e f i n polymerization

WHSV = 2.6 f o r Runs 5-6.

WHSV = 0.2 f o r Runs 1-4;

52.4

50.3

< 0.1

6

3

79.2

Amberlyst15/BF

1.92

5

3

100.0

Amberlyst15/BF

4

2.1

-

56.6

1.21

100.0

1.0

Amberlyst15/BF

3

3

25.5

47.8

1.16

96.9

-

v

Comment

CATALYST AT 40°C

Bromine No. o f Product

BF^ alone

Wt % o f Cp i n

No Product f o r A n a l y s i s

Yield

C

2

2

Olefin Conv. %

Amberlyst15 alone

Catalyst

3

3

1

Run No.*

Equiv. Ratio BF /S0 H 0.0

ISOBUTANE/TRANS-2-BUTENE ALKYLATION OVER AMBERLYST-15/BF

TABLE I I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

80

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

recovered from the r e a c t o r a t the end o f the e x p e r i ment. I t i s noteworthy that good performance was achieved a t h i g h o l e f i n space v e l o c i t i e s with low e x t e r n a l isobutane/butene r a t i o . For comparison purposes, s u l f u r i c a c i d a l k y l a t i o n operates a t an o l e f i n space v e l o c i t y o f approximately 0.2-0.4, and an e x t e r n a l i s o b u t a n e / o l e f i n r a t i o o f about 5. HF a l k y l a t i o n , while p e r m i t t i n g o p e r a t i o n a t higher o l e f i n space v e l o c i t i e s than H2SO4 a l k y l a t i o n , requires e x t e r n a l isobutane/ o l e f i n r a t i o o f about 15. I t i s w e l l known t h a t o l e f i n space v e l o c i t y and e x t e r n a l i s o b u t a n e / o l e f i n r a t i o has a pronounced e f f e c t on a l k y l a t e q u a l i t y w i t h both H2SO4 and HF a l k y l a t i o n . A s i m i l a r s i t u a t i o n was obtained with resin/BF3 catal y s t , as shown below ( c o n d i t i o n s : Amberlyst-I5/BF3 and 40°C): i-C /C =

C = WHSV

Wt. % o f TMP i n C

10

0.7

60

10

1.4

54

5

1.4

45

5

2.6

41

4

4

4

+ 5

C l e a r l y , the a l k y l a t e q u a l i t y , as measured by the trimethylpentane (TMP) content o f the a l k y l a t e , d e t e r i orates as o l e f i n space v e l o c i t y i s i n c r e a s e d . I n a d d i t i o n , a t equal o l e f i n space v e l o c i t y , reducing the e x t e r n a l i s o b u t a n e / o l e f i n r a t i o a l s o lowers the alkylate quality. For H2SO4 and HF c a t a l y s t s , three main process v a r i a b l e s a f f e c t a l k y l a t e q u a l i t y : temperature; o l e f i n space v e l o c i t y ; and e x t e r n a l i s o b u t a n e / o l e f i n r a t i o . For resin/BF3 c a t a l y s t , the above process v a r i a b l e s a l s o a f f e c t a l k y l a t e q u a l i t y . However, with the r e s i n / BF3 c a t a l y s t , the surface area o f r e s i n i n a d d i t i o n t o the f u n c t i o n a l group o f the r e s i n , may a l s o play an important r o l e i n d i r e c t i n g a l k y l a t i o n . Some r e s u l t s i l l u s t r a t i n g the e f f e c t o f the r e s i n ' s surface area on a l k y l a t e q u a l i t y are shown i n Table I I I . C l e a r l y , i n c r e a s i n g the r e s i n ' s surface area improves the a l k y l a t e q u a l i t y both i n terms o f the f r a c t i o n o f t r i m e t h y l pentanes i n the C5+ a l k y l a t e and the c l e a r research octane number (RON) o f the C s a l k y l a t e . While t h i s study o f the e f f e c t o f the r e s i n ' s s u r f a c e area was performed by using d i f f e r e n t macror e t i c u l a r r e s i n s , i t i s f e l t that the primary v a r i able being changed i s surface area, s i n c e a l l the +

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

35

45

45

110

570

Amberlyst XN-1008

Amberlite200

Amberlyst15

Amberlyst XN-1005

Amberlyst XN-1010

69.7

56.5

52.2

52.0

39.4

45.9

Wt. % o f TMP i n C 5

+

88.3

86.4

79.1

80.9

73.1

75.5

Wt. % o f TMP i n Cg

4

*100% o l e f i n c o n v e r s i o n f o r a l l r e s i n s .

28

2

Surface Area m /g dry

Amberlyst XN-1011

Macroreticular:

Type o f Resin

3

9

+

11.6

20.7

19.2

22.0

21.9

19.3

5

Wt. % o f C in C +

+

1.88

1.76

1.89

1.91

1.86

1.88

C Yield 5

C 5

+

96.5

95.6

93.6

93.7

92.4

92.3

RON Alkylate

THE RESULTS OF SCREENING TESTS ON IS OBUTANE/TRANS- 2-BUTENE ALKYLATION OVER VARIOUS RESIN/BF COMPLEXES AT 40°C AND 2.6 c ~ WHSV*. ( E f f e c t o f Surface Area o f Resin) .

TABLE I I I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

82

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

r e s i n s are composed b a s i c a l l y o f a s u l f o n a t e d styrenedivinylbenzene copolymer. II.

Amberlyst XN-1010 Resin

Since the Amberlyst XN-IOIO/BF3 c a t a l y s t produced an a l k y l a t e w i t h q u a l i t y s u p e r i o r to the other r e s i n s t e s t e d , a d d i t i o n a l work was performed w i t h t h i s r e s i n / BF3 c a t a l y s t t o explore the e f f e c t s o f p a r t i c l e s i z e and temperature, and s e n s i t i v i t y to o l e f i n type. Olef i n space v e l o c i t y was kept a t 2.6 grams C4 /gram resin-hour f o r a l l the r e s u l t s reported below.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

=

A. E f f e c t o f P a r t i c l e S i z e . The h i g h r e a c t i v i t y of Amberlyst XN-IOIO/BF3 c a t a l y t i c system suggested t h a t a d i f f u s i o n a l l i m i t a t i o n may be imposed i n t h i s system. Therefore, the e f f e c t o f p a r t i c l e s i z e on a l k y l a t i o n was i n v e s t i g a t e d i n order t o d e f i n e a proper p a r t i c l e s i z e range f o r the subsequent work. The r e s u l t s on the e f f e c t o f p a r t i c l e s i z e are summarized below (40°C, i-C4/C4 -2 = 5.1, and 100% o l e f i n conversion) : =

Run Number P a r t i c l e s i z e , mesh

7

8

9

10

30-40

100-200

100+

325+

Wt. % o f TMP

in C +

62.2

68.5

69.7

69.9

Wt. % o f TMP

in C

85.4

88.6

88.3

87.7

5

16.1

13.6

11.6

9.6

alkylate

94.6

95.9

96.5

95.9

5

8

Wt. % o f C9+ i n C + RON

clear of C s

+

For the r e s i n w i t h a p a r t i c l e s i z e o f 30-40 mesh, l e s s TMP and more C g were produced i n the 05+ r e s u l t i n g i n an a l k y l a t e w i t h a lower RON+0. With p a r t i c l e s smaller than 100 mesh, there i s almost no d i f f e r e n c e i n a l k y l a t e q u a l i t y , although the C9+ content seems t o i n crease o n l y s l i g h t l y w i t h i n c r e a s i n g p a r t i c l e s i z e . I t i s concluded t h a t p a r t i c l e s w i t h 100+ mesh are s u f f i c i e n t l y small to overcome the d i f f u s i o n l i m i t a t i o n problem. +

B. E f f e c t o f O l e f i n Feedstock. D i f f e r e n t butènes were used as feedstocks t o determine i f the Amberlyst XN-IOIO/BF3 c a t a l y s t d i s c r i m i n a t e s among them. The r e s u l t s are shown below (40°C, i - C / C 4 % o l e f i n conversion): =

=

5

-

1

a

n

d

1 0 0

4

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

HUANG

4.

Isoparaffin/ Olefin Alkyhtion

A N D YURCHAK

Run Number

9

O l e f i n feedstock C5

+

83

11

12

trans-2- 1-Butene Isobutene Butene

+

yield, g C / g C4"" converted 5

Wt. % o f TMP i n C wt. % o f TMP i n C wt. % o f C

+ 9

+ 5

8

inC + 5

RON c l e a r o f C5"*" a l k y l a t e

1.88

2.06

1.82

69.7

64.3

59.0

88.3

83.2

87.4

11.6

14.2

18.4

96.5

93.4

97.7

The unusual f i n d i n g was t h a t isobutene gave lower TMP i n C5 , but with a higher octane number f o r the C5"*" a l k y l a t e (normally, the octane number o f a l k y l a t e p a r a l l e l s t o the TMP content i n 05+). By comparison w i t h conventional HF and H2SO4 a l k y l a t i o n c a t a l y s t s as shown below, Amberlyst XN-IOIO/BF3 showed r e l a t i v e l y much l e s s d i f f e r e n c e among these three o l e f i n isomers. HF a l k y l a t i o n d i s c r i m i n a t e s s t r o n g l y against l-butene w h i l e H2SO4 a l k y l a t i o n g i v e s r e l a t i v e l y poor r e s u l t s with isobutene (2,3). T h i s suggests that the resin/BF3 system i s unique and not r e l a t e d t o conventional systems.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

+

Wt. % o f TMP i n C c

Resin/BF ***

HF*

H S0 **

2-Butene

74

72

70

1-Butene

22

70

64

Isobutene

59

52

59

2

4

+

3

*At -10°C and 5 min. contact time (see Ref. 2 ) . **At 7°C and 0.2 04= WHSV (see Ref. 2 ) . ***At 40°C, i - C / C = = 5 and 2.6 C = WHSV. 4

4

4

C. E f f e c t o f Temperature. The e f f e c t o f temperature on isobutane/trans-2-butene a l k y l a t i o n over Amberlyst XN-IOIO/BF3 c a t a l y s t was s t u d i e d a t 0°, 20°, 40°, and 60°C. The r e s u l t s are summarized below (i-C /C = 5.1 and 100% o l e f i n c o n v e r s i o n ) : =

4

A

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

84

INDUSTRIAL

I

1

1

1

100

100 (

90

L

\

\

r

ο ο

80

70

I -40

-20

Ν

80^°

V

-

60L

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

A N D LABORATORY ALKYLATIONS

0 +20 Temp.°C

-4

70

J

1 60

+ 60

+ 40

Figure 1. Percent of C isoparaffins in alkylate as function of temperature (Amberlyst XN-1010/BF catalyst) 8

3

Run Number

13

Temperature, °C

14 0

9

15

20

40

60

1.96

1.99

1.88

1.81

+

90.3

80.6

69.7

50.6

Wt. % o f TMP i n C 8 Wt. % o f C in C +

97.1

93.5

88.3

77.5

4.2

9.2

11.6

20.7

101.9

99.1

96.5

96.0

C + y i e l d , g C +/ g C^- converted 5

5

Wt. % o f TMP i n C

5

+

g

RON c l e a r o f C +

5

alkylate

As shown, the s e l e c t i v i t y f o r TMP and the RON o f C5 a l k y l a t e increased sharply w i t h decreasing temper­ ature. An a l k y l a t e w i t h a RON c l e a r o f 101.9 was pro­ duced a t 0°C and an o l e f i n space v e l o c i t y o f 2.6. The p l o t s o f wt. % o f CQ i n 05+ and wt. % o f TMP i n C3 v s . temperature are shown i n F i g u r e 1, w h i l e the p l o t o f TMP d i s t r i b u t i o n v s . temperature i s given i n F i g u r e 2. I t i s speculated t h a t the r e v e r s e trends o f 2,2,4-TMP and 2,3,4-TMP i n TMP d i s t r i b u t i o n a t 60°C (Figure 2) could be due t o increased degree o f s e l f a l k y l a t i o n and butene d i m e r i z a t i o n , followed by r a p i d h y d r i d e and methyl group t r a n s f e r s . Based on the ex­ t r a p o l a t i o n s from these two f i g u r e s , the RON o f 05+ a l k y l a t e a t -40°C was c a l c u l a t e d t o be 102.7. The RON +

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4.

HUANG A N D YURCHAK

Isoparaffin/Olefin

Alkylation

85

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

70

4

o f C5 " a l k y l a t e i s p l o t t e d a g a i n s t temperature i n F i g ure 3. The RON-temperature curve appears t o approach a plateau a t about 0°C, i n d i c a t i n g t h a t lower temperature (<0°C) would g i v e r e l a t i v e l y l i t t l e f u r t h e r improvement i n octane number. The d e t a i l s on 05+ composition a t 0°C are given i n Table IV.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

86

INDUSTRIAL

A N DL A B O R A T O R Y

ALKYLATIONS

no

— ·—·

-40

-20

0

+20

+40

+60

Temperature, C

Figure 3. RON of alkylate as function of temperature (Amberlyst XN-100/BF catalyst) S

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

TABLE IV COMPOSITION OF C PRODUCT FROM ISOBUTANE/ TRANS-2-BUTENE ALKYLATION OVER THE AMBERLYST XN-lOlO/BFo CATALYST AT 0°C, i - C / C - = 5.1 AND 2.6 C = WHSV. +

5

4

4

4

Component

Mol %

Wt %

1.0

0.6

2.3- DM-C + 2-M-C 3- Methyl Pentane

0.6 0.1

0.5 0.0

2.4- Dimethyl Pentane 2.3- Dimethyl Pentane

0.4 0.4

0.3 0.3

44.0 0.8 1.9 1.8 22.7 23.0

43.9 0.8 1.9 1.8 22.6 23.0

2.2.5- T r i m e t h y l Hexane 2,2,4-Trimethyl Hexane Other Nonanes

0.4 0.2 0.1

0.4 0.2 0.1

Decanes +

2.8

3.5

2- Methyl Butane

4

5

2,2,4-Trimethyl Pentane 2.5- Dimethyl Hexane 2.4- Dimethyl Hexane 2.2.3- T r i m e t h y l Pentane 2.3.4- T r i m e t h y l Pentane 2,3-DM-C + 2M-3E-C + 2,3,3-TMP 6

5

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

4.

HUANG

A N D YURCHAK

1soparaffin/Olefin

Alkylation

87

Summary Three phenomena were observed i n t h i s c a t a l y t i c system: 1.

BF3 alone or r e s i n alone i s i n e f f e c t i v e for alkylation.

2.

The H o f the s u l f o n i c a c i d group o f the r e s i n does p a r t i c i p a t e i n a l k y l a t i o n .

3.

Polymerization predominates when the e q u i v a l e n t r a t i o o f t o t a l BF3 t o -SO3H i s l e s s than 2.0, w h i l e a l k y l a t i o n p r e v a i l s over polymerization when the equivalent r a t i o i s g r e a t e r than 2.0.

+

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

These above three f a c t s s t r o n g l y suggest t h a t the a c t i v e species f o r hydride t r a n s f e r , and p o s s i b l y a l s o methyl group migration, may i n v o l v e one s u l f o n i c a c i d group and two BF^ molecules. Among the r e s i n s t e s t e d , the Amberlyst XN-IOIO/BF3 c a t a l y s t system appeared t o be the most s e l e c t i v e one, producing the best a l k y l a t e q u a l i t y . T h i s c a t a l y s t showed much l e s s d i f f e r e n c e among d i f f e r e n t butene feedstocks than conventional HF and H2SO4 a l k y l a t i o n catalysts. In a d d i t i o n , i t s a l k y l a t e q u a l i t y was improved as the temperature was decreased, reaching a plateau a t about 0°C a t which an a l k y l a t e with a RON c l e a r o f 101.9 i n h i g h y i e l d (1.96 grams_alkylate/gram o l e f i n converted) was produced a t a C4 WHSV o f 2.6 (g C4 /g resin/hour) and an isobutane/butene e x t e r n a l r a t i o o f 5 t o 1. The s e l e c t i v i t y and p r o d u c t i v i t y o f t h i s s o l i d c a t a l y t i c a l k y l a t i o n system appear t o be superior t o conventional HF and H2SO4 a l k y l a t i o n processes. =

Acknowledgment The authors are indebted t o Drs. H. Heinemann and A. J . S i l v e s t r i f o r t h e i r constant i n t e r e s t i n t h i s proj e c t , h e l p f u l d i s c u s s i o n s , and v a l u a b l e comments on the o r i g i n a l manuscript; and t o Mr. C. L. Tatsch f o r h i s technical assistance. Abstract Liquid

fluoride. for

phase i s o b u t a n e / b u t e n e - 2 alkylation was conducted at 0°-60°C using a stirred-tank reactor in the presence o f a catalyst comprising of a macro­ reticular acid cation e x c h a n g e resin and b o r o n triN e i t h e r B F n o r resin a l o n e was effective alkylation. For the sulfonic acid resin/BF sys3

3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

88

INDUSTRIAL AND LABORATORY ALKYLATIONS

tem, an e q u i v a l e n t ratio o f total BF to -SO H o f e x ­ ceeding 2 is essential for effective isoparaffin alkyl­ The H o f t h e sulfonic acid group o f the resin does participate in alkylation. Among t h e resins tested, the Amberlyst XN-1010/BF a p p e a r e d t o b e t h e most selective one, p r o ­ ducing the b e s t alkylate quality. This catalyst showed much less difference among various b u t e n e feedstocks, t h a n c o n v e n t i o n a l HF and H S O alkylation catalysts. In addition, the alkylate quality was i m p r o v e d as t h e t e m p e r a t u r e was d e c r e a s e d , r e a c h i n g a plateau a t a b o u t a t w h i c h an alkylate w i t h a RON clear o f 1 0 1 . 9 i n yield (1.96 g alkylate/g olefin c o n v e r t e d ) was p r o ­ d u c e d a t a n olefin WHSV of 2 . 6 (g C =/g resin/hr.) and an i s o b u t a n e / b u t e n e e x t e r n a l ratio o f 5 t o 1. 3

ation.

3

+

3

catalyst

2

0°C high

4

4

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch004

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8)

E w i n g , R. C., Oil & Gas J., 61 ( 1 9 7 1 ) . C u p i t , E . R., Gwyn, J. E., and Jernigan, E. C., P e t r o - C h e m . Eng., 43 (1961); and 49 ( 1 9 6 2 ) . G o r i n , Μ. Η., Kuhn (Jr. ), C.S., and Miles, C . Β., I n d . E n g . C h e m . , 38, 795 ( 1 9 4 6 ) . G a r w o o d , W. E., Leaman, W. Κ., M y e r s , C . G., and P l a n k , C . J., U . S . P a t e n t 3 , 251, 902 ( 1 9 6 6 ) . Kirsh, F . W . , Potts, J. D., and Barmby, D . S . , F r e n c h P a t e n t 1, 598, 716 ( 1 9 6 8 ) . Kirsh, F . W . , and Potts, J. D., R e p r i n t , D i v . P e t . Chem. A.C.S., 1 5 , A109 ( 1 9 7 0 ) . Y a n g , C . L., U . S. P a t e n t 3 , 893, 942 ( 1 9 7 5 ) . Kelly, J. T., U. S. P a t e n t 2, 8 4 3 , 642 ( 1 9 5 8 ) .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5

Isoparaffin-Olefin Alkylation over Zeolite Catalysts

KH. M. MINACHEV, Ε. S. MORTIKOV, S. M. ZEN'KOVSKY, Ν. V. MOSTOVOY, and N. F. KONONOV

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

N. D. Zelinsky Institute of Organic Chemistry, Academy of Sciences, Leninsky pr. 47, Moscow, USSR

Alkylation processes with strong acid catalysts are fraught with many difficulties. Problems involved are the handling o f highly corrosive and costly acid and the necessity of pretreatment of alkylates aimed at removal of traces of a c i d s , harmful sulphate e s t e r s , and some others. Accordingly the search f o r a novel highly active and s e l e c ­ t i v e catalyst for i s o p a r a f f i n - o l e f i n alkylation is still an objective o f numerous recent patents on the subject (1). In the present paper, c a t a l y t i c a c t i v i t y of a number o f zeolitic catalysts i n a l k y l a t i o n o f isobutane with various olefins have been investigated and some considerations o f ethylene a l k y l a t i o n have been made. Experimental Olefins used in the a l k y l a t i o n were ethylene, propylene, isobutene and 2-methyl-butene-2, all 98-99% pure; butene-1, 98% pure but containing some isobutane and traces of butene-2; and a butene-1 and -2 mixture with a component r a t i o o f about 1:2 respectively. Isobutane had a purity o f 96% with 4% o f n-butane. The experiments were performed isothermally in a stainless steel tube. Optimum reaction conditions of 8 0 - 1 0 0 ° C , 20 atm, LHSY-1hr , and an isobutane-olefin r a t i o o f 15-20 were determined by mathematical planning o f experiments and regression analysis (2). Composition of the liquid products was determined by gas chromatography, using a 100m capillary column with squalane, gas products were analyzed over vaseline o i l . The catalysts were prepared by the 1on exchange of the sodium form of zeolite Y with metal cations (3). Butyl amine titration and ammonia thermodesorptlon methods were used to determine surface acidity of the catalysts. -1

89

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

90

AND LABORATORY

ALKYLATIONS

Results and Discussion Use of Catalyst Containing Rare Earths. A number of jeollte catalysts containing polyvalent metals cations such as Ca and rare earth cations (RE ) have been prepared and Investigated. The total exchange ratio was about 90% (Table I). Table I Yields and Compositions of Alkylates Obtained over Zeolite Y Catalysts (Containing Rare Earths and Hydrogen Ions) z

3+

100°C, 20 atm, 1 h r " \ 1 C : C 4

Hydrocarbons

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

CaY C

5

C

6

C

7

8 Cg and higher C

=

=20:1

Catalyst 3.9 Ca: 82 REY 89 REY

16.6 Ca: 64.2 REY

35.8 Ca: 57.6 REY

1.2

2.8

7.7

2.1

2.8

4.4

4.3

6.5

2.1

3.1

5.5

5.8

7.6

5.1

6.3

57.6

71.8

59.9

77.7

70.2

15.3

18.3

13.0

17.6

86.0

77.5

89.5

48.0

31.3

Yield based on olefins reacted, w t %

4

2 2

'

5

Sodium forms of zeolites X and Y are known to be Inactive for alkylation. Calcium Introduction (catalyst 1) has resulted in a catalyst with some activity. Selectivity of the sample was not high; about 57% of the alkylate were octanes with a ratio of ΤMP to DMH of 2:1. The yield and quality of the alkylate were Im­ proved, i f Na cations were replaced with cations of rare-earth elements (catalysts 2 and 3). Product yield for catalysts 2 and 3 were 86.0% and 77.5% respectively with a TMP content in Cgfiractionof about 85%. Unfortunately the stabilities of these two catalysts were rather low 1n both cases, and alkylates yields and quality declined after 3 or 4 runs. For example the percent­ age of unsaturated hydrocarbons 1n the hydrocarbon product for catalyst 3 Increased from 18 up to 30%, and TMP concentration decreased to 35% after several runs. Catalyst 4 has proved to be the most active and stable catalyst and the yields and quality of alkylates obtained over 1t have been the same even after many reaction-regeneration cycles. Further Increase of calcium con­ tent in the catalyst (catalyst 5) deteriorated its catalytic properties. We believe that the difference in catalytic activity and stability of the catalysts tested may be due to the different locations of C a and R E . Calcium cations are located mainly on Sj sites of the zeolite, thus preventing RE migration from +

2+

3+

3+

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5.

MINACHEV

Alkylation

E T AL.

91

over Zeolite Catalysts

their S sites to S sites (4) and also Increasing the stability of the titalyst. These considerations have been confirmed for CaREY zeolite by the direct correlations between the heat of adsorption of benzene, on the one hand, and acidity and the catalytic activity of the catalyst for ethylene-benzene alkylation, on the other hand (5). Isobutane-olefln alkylation 1s accepted to proceed via carbonium-1on mechanism. The close similarity (Table II of the product obtained over a zeolite catalyst (Catalyst 4 of Table I) and that produced 1n the presence of hLSO. contributes to the point. TT

T

1

1

4

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

TABLE II Composition of Alkylates Obtained over CaREY (16.6:64.2) Zeolite and l-LSO.

Hydrocarbon

Catalyst zeolite

H S0 2

4

isopentane

1.9

n-pentane

0.2 2.1

8.9

1.6 0.5 2.1

4.7 1.1 0.4 6.2

C

5

2,3-dimethylbutane 2- methylpentane 3- methylpentane 6 2,2,3-trimethylbutane 2,2-di methylpentane 2,4-dimethylpentane 2- methylhexane 3- methylhexane 2,3 dimethylpentane L

7 2,2,4-tri me thy1 pen tane 2,2,3-tri me thy1pen tan e 2.3.3- trimethylpentane 2.3.4- trimethylpentane 2.2- dimethylhexane 2.3- d1methylhexane 2.4- dimethylhexane 2.5- dimethylhexane 3,4-dimethylhexane C

8 C and higher C

g

0.2 2.4 0.6 }1.9 5.1

0.2 0.2 3.4 }0.3 2.3 6.4

tr

24.3 1.2 12.3 13.0 0.2 3.0

}5.7

}6.6

3.9 77.7

0.4 61.0

13.0

17.5

16.5 3.5 29.6 18.5

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

(6)

92

INDUSTRIAL

A N D LABORATORY ALKYLATIONS

Table III Indicates alkylates composition depending on the olefin used; zeolite Y containing 16-20% of C a and 60-80% of RE was used. Table III Alkylates Obtained Using Various Olefins 2+

J+

100°C, 20 atm., 1 h r . " , 1C nC 1

Hydrocarbons

1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

C

C

6

C

7

3.2 8.7

=

=15-20:1; CaREY

3 10.9 8.5

4

5

6

7

9.9

3.6

8.9

4.8

6.5

4.4

10.3

5.1

35.6

8.1

7.2

5.8

15.0

5.0

23.1

55.8

60.6

45.4

19.7

44.4

16.7

15.8

40.8

46.1

40.7

8 C and higher 29.4 C

4

Alkylation Agent 1so1socommerc. probutene'-1 mixture butene amylene bbf pylene of n-butenes 2

5

4

g

D1str1but1 on of Cg-hydrocarbons TMP

78.7

81.3

83.7

44.0

81.8

OMH

21.3

18.7

16.3

56.0

18.2

45.5

62.5

71.7

70.3

36.2

54.5

2,2,3-TMP

\

5.7

3.0

1.9

2,3,4-TMP

J> 54.5

13.4

10.5

11.0

14.0

18.4

14.2

16.8

>I 163.8 Jf

Distribution of TMP 2,2,4-TMP

2,2,3-TMP

J

1

6.0 25.5

The products from butene-1 and n-butenes mixture containing mainly butene-2 were of comparable quality, probably because of isomeHzation of the double bonds of the b u t è n e s , as in the case of H2SO4 alkylation. This was confirmed by a special experiment where butene-1 diluted with ten-fold η-butane was passed over the catalyst employed under the conditions of alkylation. In the product obtained both butene-1 and butene-2 Isomers were present in thermodynamic quantities. Moreover unexpectedly we have found that η-butane had been alkylated with butene-1 resulting in a liquid product composed mainly of DMH. 72% of the DMH fraction was 3,4 DMH - the product of the direct Interaction of n-butane and butene-1. This reaction 1n the presence of conventional mineral acids is not known and 1s very Interesting from a theoretical standpoint.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5.

MINACHEV

Alkylation

E T AL.

over Zeolite Catalysts

93

If Isobutene (or commercial b.b.f.) was used as alkylating agent, up to 40% of heavy hydrocarbons (Cg and higher) were formed, as a result of an Increased tendency to polymerize the Isobutene. Alkylation of Isobutane with propylene or 2-methylbutene-2 resulted 1n products containing about 20% of Isooctanes (Table III, columns 2 and 6). Similarly to the sulfuric add alkylation, Ce paraffins formation may be explained by self-alkylatlon of Isobutane. Use of Catalysts Containing Transition Metal Cations. Ethylene being alkylated over certain zeolite catalysts reacts specifically. Ethylene can not, however, be alkylated with Isobutane in the presence of H2S0 , because of the formation of stable ethylsulphates. We examined the Isobutane - ethylene alkylation over crystalline aluminosillcates and found that those catalysts containing RE and/or Ca in combination with transition metal cations were most active. The alkylation has resulted 1n not hexanes as would be expected, but an alkylate containing octane isomers as the major product (about 80%). Moreover, the product composition was similar to that obtained from n-butene over CaREY. The TMP-to-DMH ratios were 7.8 and 7.1 respectively. The explanation of the experimental results is that the alkylation proceeds in two steps - first ethylene dimerization takes place (7) and then n-butene (or its precursor) formed alkylated with isobutane as follows:

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

4

3+

2

(Step 1)

2CH =CH

(Step 2)

CHCH=CHCH+H

2

• CHCH=CHCH

2

3

3

3

3

CH CH CHCH + i C H 3

tC Hg 4

2

3

4

2

3

• nC H

1Q

4

+ CHCH=CHCH ?

(dimerization)

3+

• CH CH CHCH

+

3

]0

(alkylation) + tC H + 4

g

• alkylation products.

This scheme was confirmed by the presence of n-butenes in the reaction gases, and the close similarity of the products obtained from ethylene and n-butenes over zeolite CaMEY, as indicated in Table IV. ME represents a transition metal; nickel, chromium, and cobalt were all found effective for ethylene alkylations. Nickel was the metal used for experiments reported in Tables IV and V. Dimerization presumably takes place on the transition metalcontaining sites, and alkylation on the acidic sites of zeolltic surface. The sodium form of zeolite exchanged with transition metal cations is capable of dimerization (and further polymerization), but does not practically exhibit alkylating capacity. This explains the composition of the product obtained from ethylene and isobutane over this catalyst (Table V, column 3).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

94

INDUSTRIAL

AND LABORATORY ALKYLATIONS

Table IV Composition of the Products of Alkylation of Isobutane with Ethylene and n-butenes over CaMEY (ME 1s Nickel) 80° C, 20 atm, LHSV-1 hr" Hydrocarbons C

5

C

6

C

7

n-butenes, %

Ethylene, %

8 Cg and higher C

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

1

0.7

0.4

3.2

1.2

6.0

5.6

78.2

71.6

11.9

21.2

Table V Ethylene-Isobutane Alkylation over Various Zeolitic Catalysts (ME is Nickel) 80°C, 20 atm, LHSV 1 hr"

1

Hydrocarbons

NaY %

NaMEY %

CaMEY %

CaY %

1

2

3

4

5

0.1

0.2

1.8

1.6

product

0.7

2.0

product

formed

14.8

94.5

formed

83.3

1.7

C

5

C

6

C

7

8 Cg and higher C

no

no

Cà^ cation introduction leads to the catalyst containing both kinds of catalytic sites, and the ethylene-isobutane interaction over this catalyst proceeds through dimerization to the alkylation step, yielding high quality alkylate (Table V, column 4). The alkylate yield was 120%. The reaction does not occur unless transition metal cations are present in the catalyst even though the latter may contain addle sites (CaY for example). It 1s understood that no butènes are formed 1n this case, and ethylene does not interact directly with isobutane under the conditions of this experiment. Transition metal cations are known to be responsible for dimerization (8). If this is true for ethylene-isobutane interaction, then deactivation of the active sites of dimerization occurs through the reduction of the cations into metal as follows:

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5.

MiNACHEv E T A L .

Alkyldtion

95

over Zeolite Catalysts

Me • Me° will lead to the loss of the catalyst activity. This reduction was conducted 1n a hydrogen atmosphere for 12 hours at 450°C and 100 atm. The treatment resulted 1n the catalyst as Inactive for ethylene alkylatlon as zeolyte CaY. The experiment contributes additionally to the proposed scheme of ethylene alkylatlon.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch005

2

Miscellaneous results. Runs have been conducted for four hours before the catalyst was regenerated. To restore the catalytic activity of the catalysts, the usual procedure of oxidative regeneration was used, where dried air was passed over the deactivated catalyst at 500°C for 3-4 hours. After the first regeneration, the catalytic activity decreased slightly in comparison with the Initial activity; but the activity did not change with further reaction-regeneration cycles (up to at least 20 cycles). Conclusions Further development of zeolitlc catalysts to the point of their commercial application would help to eliminate many problems of the conventional methods of high quality gasoline production. A number of important problems such as creation of a catalyst of higher activity and stability, development of more simple regeneration procedure, etc. must be solved before zeolites can be used commercially. Literature Cited 1. US Pat. 3.647.916, 7.3.72; 3.706.814, 19.12.72; 3.795.714, 5.5.74. 2. C.M. 3eHbKOBCKNÑ,

E.C.MOPTNBOB,

Α.Γ.ΠΟΓΟΡeЛΟΒ,

H.B.MOCTOBOÑ,

A.M.ДoЦeHKO, X.M.MNHaЧeB, ΗeΦΤЕΧNΜNЯ, 15,No.4,516 (1975). 3.

Χ.Μ.ΜNΗaЧeB, E.C.MOPTNKOB, H.B.MOCTOBOÑ, C.M.3eHBKOBCKNÑ, Η.Φ.ΚΟΗΟΗΟΒ N ДΡ. ΑΒΤ.CΒNД. CCCP Νo.507350,

20.Ι.Ι972Γ.,

OTKp.,N30бp., ΠpOM.Oбp., T O B . 3 H . , No.II, 1976. 4. D.H.Olson, G.T.Kokotailo, J.Charnell, Nature,215, 271, 1967. 5.

E.C.MOPTNKOB,

A.C.ЛEOHTbeB, A.A.MacлoбoeB, H.B.MNP3aбeKOBa,

Η.Φ.ΚΟΗΟΗΟΒ, Χ.Μ.ΜNaЧeB.

M3B.AH CCCP, cep.ΧNΜ. NO. 3,

Ι976Γ.

6. C.A.Zimmermann, J . T . K e l l y , J.C.Dean, Ind.Eng.Chem.Prod.Res.Dev. 1, n2, 124 (1962). 7. H.Uchida, H.Imai, Bull.Chem.Soc. Japan., 40, 321,1967. 8. X.M.MNΗaЧeB,

Я.N.NCaKOB,

Γ.Β.ΑΗΤΟШNΗ, B.Π.KaJINHNH, E.C.ШΠNpo,

N3B.AH CCCP, Cep.xNM., 2b-27 (1973).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6 Two-Step

Alkylation

of Isobutane

R e a c t i o n s of C 4 O l e f i n s

with

1

with

Sulfuric

C4 Olefins: Acid

2

LYLE F. ALBRIGHT, BHARAT DOSHI, MARTIN A. FERMAN, and ADA EWO

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

School of Chemical Engineering, Purdue University, West Lafayette, IN 47907

When isobutane-olefin mixtures are contacted with s u l f u r i c acid at alkylation conditions of commercial i n t e r e s t , the olefins often, if not always, disappear from the hydrocarbon phase at a faster rate than the isobutane (1,2). Subsequently, the i s o ­ butane reacts to produce alkylate which is often predominantly trimethylpentanes (TMP's). Other isoparaffins formed to a large extent during the initial stages of alkylation include dimethyl­ hexanes (DMH's), C 5 - C7 isoparaffins referred to as l i g h t ends ( L E ' s ) , C and heavier isoparaffins often c a l l e d heavy ends (HE's), and acid-soluble hydrocarbons sometimes referred to as conjunct polymer or red oil. The r e l a t i v e l y rapid disappearance of the olefins from the hydrocarbon phase i s undoubtedly caused in part by the r e l a t i v e l y high s o l u b i l i t y of the olefins in the acid phases. The question that has not yet been s a t i s f a c t o r i l y answered is what reactions occur as the olefins enter the acid phase and how does the isobutane eventually react in order to produce the f i n a l wide range of isoparaffins. The mechanism (3,4) that has been widely accepted and that involves a chain reaction in which isobutane and the o l e f i n react in consecutive reactions to form both TMP's and DMH's does not explain a l l the phenomena noted in the alkylation mechanism. Hofmann and Schriesheim (5) for example, suggested that the acid-soluble hydrocarbons provided a source o f hydride ions that entered into the reaction. More recently, Albright and L i (6) suggested that at least some olefins react in the acid phase with acid-soluble hydrocarbons. Goldsby (7,8) has shown that propylene often reacts with s u l f u r i c acid to form sec-propyl sulfates. These sulfates then can be reacted with isobutane to form a l k y l a t e . 9

An objective of the present Investigation was to clarify the reactions between butènes and sulfuric a d d . In subsequent and companion papers, reactions to produce alkylate will be described Present address:

1 Worldwide Construction Co., Wichita, Kansas 2 General Motors Co., Detroit, Michigan

96

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6.

ALBRIGHT

E T A L .

C Olefins with Sulfuric Acid k

97

1n which the Isobutane reacts with butyl sulfates and other pro­ ducts obtained from olefin reactions (9); 1n addition, a compre­ hensive mechanism will be proposed for the production of alkylatetype hydrocarbons under a wide variety of conditions Including alkylation conditions (10).

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

Experimental Details The reactor similar to the one used earlier (11,12) was a large glass test tube that had an internal volume of about 150 ml. Four vertical stainless-steel baffles were spaced In­ side the reactor 90° apart, and three square-pitch impellers mounted on an agitator shaft provided vigorous agitation to the contents of the reactor. The reactor was partly immersed 1n an acetone bath which could be cooled with dry ice or with a coldfinger refrigeration unit to any desired temperatures down to -50°C. A large cork provided with four holes was fitted Into the top opening of the reactor. The holes in the cork were used for the agitator shaft that could be rotated up to 1600 rpm, thermistor probe connected to a temperature-control device, and feed lines for the acid and chilled hydrocarbon liquids. The drain line at the bottom of the reactor was provided with a stopcock. In most runs, a hydrocarbon mixture of isobutane and a C4 olefin was first added to the reactor, and this mixture was cooled to the desired temperature usually - 3 0 ° , - 2 0 ° , or - 1 0 ° C . Agitation was started, and sulfuric acid was dripped in from a glass burrette. Exothermodties were noted as the acid was added, but the rate of additon was adjusted to prevent temperature rises over 2°C. The desired amounts of acid were usually added within 1-5 minutes. Agitation was maintained until a sample was to be taken. Then agitation was stopped generally for a minute or less allowing partial separation of the phases. A chilled microsyringe was used to sample the top hydrocarbon phase; this sample was quickly injected in the gas chromatographic equipment. Agi­ tation was then started and continued until the next sample was to be taken. , _ . . The chromatographic equipment was able to analyze major iso­ paraffins in the CA to Cg range. In the f i r s t portion of this investigation, an isothermal column was used, and the analyses of the HE's were less accurate than those for subsequent runs in which a temperature-programmed column was used. At least 18 compounds were separated and measured in the Co to Cf 2 range. The isobutane used was 95% pure having η-butane as the major impurity and with a trace of propane. 1-Butene was over 99% pure; trans-2-butene was about 92% pure with cis-2-butene and η-butane as major impurities; cis-2-butene was about 80% pure with 18-20% trans-2-butene as the major impurity; and isobutylene

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

98

AND LABORATORY

ALKYLATIONS

was more than 99% pure but contained traces of 2-butenes. 2,2,4trimethyl pentene-1 obtained from Phillips Petroleum Co. had greater than 99.8% purity. 95-96% sulfuric acid, fuming sulfuric acid, water, and used (or spent alkylation) sulfuric acid obtained from both Amoco 011 Co. and Sohio Oil Co. were blended as needed to produce the desired concentrations of sulfuric acid. These used acids had 88-89% acidities and contained 5-7% dissolved hydrocarbons. Additional experimental details are reported by Doshi (11, 12).

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

Results with n-Butenes Sulfuric acid reacted readily with the n-butenes in liquid hydrocarbon mixtures of isobutane and either 1-butene, cis-2butene, or trans-2-butene at -30°C to - 1 0 ° C . The olefin in all cases was extracted from the hydrocarbon phase which upon completion of the reaction was essentially pure isobutane. Although no attempt was made to prove specifically that the product was sec-butyl sulfate, all evidence as will be reported later, indicate that i t was the major, i f not exclusive, product after a small excess of acid had been added. At these conditions, l i t t l e or no isobutane reacted. The resulting butyl sulfate was soluble in the acid phase. In this Investigation, acid was rather slowly added to the Isobutane-olefin mixture. By the time sufficient acid was added to obtain an acid/olefin (A/0) molar ratio of about 1.2, all olefins had been removed from the hydrocarbon phase. While the acid was being added, acid droplets were well dispersed because of vigorous agitation throughout the hydrocarbon phase. Acids tested were 92.5 to 98% fresh acid (water being the only impurity) and both Amoco and Sohio used alkylation acids. When 98% fresh acid was used, part of the acid i n i t i a l l y froze and deposited on the walls of the reactor. Gradually, the frozen acid disappeared presumably because 1t reacted to form butyl sulfates. As the add was dripped into the hydrocarbon phase, a small temperature rise occurred. This rise was 1n all cases 2°C or less depending on the isobutane-to-olefin (I/O) ratio and on the rate of acid addition. I/O ratios of 1.5 to 20 were investigated. As the acid was contacted with the hydrocarbon phase, the volume of the add phase increased. The total volume of the two phases remained essentially constant. A series of runs were made at -20°C in which the acid was added in three to five increments to obtain a final A/0 ratio of about 1.2. Figure 1 indicates how the composition of the hydrocarbon phase changed after each addition of 96.5% fresh acid until a 1.2:1 ratio of add to 1-butene was obtained. After each addition of a d d , part of the 1-butene Isomerized to d s - and especially trans-2-butene, and part formed butyl sulfate. The sulfate formation was followed by the decrease in the C, olefin

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

6.

ALBRIGHT

C

E T A L .

20

h

40

Olefins with Sulfuric Acid

60

80

100

120

REACTION

140

TIME

99

160

180

200

220

240

( MIN. )

Figure 1. Reaction between sulfuric acid and mixture of isobutane and 1-butene

ζ

ο CO

ο û. Σ ο υ < χ CL Ζ < Ο CE Ο ~0

20"

40"

60"

80

ÏÔÔ

REACTION

Figure 2.

Ï2Ô TIME

Î4Ô (

Ï6Ô

léo

^00

MIN. )

Reaction between sulfuric acid and mixture of isobutane and trans2-butene

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

100

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

content of the hydrocarbon phase. After three additions of acid (at an A/0 ratio of about 0.85), 2-butenes became the predominant olefins. Both the isomerlzation and sulfate-forming reactions continued for about 20-40 minutes after each increment of acid was added; as butyl sulfate was produced, the concentration of free acid decreased resulting in an increased ratio of water to unreacted sulfuric acid. Below a certain acidity, both isomerlzation and sulfate formation ceased. Figure 2 shows the results of a similar run made using a mixture of isobutane and trans-2-butene. Butyl sulfate formed in a manner very similar to that shown in Figure 1 (for 1-butene). Part of the trans-2-butene isomerized to form cis-2-butene. If any 1-butene was produced, it was in quantities too small to be detected with the qas chromatographic column used. When fresh acids were used with A/0 ratios from 0.3 up to 1, a third "phase" formed at the bottom of the reactor when agitation was suspended. This layer was unstable when brought to room temperature. It is thought to be an "ice" layer that became insoluble in the acid layer as the sulfuric acid reacted and as butyl sulfate was formed. When more add was added and as the acidity of the acid layer increased at A/0 ratios greater than 1, the third phase dissolved again in the acid phase. Except for this whitish layer, the acid and hydrocarbon phases remained essentially colorless when fresh acid was used and when temperatures of -20°C or less were used. For a run at - 1 0 ° C , however, some side reactions occurred as indicated by a slight color formation in the acid phase. A run was also made in which used acid was added in several increments to a mixture of isobutane and cis-2-butene. The reactions were similar to those using fresh acid. Trans-2-butene was the only C* isomer formed, and eventually Its concentration was higher than that of cis-2-butene. A small amount of the colored materials in the acid phase were extracted by the hydrocarbon phase. Figure 3 shows a plot of olefin conversions after equilibrium had been obtained versus A/0 ratios in the feed. The conversion results were essentially identical for all n-butenes and for all sulfuric acids tested. More than 10-30% excess sulfuric acid was needed to produce butyl sulfate (and also to cause olefin isomerlzation). Stability of Butyl Sulfate Acid mixtures containing dissolved butyl sulfate and relatively small amounts of acid were stable at temperatures from - 3 0 ° to - 1 0 ° C . There was no Indication of Instability for samples stored several days at -20°C or several hours at - 1 0 ° C . Furthermore, subsequent reactions of these stored butyl sulfates with isobutane, as will be discussed later (9), resulted 1n identical products as compared to freshly prepared butyl sulfate samples.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6.

ALBRIGHT

E T AL.

•

Cj Olefins with Sulfuric

Acid

101

R-14(1-Butene,96.4%Ac i d , - 2 0 ° C )

A

R~17(2-Butene,96.42Acid,-20°C)

ο

R-59(1-Butene,Used

Δ R-130(2-Butene,Used

Acid(AMOCO),-20°C) Acid(S0HI0),-20°C)

X R-149(1-Butene,95 o5%Ac i d , - 1 0 ° C )

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

Β R-150(1-Butene,Used

A/0

Acid(SOΗ10),-10°C)

MOLE

RATIO

Figure 3. First-step reactions with n-butenes: percent olefin conversion to sulfate vs. A/Ο ratio

At 0°C and higher, mixtures of butyl sulfate and add were however, unstable resulting in the formation of both a hydro­ carbon phase and acid-soluble hydrocarbons. In these tests, the original mixture was allowed to warm up without agitation. When the mixture was warmed to room temperature, the relatively clear add phase darkened in color within about one minute; further­ more, a colorless hydrocarbon phase began to form. After 8-10 minutes, no further visual changes were noted. The hydrocarbon phase was analyzed and found to contain in each case 5-10% isobutane, and the remainder was a mixture of all isoparaffins found in alkylates (see Table I); it was essentially a lowquality (about 87-90 research octane number) hydrocarbon mixture. The acidity of the final acid indicated that 3-4% acid-soluble hydrocarbons were present in i t ; calculations indicated that approximately 20-40% of the initial olefin (used to produce the butyl sulfate) had reacted to form acid-soluble hydrocarbons. At 0 ° C , add solutions containing butyl sulfate reacted slowly. No observable changes were noted for 15-20 minutes. Slowly the color of the acid darkened, and after 1.75 hours a hydrocarbon phase began to form. Calculations indicated that more "alkylate" and less acid-soluble hydrocarbons were formed at 0°C as compared to higher temperatures. Production of isobutane, the same Isoparaffins (as found 1n alkylates), and add-soluble hydrocarbons undoubtedly occurred

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

102

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Table I Composition of Acid-Insoluble Hydrocarbons Formed by Decomposition of Butyl Sulfate

at

Various Operating Conditions

RUN

123A

Feed Acid H S0 2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

CP.

4

123B

126 A

126B

127A

95.5

97.0

97.0

97.0

97.0

88.2

0.0

0.0

0.0

0.0

0.0

0.0

8.8

0

25

(A/0)

2

2

RON

125B

95.5

Temperature °C Ratio

125A

90.0

87.9

5

26

1.5

1.5

89.0

88.1

127B 88.2 8.8

2

25

2

20

3

3

3

3

89.9

89.1

92.3

91.0

4.0

Composition (by weight) of Acid-insoluble Hydrocarbons Isopentane

2.3

2.1

6.0

11.6

9.1

10.6

4.0

2,3-DMB

3.6

4.9

5.5

9.0

6.6

7.6

4.9

5.3

2-MP

0.8

1.5

1.4

2.6

1.5

1.9

0.9

0.8

2,4,-DMP

2.5

3.2

2.9

3.5

3.2

3.5

2.2

2.2

2,2,3-TMB

1.1

1.1

1.0

1.0

0.8

1.0

0.8

1.0

2-MH

1.0

2.5

1.3

2.7

1.2

1.8

0.6

0.8

2.6

3.9

2.9

4.9

2.7

3.4

3.1

2.9

17.9

11.0

11.6

9.3

15.9

13.7

16.5

16.0

DMH's

6.3

8.0

6.5

6.9

6.5

6.7

5.6

6.4

2,2,3-TMP

1.4

1.3

1.4

1.1

1.3

1.2

1.3

1.3

7.5

6.3

15.6

13.2

7.7

7.0

12.2

10.5

2,3-DMP 2,2,4-TMP

2,3,4-TMP

12.2

8.4

7.6

8.2

2,3,3-TMP

9.1

8.4

7.7

7.2

2,2,5-TMH

18.8

10.5

16.7

13.3

19.1

18.5

18.0

17.7

Residue

20.3

24.2

24.4

16.0

13.6

13.8

11.4

14.5

Total

L.E.'s

13.9

19.3

21.0

35.3

25.2

29.8

16.5

17.0

Total Octanes

47.0

37.1

38.0

35.9

42.1

37.8

54.2

50.8

Total H.E.'s

39.1

43.6

41.0

29.0

32.7

33.3

29.4

32.2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

6.

ALBRIGHT

E T A L .

C

h

Olefins with Sulfuric

Acid

103

because of many complicated reaction steps. The Initial step likely was the decomposition of butyl sulfate Into sulfuric add and n-butenes. Based on thermodynamic considerations, the n-butenes probably contained over 99% 2-butenes. The subsequent reactions that produced Isoparaffins and add-soluble hydrocarbons will be considered later (10). Table I shows the results at 0°C and higher for several decomposition runs for acid mixtures containing butyl sulfate. These results indicate the relative comparisons including the effect of various operating conditions. The quality or research octane number (RON) of the hydrocarbon phase obtained in these butyl sulfate decomposition runs increased either with reduced temperature, with higher ratios of acid to butyl sulfate, or when more dilute acids were used to produce the butyl sulfate. More dilute acid were obtained by using either more water or more acid-soluble hydrocarbons in the acid. Increased RON in general meant more TMP's, but lesser amounts of L E ' s , DMH's, HE's, and acid-soluble hydrocarbons. Considering just the TMP, LE, or DMH family in the hydrocarbon phase, the composition of each family was very similar in each of the following hydrocarbon mixtures : (a) Product formed 1n this investigation by degradation of of butyl sulfate. (b) Alkylate formed during conventional alkylations with sulfuric acid used as the catalyst (2). (c) Alkylate formed during the two-step alkylation product to be discussed later (9). This finding is considered to be highly significant relative to the alkylation mechanism also to be considered later (10). For the TMP family, 2,2,4-TMP, 2,3,4-TMP, and 2,2,3-TMP were always the major TMP's; generally their relative importance is in the above order of listing. Results with Isobutylene Reactions between isobutylene and sulfuric acid were very different than those between n-butene and sulfuric acid. At least three types of reactions occurred. These were dimerization to form C8 olefins, formation of h*avy ends including C 9 to C]4 hydrocarbons (many of which are olefins), and acid-soluble hydrocarbons. These latter hydrocarbons probably included conjunct polymers and perhaps t-butyl sulfate. As will be reported later (9), some of the acid-soluble hydrocarbons react under select conditions in the presence of isobutane to form alkylate. When the acid was added to isobutane-isobutylene mixtures, large exothermocities were noted; higher exothmocities were noted when the acid was added to pure isobutylene. When sufficient acid to produce an A/0 ratio of 0.2 or 0.4 was added quickly to mixtures of hydrocarbons originally at -30OC, temperature rises of 4.5 to 20°C were noted. When, however, the acid was added in

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

104

INDUSTRIAL

Table II.

AND LABORATORY ALKYLATIONS

Heavy End Hydrocarbons Produced in Reactions Between Isobutylene and Sulfuric Acid

Hydrocarbon

19

Predicted Boiling Point °C 161

Probable Carbon Number 9

C

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

20

Run

29B

32

34

0.0

0.0

0.0

0.0

0.0

0.0

0.0

0.0

Run 1

2

3

181

2.8

0.7

0.0

0.0

22

199

1.9

0.6

0.0

1.2

23

201

0.0

0.3

0.0

2.4

24

209

29.3

26.3

20.7

26.2

25

215

22.0

22.7

24.0

23.6

26

218

27

224

C

10

C

12

C

12

6.8

3.6

8.8

8.9

4.8

3.1

6.8

5.0

28

2.8

1.7

1.1

3.6

29

0.0

2.3

0.0

0.0

13.3

13.7

13.3

14.9

2.3

2.8

2.9

2.4

32

2.1

5.8

5.5

1.5

33

2.0

4.8

4.3

1.3

34

2.5

2.6

3.1

0.0

0.0

1.1

2.0

1.0

0.0

0.0

0.0

0.0

96.2

93.6

92.5

92.0

30

244

31

245

36

12

C

C

12

C

C

13 13

265

C

14

19-36

\ — , 95.6% fresh acid, - 3 0 ° C , 1/0 = 10 and A/0 = 7 % — , 95.6% fresh acid, - 3 0 ° C , 1/0 = 9, and A/0 = 10 I 0.1 hour, 95.6% fresh acid, - 3 0 ° C , 1 / 0 = 5 , and A/0 =0.5 0.16 hour, 95.6% fresh acid, - 3 0 ° C , 1/0 = 10, and A/0 = 1.0 Note:

4

21

35

Total

Run

28B

Run

Residual hydrocarbons were C,. - C ' s

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

6.

ALBRIGHT E T A L .

C

4

Olefins with Sulfuric

Acid

105

relatively small increments (equivalent to an A/0 ratio of about 0.04:1), temperature rises of only 1-20C were noted. The acid phase at the end of the reaction was generally reddish-yellow indicating the presence of conjunct polymer and other acidsoluble hydrocarbons. In the present investigation, 60-90 ml of liquid mixtures of isobutane and isobutylene were first added to the reactor and then cooled to either - 3 0 ° or - 2 0 ° C . Sulfuric acid was then dripped into the hydrocarbon mixture that was vigorously agitated. The amount of isobutylene that disappeared from the hydrocarbon phase (mainly because of reactions) depended on the amount of acid added and on the temperature. At - 3 0 ° C , all of the isobutylene had reacted by the time an A/0 ratio of 0.3 was obtained. At - 2 0 ° C , a lower ratio of perhaps 0.2 resulted in complete disappearance of the isobutylene. There was no evidence at these low A/0 ratios and low temperatures that any isobutane had reacted. The acid-insoluble hydrocarbons produced as the acid was first added were dimers of isobutylene and to a lesser extent trimers. As more acid was added, the dimers reacted forming a large number of compounds in the Cg and higher range, as will be discussed in more detail later. In addition, part of the isobutylene was dissolved in the acid phase as indicated by an increase in the volume of the acid phase. Furthermore when only small amounts of acid were added, the acid phase became rather whitish and relatively viscous; the increased viscosity was noted when agitation was started after the phases were allowed to separate. When sufficient acid was added to result in A/0 ratios of about 1.0 or higher, a large number of acid-insoluble hydrocarbons were formed. At least 18 hydrocarbons that were Cg's or higher were present. These hydrocarbons designated in Table II as hydrocarbons 19 to 36* have not yet been identified. The approximate boiling points of these hydrocarbons as shown in Table II were determined using the following technique. The retention times in the chromatographic column of several known Cg through C«|4 hydrocarbons were plotted versus their boiling points. It was assumed that this plot was applicable to the unknown hydrocarbons obtained from isobutylene. Hydrocarbons 24, 25, and 30 were produced in two runs in the 13-24% range. Some alkylate had however been produced as indicated by the presence of 2,2,4-TMP; hence 1t is not clear whether the values for these three hydrocarbons are representative of values at the end of the f i r s t effect reactions. One run was made in which a 1:1 mixture of isobutylene and 2-butenes was combined with isobutane to produce a 5:1 mixture of 1/0. A used alkylation acid was then slowly added to the mixture * Based on the chromatographic analysis, hydrocarbons 1 through 4 are isobutane and C4 olefins; hydrocarbons 5 through 17 are major C5 through C8 isoparaffins found in alkylate; and hydrocarbon 18 is 2,2,5-trimethylhexane.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

106

INDUSTRIAL

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

0

Figure 4.

A N DLABORATORY ALKYLATIONS

20 40 60 80 REACTION TIME (MINUTES)

100

First-step reactions with a 50:50 mixture of isobutylene and 2-butenes at —20°C

maintained at - 2 0 ° C . At an A/0 ratio of 0.3 (see Figure 4), all isobutylene had reacted but 2-butenes were s t i l l present. Cs and heavier olefins were formed. Material balance calculations indicated that part of the 2-butenes had reacted to form acidsoluble hydrocarbons and also butyl sulfate. The next addition of acid forming an A/0 ratio of 0.75 resulted in the disappear­ ance of all of the 2-butenes and part of the CQ olefins. There was an increase in the volume of the acid phase because of dis­ solved or reacted olefins. When an excess amount of acid (A/0 = 7.5) was added, alkylation occurred as will be discussed later (9). One run was made using a hydrocarbon mixture of isobutylene and n-pentane; this η - p a r a f f i n presumably was relatively Inert. When the acid was added, isobutylene reacted as i t did in the presence of isobutane. Of interest, no isobutane was noted in the reaction product. At lower temperatures and lower A/0 ratios, Isobutane was unreactive or at least only slightly reactive with either the acid-soluble or acid-insoluble hydrocarbons; when reactions did occur, isoparaffins produced i n i t i a l l y were LE*s (particularly isopentane and 2,3-dimethylbutane) and/or 2,2,4-TMP. Both higher temperatures and higher A/0 ratios promote alkylation reactions to produce isobutane and all isoparaffins normally found during commercial alkylatlons. The approximate conditions needed to obtain alkylate is summarized below for various A/0 ratios:

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

6.

ALBRIGHT E T A L .

C

h

Olefins with Sulfuric Acid

(a)

107

At an A/0 ratio of 0.5, some LE s were first noted when the reaction mixture was heated to -10°C and maintained at this temperature for 30 minutes. (b) At an A/0 ratio of Ί . 0 , some LE's were first noted upon heating to - 2 0 ° C . (c) At an A/0 ratio of 2, no TMP's were formed until the temperature was raised to about - 1 0 ° C . (d) At an A/0 ratio of 7, alkylation occurred slowly at -30°C. These alkylation reactions will be discussed later (9).

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

Results with

1

2,2,4-Trimethylpentene-1

A series of runs were made in which sulfuric acid was added in small increments to a 4:1 mixture of isobutane and 2,2,4trimethylpentene-1 at -30°C or - 2 0 ° C . Increased amounts of the feed isoolefin reacted as more acid was added. Almost no reaction products were noted in the hydrocarbon phase at A/0 ratios of 0.25 or less. When the A/0 ratio was increased to 0.5, Cq - C hydrocarbons were formed during a 1.5 hour period during which time most of the original isoolefin reacted. 2 Q

Discussion of Results Although no specific analysis was made to identify sec-butyl sulfate in the acid phase, there seems l i t t l e doubt that this sulfate was the reaction product obtained in the n-butene runs. First, the n-butenes and acid reacted on essentially a 1:1 molar basis; only a slight excess of acid was needed in all cases. Of interest, formation of butyl sulfates has also been reported to occur in conventional alkylation reactors (13). Second, the reaction product was similar in many respects as compared to sec-propyl sulfate; the product was unstable at higher tempera­ tures and i t reacted with Isobutane in the presence of sulfuric aicd to form alkylate (9). Third, the reaction products from all three n-butenes alkylated in Identical manners as will be discussed later (9). Fourth, McCauley (14) has shown that butyl fluorides can be formed and are quite stable at low temperatures such as used here; he had contacted HF with n-butenes. No evidence was found for the formation of di-sec-butyl sulfates. Di-sec-propyl sulfates are produced when propylene and sulfuric acid are contacted. If acid-olefin reactions which occurred in this investigation at -10°C or lower also occur during conventional alkylations at 10°C or higher, some i f not all of the significant differences in the type of alkylations with n-butenes and with isobutylene can be explained, as will be discussed later (10).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

108

INDUSTRIAL AND LABORATORY ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch006

Literature

Cited

1)

Shlegeris, R. J. and A l b r i g h t , L . F., Ind. Eng. Chem. Process Des. Dev. 8, 92 (1969).

2)

Li, K. W., Eckert, R. E. and A l b r i g h t , L . F., Ind. Eng. Chem. Process Des. Dev. 9, 434 (1970).

3)

Schmerling,

4)

Schmerling, L., in "Friedel Crafts and Related Reactions in Alkylation and Related Reactions." Olah, G. A. ( e d . ) , Interscience Publishers (1964).

5)

Hoffman, J. E . and Schriescheim, Α . , J. Am. Chem. Soc., 84, 953 (1962).

6)

A l b r i g h t , L . F. and Li, K. W., Ind. Eng. Chem. Process Des. Dev. 9, 451 (1970).

7)

Goldsby, A. R . , U.S. Pat. 3,234,301 (Feb. 6, 1966).

8)

Goldsby, A. R . , U.S. Pat. 3,422,164 (Jan. 14, 1969).

9)

A l b r i g h t , L . F., Doshi, Β. M. Ferman, Μ. Α., and Ewo, Α., "Two-Step Alkylation o f Isobutane with Products of F i r s t Step Reactions", This book, Chapter 7, 1977.

10)

L.,

Ind. Eng. Chem., 45, 1447 (1953).

A l b r i g h t , L . F., "Mechanism for Alkylation of Isobutane with Light O l e f i n " , This book, Chapter 8, 1977.

11)

Doshi, Β. H. and A l b r i g h t , L . F., Ind. Eng. Chem. Process Des. Dev. 15, 53 (1976).

12)

Doshi, Β. Μ., Ph.D. Thesis, Purdue University

13)

Goldsby, A. R. and Gross, H. H., U.S. Pat. 3,083,247 (March 26, 1973).

14)

McCauley, D. Α., U.S. Pat. 3,280,211

(1975).

(1966).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

7

Two-Step Reaction

Alkylation

of

of I s o b u t a n e

Isobutane with

Initial

with

C4 Olefins:

Reaction

Products

LYLE F. ALBRIGHT, BHARAT M. DOSHI, MARTIN A. FERMAN, and ADA EWO

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

School of Chemical Engineering, Purdue University, West Lafayette, IN 47907

As has been indicated e a r l i e r ( 1 , 2 ) , C olefins react to a s i g n i f i c a n t , and maybe even predominant, extent before isotutane reacts during alkylations using s u l f u r i c acid as a c a t a l y s t . In the previous paper (3) of this series the reactions that occur when n-butene and isobutylene were contacted with r e l a t i v e l y small amounts of s u l f u r i c acid in the temperature range of about - 3 0 ° to - 1 0 ° C were investigated. These reactions defined as f i r s t - s t e p reactions in the two-step alkylation process were found to be as follows: (a) n-Butenes react with s u l f u r i c acid to form sec-butyl sulfates that dissolve in the acid phase. (b) Isobutylene reacts forming both acid-insoluble and acid-soluble hydrocarbons. Acid-soluble hydrocarbons probably include both t-butyl sulfates and conjunct polymers. The acid-insoluble hydrocarbons are mainly in the C and higher range; a large fraction of these hydrocarbons are o l e f i n s . The second step of a two-step alkylation process involves reactions of the isobutane with the products of the f i r s t - s t e p reactions. Although two-step processes were f i r s t reported many years ago (4-6), r e l a t i v e l y little i s known about the factors affecting the second step and the quality of the alkylate pro­ duced. Most investigators have largely ignored the second-step reactions, perhaps because only r e l a t i v e l y poor quality alkylates had been produced in these e a r l i e r processes. A modification of the second-step process has been employed recently though as a means of reducing acid consumption in alkylation plants using s u l f u r i c acid as a catalyst (7,8). Propyl sulfates formed using propylene are reacted with isobutane in conventional reactors; the resulting alkylates contain appreciable amounts of dimethylpentanes. Some butyl sulfates have also been reportedly formed in conventional processes when n-butenes are in the feed. Furthermore, fairly high molecular weight o l e f i n s , up to at l e a s t C ' s , react with isobutane in the presence of s u l f u r i c acid to form fairly high quality alkylates (9). 4

8

2 0

109

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

110

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

In the present investigation, extensive information was obtained on the second-step reactions of the two-step alkylation process. Alkylate (that was mainly CV - C , isoparaffins) was the main reaction product in all cases. The theoretical importance of the present findings will be considered in the next paper of this series (10). 2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

Experimental Details The reaction system and the analytical procedures were identical with those used earlier for the first-step reactions (3). Considerably more acid had to be added to the reaction mixture however in order to obtain second-step reactions as compared to first-step reactions. Operating procedures and methods of obtaining hydrocarbon samples for analysis were essentially identical to those used in the first-step investigation. Yields and research octane numbers (RON) were calculated based on the analysis of the hydrocarbon product as reported earlier (2). Second-Step Runs with Butyl Sulfates More than 30 runs were made in which sec-butyl sulfate was reacted with isobutane in the presence of sulfuric acid. Variables investigated included the following: Temperature -30, -20, - 1 0 ° C , and 0°C Ratio of acid to olefin (A/0): 2 to 20 Composition of feed acid used: 1:15 to 8.0% water and 0 to 8.8% acid-soluble hydrocarbons Agitation: 1000 to 2400 rpm The acid composition and ratio of acid to olefin reported here were those of the first-step reactions. Since the acid and n-butene reacted on a 1:1 basis, the ratio of free acid to butyl sulfate at the start of the second-step reaction was less by 1.0 than the A/0 ratio, i.e. the ratios of free acid to butyl sulfate investigated varied from an initial value of about 1 to 19. At A/0 ratios up to about 8, the emulsions formed between the acid and hydrocarbon phases were in general hydrocarbon-continuous. At ratios of 10 or greater, the emulsions were generally acidcontinuous depending to some extent on the amount of excess isobutane used. Kinetics of Butyl Sulfate Runs. In all riihs, plots of the alkylate yield versus time indicates S-shaped curves such as shown in Figure 1. The rates of alkylate production increased with time immediately after the start of the batch runs. The rates passed through maxima when approximately half of the theoretical amount of alkylate was produced, and then decreased toward zero as the

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

7.

ALBRIGHT E T A L .

Isobutane with Initial Reaction

Products

111

reactions approached completion (I.e. at theoretical alkylate yields of 204 grams of alkylate per 100 grams of feed C\. olefin). The butyl sulfate formed from 1-butene or the two 2-butenes reacted in all cases in identical manners. Such a conclusion was, of course, expected since all three n-butenes produce secbutyl sulfate. Storage of two mixtures of butyl sulfate and sulfuric acid for several days at -20°C had no effect on the subsequent alkylation reactions. Identical results were obtained as compared with freshly prepared mixtures. At -10°C and at A/0 ratios less than 2, the kinetics of second-step reactions were always low, generally too low to measure. The kinetics increased significantly both as the A/0 ratios increased and at higher temperatures. In the glass reactor (operated at atmospheric pressure), the highest temperature that could be investigated was about - 1 0 ° C ; higher temDeratures resulted in excessive vaporization. For runs at -10°C and for A/0 ratios greater than 4, the reaction was usually completed within 1.5 to 6 hours. The rates of alkylate production decreased significantly as the temperature decreased from -10°C to - 3 0 ° C . Two runs were made at 0°C in a stainless steel reactor. In these runs, isobutane and mixtures of butyl sulfate and acid were first cooled to approximately -30°C and were then added to a stainless steel reactor having a volume of 50 ml. This reactor was a nipple closed at both ends with steel caps. The reactor was then immersed in an ice-water mixture, and the reactor was shaken at the rate of 250 oscillations per minute. Although the level of agitation in the steel reactor was undoubtedly quite different (probably less) than those in the glass reactor used in the other runs, the results of these runs clearly indicate the faster rates of alkylate production at 0°C as compared to - 1 0 ° C . Figure 1 is a comparison of results at - 2 0 ° C , - 1 0 ° C , and 0°C. Comparative runs indicated that the rates of alkylate formation increased when the following occurred: (a) More concentrated feed acids were used in preparing the mixtures of acid and butyl sulfate, i.e. less water and/or less acid-soluble hydrocarbons were present in the feed acid. Comparative runs were made with 98.5% fresh acid, 95.5% fresh acid, and used alkylation acids containing several percent of both water and acid-soluble hydrocarbons. (b) As the A/0 ratio (for preparing the mixture of acid and butyl sulfate) increased from 2 to 8 which is the range in which the emulsions were hydrocarbon-continuous. At higher ratios the emulsions were acid-continuous, and changes in the ratio then had l i t t l e effect on the kinetics of alkylation production. (c) Higher ratios of isobutane to olefin (that resulted in larger amounts of excess isobutane). The initial rates

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

112

INDUSTRIAL

during a run were essentially the same regardless of the ratio of isobutane to olefin; at the start of all runs, the hydrocarbon phases were always essentially pure isobutane. As the run progressed, the rates be­ came as high as 10-15% greater for a run with a ratio of 5 as compared to one with a ratio of 2. Higher levels of agitation. Increasing the level of agitation from 1000 to 2400 rpm increased the kinetics by about 30% for the one comparison made.

(d)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

AND LABORATORY ALKYLATIONS

Modelling of Kinetic Results. To model the kinetic data for reactions between butyl sulfate and isobutane, two possibilities were considered. Either the main reactions occurred in the acid phase or the main reactions occurred at the interface between the acid and hydrocarbon phases. For both cases, the following assumptions were made: (a) The rate of alkylate formation was directly proportion­ al to the sulfate concentration in the acid phase. (b) The rate was directly proportional to the isobutane concentration in the hydrocarbon phase. (c) The rate was proportional to the square of H Q , the Hammett acidity of the acid phase. As the batch run progressed, additional acid was formed as the butyl sulfate reacted; hence the Hammett acidity increased during thp run. Second-order dependency relative to the Hammett acidity is based on the results for the degradation of TMP's in the presence of sulfuric acid (11). The acidity i s , of course, decreased because of dissolved acid-soluble hydrocarbons in­ cluding conjunct polymers and butyl sulfates and because of dissolved water. The term, - H - m(BS) - 0.065(CP), was employed to predict the effective acidity of the acids used. It 1s an expansion of the expression used earlier (11) for acids contain­ ing dissolved conjunct polymers. Equations tested for representing the experimental data were as follows: For reactions occurring in the acid phase 0

R

alk *

*

K

V

!> 0 H

" °-

"

0

6

5

< > 3 CP

For reactions occurring at the Interface R

alk

=

*

K

S

C" 0 " H

m

< > - 0.°65(CP)] BS

2

2

( 1so,A BS,A>

(C

C

1 s o >

)(C

H C

HC

B S

, ) A

(

1

)

(2)

where R

alk ° ^ ^ y l a t e production, moles alkylate/hr Κ = reaction rate constant V volume of acid phase S = interfadal area between phases H = Hammett acidity of fresh add with same water content as acid used BS • weight percent butyl sulfate in add s

r

a

t

G

a

s

Q

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

7.

ALBRIGHT

Isobutane with Initial Reaction

E T A L .

REACTION

Figure 1.

TIME

Products

(HRS)

Effect of temperature on the rate of secondstep alkyhtion reactions

200

A/0

MOLE

RATIO

Figure 2. Kinetic model for second-step reactions: variation of K' (or interfacial surface area) with A/O ratio for isobutane-to-olefin feed ratio of 5:1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

113

114

INDUSTRIAL

AND LABORATORY ALKYLATIONS

CP = weight percent acid-soluble hydrocarbons in acid m = constant for given run iso HC concentration of isobutane in hydrocarbon phase iso A ^ ° f isobutane dissolved in add phase C*BS ^ = concentration of butyl sulfate in acid phase C

=

C

=

c o n c e n t r a t

o n

To solve Equation 1, solubility date are needed to determine the dissolved concentration of isobutane in the acid phase. Experi­ mental measurements at equilibrium conditions indicated low solubilities that were hard to measure accurately. It was then assumed that Κ · (C. ) = Κ ' , and hence: Λ

Λ

1 SO » Μ

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

ο

alk ' ' C" o " " °BS,A No data are available for the interfacial area (S) in Equa­ tion 1. It was assumed that Κ" = Κ · S was a constant for a given run so that: ο alk " " » 0 " ( > - O - O M ( C P ) ] ( C )(C ) (4) A non-linear weighted regression program was used to calculate values of Κ ' , K", and m for the above equations. Based on values of the correlation coefficient that were in general 0.90 or higher, both Equations 3 and 4 qave reasonably qood correlations of the experimental data of a given run. Equation 3 was, however, discarded for the following reason. If the reactions occurred in the acid phase (as postulated via Equation 3), isobutane would need to be transferred from the hydrocarbon phase and dissolved in the acid phase. The faster rates of alkylate formation when higher rates of agitation were provided would in such a case indicate that transfer of the isobutane was a rate-controlling step. Yet calculations indicated that sufficient agitation was available so that the transfer step for isobutane was not ratecontrolling. To make these calculations, both the equilibrium solubility of isobutane 1n the acid phase and the mass transfer coefficients were needed. The equilibrium solubility was approxi­ mated in a separate experiment at 0.00015 moles/cc, and the value of Κ A of 30-1000 cc/sec as reported by Rushton et al (12) was used. The actual solubility of isobutane in the acid during a run was calculated to be 0.98 to 0.999 times the equilibrium solubility. The finding that transfer of isobutane was not rate controlling is not surprising since relatively high rates of agitation were provided and since the rates of alkylate production were quite slow (at least 1 to 1.5 hours were needed to complete the reactions). The rates of alkylate formation can be explained readily by Equations 2 and 4. Increased agitation would result in higher interfacial surface areas, S, and hence in higher K" values. Higher interfacial surface areas and hence higher K values would also occur in the hydrocarbon-continuous emulsions as the A/0 ratios increased in the range from 2 to 7 (see Figure 2 and Table I). When, however, the emulsion became acid-continuous, R

R

=

κ

v

K

H

H

m

m

BS

(

B

S

)

0 6 5

{

C

P

)

Z

]

(C

)

iso>HC

(

BS>A

M

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3

)

7.

ALBRIGHT

E T A L .

Isobutane with Initial Reaction Products 115

Increased A/0 ratios would result in no further significant increase in surface areas or in K" values. With acid-continuous emulsions, the level of agitation was probably fairly low because of the high viscosities of the acids. Values of m for Equation 4 increased rather linearly with increased A/0 ratios as indicated by Table I. Such an increase cannot be explained on a theoretical basis.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

Table I K" and m Values for Various Second-Effect Runs Feed Acid A/0 Concentration 5 95.5 5 95.5 5 95.5 10 95.5 20 89.3 2 98.8 18 95.5 3 95.5 4 95.5 5 89.3 (used) 15 89.3 (used) 3.5 98.8 4 94 5 95.5 10 89.3 (used)

Isobutane to Olefin ratio 5 5 5 5 5 5 5 5 5 5 5 5 5 2 2

K" 128 113 15* 166 145 61 175 40 78 120 165 118 100 234 300

m 0.34 0.33 0.34 0.63 1.12 0.23 1.18 0.23 0.32 0.53 1.0 0.31 0.29 0.34 0.64

Correlation Coefficient 0.97 0.93 0.97 0.93 0.83 0.99 0.90 0.90 0.92 0.90 0.99 0.93 0.97 0.94 0.91

Although Equation 4 correlates the data for batch runs reasonably well, there were several simplifying assumptions. Equation 4 is at best only a semi-theoretical equation. Improved ways of measuring the acidity of an alkylation acid need to be developed. Reliable values for the interfacial surface area and the amount of isobutane dissolved in the acid phase are also needed. Characteristics of Alkylate Produced in Butyl Sulfate Runs. The alkylate (produced from butyl sulfate and isobutane) contained the identical CV to Cg isoparaffins found in alkylates obtained in conventional one-step alkylation processes. The isoparaffins in the heavy end (H.E.) fraction, i.e. CVs and hiqher, were also presumably identical. Unfortunately the gas chromatographic analyses for some hydrocarbon samples resulted in heavy end analyses that were too low. Most analyses were made using an isothermal two-column unit in which the second column was designed to analyze the heavy-ends. This column generally indicated only 1 to 5% heavy ends whereas subsequent analyses indicated that values up to 15 to 20% sometimes occurred. These latter analyses were made employing a temperature-programmed

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

INDUSTRIAL

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

7.

ALBRIGHT

E T A L .

Isobutane with Initial Reaction Products

column and were also confirmed by an analytical group at Phillips Petroleum Co. The analytical results as obtained by the two analytical techniques for CV to C isoparaffins were, however, found to be in excellent agreement. Although the isothermal gas chromatographic column did not measure the heavy ends correctly, the results obtained with i t give good comparisons of the composition and quality of the alkylates on essentially a heavy-end-free basis. These qualities are reported as the research octane number (RON) that was calculated (2) based on the composition of the alkylates as determined analytically. On essentially a heavy-end-free basis, RON values of 98-101 were common. Reanalyses of the alkylate in order to determine the heavy ends more correctly indicated that the above RON values were in general too high by 3-4 units. RON values of 94.5 to 98 are thought to have occurred. The composition of the alkylate and especially of the t r i methylpentane (TMP) family varied significantly as a batch run progressed (and as alkylate was produced). The first alkylate produced during a run generally contained a relatively large fraction of 2,3,4-TMP. In two cases, over 50% of the initial alkylate was 2,3,4-TMP. As a run progressed, the ratio of 2,2,4TMP to 2,3,4-TMP increased. Of interest, the amounts of 2,2,4-, 2,3,3-, and 2,3,4-TMP were generally similar at the end of all batch runs (see Table II). The change of the composition of the TMP family was a major cause of the lower RON values for the alkylate as the run progressed. Figure 3 shows the decrease in RON as three batch runs progressed. Alkylates produced in runs made at different operating conditions often were found to have relatively different amounts of the four main groups (or families) of isoparaffins, namely TMP's, LE's, DMH's, and HE's. As a general rule, increased RON values resulted because of increased fractions of TMP's and decreased fractions of the other three. Variables that had a significant effect on the alkylate quality were as follows: (a) Feed acid composition. Acids with lower acidities produced higher quality alkylates, as shown in Fioure 3. The alkylate qualities at the end of a run varied from about 101 when used alkylation acid was employed to 93 with 98.8% fresh acid. Little or no differences in quality were noted, however, for the alkylates produced using 95.5% and 92% acids. (b) Ratio of isobutane to n-butene used in the feed to the first effect. The calculated RON decreased by perhaps 1 to 2 as the ratio decreased from 5 to 1.5; relatively l i t t l e change, however, occurred in the 5 to 20 range. (c) Temoerature. Temperature had a major effect on both the relative amounts of TMP's and LE's in the alkylate and also the compositions of these two families; tentperature was the only variable that had such an effect. Tables II and III indicate the effect of temperature on g

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

117

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

*

---

13

2,2,3-TMB

2,3-DMP

Average values.

2-MH

13.5

2,4-DMP

3.5

2,3-DMB

3-MP

21

44

Isopentane

Family

27.5

2,3,3-TMP

L.E.

45

1.5

26

2,3,4-TMP

2,2,3-TMP

2,2,4-TMP

TMP Family

-20 C Two-Step Process

e

II

16

1.5

1.7

13

3.8

39

26

30

37

2

31

e

-10 C Two-Step Process

16

1

3

11

4

35

30

26

34

3

37

e

0C Two-Step Process

(16)

(1)

(3)

(12)

(6)

(26)

(34)*

-----

e

(0°-25 C) Sulfate Stability

10

3

1.4

14

4.5

27

41

27

17

5

50

10°C Conventional Process

10

2.5

1.0

15

4

26.5

41

26

16

6

52

20°C Conventional Process

and Light Ends Produced Using n-Butenes As the O l e f i n s

E f f e c t of Temperature on the Compositions of Trimethylpentanes

Table

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

9

3

1

14

5

27

42

26.5

13

5.5

54

e

30 C Conventional Process

7.

ALBRIGHT

E T AL.

Isobutane with Initial Reaction

Table

Products

119

III

Effect of Temperature on the Compositions of Trimethyl pentanes and Light Ends Produced Using Isobutylene as the Olefin -20 C Two-Step Process

10 C Conventional Process

2,2,4-TMP

63

59

2,2,3-TMP

2

2,3,4-TMP

13

13

13

14.0

2,3,3-TMP

22

23.5

24

24

Isopentane

29

36

43

45

2,3-DMB

39

26

26

24.4

4

4.5

e

e

20 C Conventional Process e

30 C Conventional Process e

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

TMP Family

4.5

58 5.0

57 5.3

L . E . Family

3-MP

2

2,4-DMP

15.4

3.5 19

13

12

2,2,3-TMB

2

1.5

1.0

1.6

2-MH

0.6

0.8

2.5

1.5

12.5

10.5

9.5

2,3-DMP

11

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

120

INDUSTRIAL

AND LABORATORY ALKYLATIONS

the compositions of both TMP and LE groups produced by second-step reactions using n-butenes and isobutylene as feed olefins respectively. For LE's, the ratio of isopentane to 2,3-dimethylbutane increased significantly with temperature, (d) C\ olefin: As shown in Tables II and III, alkylations with n-butenes and isobutylene resulted in significantly different compositions for TMP's as will be discussed later. The compositions of the TMP's and LE's as determined for this investigation showed important differences as compared to the compositions calculated for alkylates produced in conventional processes operated at 10 to 15°C. The alkylates of this investigation produced from sec-butyl sulfates containpd larger relative amounts of 2,3,4- and 2,3,3-TMP's but lesser amounts of 2,2,4-TMP. The ratios of 2,3-dimethylbutane to isopentane were much higher in the alkylates of the present investigation. Second-Step Runs with Reaction Products from Isobutylene More than 20 runs were made to investigate the reaction between isobutane and the products of first-effect reactions with isobutylene. Alkylate was not produced until excess acid was used; and larger amounts of excess acid were needed for runs at -30°C as compared to runs at -10°C (3). An acid-to-olefin ratio of about 1.0 was required at -10°C to obtain TMP's whereas a 7:1 ratio was needed at -30°C. In the present investigation, additional acid was generally added to the agitated acid-hydrocarbon emulsion resulting from the first-step reactions of isobutylene. The rate of alkylate formation was generally highest at the start of the run and decreased toward zero as alkylate yields of 80-120 were approached. Appreciable amounts of acid-soluble hydrocarbons remained in the acid at the end of all two-step runs using isobutylene, and these hydrocarbons caused alkylate yields to be much less than the theoretical value of 204. The yields of alkylate depended on the operating conditions investigated, as will be discussed later. In several runs, the kinetics of alkylate formation were slightly less at the start of the run and then increased to a maximum at intermediate conversions. The rates of alkylate production increased when the following occurred: (a) The A/0 ratio increased. Such a conclusion is based on several runs at -10°C with ratios between 1.0 and 9; the emulsions formed were hydrocarbon-continuous. For a run at a ratio of 1.0, 4.5 hours resulted in an alkylate yield of 52. With a ratio of 9, a yield of 98 was obtained 1n 4 hours. (b) Increased temperatures in the - 3 0 ° to -10°C range.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

7.

ALBRIGHT

Isobutane with Initial Reaction Products

E T AL.

121

The rates of alkylate formation were affected to only a small, and as yet undetermined, degree by changes of the ratio of isobutane to isobutylene in the 5 to 11 range and by changes in the feed acids used. Comparative runs were made with 96.5% fresh acid and with used alkylation acid. All alkylates produced by second-step reactions in which isobutylene was the feed olefin had relatively low RON's and contained relatively large amounts of LE's, DMH's, and HE's as compared to alkylates produced from butyl sulfate. The LE content of the alkylate generally varied between 23 to 28%, and the HE content between 30 to 40% (based on analyses with the temperature-programmed unit). The calculated RON values of the alkylate varied from about 88-91. The compositions of the TMP family were considerably different for the isobutylene runs (see Table III) as compared to those of the n-butene runs (see Table II). For runs using isobutylene, 2,2,4-TMP accounted for about 60% of the TMP family. The LE's had similar compositions, however, at a given temperature for both n-butene and isobutylene runs. Several samples of the hydrocarbon phase were obtained during the course of each batch run to determine how the composition was changing. As a run progressed, LE's, DMH's, and TMP's, were the major compounds produced. Several heavy end hydrocarbons decreased toward zero as the run progresses: hydrocarbons 24, 25, and 30 as defined earlier (3) in particular disappeared as a result of reactions with isobutane. These reactive hydrocarbons were presumably C or heavier olefins. There were however large amounts of unreactlve heavy ends, which are heavy isoparaffins. Calculations indicated that the heavy ends in the alkylate were produced for the most part during the first-step reactions. Slightly higher quality alkylates were produced using isobutylene at lower temperatures and at higher I/O ratios. The improvement in quality was, however, less for isobutylene runs as compared to those with n-butenes. Two runs were made using the products of first-step reactions in which mixtures of isobutylene and 2-butene had been used. The second-step reactions in such cases resulted in products that were intermediate between those products for runs with pure Isobutylene and for runs with pure n-butenes. The RON of the alkylates obtaining using isobutylene, a 1:1 mixture of isobutylene and 2-butene, and 2-butene were 89.7, 93.0, and 100.8 respectively. The composition of the TMP family obtained with the mixed olefins also appeared to be intermediate in nature. The alkylation mechanism for second-step reactions with isobutylene as the olefin have been significantly clarified by two runs, each conducted as follows. The acid and hydrocarbon phases produced by first-step reactions involving isobutylene and sulfuric acid were separated. The acid phase which contained some acidsoluble hydrocarbons or reaction products such as perhaps t-butyl sulfate was then contacted with fresh isobutane. This resulting mixture of reactants was designated as A below. The hydrocarbon 1 2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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phase for each run was contacted with fresh 96.5% acid; this mixture was designated as B. [A]

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

(Acid Phase Including

A summary of the amount of reactants and of the results for these two runs are shown in Table IV. In both runs, approxi­ mately the same amount and quality of alkylate was produced by mixtures A and Β, and the calculated RON of the alkylates were in the 88.6 to 91 range. The qualities of the alkylates in the second run were somewhat higher than those of the f i r s t run, but i t is now known i f the differences are significant. The higher rates of reaction for mixtures A are thought to be caused by the larger amounts of acid used. When isobutane was contacted in route A with the acid phase, some colored materials were extracted from the acid phase. Further more, apparently some isoparaffins wer* also extracted based on the analysis of the first sample of the hydrocarbon Dhase; more isoparaffins were present in the hydrocarbon phase than would seem probable based on the expected amount formed by i n i t i a l alkylation reactions. Tentatively i t is concluded that some lighter isoparaffins had been dissolved in the acid phase. Second-Step Runs with Reaction Products from 2,2,4-Trimethylpentene-1 Several runs were made using the reaction oroducts obtained when sulfuric acid was slowly dripped into a mixture of isobutane and 2,2,4-trimethylpentene-l. The yield, quality, and composition of the alkylates produced were similar to those for runs using isobutylene. Discussion of Results The results of this and a companion investigation (3) report significant information on a two-step alkylation process which has been investigated at Purdue University since 1970 and which appears to be of considerable commercial interest. This two-step process requires a much more selective choice of operating variables as compared to earlier processes (4-6). The current

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

7.

ALBRIGHT

E T A L .

Isobutane with Initial Reaction

123

Products

Table IV Mechanistic Investigation of Second-Step Reactions Using Isobutylene and 96.5% Sulfuric Acid 1

2

43 9 16 -30

47 10 25 -30

52 -10 30-40 1.5

47 -10 45-60 1.5

10 -10 30-40 3

15 -10 55-60 2.5

RUN First-Step Reactions Isobutane, ml Isobutylene, ml Acid, ml Temperature, °C

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

Second-Step Reactions (Part A) Isobutane Added, ml Temperature, °C Yield of Alkylate Time, Hr. Second-Step Reactions (Part B) Acid Added, ml Temperature, °C Yield of Alkylate Time, Hr.

process, however, offers several key advantages that will be discussed later. The proposed new process has the following unique features. First, hydrocarbon-continuous emulsions have proved to be most satisfactory and probably are preferred. Yet acid-continuous emulsions have been shown in the past (2) to be highly preferred for conventional (one-step) alkylation processes. Second, lower temperatures are preferred. Although past Investigators have thought that such temperatures might offer advantages, no one had realized that both hydrocarbon-continuous systems and/ or longer residence times in the reactor were then required in order to operate satisfactorily at low temperatures. Although further investigations are required in order to determine the specific chemical steps of the second-step reactions with butyl sulfate, butyl sulfate perhaps first decomposes to release n-butene as follows: sec-C H 0S0 H 4

g

3

• n-butene

+

H S0 ?

4

Thermodynamic information indicates that 2-butenes would be the predominant olefins released. The resulting 2-butenes presumably react in this process with a t-butyl cation to produce a trimethylpentyl ion. Hydride transfer from isobutane or more likely an acid-soluble hydrocarbon would result in the production of a trimethylpentane. The relatively small amount of LE's and DMH's produced in reactions with butyl sulfates were probably because of the high ratios of isobutane to n-butenes in the reaction zone. Such a

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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high ratio would be expected because of the relatively slow rate of 2-butene formation as butyl sulfate decomposed at the low temperatures used. High isobutane to 2-butene ratios would result in the production of only small amounts of C*|2 or higher ions; these ions are thought to be precursors for both LE's and DMH's. The relatively large amount of HE's formed suggests that HE's were formed as a result of polymerization reactions in the acid phase. The n-butenes were presumably present primarily in the acid phase when they were released from butyl sulfate; such a conclusion is based on the fact that butyl sulfate is dissolved in the acid phase. For the experiments in which the first-step reaction products of isobutylene were employed, reactions between high molecular weight olefins and isobutane were of major importance. Presumably a f i r s t step in the overall process was the protonation of the heavier olefins to form heavier isoalkyl cations. These cations apparently fragmented to a large extent to form mainly C.-CQ cations and olefins. The latter olefins also quickly protonated forming cations. Hydride transfer from isobutane or acid-soluble hydrocarbons resulted in the production of C\ to Cg isoparaffins. Heavy ends and conjunct polymers were, of course, produced to some extent during the second-step reactions, but most of these compounds were probably produced during the f i r s t step reactions. The results of the present investigation support the hypothesis that the main alkylation reactions occurred at the acid-hydrocarbon interface. though such information does not apply directly to the phenomena occurring in industrial alkylation units, it is of interest that Kramer (13) supports this hypothesis in such units, and Doshi et al (11) have found that the interface is the location of degradation reactions for C isoparaffins. One might expect the location of the main reactions to be the same in all three cases. Two-step alkylation of isobutane with C, olefins not only helps clarify the mechanism of alkylation, but may be of commercial importance. Some of the advantages of the new process as compared to the conventional processes are as follows: (a) Quality of alkylate that is at least comparable when butyl sulfates are used in the second step of the process. In considering the alkylate quality, some thought has to be given to the best way for reporting the quality, either as research octane number (RON) or motor octane number (MON). 2,3,4-TMP and 2,2,3-TMP both have higher RON values than 2,2,4-TMP; the reverse is true for MON values. This point is of interest since the relative amounts of these three TMP's differ significantly in the alkylates produced in the two-step and the conventional processes. One of the favorable features of the alkylate produced by the new two-step process is the low amount of LE's; unfortunately the HE content has been

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch007

+

g

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

7.

ALBRIGHT

E T A L .

Isobutane with Initial Reaction Products

high 1n all experiments conducted to date. Isobutane-to-olefin ratios in the feed streams to the reactor can be low, perhaps as l i t t l e as 1.5 and certainly no higher than 5. Cost of recovering and recycling the excess isobutane would be drastically reduced. (c) The amount of acid that needs to be recycled will be low because of the low acid-to-hydrocarbon ratios used. The acid recycle costs would be decreased as compared to conventional processes. (d) Agitation costs should be relatively low since hydrocarbon-continuous emulsions have fairly low viscosities. Based on the present investigation, current disadvantages of the two-step alkylation process are as follows: (a) Relatively poor quality alkylates are obtained when isobutylene is the feed olefin. Such low quality alkylates are produced in both the two-step process and the conventional alkylation process. There is hope that major improvements in quality can, however, be obtained for the two-step process. If t-butyl sulfates can be produced in high yields from isobutylene, then much improved alkylates likely would result. Tests to date indicate that the alkylate produced from mixed C* olefins is at least similar in quality to alkylates produced in commercial units. It is recommended that different composition acids and different temperatures be tested in future runs using Isobutylene in the feedstock. Acids containing relatively large amounts of conjunct polymers, butyl sulfates (such as obtained using n-butenes), and/or water may result in improved performance. (b) Large amounts of HE's in the alkylate. Further investigations need to be made to learn how HE production can be reduced. It is not known during what time period of batch runs using butyl sulfates that HE production is greatest. Future investigations with analytical techniques that will accurately measure the HE content should help develop improved methods of minimizing the formation of HE's. (c) Refrigeration to provide rather low temperatures will be needed. The energy demands for refrigeration may be relatively moderate, however, since lesser amounts of isobutane and add will need to be recycled. Although residence times 1n the reactor will be relatively long, perhaps 1.0 - 1.5 hours, the volume of the reactor may not be greater than those of many current reactors. Such a conclusion is based on the considerable reductions of the volumes of excess isobutane used and the low ratios of add to hydrocarbons in the reactor. Further investigations of the two-step alkylation processes are recommended. There is a chance that alkylate can be produced cheaper by the two-step process and/or be of better quality. (b)

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125

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Although the Purdue work has been restricted only to runs with sulfuric acid, similarly promising processes can probably also be developed with both HF and AlC^-typ* catalysts. Possibly HF would even be a preferred catalyst since i t 1s not an oxidizing catalyst such as sulfuric add often i s . The results reported by McCaulay (14) strongly support the postulate that a two-step alkylation process will be feasible with HF as the catalyst. Although he had emphasized the advantages of intermittently adding the olefin to HF cataysts, he reports two features of particular Interest relative to the two-step process. (a) Butyl fluorides are desired intermediates in his process. (b) Alkylates produced from butyl fluorides at low temperatures ( - 1 8 ° and -15°C) had RON values of 100.1 to 101.9. For commercial development of a two-step process, provisions must be provided so that high yields of the desired products are obtained in both the first and the second steps of the process. In some cases at least, i t may be necessary to provide a different reactor for each step 1n order to obtain the desired operating conditions. McCaulay had apparently not considered such a system for alkylation. Furthermore, he had apparently not succeeded in producing butyl fluorides with either 1-butene or isobutylene since the qualities of the alkylates obtained using these olefins were significantly lower than those obtained using 2-butenes. The results of Roebuck and Evering (15) who used A l ^ - t y p e catalysts and temperatures down to -20°C can also be explained by the production of esters with both 2-butene and ethylene. They had found that improved alkylate qualities occurred as the reaction temperature was decreased, but yields of alkylate were significantly reduced at lower temperatures. Probably they would have obtained in all cases high yields of alkylate i f they had provided longer residence times for some of the lower temperature runs; presumably sufficient time had not always been allowed for complete reaction of all the esters. The present investigation clearly Indicates that in the range of temperatures from at least -30 to 0°C a two-step alkylation sequence is the predominant one. A logical question i s , does a similar two-step sequence occur at higher temperatures such as employed in cornnercial reactors? Since some butyl sulfate and some butyl fluorides are known to be formed 1n commercial reactors, i t seems obvious that the two-step process 1s of at least some importance at higher temperatures. The mechanism for alkylation will be considered 1n further detail in the next paper of this series (10). Literature 1) 2)

Cited

S h l e g r i s , R. J. and A l b r i g h t , L . F., Ind. Eng. Chem. Process Des. Dev. 8, 92 (1969) Li, K. W., Eckert, R. E., and A l b r i g h t , L . F., Ind. Eng. Chem.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

7.

3)

ALBRIGHT E T A L .

Isobutane with Initial Reaction Products

Process Des. Dev. 9, 434 (1970) A l b r i g h t , L . F., Doshi, B. M . , Ferman, M. Α., and Ewo, A . , "Two-Step Alkylation of Isobutane with C Olefins: Reactions of C Olefins with S u l f u r i c Acid", This book, Chapter 6 (1977) L i n n , C. B., U.S. Pat. 2,307,799 (Jan. 12, 1943) Matuszak, M. P., U.S. Pat. 2,387,162 (Oct. 16, 1945) Goldsby, A. R . , U.S. Pat. 2,420,369 (May 13, 1947) Goldsby, A. R . , U.S. Pat. 3,234,301 (Feb. 6, 1966) Goldsby, A. R . , U.S. Pat. 3,422,164 (Jan. 14, 1969) Esso Research and Engineering Co. (by J. R. Lawley, e t . a l . ) Fr. 1,334,799 (Aug. 9, 1963) A l b r i g h t , L . F., "Mechanism f o r Alkylation o f Isobutane with Light Olefins", This book, Chapter 8 (1977) Doshi, Β. Μ., and A l b r i g h t , L. F., Ind. Eng. Chem. Process Des. Dev. 15, 53 (1976) Rushton, J . H., Nagata, S . , and Rooney, T. B., AIChE Journal 10, 298 (1964) Kramer, G. M . , J. Org. Chem. 30, 2671 (1965); U.S. Pat. 3,231,633 (Jan. 25, 1966) McCaulay, D. Α . , U.S. Pat. 3,280,211 (Oct. 18, 1966) Roebuck, A. K. and Evering, B. L., Ind. Eng. Chem. Prod. Res. Dev. 9, 76 (1970) 4

4

4) 5) 6) 7) 8) 9) 10) 11)

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12) 13) 14) 15)

127

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8

Mechanism

for

Alkylation

of

Isobutane

with

Light

Olefins

LYLE F. ALBRIGHT

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

School of Chemical Engineering, Purdue University, West Lafayette, IN 47907

Considerable information has been obtained in the last several years at Purdue University that provides new insights to the mechanism of a l k y l a t i o n . Such information has been obtained by investigating conventional alkylation processes using s u l f u r i c acid as a catalyst and several related reactions that employ s u l f u r i c a c i d . These reactions include the following: 1) Conventional alkylations at 4 to 25°C employing e i t h e r 1-butene, 2-butenes, isobutylene, mixtures of C o l e f i n s , propylene, and trimethylpentenes ( 1 , 2 , 3 , 4 ) . 2) Two-step alkylations at -30 to 0°C employing e i t h e r n-butenes, isobutylene, mixed C o l e f i n s , or 2,2,4-trimethylpentene-1 (5,6). 3) Degradation reactions that occur when trimethylpentanes, dimethylhexanes, or isobutane are contacted with s u l f u r i c acid at - 1 0 ° to 25°C (7). 4) Decomposition reactions of sec-butyl sulfate (when d i s ­ solved in s u l f u r i c acid) at 0° to 25°C (5). 5) Reactions of C olefins when contacted with s u l f u r i c acid at 10°C (1,3). When the results for these five reactions were considered in t h e i r e n t i r e t y , two important observations were made. First the same isoparaffins were produced in each case. A total of 17 C5-C8 isoparaffins were detected in each product. Additional isoparaffins were probably also produced in minor q u a n t i t i e s , but l i m i t a t i o n s with the analytical equipment did not permit conclusive evidence. Isobutane was also produced in each case based on the alkylation results of Hofmann and Schriesheim (8) who used C tagged olefins and on the results for reactions 3,4, and 5 l i s t e d above. Within the l i m i t s of analytical p r e c i s i o n , the same heavy end isoparaffins were also present in each hydrocarbon product. At least 18-20 isoparaffins in the C and higher range were usually detected. The acid-soluble hydrocarbons were also apparent­ ly identical in a l l cases. Dividing the hydrocarbon products into five families or groups indicated another important piece of information. These families 4

4

4

1 4

9

128

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8.

ALBRIGHT

Isobutane with Light Olefins

129

are trimethylpentanes (TMP's), light ends (LE's or C 5 - C 7 isoparaffins), dimethylhexanes (DMH's), heavy ends (HE's), and acidsoluble hydrocarbons (conjunct polymers, ester, red o i l , acid sludge, etc.). It was found that the composition of each family was essentially a function of temperature only and was similar for all five reactions. This later point was tested for especially TMP's and LE's (6). The relative importance of each family in the reaction products often varied over wide ranges depending on the specific reactions being tested and on the operating conditions employed. At preferred operating conditions, up to 90% of the product was TMP's for alkylates obtained by both conventional and two-step alkylation processes. Much smaller fractions of TMP's were produced by decomposition of butyl sulfate or by reaction of C olefins in contact with sulfuric acid. Larger amounts of the other four families were produced in such cases. As a general rule, whenever the fraction of TMP's in the product decreased, the relative importance of the other four families increased. Based on these findings, 1t has been concluded that each of the above families 1s formed from a common Intermediated). Such a conclusion is of importance since the combined results for the five reactions outlined above can be employed to clarify and develop an Improved mechanism for alkylation. The mechanism proposed 1n the paper is considered to be applicable for all five reactions; special attention w i l l , however, be given to conventional alkylation.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

4

General Comments on Past Mechanisms Production of TMP's has frequently been reported to be p r i marily by the following simple chain reaction (9,10): t-C H 4

. g

+

2-butene . or — TMP isobutylene

TMP + isobutane — TMP + t - C H +

4

g

+

where TMP and TMP represent one of several trimethylpentyl cations and trimethylpentanes respectively. Clearly such a simple chain mechanism 1s not, however, occurring 1n a two-step alkylation process (f>). Neither does this simple chain mechanism occur when butyl sulfate decomposes, when TMP's are degraded by sulfuric acid, or when C* olefins react 1n the presence of sulfuric acid. Furthermore, even during conventional alkylations, there is extensive evidence that at least some olefins react with the acid during the Initial stages of the reaction (2,3); in such cases, Isobutane reacts to a greater extent during the final stages of the reaction to form TMP's. Such evidence strongly suggests that other methods for production of TMP's are also often important, even during +

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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ALKYLATIONS

conventional alkylation. Differences of opinion s t i l l exist when sulfuric add 1s use£ as the catalyst as to the main route for production of DMH 's (the precursors for DMH's). Although both Hofmann and Schr1eshe1m (8) and Albright and L1 (11) have Indicated reasons why the reaction in which 1-butene reacts with a t-butyl cation to form DMH 1s generally of l i t t l e or no importance, recent authors s t i l l refer to the 1-butene route as an important one but without rebutting the earlier arguments. An even more complete summary of reasons why the 1-butene reaction is of l i t t l e importance when sulfuric acid is the catalyst 1s reported below. First almost identical amounts of DMH's and TMP's are generally produced when either 1-butene or 2-butenes are used as the olefins. A favorite explanation given is that 1-butene and 2-butene rapidly isomerize to form an equilibrium mixture of the two. Although isomerization 1s without question fast (5), the isomerlzation explanation alone is not sufficient as next Indicated: (1) The TMP/DMH ratio in alkylates produced by both 1- butene and 2-butene alkylations varies significantly from about 1 to as high as 15 depending on the operating conditions employed. For example, increased levels of agitation act to increase the ratios significantly. Production of TMP s (from 2-butenes) and of DMH 's (from 1-butene) would mean that the ratio of TMP/DMH would depend primarily on the equilibrium ratio of 2- butenes/l-butene. Obviously factors other than the equilibrium ratio are however of importance because this ratio does not change because of operating variables such as agitation. (2) If isomerlzation of 1-butene (or 2-butenes) was rapid and i f the main routes to produce TMP s and DMH s occurred when 2-butenes and 1-butene reacted with t-butyl cations, then use of a Cl4-tagged n-butene would result in TMP's and DMH's with similar amounts of C . The results of Hofmann and Schriesheim (8) however indicate that DMH's (and also LE's and HE's) contain higher amounts of 0* than do TMP's. (3) Purdue results (2,3) have shown that DMH's (and also LE's and HE's) are produced to a larger extent by Initial reactions involving predominantly olefins; later reactions involving predominantly Isobutane lead primarily however to TMP's. The 1-butene method for producing DMH 's would however result in simultaneous production of TMP's and DMH's. Second, there 1s the Indirect evidence: DMH's are often formed by routes in which 1-butene does not exist 1n significant amounts. One such reaction is alkylation of Isobutane with Isobutylene; more DMH's are produced than in comparable reactions +,

+

+,

1 4

+

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

+,

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

8.

ALBRIGHT

Isobutane with Light

Olefins

131

with either 1-butene or 2-butenes. It seems quite unlikely that isobutylene isomer!zes to 1-butene. A second reaction 1s the degradation of TMP's or of isobutane when contacted with sulfuric add at 0 ° - 3 0 ° C (7). The above discussion was devoted to alkylations with sulfuric acid. In the case of HF alkylations, considerable amounts of DMH's are produced however by means of the 1-butene reaction as will be considered in detail later. Although the composition of sulfuric add phase in conventional alkylation is known to have an important effect on alkylate quality (1,4,8,12), the exact role of acid-soluble hydrocarbons during alkylation has as yet not been well defined. During the start-up of an alkylation process that employs fresh sulfuric acid as the catalyst, an apparent Induction period occurs (13). During this period, considerable acid-soluble hydrocarbons are produced, but relatively l i t t l e alkylate 1s produced. A somewhat similar induction period also sometimes occurs when TMP's are degraded in the presence of sulfuric acid (7). Definitely there is a need to better describe the roles of add-soluble hydrocarbons during alkylation. Increased levels of agitation have been found to be a major factor in obtaining Improved quality alkylates (1,3). Agitation clearly has an Important effect on the physical steps of the overall process. The interfadal surface is one such variable that would be increased by increased agitation. Careful consideration needs to be given in any proposed mechanism as to the role of agitation. Proposed Mechanism The proposed mechanism 1s divided into six broad types of reactions as follows: 1) Formation of t-butyl cations. Six methods have been identified. 2) Reactions of C4 olefins. Specific reactions have been identified for both n-butenes and isobutylene when they react with t-butyl and heavier cations. 3) Reactions of butyl sulfates. 4) Reactions of acid-soluble hydrocarbons. 5) Production of TMP's. TMP 's are formed by at least three different methods. 6) Production of undeslred (or at least less desired) products such as LE's, DMH's, HE's, and acid-soluble hydrocarbons. +

Production of t-Butyl Cations. Table I outlines six methods for production of t-butyl cations. The first two listed (Reactions A and B) are considered to be of major Importance in most commercial reactors. Reaction A is always of importance whenever isobutylene is

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

TABLE I PRODUCTION OF t-BUTYL CATIONS Formation from Isobutylene Isobutylene + H t-C H Initiation when Isobutane 1s contacted with adds contain­ ing add-soluble hydrocarbonT +

4

g

+

R (polymer cations) + ^" 4 IQ

RH(add-solub1e polymer) • t-C H Initiation when mixtures of Isobutane and n-butenes are contacted with sulfuric add n-C H + H — sec-C H sec-C H + 1-C H n-butane + t-C H +

C

H

4

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

4

+

8

4

g

4

+

4

g

g

+

+

1Q

4

g

+

Reactions between isoalkyl cations and Isobutane C and higher cations + 1-C>,H, C and higher c

n

5

+ t-C^H.*

c

4 10

5

1

s

o

p

a

r

a

f

f

1

n

Isomerlzation of 2-butene and production of t-C H 4

(1)

*»

s

g

+

Isomerlzation via TMP t-C H + 2-C H ^ 2,2,3-TMP +

4

g

+

4

+

8

2.2.3- TMP ς* 2,2,4-TMP +

+

2.2.4- TMP ς* t-C H + 1-C H 1-C H + H - t-C H Some t-C H s are also formed by related reactions (fragmentation of heavier Isoalkyl cations, as shown 1n Table III). Via conjunct polymers (11); R 1s an add-soluble cation. +

4

8

4

(2)

4

+

g

4

g

+

4

g

g

+

+,

ÇH

3

+

R + 2-C,H — R - C - C - CH. +

Q

rl

CH. I

3

+

A

CH.

+

ι

ι

I

R-C-C-CH. — R-C-C I

3

I

H

H

r

H

u

ι 3

U

ι

CH. I

- CH. — R - C - C 0

H

I

H

0

+

R - CH - C - CH ^ R + 1-C H 2

1-C H 4

8

3

+ H

+

+

t-C H 4

4

g

- CH.

g

+

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8.

Isobutane with Light

ALBRIGHT

133

Olefins

Table I (continued) (F) Oxidation of Isobutane with sulfuric add (7). 1-C H + 4H S0 — t-C H + 2H 0 + 3HS0 + S0 Other Isoparaffins Including both TMP's and DMH's are also oxidized 1n a comparable manner (7,17,18). 4

1Q

2

4

4

g

+

+

3

4

2

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Notes : 1) Reactions A, B, and D are predominant routes for most alkyla tlons using sulfuric add as the catalyst. 2) Reaction C 1s of more Importance when HF 1s the catalyst. 3) Reactions Ε-Ί and F are of Importance for degradation of Isoparaffins with sulfuric add (7). 4) Reactions E-2 are probable when Isobutane reacts with addsoluble hydrocarbons to form alkylate (6).

TABLE II REACTIONS OF C OLEFINS, EXCLUDING t-C H FORMATION 4

(G)

4

Reaction with t-C H 4

1)

g

(H)

+

to form C s

+

8

+,

2-butene or . _ TMD «C Isobutylene *~°4 9 ^ 1-butene + t-C H ^ D M H S Reaction G-2 that produces DMH 's (dimethylhexyl cations) 1s of minor Importance (11) when sulfuric add 1s used as the catalyst, but 1s of major Importance when HF 1s the catalyst (19). T

Γ

+

M

Η

2)

g

4

+

T

M

P

s

g

Isomerlzation of n-Butenes 1)

1-butene ^ trans-2-butene ds-2-butene Isomerlzation occurs readily 1n presence of sulfuric add (5), but less so 1n presence of HF (19).

2)

2-butenes Table I)

Isobutylene (see Reactions E-l and E-2 of

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL

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ALKYLATIONS

Table II (continued) (I)

Formation of Butyl Sulfates 1) n-butenes + HgSO^ sec-butyl sulfate Butyl sulfate formation 1s the primary Intermediate to alkylate when n-butenes are used with sulfuric acid at temperatures up to at least 0°C (6). Butyl fluorides are also produced at low temperatures with HF (23).

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2)

(J)

Isobutylene + H S0 t-butyl sulfate The Importance of Reaction 1-2 has not yet been proved; however, some as yet unidentified add-soluble hydrocarbons (formed from Isobutylene) react with Isobutane to form alkylate (6). 2

Complexlng or reactions with add-soluble 1ons (R*) . 2-butene R+ or Isobutylene

(K)

4

+ M

x R-C4H8

^

C

4H

ft +

(see Reaction E-2)

Polymerization of C olefins 4

C

7

R

(TMP's or DMH's) +

8

1-C ii1-C * 8

1

+

8

- 1 V - 12 C

1

2

C

+

H

+

2-butene or Isobutylene

. . 1-C,, , 1-C., , etc. 1

2

1 6

+

H +

1-C 1-C " H Polymers (olefins) were formed 1n small amounts when alkylate leaving a reactor was quickly quenched with a caustic solution (1). When, however, the add and hydrocarbon phases were allowed to separate by decanting, few 1f any olefins were detected. Isobutylene 1s particularly susceptible to formation of Cg and heavier cations ( 5 , 6 ) ; such cations are probably Important Intermediates whenever Isobutylene 1s used as olefin for alkylation. 16

+

16

+

+

Note: Reactions I and/or J are of major Importance 1n conventional alkylation since olefins react 1n some manner with sulfuric add to form add-soluble hydrocarbons that later react with Isobutane to form alkylate (2,3).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8.

Isobutane with Light

ALBRIGHT

135

Olefins

present 1n the feed steeam. It is well known that t-butyl cations form rapidly whenever isobutylene contacts strong acid. The reaction may not stop however at the t-butyl cation; as will be discussed later, polymerization reactions also occur forming i - C 8 > 1-C*|2 » etc., that eventually results in a wide variety of isoparaffins and conjunction polymers. Although Reactions C have been widely accepted as the major method of initiating the formation of t-C4Hg whenever n-butenes are employed as feed olefins, Reaction Β involving polymer cations (R ) dissolved in the acid phase is considered to be more important especially when sulfuric acid is employed as the catalyst. Albright and Li (11) have previously discussed reasons for this choice, and recent experimental information further substantiates this choice. Two reasons are as follows: 1) No η-butane is produced when sulfuric acid is employed as the catalyst. When HF is used, however, some pro­ pane and η-butane are produced when propylene and n-butenes are used as olefins. Reactions C are of more importance when HF is employed probably because in part at least isobutane is more soluble in HF and the isobutane is hence more available to react. 2) When fresh sulfuric acid 1s employed, there 1s a start­ up or Induction period. During this period, l i t t l e alkylation occurs, the quality of the initial alkylate 1s poor, and considerable amounts of acid-soluble hydro­ carbons are produced. Some polymers are also formed. When, however, an acid containing dissolved hydrocarbons 1s employed, no induction period 1s noted. These a d d soluble hydrocarbons are highly Ionized (14); they could readily accept hydride ions from Isobutane, as shown in Reaction B. The relative importance of Reactions Β and C depend to at least some extent on the concentrations of R and of sec-butyl cations at the reaction site, thought to be the interface between the two liquid phases (7,15,16). In general, there will always be a fairly high concentration of R after the induction period, but the concentration of sec-butyl ions will presumably always be low. It also seems quite probable that R s are more reactive than sec-butyl cations relative to isobutane. Reaction D includes reactions of isoalkyl cations ( C 5 and higher cations) with isobutane to form Isoparaffins (that become part of the alkylate) and t - C 4 H g . This reaction is thought to be of some but not major importance for sulfuric acid alkylations, as will be discussed in more detail later. Most isoparaffins are, however, probably formed by the reaction of Isoalkyl cations with RH (acid-soluble polymers). Reactions Ε and especially F are probably of minor importance in commercial alkylators. Reactions E-l and F were, however, of major importance whenever TMP's, DMH's, and isobutane degraded (or reacted) in the presence of sulfuric acid (7,17,18). Reactions E-2 +

+

+

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

+

+

+

+,

+

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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ALKYLATIONS

were first suggested by Albright and Li (11); although no conclusive evidence has yet been obtained to prove these reaction steps, the reactions appear most probable based on experimental findings relative to the role of acid-soluble hydrocarbons during alkylations, as described later. A seventh method for producing t-butyl cations is described in Table III (to be presented later). Main Olefin Reactions. Although some olefins react to form t-butyl cations, i.e. to initiate the alkylation steps as shown in Table I, most olefins react by Reactions G through K, as summarized 1n Table II. Reaction G-l is the reaction in which either 2-butene or isobutylene reacts with a t-C4Hq to form a TMP . This reaction is of major importance, and i t is widely accepted as being a key step in alkylation (9,10). It should be emphasized, however, that the reaction as postulated here can be but is not necessarily part of a chain sequence of reactions. Instead much of the 2-butene or isobutylene is likely regenerated as a result of the decomposition of butyl sulfates or of acidsoluble hydrocarbons, as will be discussed later. When sulfuric acid is employed as the catalyst, relatively few dimethylhexyl cations (DMH+) are produced by reactions of 1-butene with t-butyl cations (11), see Reaction G-2; the reasons for this conclusion have already been discussed 1n detail earlier in this paper. Yet when HF 1s the catalyst, considerably more DMH's and less TMP's are produced with 1-butene than with 2-butene (19). Isomerlzation (Reaction H-l) of 1-butene to 2-butenes is considerably slower with HF as compared to sulfuric acid. Hence Reaction G-2 is of importance in the presence of HF. As indicated earlier (2,3) for sulfuric add alkylations, the rates of reaction for olefins are often higher during the i n i t i a l stages of alkylation than the rates of reaction for isobutane. In the case of n-butenes, isomerlzation of the n-butenes occurs readily in the presence of sulfuric acid, see Reactions H-l and H-2. Considerable information on these isomerlzations were reported earlier (5); the rates of isomerization Increase as the amounts of excess add or as the acidity of the acid phase increase. Certainly at the conditions employed in commercial alkylators, isomerlzation would be very rapid. Recent Purdue results (5) have now shown at -10°C or less and in the presence of relatively l i t t l e excess sulfuric add that n-butenes both Isomerize and form sec-butyl sulfate, see Reaction 1-1. It seems safe to conclude that significant amounts of sulfate formation also occur 1n commercial alkylation reactors operated at about 5 to 15°C. The evidence supporting the formation of sulfates 1s as follows: (a) Butyl sulfates are present 1n small quantities 1n sulfuric acid leaving commercial alkylation units (20). Butyl sulfates react readily with Isobutane; the rates of reaction Increase rapidly with Increased temperatures in the range of - 3 0 ° to 0°C (5). Even faster rates +

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

+

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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8.

Isobutane with Light

ALBRIGHT

Olefins

137

presumably occur at 10° and 15°C. Consequently 1t is not surprising that only small amounts of butyl sulfates are detected in the exit acid, (b) Experiments conducted in a four-staged reactor indicated that acid-soluble hydrocarbons that in part could have been butyl sulfates reacted in significant amounts with isobutane at 10°C to form TMP's (2). Albright and Li (11) have also proposed that at least some olefins react with cations present in the acid-soluble hydro­ carbons (Reaction E-2 of Table I and Reaction J of Table II). No direct evidence has yet been obtained to support this hypothesis, but on the other hand no evidence 1s known that 1s contrary to the above postulate. Definitive evidence 1s clearly needed. First effect results with isobutylene (5) clearly indicate that i t forms some add-insoluble low polymers, mostly in the to C-jg range (see Reactions G-l and Κ of Table II), when 1t is contacted with sulfuric acid. Small amounts of polymers (that were olefins) were also noted when the hydrocarbon effluent of a laboratory alkylation reaction was quenched with a caustic solu­ tion (1); 1-butene was employed as olefin in this system. It can be concluded that during alkylation some Cg-C-jg olefins are present, but these olefins are ionized in the presence of the acids to form C0-C15 cations (that are highly reactive as will be discussed later). Of the C4 olefins, isobutylene is without question the easiest to polymerize. Isobutylene was also found to react in the presence of sul­ furic acid to form acid-soluble hydrocarbons that reacted with isobutane to form alkylate (5). Although the exact nature of these acid-soluble hydrocarbons is not known, 1t is thought that they are in part at least t-butyl sulfates (see Reaction 1-2) or that they complex (or react) with the conjunct polymer cations (R ), as shown 1n Reaction J . In both cases, isobutylene would be liberated by reverse reactions, and the isobutylene would then alkylate isobutane. When propylene is in the feed, i t will react with t-C Hg to form dimethylpentyl cations; this reaction is very similar to Reaction G shown in Table II. In addition, propylene reacts with sulfuric acid to form sec-propyl sulfates similar to Reaction 1-1. Goldsby (21,22) has described the production of sec-propyl sul­ fates; in some cases, di-sec-propyl sulfate is formed. These propyl sulfates are more thermally stable than butyl sulfates. 4

+

Reactions of Butyl Sulfates. At 0°C or higher, sec-butyl sulfate 1s unstable (5). When i t decomposes in the absence of isobutane, both a low quality (i.e. low octane number) hydro­ carbon mixture and acid-soluble hydrocarbons are produced. The products obtained by such decompositions are very similar to those produced when pure C4 olefins are contacted with sulfuric acid at 10 C (1,3). It seems safe to conclude that the initial reaction is the reverse of Reaction 1-1 as shown next: U

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

138

INDUSTRIAL

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(1-1)

sec-butyl sulfate —•

AND

LABORATORY

trans-2-butene and + H SQ ci s-2-butene 2

ALKYLATIONS

4

Some 1-butene may also be formed, but based on equilibrium considerations, 2-butenes are formed in much larger amounts. The rate of decomposition certainly increases with increased temperatures (5). Since sec-butyl sulfate is soluble in the acid phase, presumably 2-butenes will be released primarily in the acid phase. Two points can be made based on the hypothesis that olefins are regenerated as a result of butyl sulfate decomposition in the alkylation reactors. (a) The regeneration of C4 olefins is relatively slow even at 1 0 - 1 5 ° C . The ratio of isobutane to regenerated C4 olefins is hence high at the acid-hydrocarbon interface where the main alkylation reactions occur (7,15,16). High ratios for th^se two reactants promote high ratios of TMP's to LE's. This is because production of 1-Cj and heavier isoalkyl cations (Reactions K) are minimized. Of interest, there was a high TMP's/LE's ratio in the alkylate of two-step alkylations (6). (b) In the acid phase i t s e l f , however, the ratio of isobutane to regenerated C4 olefin may be low since isobutane is only slightly soluble in sulfuric acid. In the acid phase, some released C4 olefins polymerize with the production of heavy ends and acid-soluble hydrocarbons (or conjunct polymers). Sufficient agitation should be provided then to transfer the olefins to the acidhydrocarbon interface. This conclusion is supported by the experimental results for two-step alkylations in which relatively large amounts of heavy ends were produced. Based on the above reasoning, rather significant differences likely occur when HF is used for two-st*p alkylations as compared to two-step processes using sulfuric acid. For HF alkylations, butyl fluorides have been reported to be intermediates (23). Since isobutane is much more soluble in HF as compared to sulfuric acid, there 1s a strong possibility that less heavy ends or conjunct polymers would be produced in two-step alkylations using HF. When propyl sulfates are present, they will decompose relatively slowly to produce propylene and free sulfuric acid. The resulting propylene will then react primarily with t-butyl cations and heavier cations forming dimethylpentyl and s t i l l heavier cations. When aluminum chloride catalysts are use, esters undoubtedly also are produced as they are with sulfuric add and HF. The results of Roebuck and Evering (24) strongly imply that the olefins i n i t i a l l y reacted forming esters that then slowly reacted with isobutane to form alkylate. The low yields noted for low tempera2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

+

8.

ALBRIGHT

Isobutane with Light

Olefins

139

ture runs resulted because insufficient time was allowed for more complete reactions of the esters. Decomposition of Acid-Soluble Hydrocarbon Complexes. As reported earlier (11), it has been postulated that 2-butenes may react with the acid-soluble hydrocarbon cations (see Reaction E-2 of Table I). Isobutylene may also react similarly. The resulting acid-soluble ion could later decompose via β - s c i s s i o n to release isobutylene: C H

I

3

R-CH -C — R + 1-C H +

2

+

4

8

CH The isobutylene released would be either at the acid-hydro­ carbon interface or in the acid phase itself. The exact location at which the Isobutylene is released would depend to a consider­ able extent on the location of the Initial 1on 1n the acid phase. Although no direct Information is available, the acid-soluble hydrocarbon cations (14) appear to have surfactant-type character­ istics and may be located primarily at the acid-hydrocarbon inter­ face.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

3

Production of TMP* and TMP. TMP's are the preferred hydro­ carbons produced by alkylation, and they are produced in all cases by transfer of a hydride 1on to TMP s. There are at least three methods by which TMP s are formed during alkylation: (1) Reaction G-l that was shown in Table II is always the predominant route for alkylations employing C4 olefins. In this case, either 2-butene or isobutylene reacts with a t - C 4 H n . This reaction has been considered in detail by Schmerling (9,10). (2) i-C-|2 » 1 -C-|5 , or other heavy isoalkyl cations fragment via 3-scission. A wide variety of isoalkyl cations and iso-olefins are produced including TMP s and t r i methylpentenes (see fragmentation of heavy isoalkyl cations as described in Table III). This method is an expansion of the one described by Hofmann and Schrieshelm (8); 1t will be considered in detail later when the production of LE's and DMH's are discussed. (3) Trimethylpentenes protonate rapidly to form TMP's. As indicated above, trimethylpentenes can be formed by fragmentation of heavy isoalkyl cations. Furthermore the protonations of trimethylpentenes and other olefins are to some extent at lease reversible. Hence, small concentrations of trimethylpentenes are present in alkylation reactors during especially the initial stages of alkylation; Mosby and Albright (1) for example found small amounts of olefins when the alkylation product was quenched and neutralized. +,

+,

+

+

+

+,

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

140

INDUSTRIAL

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ALKYLATIONS

TABLE III FRAGMENTATION OF HEAVY ISOALKYL CATIONS (L)

Fragmentation of Heavy Isoalkyl Cations 1)

Isoalkyl cations 1n the C and higher range fragment. β-sdsslon of 2,2,4-TMP 8s shown 1n Reaction Ε 1s an example. Isoalkyl cations that frequently fragment are thought to Include 1-C] and 1-C]6 . Examples of how they might fragment are as follows: g

+

+

+

2

1-C 1

2)

C

+ ]2

— +

1-C 1

+

+ 1-C

5

C

- 16 ^ - 5

+ + 1

=

or 1-C

7

C

- 5

= + 1

C

- 6

+ 6

+

1-C

= 6

S

Protonation of olefins

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Olefins rapidly protonate to form Isoalkyl cations, e.g. 1-C Note:

= 5

+ H

+

^

i-C^

Isoalkyl cations formed by fragmentation and protonation of olefins generally contain 4 to Ί0 carbon atoms. Some t-C-Hq+'s are formed 1n this manner, as are both DMH's •and TMP's. This method 1s thought to be the major method for production of the precursors for LE's and for DMH's (when sulfuric a d d 1s used as the catalyst). +

TABLE IV HYDRIDE ION TRANSFER STEPS (M)

Hydrlde Ion Transfer Steps 1)

From Ac1d-Soluble Polymers

2)

(RH) +

Isoalkyl cation + RH

Isoalkane + R

(polymer cations)

From Isobutane and Other Isoalkanes Isoalkyl cation + 1-C H 4

1Q

^

Isoalkane + t-C H 4

Isoalkyl cation + Isoalkane ^

+ g

Another + Another Isoalkyl Isoalkane cation

This reaction 1s an expansion of Reaction D shown on Table I; the solubilities of Isobutane and Isoalkanes 1n the a d d may be key factor affecting Importance of this re­ action. Higher Isoalkanes are less soluble 1n add phase. 3)

From Isobutylene Isoalkyl cation + 1-C,H

g

Note:

Isoalkane + CH

2ir

^ ι 3 C ^H-

Hydride transfer leads to production of TMP's, DMH's, LE's, HE's, and Isobutane.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8.

ALBRIGHT

Isobutane with Light

Olefins

141

Transfer of a hydride 1on to an Isoalkyl cation 1s often the rate controlling step 1n the overall reaction scheme (16). Iso­ alkyl cations including C5 and higher ones react forming the various isoparaffin molecules found in alkylate, e . g . , TMP s react to fonn TMP's. Schmerling (9,10) had originally postulated that a hydride ion transfer from isobutane was both the most important method of hydride transfer and also part of the chain set of reactions (see Reaction C of Table I and Reaction M-2 of Table IV). Other hydride transfer steps that have now been suggested include trans­ fer with the acid-soluble hydrocarbons (RH), see Reaction M-l of Table IV (8,11), and with isobutylene, see Reaction M-3 (8). Reaction M-3 is however considered to be of minor Importance since only trace amounts of free isobutylene are likely ever present at the acid-hydrocarbon interface (the probable location of alkyla­ tion reactions); Isobutylene quickly protonates to form t - C 4 H g . Reaction M-l is considered to be more important than Reaction M-2 especially when sulfuric acid 1s used as the catalyst for the reasons listed as follows: (a) Alkylate (or isoparaffins) are produced preferentially as compared to polymers (or olefins) only after acidsoluble hydrocarbons form in the acid phase. Hence, hydride transfer becomes important only after acidsoluble hydrocarbons are produced. (b) When several percent of acid-soluble hydrocarbons are present in the acid, improved alkylate occurs as com­ pared to fresh acids (that contain l i t t l e or no acidsoluble hydrocarbons). Obviously such acid-soluble hydrocarbons would be present in significant amounts at or close to the add-hydrocarbon interface and are hence available for hydride transfer. Isobutane is however only slightly soluble in sulfuric acid, and there is probably only limited availability of i t for the reaction. When HF is used however, isobutane 1s much more soluble and reaction M-2 is likely of greater importance. (c) If Reaction M-2 was of major importance when sulfuric acid is used, it would be expected that hydride trans­ fer with other isoalkanes such as TMP's and LE's would also be of some importance; there is no evidence that such isoparaffins react to any appreciable extent. Additional discussions on the role of acid-soluble hydro­ carbons as a reactant during alkylation has been discussed earlier (4,8,11). The acid-soluble hydrocarbons clearly act as a reservoir of hydride ions. Hydride ions are furnished to the acid-soluble hydrocarbons primarily from isobutane (Reaction Β of Table I) and they are withdrawn from the hydrocarbons princi­ pally by Reaction M-l. The acid-soluble hydrocarbons furthermore also tend to i n ­ crease the solubility of isobutane and other isoparaffins in the +,

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+

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AND

LABORATORY

ALKYLATIONS

acid phase. In addition to the viscosity, the Interfadal surface tension Is changed. Such factors are Important since transfer of reactants to the interface and/or of products away are obviously rate-controlling steps. Such a conclusion is obvious since agitation was found to be an important, 1f not most important, operating variable relative to the quality of alkylate produced (3). Production of Light Ends and Dimethylhexanes. Hofmann and Schrieshelm ( 8 ) proposed two mechanisms and evidence to support each. The mechanism based on fragmentation of large Isoalkyl cations (see Table III) 1s preferred as the major route for production of both LE's and DMH's; the mechanism proposed here has been modified somewhat as compared to the original one that suggested 1-C-j2 cations fragmented. Evidence supporting the fragmentation route 1s presented as follows: (1) LE's and relatively small isoparaffins are produced when heavy olefins are used as feedstock for alkylation. The products obtained when isobutylene or 2,2,4-trimethy 1 pentene-1 is used as the olefin for alkylation resulted 1n almost Identical products including LE's and DMH's (6,19). Even heavier olefins produce LE's, and fragmentation is obviously of major Importance. (2) Degradation of TMP's or DMH's 1n the presence of sulfuric acid leads to the formation of significant, and even major amounts of isobutane and LE's ( 7 ) . Fragmentation reactions obviously must be occurring. (3) The ratio of LE's to DMH's produced 1s generally relatively constant regardless of the operating conditions or the olefin used. Similar constant ratios are also obtained in the products of conventional alkylations, two-step alkylations (1n which butyl sulfates react), and degradation reactions between TMP's and sulfuric acid. This finding suggests that a common intermediate 1s Involved in the production of most LE's and DMH's. 1-Butene cannot be considered this Intermediate since 1t is sometimes present only in at most minute quantities. 1-Butene is mentioned since 1t has been suggested as the C4 olefin that leads to production of DMH's (9, 10). Although 1-butene is probably of minor importance for production of DMH's when sulfuric acid is used as a catalyst (11), considerable DMH's are likely formed via Reaction G-2 (with 1-butene) when HF 1s the catalyst. (4) There 1s a question whether 1 - C « | cations are the most important cations that fragment, as was originally proposed by Hofmann and Schriesheim ( 8 ) . If i - C ^ cations were the most Important Intermediates, then the amounts of Cc and C7 isoparaffins produced would likely be essentially identical (see Reaction L). Yet Isopentane (the only C5 Isoparaffin produced) is generally

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+

2

+

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8.

Isobutane with Light Olefins

ALBRIGHT

formed 1n much larger amounts than the C7 Isoparaffins. Possibly part of the C5 or C7 cations or iso-olefins react, but C c ' s and not C-j's would probably be the more reactive. The experimental results can, however, be explained i f 1-C]6 cations were the key intermediates. Two isopentane molecules and one Ce isoparaffin could be produced from each i - C ] ç cation (as shown by Reaction L); such a ratio is approximated in many alkylates. (5) 1-Ci2 heavier isoalkyl cations are produced during alkylation primarily because of polymerization reactions involving olefins. The C ^ results of Hofmann and Schriesheim (8) Indicating that higher levels of olefin reacted during production of DMH's and LE's as compared to TMP's is consistent with this postulate. (6) Production of heavy isoalkyl cations, including I-C12 and i-C-jg cations, would logically occur during conventional alkylations, two-step alkylations, degradation of TMP's and DMH's, and reactions between olefins and sulfuric acid at 10°C or higher. In the case of alkylations, higher ratios of isobutane to C4 olefin at the reaction site result in relatively smaller amounts of heavy isoalkyl cations and hence lower amounts of DMH's and LE's. This experimental finding 1s consistent with thé fragmentation mechanism. Hofmann and Schriesheim (8) also postulated that DMH's were formed when isobutylene reacted with an a l l y l i c cation (formed via Reaction M-3) as follows: CH CH CH CH a

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143

n

d

3

3

(N) CH r==C==CH + CH=C 2

2

2

3

3

- » CH=C — C H - C H « C - C H 2

2

2

3

Transfer of two hydride 1ons and one proton would result 1n DMH. Since the methyl groups could migrate on the chain, DMH's other than 2,5-DMH could be produced. Some t-butyl cations dissociate Into isobutylene and protons; hence this method could occur during alkylation with olefins other than isobutylene. Reaction Ν is probably only of minor importance in most cases, however, since only small concentrations of free isobutylene are thought to occur at the add-hydrocarbon interface; most Iso­ butylene quickly protonates to form t-butyl cations. Production of Heavy Ends and Acid-Soluble Hydrocarbons. Heavy ends (HE's) are produced in large amounts by reactions involving primarily olefins; these reactions are primarily polymerizationtype reactions. The olefins are quite soluble in the acid phase, but isobutane 1s not. High ratios of isobutane to olefins and high levels of agitation are necessary to minimize formation of heavy ends (3). The large isoalkyl cations formed by polymeriza­ tion-type reactions obviously fragment to some extent to produce some Cg and C]o isoparaffins (found in appreciable quantities 1n

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

HE's). It is thought however, that significant fractions of the HE's result from acid phase reactions as comnared to reactions at or close to the acid-hydrocarbon interface where most alkylation reactions occur; this latter conclusion is based on the results for two-step alkylations (6). Both acid-insoluble and acid-soluble hydrocarbons are also produced to a small, and probably as a rule insignificant, extent from isobutane and other isoparaffins when sulfuric acid is used as the catalyst (7). The sulfuric acid acts as a mild oxidizing agent producing sulfur dioxide even at temperatures as low as 0 ° C . The acid-soluble hydrocarbons apparently have in all cases similar structures to the acid-soluble hydrocarbons removed from used alkylation acids by Miron and Lee (25). These hydrocarbons contained C5 cyclic rings; were highly unsaturated and frequently had conjugated double bonds; had fairly high molecular weights; and had carbon-to-hydrogen ratios higher than those of the reacting hydrocarbons. Clearly polymerization and dehydrogenation steps occur 1n the production of these acid-soluble hydrocarbons. Deno and associates (26,27) have shown that some t-butyl cations react forming cyclopentenyl cations. These latter ions likely are precursors to acid-soluble hydrocarbons formed during alkylation. Purdue findings have shown that the viscosity and color of the acid-soluble hydrocarbons removed from the acid increased as the acid was used and as the acid was aged in drums stored at room temperature. Sulfur dioxide was also produced. Undoubtedly some olefins added to or polymerized with the acid-soluble cations during alkylation. The net result of these reactions was that the molecular weight of these acid-soluble hydrocarbons increased. The sulfur dioxide produced indicates that some sulfuric acid had acted as an oxidizing agent (and apparently also as a dehydrogenation agent causing double bond formation in the acid-soluble hydrocarbons). Recently Doshi and Albright (7) presented evidence that suggests significant fractions of the acid-soluble hydrocarbons are often produced while the acid phase 1s outside of the alkylation reactor, I.e., while the acid is being separated from the organic phase and while it 1s being recycled. Clearly more information 1s, however, needed to determine the complete role of acid-soluble hydrocarbons during alkylation. Physical Steps During Alkylation. Physical steps that occur during alkylation of isobutane have key roles in affecting the overall process and in the composition (and quality) of the alkylate produced (3). The transfer of Isobutane to the reaction site (which 1s at or close to the interface between the two phases) is in general the controlling physical step. It is affected by several operating variables. Agitation i s , of course, an obvious variable since 1t affects not only the isobutane transfer step but also the interfadal area. Other variables that affect the isobutane transfer step include the 1sobutane-to-olef1n feed ratio,

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

8.

ALBRIGHT

Isobutane with Light

145

Olefins

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

the residence time in the reactor, the concentration of inerts in hydrocarbon phase, the volumetric ratio of acid to hydrocarbon phases, and which phase is the continuous phase in the emulsion. Variables affecting both the isobutane transfer step and also the chemical kinetics include temperature, composition of acid, and the specific olefin used (4). Although the main alkylation reactions are thought to occur at or close to the interface between the acid and hydrocarbon phases (7,15,16), the acid boundary layer at the interface seems more probable. This conclusion is based on the fact that other isoparaffins (including LE's, TMP's, DMH's, and HE's) appear to be much less reactive relative to hydride transfer steps as compared to isobutane; yet many of these isoparaffins contain one or more tertiary carbon-hydrogen bonds. These heavy isoparaffins are, however, even less soluble in the- acid phase than isobutane. Conclusions Alkylation of isobutane with light olefins in the presence of sulfuric acid involves considerable more chemical steps than have generally been considered in the past. Olefins tend to react to a higher extent during the initial stages of the alkyla­ tion reactions and isobutane during the latter stages. Most alkylation reactions occur at the acid-hydrocarbon interface, but reactions resulting primarily in the production of heavy ends and acid-soluble hydrocarbons may occur primarily in the acid phase. Alkyl sulfates and acid-soluble hydrocarbons have key roles relating to the overall chemistry of alkylation. Although experimental data for alkylations using sulfuric acid and primarily C4 olefins were employed in development of the proposed mechanism, the mechanism has been expanded to include alkylations with HF, other acids, and other olefins. Literature 1. 2. 3. 4. 5.

Cited

Mosby, J . F. and A l b r i g h t , L . F., Ind. Eng. Chem. Prod. Research Dev. 5, 183 (1966). Shlegeris, R. J. and A l b r i g h t , L. F., Ind. Eng. Chem. Process Des. Dev., 8, 92 (1969). Li, K. W., Eckert, R. E . and A l b r i g h t , L . F., Ind. Eng. Chem. Process Des. Dev. 9, 434 (1970). Li, K. W., Eckert, R. E . and A l b r i g h t , L. F., Ind. Eng. Chem. Process Des. Dev. 9, 441 (1970). A l b r i g h t , L . F., Doshi, Β. Μ., Ferman, Μ. Α., and Ewo, Α., "Two-Step Alkylation of Isobutane with C Olefins: Reactions of C Olefins with S u l f u r i c Acid", This Book, Chapter 6, 1977. A l b r i g h t , L . F., Doshi, Β. Μ., Ferman, Μ. Α., "Two-Step A l k y l a ­ tion of Isobutane with C Olefins: Reaction of Isobutane with I n i t i a l Reaction Products", This Book, Chapter 7, 1977. 4

4

6.

4

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

146 7. 8. 9. 10.

11. 12. 13.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch008

14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27.

INDUSTRIAL AND LABORATORY ALKYLATIONS

Doshi, Β. M. and A l b r i g h t , L . F., Ind. Eng. Chem. Process Des. Dev. 15, 53 (1976). Hofmann, J. E . and Schriescheim, Α . , J. Am. Chem. S o c . , 84, 953-961 (1962). Schmerling, L., Ind. Eng. Chem., 45, 1447 (1953). Schmerling, L., in "Friedel Crafts and Related Reactions in Alkylation and Related Reactions". 0lah, G. A. Ed., Inter­ science Publishers (1964). A l b r i g h t , L. F. and Li, K. W., Ind. Eng. Chem. Process Des. Dev. 9, 451 (1970). A l b r i g h t , L . F., Houle, L., Sumutka, Α. Μ., and Eckert, L . E., Ind. Eng. Chem. Process Des. Dev. 11, 446 (1972). Stewart, T. D. and Calkins, W. H., J. Amer. Chem. Soc. 70, 1006 (1948). L e f t i n , H. P. and Hobson, M. C., Advan. Catalysis 14, 189, (1963). Kramer, G. Μ., This Book, Chapter 1 (1977). Kramer, G. M . , J. Org. Chem. 30, 2671 (1965); U.S. Pat. 3,231,633 (Jan. 25, 1966). Hofmann, J. E., J. Org. Chem. 29, 3627 (1964). Kramer, G. M . , J. Org. Chem. 32, 920 (1967). Innes, R. A., This Book, Chapter 3, 1977. Goldsby, A. R. and Gross, Η. H., U.S. Pat. 3,083,247 (March 26, 1963). Goldsby, A. R . , U.S. Pat. 3,234,301 (Feb. 6, 1966). Goldsby, A. R . , U.S. Pat. 3,422,164 (Jan. 14, 1969). McCaulay, D. A., U.S. Pat. 3,280,211 (Oct. 18, 1966). Roebuck, A. K. and Evering, B. L., Ind. Eng. Chem. Product Res. Develop. 9, 76 (1970). Miron, S. and Lee, R. J., J. Chem. Engr. Data 8, 150 (1963). Deno, N. C., Chem. Engr. News, Oct. 5, 1964, pp 88-100. Deno, N. C., Boyd, D. Β., Hodge, J. D . , Pittman, C. U., and Turner, J. O., J. Amer. Chem. Soc. 86, 1745 (1964).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9

Free Radical-Induced Monoethylation with Ethylene

LOUIS SCHMERLING

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

UOP Inc., Des Plaines, IL 60016

The f r e e radical-induced reaction of a s a t u r a t e d hydrocarbon with ethylene produces chiefly greasy t e l o m e r s f o r m e d by t h e addition of a hydrocarbyl radical a t one end o f a p o l y m e t h y l e n e c h a i n and a h y d r o g e n atom a t t h e o t h e r end (1). F o r e x a m p l e , when a solution of a catalytic amount o f di-t-butyl peroxide in c y c l o h e x a n e i s h e a t e d a t 130-140°C (the t e m p e r a t u r e range a t which the r a t e of d e c o m p o s i t i o n of the p e r o x i d e i s a p p r e c i a b l e ) under e t h y l e n e p r e s s u r e , t h e r e is f o r m e d viscous, high-boiling, grease-like product, some o f w h i c h is solid; it is a m i x t u r e o f ethylcyclohexane and t e l o m e r s (i.e., butyl-, hexyl-, octyl-, and higher molecular weight a l k y l c y c l o h e x a n e s i n which the alkyl groups contain an e v e n number o f c a r b o n a t o m s , r a n g i n g from 2 t o 40 o r m o r e ) . The reaction apparently involves the following free radical c h a i n mechanism: (CH3) COOC(CH )3 > 2(CH ) CO(CH )3CO. + C - C H > (CH ) COH + c - C H n . Ç_- 6 11CH2=CH > c-C6H CH CH . c - C 6 H C H C H . + nCH =CH > C-C6H11(CH CH ) CH CH . Ç_~ 6 11 ( C H C H ) C H C H . + ç - C e H > c-CeHxxtCI^CI^JnCI^CI^ + Ç - C H 3

3

3

3

C

6

H

3

3

6

+

2

1 1

2

l ; L

2

2

2

2

2

2

2

2

C

(1) (2) (3) (4)

3

1 2

2

n

H

2

2

n

2

2

6

The c y c l o h e x y l new cycle as in Inhibition

of

(5)

1 2

radical formed E q u a t i o n 3.

in

Equation 5

1 ; L

starts

. a

Telomerization

Procedure. A glass liner containing the quanti­ ties of s a t u r a t e d hydrocarbon, alkyl chloride or ether, of hydrochloric acid (aqueous o r a n h y d r o u s ) and di-t147 American Chemical Society

Library

1155 16th St., M.W. In Industrial and Laboratory Alkylations; Albright, L., el al.; Washington, D . C . 20036 ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

148

INDUSTRIAL

A N D LABORATORY

ALKYLATIONS

b u t y l peroxide t a b u l a t e d i n Tables I t h r u V was sealed i n t o an I p a t i e f f - t y p e r o t a t i n g autoclave of 850 ml c a p a c i t y . Ethylene was charged to an i n i t i a l pressure of from 15 to 40 atm. (about 0.5 to 1.3 mois ethylene) and the autoclave was r o t a t e d while being heated during four hours from 130 to 140°C, a range a t which the peroxide decomposition proceeds a t a p r a c t i c a l r a t e . The f i n a l pressure was u s u a l l y about 5-25 atm. a t room temperature. By charging ethylene t o a lower i n i t i a l pressure, l e s s e r amounts of ethylene were employed. The pressure drop showed t h a t the r e a c t i o n was u s u a l l y completed i n l e s s than two hours, but heating was continued f o r four hours t o ensure optimum conversions. The autoclave was allowed t o stand overnight, the gaseous product was discharged, the autoclave was opened and the l i q u i d product (usually c h i e f l y i n the l i n e r ) was recovered. The organic product was washed with water, d r i e d and d i s t i l l e d and/or i n s p e c t e d by gas chromatography. Experiments with gaseous r e a c t a n t s (propane and isobutane, Table III) were c a r r i e d out by charging the l i q u e f i e d gas from a weighed s t a i n l e s s - s t e e l sampling c y l i n d e r i n t o the sealed autoclave c o n t a i n i n g hydroc h l o r i c a c i d and, when used, a l i q u i d alkane a f t e r which ethylene was charged and the autoclave was r o t a t e d and heated. Cyclohexane. I t i s the purpose o f the present paper to d i s c u s s a unique m o d i f i e r f o r the r e a c t i o n which very markedly i n h i b i t s the t e l o m e r i z a t i o n and r e s u l t s i n the formation of ethylcyclohexane as the p r i n c i p a l s i n g l e r e a c t i o n product together with some butylcyclohexane and d i e t h y l c y c l o h e x a n e s . The r e a c t i o n m o d i f i e r c o n s i s t s of hydrogen c h l o r i d e which may be added as the anhydrous gas or as an aqueous s o l u t i o n . I t s e f f e c t i v e n e s s i n the monoe t h y l a t i o n of s a t u r a t e d hydrocarbons, a l k y l h a l i d e s and ethers w i l l be d e s c r i b e d . Thus, when 47 g (0.47 mol HC1) of 38% h y d r o c h l o r i c a c i d and 96 g (1.14 mois) of cyclohexane c o n t a i n i n g 6 g of d i s s o l v e d d i - t - b u t y l peroxide were heated a t 130-140° under 40 atm. (1.3 mois) i n i t i a l ethylene pressure (51 atm. a t 130°C)in a g l a s s l i n e r i n a r o t a t i n g autoclave of 850 ml c a p a c i t y for four hours, the f i n a l pressure a t room temperature was 22 atm. The product i n c l u d e d 24 g (18 mol % y i e l d ) of ethylcyclohexane and 18 g of h i g h e r - b o i l i n g product, c o n s i s t i n g c h i e f l y of n-butylcyclohexane, d i e t h y l c y c l o hexanes, and n-hexylcyclohexane (and d i a l k y l isomers) p l u s a smaller amount o f h i g h e r - b o i l i n g compounds (Expt. 2, Table I ) . On the other hand, when the same

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

Monoethylation with

SCHMERLING

Table

I

Reaction of Cycloalkanes with

Expt.

a

<-Reactants, m o i s — > c-RH mois C HA 9

1

2

1.07

C H

1.14

6

3

1 2

H

C6 12

4

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

C6H12

C6H12

5

C6%2

6

H

C6 12

1.15

1.37

1.72

1.15

1.3*

1.3

1.3

1.0

0.5

0.6

149

Ethylene

Ethylene

>

< Chief Kind

0

c-C H Et Higher m o l wt

29b

c-C6H Et Higher m o l wt

29 18

c-C^HxiEt H i g h e r m o l wt

20

c-C H Et Higher m o l wt

36 19

c-C H Et H i g h e r m o l wt

19 3

c-C H Et

24e

<—HCl Kind mois H 0 2

0.5

38%

100%

0.1

0.2

38%

100%

38%

0.1

d

0.1

1

u

6

n

1 ; L

6

—>

Productsg %

u

6

u

6

6

1 ] L

Me

1.28

1.3

38%

0.1

Et

8

5H

1.57

1.3

38%

0.2

1 0

C H Me 5

9

1.34

1.3

19%

0.5

e

f

36 17

9 18 11 22 Higher m o l wt

31 16 7 21

24 20 10

MeC5H Et Higher m o l wt

38 28

1 Q

c-C H Et 5

C

j

34 C

13 7

6

C

9

32 c

22 7δ 12

MeC H

Higner m o l wt C

16

7 6

0

C H

18 c

26C

Cl H20 H i g h e r m o l wt 7

1

9

H

H

g

h

1

k

26

( a ) T h e c y c l o a l k a n e s o l u t i o n o f 0.04 m o l d i - t - b u t y l p e r o x i d e a n d h y d r o c h l o r i c a c i d ( o r a n h y d r o u s h y d r o g e n c h l o r i d e ) was h e a t e d a t 130-140° d u r i n g f o u r h o u r s i n a g l a s s l i n e r i n a n I p a t i e f f type r o t a t i n g a u t o c l a v e under e t h y l e n e p r e s s u r e . (b) C h i e f l y g r e a s y l i q u i d a n d wax. ( c ) I n c l u d e s much b u t y l c y c l o h e x a n e a n d d i e t h y l c y c l o h e x a n e s . (d) D e u t e r o c h l o r i c a c i d i n 9 9 % D 0 ( 3 8 % b y w e i g h t ) . (e) I n c l u d e s d e u t e r a t e d p r o d u c t ; c f . t e x t . (f) Consists of 1-methy1-1-ethylcyclohexane mixed w i t h s m a l l e r amounts o f c i s - 1 - m e t h y 1 - 3 - e t h y I c y c l o h e x a n e , c i s - and t r a n s - 1 m e t h y l - 4 - e t h y l c y c l o h e x a n e and other isomers. (g) M i x t u r e o f m e t h y l b u t y l c y c l o h e x a n e s , a n d m e t h y l d i e t h y l c y c l o hexanes. (h) B.p. 150-155°, g c shows 3 m a j o r p e a k s . ( i ) B . P . 192-200°; g c s h o w s 2 m a j o r p e a k s , ( j ) H e a t e d a t 120-128° d u r i n g 16 h o u r s , (k) C h i e f l y 1-methy1-1-ethylcyclopentane. (£) 4 0 a t m p r e s s u r e . 2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

150

A N D LABORATORY

ALKYLATIONS

amounts o f c y c l o h e x a n e and t h e p e r o x i d e were h e a t e d w i t h e t h y l e n e u n d e r t h e same c o n d i t i o n s , b u t i n t h e presence o f water i n s t e a d o f h y d r o c h l o r i c a c i d , the p r o d u c t c o n t a i n e d o n l y 1 g o f e t h y l c y c l o h e x a n e and 29 g o f h i g h e r - m o l e c u l a r w e i g h t l i q u i d , g r e a s y and waxy t e l o m e r s ( E x p t . 1 ) . I t was shown by g a s c h r o m a t o g r a p h y (gc) f o l l o w e d by mass s p e c t r o s c o p y (ms) t h a t e t h y l - , η - b u t y l - , n - h e x y l - and n - o c t y l c y c l o h e x a n e made up a l a r g e p o r t i o n o f the product, the remainder consisting o f d e c r e a s i n g amounts o f h i g h e r n - a l k y l c y c l o h e x a n e s h a v i n g an e v e n number o f c a r b o n atoms up t o a t l e a s t n-tetracontylcyclohexane. M i n o r amounts o f t r i - and t e t r a e t h y l c y c l o h e x a n e were a l s o d e t e c t e d . The h i g h e r - b o i l i n g p r o d u c t s o b t a i n e d i n t h e h y d r o ­ gen c h l o r i d e - p r o m o t e d r e a c t i o n c o n s i s t e d c h i e f l y o f 10 20' 12 24' 1 4 2 8 hydrocarbons. The C-1QH20 f r a c t i o n was a m i x t u r e o f n - b u t y l c y c l o h e x a n e and diethylcyclohexanes. The C i 2 2 4 p r o d u c t c o n t a i n e d n h e x y l c y c l o h e x a n e and more e t h y l b u t y l c y c l o h e x a n e s t h a n triethylcyclohexanes. n - O c t y l c y c l o h e x a n e was d e f i n i t e l y i d e n t i f i e d i n the C14H28 m i x t u r e . A n o t h e r b y p r o d u c t o f t h e r e a c t i o n was a m i x t u r e o f a l k y l c h l o r i d e s i n w h i c h t h e a l k y l g r o u p s had an e v e n number o f c a r b o n a t o m s . T h e s e were o b v i o u s l y f o r m e d by t e l o m e r i z a t i o n o f e t h y l e n e and h y d r o g e n c h l o r i d e (2^) . C

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

INDUSTRIAL

H

C

H

a

n

d

C

H

H

CI-

n-C2H4 > + CH =CH2 > ClCH CH . pY-^ C1CH CH (CH -CH )·η > Cl(CH CH2)nCH CH3 + CI2

2

2

2

2

2

2

H

2

2

(6)

A h i g h e r consumption o f the hydrogen c h l o r i d e i n t h e a q u e o u s a c i d , a c c o m p a n i e d by a h i g h e r y i e l d o f a l k y l c h l o r i d e , o c c u r r e d when c o n c e n t r a t e d h y d r o c h l o r i c a c i d r a t h e r t h a n d i l u t e d a c i d (15-20%) was u s e d . As i s a p p a r e n t f r o m t h e r e s u l t s summarized i n T a b l e 1, b o t h h y d r o c h l o r i c a c i d ( d i l u t e o r c o n c e n t r a t e d ) and a n h y d r o u s h y d r o g e n c h l o r i d e were e f f e c t i v e i n g r e a t l y increasing the r a t i o s of ethylcyclohexane to h i g h e r - b o i l i n g product. Mechanism. The h y d r o g e n c h l o r i d e a p p a r e n t l y b e h a v e s as a c h a i n t r a n s f e r a g e n t , f u r n i s h i n g a h y d r o g e n atom t o t h e c y c l o h e x y l e t h y l r a d i c a l (1,) and f o r m i n g a c h l o r i n e atom w h i c h s t a r t s a new c y c l e by a b s t r a c t i n g h y d r o g e n f r o m c y c l o h e x a n e , p r o d u c i n g a new c y c l o h e x y l r a d i c a l and r e g e n e r a t i n g h y d r o g e n c h l o r i d e .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

SCHMERLING

ÇYCH CH 2

2

M onoethyhtion

+

with

151

Ethylene

(7)

HCl

Θ 1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

CI-

+f

Si

> HCl +

fsT

(> 8

The c y c l o h e x y l e t h y l r a d i c a l (1) appears to a b s t r a c t h y d r o g e n more r a p i d l y f r o m h y d r o g e n c h l o r i d e t h a n f r o m c y c l o h e x a n e and more r a p i d l y t h a n i t a d d s t o e t h y l e n e to y i e l d c y c l o h e x y l b u t y l or higher molecular weight radicals. C h a i n t e r m i n a t i o n p r e s u m a b l y o c c u r s by condensation or d i s p r o p o r t i o n a t i o n of a p a i r of free r a d i c a l s , o r by any o t h e r o f t h e c h a i n - t e r m i n a t i n g r e a c t i o n s which normally occur. No a t t e m p t was made t o i s o l a t e or i d e n t i f y the so-formed b y p r o d u c t s . The pathway by w h i c h t h e h y d r o g e n c h l o r i d e i n h i b i t s t h e t e l o m e r i z a t i o n and t h u s p r o d u c e s monoe t h y l c y c l o h e x a n e was s u p p o r t e d by u s e o f a s o l u t i o n o f d e u t e r i u m c h l o r i d e (38%) i n h e a v y w a t e r (99% d e u t e r i u m o x i d e ) as p r o m o t e r u n d e r t h e s t a n d a r d c o n d i t i o n s . The r e a c t i o n m i x t u r e i n c l u d e d 1.15 m o i s o f c y c l o h e x a n e and 0.1 mol o f d e u t e r i u m c h l o r i d e as t h e a c i d . Ethylcyclo­ h e x a n e was o b t a i n e d i n 36% y i e l d ; d i e t h y l c y c l o h e x a n e p l u s n - b u t y l c y c l o h e x a n e , i n 17% y i e l d . Mass s p e c t r o m e t r i c a n a l y s i s o f t h e m o n o e t h y l c y c l o h e x a n e showed t h a t d e s p i t e t h e h i g h r a t i o (138:1) o f h y d r o g e n i n c y c l o ­ hexane t o d e u t e r i u m i n d e u t e r i u m c h l o r i d e i n t h e r e a c t i o n m i x t u r e , t h e m o n o e t h y l a t e d compound c o n s i s t e d o f o n l y a b o u t 60% u n d e u t e r a t e d compound; t h e r e was p r e s e n t a b o u t 32% m o n o d e u t e r a t e d , a b o u t 8% d i d e u t e r a t e d , and a b o u t 1% t r i d e u t e r a t e d h y d r o c a r b o n . A b o u t 60% o f t h e d e u t e r i u m was i n t h e e t h y l g r o u p and t h e r e m a i n i n g 40% was i n t h e c y c l o h e x a n e r i n g . A b o u t 19% o f t h e r e c o v e r e d c y c l o h e x a n e was m o n o d e u t e r a t e d , 3% was d i ­ d e u t e r a t e d and l e s s t h a n 1% was t r i d e u t e r a t e d . Simi­ l a r l y , t h e p o l y e t h y l a t e d p r o d u c t c o n t a i n e d mono- and p o l y d e u t e r a t e d compounds. The r e c o v e r e d a c i d was c h i e f l y HCl d i s s o l v e d i n H 0 p l u s HOD. 2

I t may be c o n c l u d e d t h a t t h e r o l e o f t h e d e u t e r o c h l o r i c a c i d i n the e t h y l a t i o n r e a c t i o n i s that s u g g e s t e d by E q u a t i o n s 7 and 8. The d e u t e r i u m c h l o r i d e a c t s as a c h a i n t r a n s f e r a g e n t by t e r m i n a t i n g t h e c y c l e and y i e l d i n g a c h l o r i n e atom w h i c h i n i t i a t e s a new c y c l e by a b s t r a c t i n g h y d r o g e n f r o m c y c l o h e x a n e : c-C6H CH CH Cl- + ç-C6H 1 1

2

+ DC1

2

1 2

> c - C 6 H C H C H D + CI> HCl + C-C6HH1 1

2

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

(9) (8)

152

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Formation of ethylcyclohexane which i s deuterated i n the r i n g suggests t h a t the c y c l o h e x y l r a d i c a l formed, f o r example as i n Equation 8, underwent intermediate exchange with the deuterium c h l o r i d e . + DC1

> (^J°

+

(jTj'

+ CI-

> (^-D

+ HCl

10

'

< ) (11)

X

D + C=C

>f £U_D 2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

c 1

fs^

HCl or c-C6H >

C

(12) "

C

ΓΜ^Ο \^\>CH

12

+ CI-

(or c - C H 6

i r

)

(13)

2DC1

>

+ CI-

(14)

^"^C-CD Equation 10 e x p l a i n s the recovery of deuterated cyclohexane. Equation 14 i l l u s t r a t e s a pathway f o r the formation of a polydeuterated compound. C a l c u l a t i o n s showed t h a t the amount of deuterium i n the cyclohexane, ethylcyclohexane and other hydro­ carbons was a c t u a l l y more than t h a t present i n the deuterium c h l o r i d e charged. Hence, i t was concluded t h a t the deuterium present i n the deuterium oxide a l s o underwent exchange. T h i s was confirmed by a n a l y s i s of the recovered a c i d s o l u t i o n . I t s mass spectrum showed that most of the D 0 was converted i n t o DOH and H 0. Exchange of the proton of hydrogen c h l o r i d e with deuterium of the "heavy water" occurred v i a formation of a hydrated proton, (H-OD ) i n which the hydrogen and deuteriums are i n d i s t i n g u i s h a b l e . Decreasing the r a t i o of ethylene to cyclohexane from 1.14 to 0.73 r e s u l t e d i n an i n c r e a s e i n the y i e l d of monoethylcyclohexane (from 18 to 32%) and a marked decrease i n the y i e l d of higher molecular weight com­ pounds ( c f . Expts. 2 and 4). F u r t h e r decrease i n the r a t i o to 0.29 r e s u l t e d i n a smaller i n c r e a s e i n the y i e l d of monoethylcyclohexane (34%, Expt. 5). 2

2

2

Other M o d i f i e r s . No other substance seems to e x h i b i t the c h a i n - t r a n s f e r a c t i v i t y shown by hydrogen c h l o r i d e . Even hydrobromic a c i d was i n e f f e c t i v e .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

SCHMERLING

Monoethylation

with

Ethylene

153

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

Other reagents which d i d n o t i n h i b i t t e l o m e r i z a t i o n i n d u c e d by d i - t - b u t y l p e r o x i d e a t 1 3 0 - 1 4 0 ° i n c l u d e d hydriodic acid, acetic acid, trichloroacetic acid, t r i f l u o r o a c e t i c acid, phosphoric a c i d , s u l f u r i c acid, h y d r o g e n s u l f i d e , h y d r o g e n , and ammonium c h l o r i d e . The c h i e f c o n d e n s a t i o n p r o d u c t o b t a i n e d when any o f t h e s e reagents r e p l a c e d hydrogen c h l o r i d e o r h y d r o c h l o r i c a c i d were h i g h - m o l e c u l a r w e i g h t t e l o m e r s o f g r e a s y ( " V a s e l i n e - l i k e " ) o r waxy c o m p o s i t i o n . Other C y c l o a l k a n e s . Hydrogen c h l o r i d e promoted monoethylation o f o t h e r c y c l o p a r a f f i n s (e.g., c y c l o pentane, m e t h y l c y c l o p e n t a n e and m e t h y l c y c l o h e x a n e ) and many p a r a f f i n s ( e . g . , p r o p a n e , i s o b u t a n e , n - p e n t a n e , isopentane, 2,2-dimethylbutane, 2,3-dimethylbutane, η - h e p t a n e and 2 , 2 , 4 - t r i m e t h y l p e n t a n e ) . The r e a c t i o n o f m e t h y l c y c l o h e x a n e w i t h a n e q u i molar q u a n t i t y o f e t h y l e n e i n the presence o f d i - t b u t y l p e r o x i d e and h y d r o c h l o r i c a c i d r e s u l t e d i n e t h y l a t i o n b o t h a t t h e t e r t i a r y c a r b o n atom and a t s e c o n d a r y c a r b o n atoms ( E x p t . 7 ) . The m e t h y l e t h y l c y c l o hexane w h i c h was o b t a i n e d i n 13% y i e l d c o n s i s t e d (according t o i n f r a r e d ( i r ) comparison w i t h a u t h e n t i c samples) c h i e f l y o f 1 - m e t h y l - l - e t h y l c y c l o h e x a n e mixed w i t h s m a l l e r amounts o f 1 - m e t h y 1 - c i s - 3 - e t h y l c y c l o h e x a n e and 1 - m e t h y 1 - c i s - (and t r a n s - ) 4 - e t h y l c y c l o h e x a n e , a n d other isomers. The compounds p r o d u c e d by t h e r e a c t i o n o f 2 mois o f e t h y l e n e p e r mol o f c y c l o h e x a n e (7% y i e l d ) c o n s i s t e d o f a m i x t u r e o f m e t h y l b u t y l c y c l o h e x a n e s and methyldiethylcyclohexanes. P r o d u c t s f o r m e d by t h e r e a c t i o n o f c y c l o p e n t a n e w i t h 1, 2 o r 3 m o l e c u l a r p r o p o r t i o n s o f e t h y l e n e were the c h i e f products o f the r e a c t i o n o f approximately e q u i m o l a r amounts o f t h e c y c l o a l k a n e and t h e o l e f i n under t h e s t a n d a r d c o n d i t i o n s (Expt. 8 ) . 1 - M e t h y l - l - e t h y l c y c l o p e n t a n e mixed w i t h l e s s than 5% o f l - m e t h y l - c i s - 3 - e t h y l c y c l o p e n t a n e was o b t a i n e d i n 26% y i e l d by t h e e t h y l a t i o n o f m e t h y l c y c l o p e n t a n e ( E x p t . 9 ) . The p r e s e n c e o f m e t h y l d i e t h y l c y c l o p e n t a n e and m e t h y l b u t y l c y c l o p e n t a n e i n t h e h i g h e r m o l e c u l a r w e i g h t b y - p r o d u c t was s u g g e s t e d by g c c o u p l e d w i t h ms. L i q u i d Alkanes. The p e r o x i d e - i n d u c e d r e a c t i o n o f e t h y l e n e w i t h a molar excess o f n-pentane i n t h e p r e s e n c e o f h y d r o c h l o r i c a c i d p r o d u c e d h e p t a n e s i n 27% y i e l d t o g e t h e r w i t h o n l y a r e l a t i v e l y s m a l l amount o f h i g h e r - b o i l i n g p r o d u c t ( E x p t . 10, T a b l e I I ) . The c h i e f h e p t a n e was 3 - m e t h y l h e x a n e (3) w h i c h was o b t a i n e d i n more t h a n t h r e e t i m e s t h e q u a n t i t y o f 3 - e t h y l p e n t a n e (4).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

154

INDUSTRIAL AND

LABORATORY ALKYLATIONS

Table II Reaction of Liquid Alkanes with Ethylene

Expt.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

10

<-Reactants, mols-> RH mois Ç2H4 n-C H 5

12

11

i-C H

12

Me CEt

13

5

1 2

3

BIP

e

1.78

0.8

<—HCl > Kind mois 35%

0.3

< Kind

Chief Products

C H Higher mol wt

2 2

7

n-C H 7

0.8

38%

0.3

C H Higher mol wt

25 3

c

31

1.46

0.8

20%

0.4

Octanes Higher mol wt

6 3

d

6

1.3

18%

0.5

2,3,3-Me C5H 2,3,3-Me C H Higher mol wt

10 6 17S

7

1 6

3

1.58

0.6

100

0.1

r

9

7

13

C H Q 9

8 8

2

Higher mol wt 15

TMP

2 7

6

1.76

1.34

16

b

1 6

3

14

>

0.63

0.6

19

0.3

2,2,4,4-Me C H 2,2,4,4,5-Me C H J Higher mol wt 4

6

h

10

lc

5

7

u

1 2

8 2

(a) The cycloalkane solution of 0.04 mol d i - t - b u t y l peroxide and hydrochloric acid (or anhydrous hydrogen chloride) was heated at 130-140° during four hours i n a glass l i n e r i n an I p a t i e f f type rotating autoclave under ethylene pressure. (b) Includes 69% 3-methylhexane and 21% 3-ethylpentane (by gc+ ir> (c) Includes 86% 3,3-dimethylpentane

and 13%

2,3-dimethylpentane.

(d) Consists of 75% 2,2,3-trimethylpentane, 19% 2,2- and 6% dimethylhexane. (e) 2,3-Dimethylbutane

3,3-

(i.e., biisopropyl).

(f) Also about 2 g acetone and t-butyl alcohol and 3 g 1-chlorohexane. (g) Includes 1-chloroalkanes with even-numbers of carbon atoms and branched-chain p a r a f f i n s , most of which had the 2,3,3-trimethylalkane structure. (h) 75% 3-Methyloctane and small amounts of 3- and 4-ethylheptane. (i)

2,2,4-Trimethylpentane.

(j) Or 2,2,4,4-tetramethyloctane.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

SCHMERLING

Monoethylation

with

Ethylene

155

Based only on the presence of four hydrogen atoms attached to the second carbon atom from e i t h e r end of the c h a i n and the presence of two hydrogen atoms attached to the middle carbon atom, i t would be ex­ pected that there would be formed twice as much 3 as 4. c-c-c-c-c

I

c=c

c-c-c-c-c ι ά-c·

HC1 -CI . c-c-c-c-c

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

ό-c

c-c-c-c-c

4,c=c

c-c-c-c-c

o-c-

HClI-CIc-c-c-c-c

o-c

More than three times as much 3, as 4, was obtained because f r e e r a d i c a l s tend to a b s t r a c t a hydrogen atom attached to a penultimate carbon atom of an n-alkane more r e a d i l y than one attached to a more i n t e r n a l l y l o c a t e d carbon atom (see, f o r example, the r e s u l t s of the e t h y l a t i o n of n-heptane, Expt. 14). There are i n pentane twice as many penultimate carbon atoms as the i n t e r n a l l y l o c a t e d carbon atom; however, the more ready r e a c t i o n at the penultimate carbon atom i s confirmed by the products obtained with n-heptane. The r e a c t i o n of isopentane with ethylene under the same c o n d i t i o n s as those used f o r n-pentane r e s u l t e d i n about the same y i e l d of heptanes (31%) and a very small amount of h i g h e r - b o i l i n g product (Expt. 11). The heptanes c o n s i s t e d of more than 6.5 times as much 3,3dimethylpentane as 2,3-dimethylpentane. I t may be concluded that a b s t r a c t i o n of the s i n g l e hydrogen atom attached to the t e r t i a r y carbon atom takes p l a c e much more r e a d i l y than does a b s t r a c t i o n of one of the two hydrogen atoms attached to the secondary (penultimate) carbon atoms. A low y i e l d of octanes was formed when ethylene was heated with 2,2-dimethylbutane ( i . e . , neohexane) i n the presence of d i - t - b u t y l peroxide and 20% hydro­ c h l o r i c a c i d (Expt. 12). The low conversion was pro­ bably due to the d i f f i c u l t y i n a b s t r a c t i n g a hydrogen atom attached to a neopentyl carbon atom ( i . e . , a secondary carbon atom attached to the t e r t i a r y carbon atom of a t - b u t y l group). The p r i n c i p a l octane (about 75% of the octane product) was 2,2,3-trimethylpentane formed by e t h y l a t i o n at the secondary carbon atom; 2,2dimethylhexane formed by condensation at a primary carbon atom (the neohexyl carbon atom) was obtained i n

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

156

INDUSTRIAL AND LABORATORY

ALKYLATIONS

19% y i e l d while 3,3-dimethylhexane formed by r e a c t i o n at one of the three primary neopentyl ions was obtained i n only 6% y i e l d . On the other hand there was a f a i r amount of conversion when equimolar q u a n t i t i e s o f 2,3-dimethylbutane and ethylene were reacted (Expt. 13). 2,3,3Trimethylpentane was produced by e t h y l a t i o n a t a t e r t i a r y carbon atom and more h i g h l y end-chain e t h y l a t e d compounds (up t o 2,3,3-trimethylpentadecane) were formed by t e l o m e r i z a t i o n as were chloroalkane by­ products. As i n d i c a t e d i n the d i s c u s s i o n of the r e a c t i o n of n-pentane, e t h y l a t i o n of η-heptane took p l a c e c h i e f l y at a penultimate carbon atom, y i e l d i n g 3-methyloctane as the p r i n c i p a l product? only small amounts of 3- and 4-ethylheptane were produced (Expt. 14). Rather low y i e l d s o f e t h y l a t i o n products were obtained by r e a c t i o n of 2,2,4-trimethylpentane with ethylene. I t seems probable t h a t the a b s t r a c t i o n of hydrogen even from the t e r t i a r y carbon atom was d i f f i ­ c u l t because i t was a neohexyl carbon atom. I t was suggested by gc and ms a n a l y s i s that the major r e a c t i o n d i d occur a t the t e r t i a r y carbon atom, y i e l d i n g 2,2,4,4-tetramethylhexane (5,). I t was mixed with about 10% of i t s weight of what appears t o be e i t h e r 2,2,4,4,5-pentamethylheptane (6) formed by e t h y l a t i o n at the e x t e r n a l secondary carbon atom of £ or 2,2,4,4tetramethyloctane ( 7 ) formed by end-chain e t h y l a t i o n . C C-Î-C-Ç-C

ό

c

ç

ç

t

b

+

C=C

>

l\

E(

"

c

Ç C C - C - C - Ï - C - C

"

l

c

Ί

"

c

> c-i-c-o-c-c-c

c - c - c - c - c - c + c=c c

l

e

(15)

t

δ

c

(16)

i t

6

9

9

6

à

C-C-C-C-C-C.

+

C=C

HC] 2%R->

" c l

9

9

C-C-C-C-C-C-C-C

c o

7 Gaseous Alkanes. Normally gaseous alkanes cont a i n i n g a secondary or t e r t i a r y carbon atom could be monoethylated by the peroxide-induced r e a c t i o n with ethylene i n the presence of hydrogen c h l o r i d e (Table I I I ) . The y i e l d s were markedly increased by adding a normally l i q u i d saturated hydrocarbon as

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

(17)

9.

SCHMERLING

Monoethyhtion

with

Ethylene

157

Table I I I Reaction of Gaseous Alkanes with Ethylene

Expt.

<-Reactants, mois—> RH mois C9H4

16

C H

17

C H

3

19

20

8

3

18

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

a

i-C4H

g

b 8

<—HCl > Kind mois

< Chief Products > Kind _g _%

1.70

0.8

19%

0.3

Liquid product

1.70

0.8

18%

0.3

C H C7H16 Higher mol wt

3 5 2d 5 15

5

1 2

< 1 C

e

f

0.96

1.0

38%

0.4

Alkanes Alkenes A l k y l chlorides

10 25 5

1.72

0.8

19%

0.3

Me CEt Higher mol wt

5 7 39*

i-C4H J 1.72

0.8

19%

0.3

Me CEt Higher mol wt

9 13 28

i-C H 4

10

h 1 0

1Q

3

3

k

(a) The hydrocarbon reactant, hydrochloric acid, and 0.04 mol d i _t-butyl peroxide was heated at 130-140° during four hours i n a glass l i n e r i n an Ipatieff-type rotating autoclave under ethylene pressure. (b) Also 0.17 mol n-heptane. (c) 81% Isopentane (by gc). (d) Other than n-C-jE^. Gc suggests 75% 2,3-dimethylpentane and/or 2-methylhexane, 18% 3,3-dimethylpentane and 7% 3methylhexane. (e) Includes about 6 g nonanes (28% y i e l d based on n-heptane). (f) Gc showed the presence of 28.6 wt % 2,2-dimethylbutane, 4.9% 2-methylpentane, 14.9% 2,2-dimethylhexane, 5.5% other dimethyl hexanes, 12.0% decanes, 7.6% dodecanes and 4.9% tetradecanes. (g) Heated at 125-135° during 16 hours. (h) Also 0.37 mol cyclohexane. (i) Contains at least 0.08 mol (22% y i e l d ) ethylcyclohexane. (j) Also 0.51 mol

n-CjEi^.

(k) Other than n-CyH]^, about 0.25 mol of which was recovered.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

158

INDUSTRIAL AND LABORATORY ALKYLATIONS

s o l v e n t f o r t h e gaseous a l k a n e . F o r example, v e r y l i t t l e r e a c t i o n o c c u r r e d when p r o p a n e was h e a t e d a t 130-140° w i t h e t h y l e n e , d i - t - b u t y l p e r o x i d e , and hydro­ c h l o r i c a c i d (Expt. 1 4 ) . R e p e t i t i o n o f t h e r e a c t i o n u n d e r t h e same c o n d i t i o n s b u t i n t h e added p r e s e n c e o f n-heptane s o l v e n t r e s u l t e d i n a 5 mol-% y i e l d o f p e n t a n e ( c h i e f l y i s o p e n t a n e ) and a 5 m o l - % y i e l d o f b r a n c h e d - c h a i n h e p t a n e s ( c h i e f l y 2,3- and 3 , 3 - d i m e t h y l p e n t a n e s ( E x p t . 1 7 ) . A c o m p a r a t i v e l y l a r g e amount o f nonanes ( l a r g e l y 3 - m e t h y l o c t a n e together with smaller amounts o f 3- and 4 - e t h y l h e p t a n e ) were f o r m e d , s u g g e s t ­ i n g t h a t a b o u t 28 m o l - % o f t h e h e p t a n e s o l v e n t (used i n s m a l l e r amount) was m o n o e t h y l a t e d . The l o w y i e l d o f p e n t a n e by t h e r e a c t i o n o f p r o p a n e i n t h e a b s e n c e o f s o l v e n t was p r o b a b l y due t o t h e f a c t t h a t most o f t h e p r o p a n e was i n t h e v a p o r p h a s e w h e r e a s the e t h y l a t i o n r e a c t i o n proceeds p r i n c i p a l l y i n t h e l i q u i d phase. S i m i l a r l y , i n t h e a b s e n c e o f added l i q u i d s a t u r a t e d hydrocarbon s o l v e n t , e t h y l a t i o n o f i s o b u t a n e even i n the presence o f h y d r o c h l o r i c a c i d y i e l d e d a mixture o f 2,2-dime,thylbutane, 2 - m e t h y l p e n t a n e , 2,2- and o t h e r d i m e t h y l h e x a n e s , and u n c h a r a c t e r i z e d d e c a n e s , d o d e c a n e s and t e t r a d e c a n e s ( E x p t . 1 8 ) . The p a r a f f i n s , however, c o m p r i s e d o n l y 30 v o l - % o f t h e r e a c t i o n p r o d u c t w h i c h c o n t a i n e d 58 v o l - % l i q u i d o l e f i n s and 12 v o l - % a l k y l chlorides. A l k y l a t i o n o c c u r r e d i n b e t t e r y i e l d when t h e r e a c t i o n was c a r r i e d o u t i n t h e p r e s e n c e o f c y c l o ­ hexane s o l v e n t w h i c h c a u s e d more o f t h e r e a c t i o n t o o c c u r i n t h e l i q u i d phase (Expt. 1 9 ) . 2,2-Dimethylb u t a n e was o b t a i n e d i n a b o u t 7-mol % y i e l d and e t h y l ­ c y c l o h e x a n e i n a b o u t 22 m o l - % y i e l d ; a m i n o r amount o f 2 - m e t h y l p e n t a n e was f o r m e d b y c o n d e n s a t i o n a s a p r i m a r y c a r b o n atom. Use o f n - h e p t a n e a s s o l v e n t r e s u l t e d i n a 13 m o l - % y i e l d o f 2 , 2 - d i m e t h y l b u t a n e (Expt. 2 0 ) . Higher-molecular weight product c o n s i s t e d l a r g e l y o f a l k a n e s h a v i n g an e v e n number o f c a r b o n atoms. The s e c o n d a r y c a r b o n atoms i n h e p t a n e were a p p a r e n t l y l e s s r e a d i l y e t h y l a t e d t h a n t h e t e r t i a r y h y d r o g e n atom i n isobutane. A l k y l C h l o r i d e s . H y d r o c h l o r i c a c i d a l s o promoted the peroxide-induced monoethylation o f c h l o r o a l k a n e s . R e s u l t s w i t h η-butyl c h l o r i d e , i s o b u t y l c h l o r i d e and i s o p e n t y l c h l o r i d e a r e d e s c r i b e d b r i e f l y i n t h i s paper. V e r y l i t t l e r e a c t i o n o c c u r r e d when n - b u t y l c h l o r i d e w a s h e a t e d a t 130-140° w i t h e t h y l e n e i n t h e p r e s e n c e o f d i - t - b u t y l p e r o x i d e ( E x p t . 21, T a b l e I V ) . On t h e o t h e r hand, a f a i r y i e l d o f r e a c t i o n p r o d u c t s was o b t a i n e d when t h e e x p e r i m e n t was r e p e a t e d i n t h e

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

SCHMERLING

Monoethylation

with

Ethylene

159

Table IV Reaction of A l k y l Chlorides with Ethylene

Expt. 21 22

a

<-Reactants, mols-> RC1 mois Ç2J4 n-BuCl n-BuCl

0.79 0.79

0.8 0.6

<—HCl > Kind mois

< Chief Kind

None 38%

L i t t l e reaction EtCKMeCH CH Cl PrCHClEt n-C H Cl

0.0 0.2

Products— g

2

6

C

H

7 4 1 6 1

10 6 4 14

5 1 1 0.5 0.2

8 2 4 1 5

2

13

C 1 ? S

8 11 Miscellaneous 23

i-BuCl

0.50

0.6

19%

0.2

EtCMe CH Cl PrCHMeCH Cl n-HexCl i-PrCHClEt BuCMe2CH Cl 2

2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

2

2

24 25

i-PenCl 0.31 i-PenCl 0.49

0.6 0.6

None 19%

0.0 0.2

> %

b

Telomer 12 12 EtCMe CH CH Cl i-BuCClEt n-HexCl } 2 2

2

2

CgHxgCl's

(a) The a l k y l chloride containing 0.04 mol dissolved d i - t - b u t y l peroxide was heated at 130-140° with the hydrochloric acid during four hours i n a glass l i n e r i n an Ipatieff-type rotating autoclave under ethylene pressure. (b) Boiled c h i e f l y from 200° to above 400°.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

18

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

160

INDUSTRIAL AND LABORATORY

ALKYLATIONS

added presence of concentrated h y d r o c h l o r i c a c i d (Expt. 22). The major product was l-chloro-3-methylpentane which was formed by e t h y l a t i o n a t the penultimate carbon atom of the b u t y l c h l o r i d e v i a a b s t r a c t i o n of the hydrogen atom attached to the penultimate carbon atom c h i e f l y by the c h l o r i n e atom formed from the hydrogen c h l o r i d e . Product which was formed i n about one-half the amount of t h i s chlorohexane was an isomer, 3-chlorohexane, formation of which i n v o l v e d a l k y l a t i o n at the carbon atom h o l d i n g the c h l o r i n e atom. The presence of a very minor q u a n t i t y of 1-chlorohexane was a l s o noted. This was formed e i t h e r by a l k y l a t i o n a t the methyl carbon atom or by t e l o m e r i z a t i o n o f ethylene and hydrogen c h l o r i d e . More i s o m e r i c o c t y l c h l o r i d e s than hexyl c h l o r i d e s were formed by a t e l o m e r i z a t i o n r e a c t i o n i n v o l v i n g a second molecule of ethylene. Nuclear magnetic r e s o nance (nmr) suggested that the product was a mixture of about equal weight o f primary and secondary c h l o r i d e s . Since many o c t y l c h l o r i d e isomers e x i s t , no c o n c l u s i o n was reached as t o the probable s t r u c t u r e s . I t may be concluded that e t h y l a t i o n of n - b u t y l c h l o r i d e occurs most r e a d i l y a t the penultimate carbon atom and next most r e a d i l y a t the carbon atom h o l d i n g the c h l o r i n e atom. I t probably a l s o occurs a t the other primary carbon atom. The peroxide-induced e t h y l a t i o n of i s o b u t y l c h l o r i d e i n the presence of 19% h y d r o c h l o r i c a c i d i n v o l v e d monoethylation a t a l l of the carbon atoms i n the molecule (Expt. 23). As might be expected, the c h i e f product was l-chloro-2,2-dimethylbutane, produced v i a a b s t r a c t i o n of the hydrogen atom attached t o the t e r t i a r y carbon atom. A l s o formed were l - c h l o r o - 2 methylpentane ( e t h y l a t i o n a t a methyl group) and 3chloro-2-methylpentane ( e t h y l a t i o n a t the carbon atom h o l d i n g the c h l o r i n e atom). Some 1-chlorohexane was a l s o obtained; i n t h i s case, i t s formation was undoubtedly due t o t e l o m e r i z a t i o n of the ethylene with hydrogen c h l o r i d e r a t h e r than by a r e a c t i o n i n v o l v i n g the i s o b u t y l c h l o r i d e . The presence of small amounts (a) of l - c h l o r o - 2 , 2 dimethylhexane (9) formed by f u r t h e r r e a c t i o n with ethylene of the r a d i c a l (8) r e s p o n s i b l e f o r the format i o n of the major product^(l-chloro-2,2-dimethylbutane) and (b) of 3-chloro-2-methylheptane (11) by f u r t h e r r e a c t i o n with ethylene of the r a d i c a l (10) r e s p o n s i b l e f o r the p r o d u c t i o n of 3-chloro-2-methylpentane was a l s o observed.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

SCHMERLING

Monoethylation

with

Cl-C-C-C - | k - > C1-C-Ç-C - ^ 2 u i > t

~

H

C

ci-C-Ç-C-C.

c

1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

C

2

> Cl-C-C-C-C + C L b c > ci-c-ï-c-c-c-ct

H 4

H

ίο—I 2

*

»

Cl-C-C-C — £ ^ f - > b ~ HCl

C

(18)

c

ç HCl

161

Ethylene

H

4

C

1

Cl-C-C-C b

C

(19)

H

ç ^ j - > Cl-C-C-C-C-C-C " " ά 9 Cl ^ > -C-C-ά—C-C c 10 c

2

H

4

Cl -> C-C-O—C-C + C l b > .c-c-c-c-ά—c-c

(20)

l

(21)

(22) H

ό

£j-

"

c-c-c-c-ά—c-i

'

2 3 )

b 11 The p r o d u c t f o r m e d i n l a r g e s t amount by t h e h y d r o ­ c h l o r i c a c i d - p r o m o t e d and p e r o x i d e - i n d u c e d r e a c t i o n o f i s o p e n t y l c h l o r i d e w i t h e t h y l e n e was a l s o t h a t f o r m e d by a l k y l a t i o n a t t h e t e r t i a r y c a r b o n atom, namely 1c h l o r o - 3 , 3 - d i m e t h y l p e n t a n e (12,) ( E x p t . 2 5 ) . The remain­ i n g c o n s t i t u e n t s o f t h e r e a c t i o n p r o d u c t were a l l o b t a i n e d i n v e r y m i n o r amount a n d were a l l a l k y l chlorides. Among t h e s e were 4 - c h l o r o - 2 - m e t h y l h e x a n e ( 1 ^ ) , 1 - c h l o r o h e x a n e (formed by t e l o m e r i z a t i o n ) and some c h l o r o n o n a n e s i n c l u d i n g 5 - c h l o r o - 3 , 3 - d i m e t h y l h e p t a n e (16) f o r m e d by e t h y l a t i o n o f 12, 4 - c h l o r o - 2 m e t h y l o c t a n e (15) and l - c h l o r o - 3 - m e t h y l o c t a n e (17,) .

C1C-C-C-C b

C

1

"

> Cl-C-C-C-C b

0

2

H

4

c 1

> C1C-C-C-C-Cb

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

162

INDUSTRIAL AND LABORATORY ALKYLATIONS

HCl n

— >

l

C1C-C-C-C-C

-ci-

t

cic-c-c-c-c-

12

C2H4

C1C-C-C-Ç-C-C-C-C-

>

c HCl

-Cl-

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

Cl-C-C-^-C-C-C-C c

(24)

13. Also,

Cl-

ClG-C-C-C

-> c i c - c - c - c t

cic-c-c-c

ά

°

2

H

4

> - c - c - c — c - c - c —^=->

C-C-C—C-C-C

" "

ά

c

c l

14

A A ^

C 2 H

Cl > · C-C-C-C-ï—C-Ç-C c

4

-HCl -Cl-

>

C-C-C-C-ÎUc-Ç-C (25) 15

C 1

* -HCl

12

Ç -> Cl-C-C-C-C-C

C

Cl ç > C-C-t—C-C-C-C

ffi -HCl

(26)

16 > C1-C-C-Ç-C-

-^2M_>

C l - C - C - C-c-c-c-C

à

c

Β

C

2

H

4

> ci-c-c-c-c-c-c-c-c-

ά

^k->

"

Cl-C-C-C-C-C-C-C-C b

c l e

17

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

(27)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

9.

SCHMERLING

Monoethylation

with

Ethylene

163

Under t h e same c o n d i t i o n s b u t i n t h e a b s e n c e o f h y d r o c h l o r i c a c i d , t e l o m e r i z a t i o n o c c u r r e d (Expt. 24). A t r a c e amount o f m o n o e t h y l a t i o n p r o d u c t may have b e e n produced, b u t t h e r e a c t i o n p r o d u c t b o i l e d c h i e f l y from a b o u t 200° t o h i g h e r t h a n 4 0 0 ° . I t may be c o n c l u d e d t h a t p r i m a r y a l k y l c h l o r i d e s undergo p e r o x i d e - i n d u c e d , hydrogen chloride-promoted, a l k y l a t i o n w i t h e t h y l e n e t o y i e l d p r o d u c t s f o r m e d by a l k y l a t i o n a t a t e r t i a r y c a r b o n atom, a t a p e n u l t i m a t e s e c o n d a r y c a r b o n atom, o r a t a p r i m a r y c a r b o n atom h o l d i n g a c h l o r i n e atom. In t h e absence o f hydro­ c h l o r i c a c i d , η-butyl c h l o r i d e underwent l i t t l e peroxide-induced r e a c t i o n w i t h ethylene presumably because hydrogen c h l o r i d e i s necessary f o r p r o p a g a t i n g the r e a c t i o n c h a i n v i a a b s t r a c t i o n o f hydrogen from t h e hydrogen c h l o r i d e t o p r o d u c e t h e e t h y l a t e d p r o d u c t and a c h l o r i n e atom w h i c h m a i n t a i n s t h e c h a i n by a b s t r a c ­ t i o n from t h e a l k y l c h l o r i d e . Ethers. Low y i e l d s o f s e v e r a l compounds were o b t a i n e d when e t h y l e t h e r was h e a t e d a t 1 3 0 - 1 4 0 ° u n d e r ethylene pressure i n the presence o f d i - t - b u t y l p e r o x i d e and h y d r o c h l o r i c a c i d ( E x p t . 26, T a b l e V ) . E t h y l a t i o n took p l a c e i n t h e normal f a s h i o n t o y i e l d e t h y l s e c - b u t y l e t h e r by m o n o e t h y l a t i o n t o g e t h e r w i t h a t l e a s t t h r e e e t h e r s h a v i n g e i g h t c a r b o n atoms; d i s e c - b u t y l ether, ( e t h y l a t i o n a t both secondary carbon atoms o f t h e e t h y l e t h e r ) , e t h y l 1 - m e t h y l - l - e t h y l p r o p y l e t h e r ( e t h y l a t i o n a t t h e t e r t i a r y c a r b o n atom o f t h e p r i m a r y p r o d u c t ) and e t h y l - l - m e t h y l p e n t y l e t h e r f o r m e d by t e l o m e r i z a t i o n o f t h e p r i m a r y r a d i c a l w i t h two molecules of e t h y l e n e ) . Some C i o e t h e r s were a l s o formed. η - B u t y l c h l o r i d e was p r o d u c e d i n a b o u t t h e same amount a s e t h y l s e c - b u t y l e t h e r . I t s formation pre­ sumably i n v o l v e d t e l o m e r i z a t i o n o f e t h y l e n e w i t h hydrogen c h l o r i d e . E t h y l a t i o n o f t e t r a h v d r o f u r a n t o o k p l a c e i n good y i e l d u n d e r t h e s t a n d a r d c o n d i t i o n s ( E x p t . 1 7 ) . The p r i n c i p a l p r o d u c t was 2 - e t h y l t e t r a h y d r o f u r a n m i x e d w i t h a s m a l l e r amount o f 3 - e t h y l t e t r a h y d r o f u r a n . Diethylt e t r a h y d r o f u r a n s and b u t y l t e t r a h y d r o f u r a n s were a l s o f o r m e d a s was much h i g h - b o i l i n g p r o d u c t .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

164

INDUSTRIAL AND LABORATORY ALKYLATIONS

Table V Reaction of Ethers with Ethylene

Expt. 26

a

<-Reactants, mols-> Ether mois Ç 2 H 4 Et 0 2

1.49

1.0

<—HCl > Kind mois 38

0.2

< Chief ProductsKind g EtOBu-s n-BuCl C8Hl60 Miscellaneous

4 4 5 1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

b

27

THF

28

p-D

29

p-D*

0

f

1.97

1.0

38

1.05

1.3

None

0.92

1.3

19

0.2

22 25

22

p-D EtDioxane Telomere

82 8 46

89 7

2-EtDioxane (C1CH CH2)20 C1C H 0C H40H

3 13 3

3 10 3

2-EtDioxane (C1CH CH ) 0 C1C H 0C H 0H

8 20 3

11 18 3

e

EtC4Hy0 Higher-boiling f

0.2

2

p-D

4 9 8

d

2

30

>

%

f

0.78

0.6

38

1.2

4

2

2

2

4

2

2

2

2

4

(a) The ether, hydrochloric acid (when used) and 0.04 mol d i - t butyl peroxide were heated at 130-140°C i n a glass l i n e r i n an Ipatieff-type rotating autoclave under ethylene pressure (b) Includes Et-0-C(Me)Et2,

Et-0-CH(Me)Bu, and (s-Bu) 0. 2

(c) Includes CJ^Q ethers and n-CgH-j^Cl and 11-C3H-QCI. (d) Tetrahydrofuran. (e) Mixture of 2- and 3-ethyltetrahydrofuran. (f) p-Dioxane. (g) Product of higher molecular weight than the ethyldioxane. Most (44 g ) boiled above 195° and was a very viscous yellow o i l at room temperature.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

9.

SCHMERLING

Monoethylation

with

C H |/HC1 2

4

165

Ethylene

C2H4 /HCl

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

(28)

2-Ethyldioxane (18) was a product of the r e a c t i o n of p-dioxane with ethylene i n the presence of hydroc h l o r i c a c i d and d i - t - b u t y l peroxide a t 130-140°C (Expts. 29 and 30). However, the major product was b i s - ( 2 - c h l o r o e t h y l ) ether (20,) and a smaller amount of 2 - c h l o r o e t h y l 2-hydroxyethyl ether (19). These were formed by h y d r o l y s i s of the p-dioxane by r e a c t i o n with the hydrogen c h l o r i d e .

û

Cl-HCl

C2H4 /HCl

c

C-C

y (29)

(C1-C-C) 0 2

(30)

20 More h y d r o l y s i s occurred i n the presence of a l a r g e r p r o p o r t i o n of more concentrated h y d r o c h l o r i c a c i d ( c f . Expts. 29 and 30). In the absence o f h y d r o c h l o r i c a c i d , t e l o m e r i z a t i o n occurred, y i e l d i n g very high molecular weight t e l o mer (Expt. 28). Hanford and Roland (3) found that the benzyl peroxide-induced r e a c t i o n of dioxane with e t h y l ene a t 80°C r e s u l t e d i n products formed by r e a c t i o n of 54 mois of ethylene per mol of p-dioxane. In Expt. 28 using d i - t - b u t y l peroxide a t 13ÏÏ-140 14 mois of e t h y l 0

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL AND LABORATORY ALKYLATIONS

166

ene was consumed f o r e a c h m o l o f p - d i o x a n e w h i c h was not recovered. A f t e r d i s t i l l i n g o f f the unreacted dioxane, t h e r e remained a r e a c t i o n p r o d u c t c o n t a i n i n g some e t h y l d i o x a n e (7 m o l % y i e l d ) , t h e r e m a i n d e r c o n ­ s i s t i n g o f p r o d u c t , o v e r 95 wt % o f w h i c h was a v e r y v i s c o u s o i l b o i l i n g above 1 9 5 ° . I t may be c o n c l u d e d t h a t h y d r o c h l o r i c a c i d promotes t h e p e r o x i d e - i n d u c e d m o n o e t h y l a t i o n o f pdioxane. However, t h i s s e l e c t i v e a l k y l a t i o n r e a c t i o n i s a c c o m p a n i e d by h y d r o l y s i s o f t h e d i o x a n e .

Literature Cited 1. Schmerling, Louis, U.S. Patent 2,769,849 6, 1956, o r i g i n a l l y f i l e d May 31, 1946). 2. Hanford, W. E., and Harmon, J., U.S. Patent 2,418,832 (April 15, 1947, f i l e d June 17, 1942). 3. Hanford, W. Ε., and Roland, J. R., U.S. Patent 2,402,137 (June 18, 1946, f i l e d January 1, 1943). It is interesting to note that the word "telomer" seems to have been introduced in this patent.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch009

(Nov.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

10 C o u p l i n g of

Alkyl

G r o u p s U s i n g Transition

M e t a l Catalysts

JAY K. KOCHI

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

Department of Chemistry, Indiana University, Bloomington, IN 47401

The formation of carbon-carbon bonds is one of the most important operations in organic synthesis, and it can be repre­ sented by the coupling of organometallic reagents (including alkyllithium and Grignard reagents) with organic derivatives, such as alkyl halides among others. M

1

RMgX + R'-X t l » R-R + MgX

2

[l]

The organic moieties, R and R' in Equation 1, can either be saturated alkyl, aryl, vinyl or acetylenic groups leading to a wide variety of hydrocarbon structures. The most effective catalysts represented in Equation 1 as [M] are derived from transition metal complexes. The role of the metal catalysts is varied in these reac­ tions, but they are most commonly involved in the formation of organometallic intermediates RM which subsequently reductively eliminate to the coupled product. Reactions leading to the forma­ tion of the key intermediate R-M and the elucidation of the path­ ways for its decomposition are thus central to the understanding of these catalytic processes. We will first summarize briefly the processes involved in the formation and destruction of RM, which will be followed by our studies of various catalytic systems leading to the coupling of alkyl groups. Formation of Alkylmetal Complexes Organometals R-M are commonly prepared by metathesis of a transition metal complex with substitution-labile carbanio­ noid reagents such as Grignard and lithium derivatives. CHi

CHî

Œ

ID:

CH3-Au -PPh + C D L i 3

CH -Au -PPh3 + L i l

3

3

I

CD, 167

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL AND LABORATORY ALKYLATIONS

168

The f o r m a l oxidation state of the m e t a l under these c i r c u m stances does not change. S i m i l a r l y , no change in the f o r m a l oxidation state of the metal results f r o m the insertion of an olefin into a ligand-metal bond.

L Pt*

+ CH =CH

2

N

2

2

—> L Pt^ C1

[3](2)

2

X

C1

On the other hand, when either a l k y l r a d i c a l s or a l k y l c a r b o n i u m ions (or their p r e c u r s o r s ) are used as alkylating agents, the metal center undergoes a change i n the f o r m a l oxidation state of either one or two, respectively. CH . Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

3

+cAn

+ 2

n

- CH -Cr en

2

3

CH CDjI + ( C H ) A u L i 3

2

P

P

h

+ 2

[4](3)

2

3

Œ

CD -Au -PPh

3 »

3

CH

3

+ Lil

[5](4)

3

A l k y l a t i o n s of metal centers under these c i r c u m s t a n c e s a r e considered as oxidative additions. Decomposition

of A l k y l m e t a l Complexes

T h e r e a r e a number of modes by which carbon-metal bonds can be cleaved. Conceptually, they can be represented by the m i c r o s c o p i c r e v e r s e of each of the p r o c e s s e s in Equations 2-5 which lead to the alkylation of the m e t a l center. Thus, the r e v e r s e of Equation 2 i s represented by the well-known e l e c t r o philic cleavage of organometals.(5) (CHa^Au^PPha+HOAc — ( C H ^ A u ^ O A c J P P l ^ + C H - H 3

[6]

S i m i l a r l y , β-elimination of hydrogen i s probably the most common route by which a l k y l m e t a l s decompose. CH CH CH CH L P< * CH CH CH CH 2

2

2

3

2

2

2

3

CH

2

— CHCH CH 2

3

+

2

[7](6)

L Pt^

etc.

2

CH CH CH CH 2

2

2

3

The homolytic cleavage of a l k y l m e t a l bonds, p a r t i c u l a r l y those of M a i n Group metals, i s known f r o m Paneth s c l a s s i c experiments to occur at high temperatures. T h e r e v e r s e of Equation 4, however, does not u s u a l l y represent the energeti!

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

10.

KOCHi

169

Transition Metal Catalysts

c a l l y m o s t f a v o r e d p a t h w a y i n the d e c o m p o s i t i o n of R - M . Alkyl c o u p l i n g as a r e s u l t of h o m o l y s i s to f r e e r a d i c a l s , f o l l o w e d b y dimerization R-M

[ M - + R-] — *

R-R,

etc.

[8]

i s not u b i q u i t o u s , a l t h o u g h s u c h v i e w s w e r e w i d e l y h e l d due to the m i s g u i d e d b e l i e f that c a r b o n - m e t a l bonds, p a r t i c u l a r l y those involving transition metals, are extremely weak. If a l k y l r a d i ­ c a l s a r e i n t e r m e d i a t e s i n the c a t a l y z e d c o u p l i n g of a l k y l g r o u p s , t h e y s h o u l d u n d e r g o d i s p r o p o r t i o n a t i o n i n a d d i t i o n to d i m e r i z a ­ tion. CH 2

2

=C H

3

+ CH3CH3

[9a]

2

CH CH CH CH 3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

2

CH CH 2

2

[9b]

3

E i t h e r b i m o l e c u l a r p r o c e s s i s not p o s s i b l e w i t h o u t the other, s i n c e the r a t i o of the r a t e c o n s t a n t s i s f i x e d b y the s t r u c ­ t u r e of the r a d i c a l . ( 7 ) H o w e v e r , a n u m b e r of m e t a l - c a t a l y z e d c o u p l i n g s a r e k n o w n to p r o c e e d w i t h o u t the f o r m a t i o n of a n y d i s ­ p r o p o r t i o n a t i o n p r o d u c t s , c e r t a i n l y i n the a m o u n t s d i c t a t e d by the v a l u e s of 1 ^ / F u r t h e r , the c o u p l i n g r e p r e s e n t e d i n E q u a ­ tion 1 c a n o c c u r without the s c r a m b l i n g of R and R , as w o u l d be e x p e c t e d of f r e e r a d i c a l intermediates.(8) T h e m i c r o s c o p i c r e v e r s e of o x i d a t i v e a d d i t i o n i n E q u a t i o n 5 is r e p r e s e n t e d by r e d u c t i v e e l i m i n a t i o n w h i c h c a n be i n t e r m o l e c u l a r ( E q u a t i o n 10) o r i n t r a m o l e c u l a r ( E q u a t i o n 11). 1

dmgCo^CHa (CH ) Au 3

3

1 I

+ Br"

—>

dmgCo

PPh3

—>

CH AuPPh 3

1

+ CH Br

[10](9)

3

3

+ CH CH 3

3

[H](10.)

I n d e e d , the c o m b i n a t i o n of o x i d a t i v e a d d i t i o n i n E q u a t i o n 5 a n d r e d u c t i v e e l i m i n a t i o n i n E q u a t i o n 11 i s t h e b a s i s f o r a c a t a l y t i c m e c h a n i s m for alkyl coupling. Alkyl Transfers from Organometallic in Catalytic P r o c e s s e s

Intermediates

T h e o x i d a t i o n - r e d u c t i o n r e a c t i o n s of o r g a n o m e t a l l i c i n t e r ­ m e d i a t e s p r e s e n t e d i n the f o r e g o i n g d e s c r i p t i o n c a n be a p p l i e d , i n c o m b i n a t i o n , to a v a r i e t y of c a t a l y t i c p r o c e s s e s , s u c h as the m e t a l - c a t a l y z e d a l k y l t r a n s f e r r e a c t i o n s of G r i g n a r d r e a g e n t s originally investigated by K h a r a s c h and c o w o r k e r s . ( l 1 ) W e have found that the c a t a l y t i c r e a c t i o n s b e t w e e n l a b i l e o r g a n o m e t a l s and a l k y l h a l i d e s can be g e n e r a l l y c l a s s i f i e d into two c a t e g o r i e s , c o u p l i n g i n E q u a t i o n 12 a n d d i s p r o p o r t i o n a t i o n i n E q u a t i o n 1 3 ,

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

170

INDUSTRIAL AND LABORATORY ALKYLATIONS

depending on the catalyst. F o r example, silver(l) and a r e e f f e c t i v e c a t a l y s t s i n t h e c o u p l i n g of a l k y l g r o u p s ,

R-m

+ R-X

r—*

R-R

( V_>-

RH + R(-H) + m X

copper(l) whereas

+ m X

[12] [13]

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

i r o n effects only disproportionation except when a r y l and vinylic halides are employed. E a c h catalyst shows unique features w h i c h a r e best d e s c r i b e d within the f o l l o w i n g m e c h a n i s t i c context. A. N i c k e l C a t a l y s i s i n the C r o s s C o u p l i n g of A r y l H a l i d e s w i t h A l k y l m e t a l s. T h e R o l e of A r y l a l k y l n i c k e l ( I I ) S p e c i e s a s Intermediates. F o r the s t u d y of n i c k e l c a t a l y s i s i n the f o r m a t i o n of a r a l k a n e s , w e e m p l o y e d the s y s t e m c o n s i s t i n g of a r y l b r o ­ m i d e s and m e t h y l l i t h i u m or m e t h y l m a g n e s i u m b r o m i d e . A r - B r

+ C H

3

- m

(

E t

3P) NiBr 2

2 >

A

_

r

C

H

j

+

m

_

B

r

[

where m = L i or

M

]

M g X

A l t h o u g h the t r i e t h y l p h o s p h i n e c o m p l e x e s of n i c k e l ( l l ) m a y not n e c e s s a r i l y r e p r e s e n t o p t i m u m e x a m p l e s of c a t a l y s t s , ( 1 2 ) ( l 3 ) t h e y a l l o w e d u s a c c e s s t o t h e k e y i n t e r m e d i a t e , v i z . , tn~e a r y l m e t h y l - n i c k e l c o m p l e x e s s u c h as l a and b. A n y catalytic cycle PEt

JCH PEt

3

3


((JS

la

3

3

Ni-CH PEt

3

lb

3

3

w h i c h i s d e v e l o p e d a r o u n d this i n t e r m e d i a t e m u s t d e p e n d on the a v a i l a b i l i t y of p a t h w a y s f o r i t s r a p i d f o r m a t i o n a n d f a c i l e d e c o m ­ position.(14) The most straightforward formulation simply c o n s i s t s ôT"a s e q u e n c e o f s t e p s i n v o l v i n g ( a ) r e d u c t i v e e l i m i n a ­ t i o n f o l l o w e d b y (b) o x i d a t i v e a d d i t i o n a n d (c) m e t a t h e s i s as shown in Scheme 1 (L = triethylphosphine). Scheme 1

. J\r L Ni<ç

τ

A r X

L N i C ^ •λ 2

Indeed,

a

Λ Τ

2

r

H

+ L Ni

, » fast

+ CH m

— — • fast

2

each

3

b

_ A r C H

A

τ

L

2

, . + L Ni

τ

τ

3

τ

Γ ι

2

N < £ -Χ-

X m

step in this catalytic

l

[16]

r

+ L

c

[15]

2

N < ^

etc.

c y c l e c a n be

[17]

documented

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

10.

KocHi

Transition Metal Catalysts

171

separately. W e h a v e s h o w n that r e d u c t i v e e l i m i n a t i o n i n s t e p (a) proceeds to a nickel(O) species w h i c h c a n undergo r a p i d oxidative a d d i t i o n i n s t e p (b) a s d o e s t h e m e t a t h e s i s i n s t e p ( c ) . S i m i l a r observations have been m a d e qualitatively b y P a r shall and o t h e r s . ( l 5 ) ( l 6) T h e r e a r e , h o w e v e r , t w o s e r i o u s p o i n t s t o b e raised on this s i m p l e m e c h a n i s m . M o s t i m p o r t a n t l y , w e find that t h e r a t e o f r e d u c t i v e e l i m i n a t i o n i n s t e p (a) i s t o o s l o w t o allow for a catalytic process. Secondly, a r y l - m e t h y l - b i s ( t r i ethylphosphine)nickel(ll) c o m p l e x e s l a a n db exist e x c l u s i v e l y i n the t r a n s c o n f i g u r a t i o n . O x i d a t i v e a~ddition~to n i c k e l ( O ) s p e c i e s i n s t e p (b) a l s o a f f o r d s o n l y t h e t r a n s a d d u c t s . Our demonstra­ tion of the i n t r a m o l e c u l a r r o u t e f o r r e d u c t i v e e l i m i n a t i o n of l a and b d e m a n d s that i t p r o c e e d i n a c o n c e r t e d f a s h i o n v i a a transition state i n which the a r y l and m e t h y l groups a r e juxta­ posed. Thus, a cis square planar or tetrahedral geometry for r e d u c t i v e e l i m i n a t i o n w o u l d b e s i m i l a r to that p r e v i o u s l y s h o w n for the somewhat analogous e x a m p l e of the t r i a l k y l g o l d ( l l l ) c o m ­ p l e x e s i n E q u a t i o n 18.(17) S i n c e w e c o u l d find n o e v i d e n c e of t h e i s o m e r i z a t i o n of the trans to either a c i s i s o m e r o r a t e t r a h e d r a l CH R-Au

3

I I L

CH

PPh3 — • R - C H

3

+ CH AuPPh 3

[18]

3

3

s p e c i e s even at 8 0 ° , w e t e n t a t i v e l y c o n c l u d e that r e d u c t i v e e l i m i ­ nation of l a a n db does not p r o c e e d v i athese stereoisomeric forms. I n s u c h a n event, r e d u c t i v e e l i m i n a t i o n c a n p r o c e e d d i r e c t l y f r o m the trans c o m p l e x v i aa t e t r a h e d r a l - l i k e t r a n s i t i o n state. O n t h e o t h e r h a n d , r e t a r d a t i o n of r e d u c t i v e e l i m i n a t i o n b y a d d e d t r i e t h y l p h o s p h i n e s u g g e s t s that i t p r o c e e d s b y a d i s s o c i a ­ tive m e c h a n i s m , since no five-coordinate species c a nbed e ­ tected i n the P N M R spectrum(18) i n sufficient concentrations t o account quantitatively f o r t h e Tate r e d u c t i o n . 3

1

(Et P) Ni<J* 3

2

^

Et P + Et PNi<£^ 3

3

etc.

[19]

T h e t h r e e - c o o r d i n a t e i n t e r m e d i a t e i n E q u a t i o n 19 w o u l d t h e n a l l o w f o r greater m o b i l i t y of the groups f r o m w h i c h r e d u c t i v e elimination could proceed.(19) Rearrangement followed by a very rapid reductive elimination of the cis isomer is also a possibil­ ity. H o w e v e r , o u r u n s u c c e s s f u l attempts to synthesize c i s - a r y l m e t h y l - n i c k e l ( l l ) c o m p l e x e s s t i l l l e a v e o p e n t h e q u e s t i o n of reductive elimination from such stereoisomers. The results we obtained i n studies w i t h the bidentate d i p h o s p h i n e l i g a n d (dppe), though qualitatively i n this d i r e c t i o n , unfortunately lack définitiveness as yet. T h e f o r e g o i n g d i s c u s s i o n i n d i c a t e s that other c o n s i d e r a ­ tions m u s t be i n v o k e d i n o r d e r to a l l o w f o r the f a c i l e e x p u l s i o n of -

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

172

INDUSTRIAL AND LABORATORY ALKYLATIONS

a r y l and m e t h y l g r o u p s f r o m l a and b n e c e s s a r y for a c a t a l y t i c cycle. I n d e e d , the o b s e r v a t i o n t h a t ~ ô x y g e n i n d u c e s the r a p i d r e d u c t i v e e l i m i n a t i o n of l a a n d b p r o v i d e s t h e k e y to t h i s u n d e r standing. In o r d e r to d e v e l o p trlis t h e s i s , w e p r e s e n t f i r s t t h e a u t o x i d a t i o n of o r g a n o m e t a l s w i t h i n t h e g e n e r a l c o n t e x t of e l e c tron transfer processes. T h e r a p i d r e a c t i o n of a v a r i e t y of o r g a n o m e t a l l i c c o m plexes with m o l e c u l a r oxygen proceeds f r o m a p r i o r electron t r a n s f e r s t e p s u c h a s E q u a t i o n 20,

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

0

+ [R-M] — • 0 ~

2

2

+ [R-Mji"

,

etc.

[20]

in w h i c h oxygen a c t s as a n e l e c t r o n a c c e p t o r . This process is i m p o r t a n t i n d e p e n d e n t l y of w h e t h e r the s u b s e q u e n t s t e p s i n autoxidation i n v o l v e a s t o i c h i o m e t r i c or r a d i c a l c h a i n process^20) S i m i l a r l y , o r g a n i c h a l i d e s s u c h as a r y l b r o m i d e s a r e a l s o known to b e a c c e p t o r s i n e l e c t r o n t r a n s f e r p r o c e s s e s . ( 8 ) ( 2 1 ) Furtherm o r e , organometals being generally electron-rich"species are c a p a b l e of a c t i n g as d o n o r s i n a n u m b e r of e l e c t r o n t r a n s f e r r e a c t i o n s . ( 2 2 ) T h e e n h a n c e d l a b i l i t y of the r e s u l t a n t c a t i o n r a d i c a l t o w a r d r e d u c t i v e e l i m i n a t i o n has been d i s c u s s e d r e c e n t l y w i t h r e g a r d to s o m e m a i n g r o u p a s w e l l a s t r a n s i t i o n m e t a l organic complexes.(23) A s structurally"clifierent as they a r e , nonetheless oxygen a n d a r y l b r o m i d e s b e a r i n t e r e s t i n g r e s e m b l a n c e s , i n that t h e i r i n t e r a c t i o n with a r y l - m e t h y l - n i c k e l c o m p o u n d s l a and b both l e a d to t h e e l i m i n a t i o n of a r y l a n d m e t h y l g r o u p s . For purposes of f u r t h e r d i s c u s s i o n , w e p r o p o s e a c h a r g e t r a n s f e r i n t e r a c t i o n c o m m o n to b o t h , i n w h i c h r e a c t i o n s a r e p r o m o t e d b y a p r i o r e l e c t r o n t r a n s f e r f r o m I to o x y g e n o r a r y l b r o m i d e a c t i n g a s electron acceptors (A).~ A

+ ( E t

3

P )

2

N i ^

- >

3

A"(Et P) Ni<^ 3

2

,

3

etc.

[21]

A c o n c e r t e d p r o c e s s f o r r e d u c t i v e e l i m i n a t i o n f r o m the nickel(n) s p e c i e s ( 2 4 ) i n E q u a t i o n 21 i s i n d i c a t e d b y t h e r e a s o n a b l e y i e l d s of A r C H obtainable even when A is oxygen. M o r e o v e r , the p a r t i a l s c r a m b l i n g o b s e r v e d w h e n A i s a r y l b r o m i d e (and t h e a r y l g r o u p s o n the n i c k e l c o m p o u n d I a n d t h e a r y l b r o m i d e a r e d i f f e r e n t ) s u g g e s t s t h a t the i o n p a i r In E q u a t i o n 21 m a y b e i n t i mately associated. A c c o r d i n g to t h i s f o r m u l a t i o n , t h e s c r a m b l i n g of t h e a r y l g r o u p s i n t h e c r o s s c o u p l e d p r o d u c t m u s t o c c u r after electron transfer, s i n c e t h e r e c o v e r e d a r y l b r o m i d e i s not exchanged. S e v e r a l p o s s i b i l i t i e s c a n be e n v i s a g e d , i n c l u d i n g i r r e v e r s i b l e c o l l a p s e to a f i v e - c o o r d i n a t e i n t e r m e d i a t e ( 2 5 ) s u c h as: 3

(Et P) NiÇ^ ArBr" 3

2

( E t P ) N i ^ Br" 3

2

(Et P) Ni<^ +A r C H 3

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3

[22]

10.

Transition Metal Catalysts

KOCHi

173

f o l l o w e d b y t h e e l i m i n a t i o n of the a r y l and m e t h y l g r o u p s i na subsequent step. W e have a l s o o b s e r v e d that t h e s e n s i t i v i t y of a r y l - m e t h y l nickel compounds l a and b to oxygen i s greatly enhanced b y the a d d i t i o n o f methyllithiumT U n d e r these conditions, t h e p r e s e n c e of l a a n d b a s n i c k e l a t e c o m p l e x e s III i s i n d i c a t e d b y i s o t o p i c excKange s t u d i e s . T h e s e a n i o n i c n i c k e l c o m p l e x e s s h o u l d b e e v e n b e t t e r d o n o r s t h a n t h e i r n e u t r a l c o u n t e r p a r t s 1,(26) a n d t h e y a r e thus expected a l s o to show enhanced reactivity"to"~âryl bro­ mides i nthose interactions proceeding b y electron transfer. R e d u c t i v e e l i m i n a t i o n s s i m i l a r t o those p r e s e n t e d f o rI c a n b e formulated as: ~~ (Et P) Ni<^

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

3

2

c

r

H 3 ) 2 L

.

+ A r X

(Et P) N<£^ 3

2

+A r C H

3

+L i X

[23]

T h e v a r i o u s s t o i c h i o m e t r i c r e a c t i o n s o f the a r y l - m e t h y l n i c k e l compounds of l a and b leading to reductive e l i m i n a t i o n can be a s s e m b l e d a s c o m p o n e n t s to a c a t a l y t i c c y c l e i n t h e c r o s s coupling process. S c h e m e 2 i s consistent with thefacts i n hand, i n c l u d i n g t h ep r o d u c t s , s t o i c h i o m e t r y , kinetics, exchange and scrambling experiments. Scheme 2 L Ni(Ar)CH 2

3

+A r X

L Ni(Ar)CH 2

L Ni 2

+

3

+

+A r X "

s

l

o

f

a

f

a

w

>

[L Ni(Ar)CH

t

>

L Ni

S

s

t

2

2

>-

+

+

3

4- A r C H

ArX"]

3

L NiArX

[24] [25] [26]

2

S c h e m e 2 i s p r e s e n t e d s t e p w i s e only to e m p h a s i z e the m e c h a n i s ­ tic f a c t o r s b r o u g h t out b y the s t u d y o f l a a n d b . T h u s , i t i s p r o ­ b a b l y that E q u a t i o n s 2 4 - 2 6 o c c u r i n one~to t w o s t e p s s u c h a s E q u a t i o n 22, o r i n r a p i d s u c c e s s i o n b e f o r e any of the i n t e r m e ­ diates diffuse apart. Furthermore, Scheme 2 is obviously i n ­ complete without considering the nickelate species ΙΠas p a r t i c i ­ p a t i n g i n r e a c t i o n s s u c h a s E q u a t i o n 23 w h i c h a r e m e c h a n i s t i c a l l y e q u i v a l e n t t o t h e r a t e - l i m i t i n g s t e p s h o w n b y I i n E q u a t i o n 24 o f the catalytic c y c l e . F i n a l l y , t h e r e a r e s e v e r a l m e c h a n i s t i c points y e ttob e clarified. F o rexample, t h eo r i g i n of side products such as reduced arene i s unclear. P r e l i m i n a r y r e s u l t s s u g g e s t that t h e arene arises f r o m a na r y l - m e t h y l exchange process such as, (Et P) Ni<^^ + C H j L i ^ 3

2

since deuterolysis

(Et P) Ni<£ 3

2

r

H j ) 2 : L i

^

(Et P) Ni
of the r e a c t i o n m i x t u r e leads

2

partly to deuter-

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

174

INDUSTRIAL AND LABORATORY ALKYLATIONS

ated arene. It d o e s not a p p e a r , h o w e v e r , t h a t a l l o f t h e gen i s d e r i v e d f r o m p r o t o n o l y s i s , a n d it i s p o s s i b l e that other s o u r c e s u c h as that f r o m the m e t h y l g r o u p m a y be

hydro­ some involved.

B. I r o n C a t a l y s i s i n the C r o s s C o u p l i n g of A l k e n y l H a l i d e s and G r i g n a r d Reagents! Grignard reagents are cross coupled s t e r e o s p e c i f i c a l l y with a l k e n y l halides such as 1-bromopropene i n t h e p r e s e n c e of c a t a l y t i c a m o u n t s of i r o n c o m p l e x e s . ( 2 7 ) RMgBr

+ X; = C C

B

r

(

F

e

^

+

" C =CC

R

+ MgBr

2

[28]

I r o n ( l l l ) c o m p l e x e s a r e e m p l o y e d , but they a r e r a p i d l y r e d u c e d b y G r i g n a r d r e a g e n t i n s i t u to g e n e r a t e a c a t a l y t i c a l l y a c t i v e reduced iron species~pr esumably iron(l). Among various iron complexes examined, tris-dibenzoylmethidoiron(lll), Fe(DBM) , w a s found to be the m o s t e f f e c t i v e , p a r t i c u l a r l y w i t h r e s p e c t to d e a c t i v a t i o n of the c a t a l y s t . ( 2 8 ) T h e y i e l d s of o l e f i n s o b t a i n a b l e b y t h i s c a t a l y t i c p r o c e s s v a r y ~ a c c o r d i n g to the s t r u c t u r e of the a l k y l m o i e t y i n the G r i g n a r d r e a g e n t as s h o w n i n T a b l e I. Thus, h i g h y i e l d s of c r o s s c o u p l e d p r o d u c t s a r e o b t a i n a b l e w i t h m e t h y l magnesium bromide. U n d e r the s a m e conditions, ethylmagnesi u m b r o m i d e afforded ethane and ethylene as side products i n a d d i t i o n to the expected c r o s s c o u p l e d p r o d u c t . The difference c a n be a t t r i b u t e d to the a v a i l a b i l i t y of (3-hydrogens i n the l a t t e r , a f a c t o r w h i c h i s a l s o i m p o r t a n t i n a v a r i e t y of other o r g a n o ­ metallic reactions.(29)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

3

In t h i s s t u d y w ë " h a v e c a r r i e d out a t h o r o u g h a n a l y s i s of the p r o d u c t s f o r m e d d u r i n g the r e a c t i o n of e t h y l m a g n e s i u m b r o m i d e w i t h ( Z ) - a n d ( E ) - l - b r o m o p r o p e n e i n t h e p r e s e n c e of t r i s - d i benzoylmethido-iron(lll). A c o m p l e t e a c c o u n t i n g of the m a t e r i a l b a l a n c e as w e l l as the e l e c t r o n b a l a n c e has been a c h i e v e d . Together with stereochemical and isotopic labelling studies, they p r o v i d e substantial m e c h a n i s t i c i n f o r m a t i o n about this i n t e r e s t i n g catalytic process. F i v e m a j o r t y p e s of s i d e p r o d u c t s a r e p r o d u c e d d u r i n g the catalytic process, i n g r e a t e r or l o w e r y i e l d s d e p e n d i n g on the r e l a t i v e c o n c e n t r a t i o n s of the r e a c t a n t s , the t e m p e r a t u r e of the r e a c t i o n a n d the s t r u c t u r e of the a l k y l m a g n e s i u m b r o m i d e . Thus, a l k e n e R ( - H ) and a l k a n e R H f r o m the G r i g n a r d c o m p o n e n t as w e l l as propylene, p r o p e n y l m a g n e s i u m b r o m i d e and 2,4-hexadiene from 1-bromopropene are always formed. No simple relation­ s h i p c o u l d be found f o r the f o r m a t i o n of t h e s e s i d e p r o d u c t s i n r e l a t i o n s h i p to the p r e d o m i n a n t c r o s s c o u p l e d p r o d u c t . The l a t t e r s u g g e s t s that the s i d e p r o d u c t s a r e i n t i m a t e l y c o n n e c t e d w i t h the p r i n c i p a l r e a c t i o n , and that both p r o c e s s e s i n v o l v e common reactive intermediates. A l t e r n a t i v e l y , the side p r o ­ ducts c o u l d a r i s e v i a c o n c u r r e n t but l a r g e l y independent r e a c ­ tions f r o m the c r o s s c o u p l i n g p r o c e s s . The rigorous delineation between these basic mechanistic categories is extremely difficult to m a k e i n a c a t a l y t i c s y s t e m i n w h i c h the i s o l a t i o n of i n t e r m e -

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3

e

8 ,

1

Z

0.08

tr

0.15E

0.56Z, 0.15E

(

(

6

7

0

6

)

)

3

d

85 86

0 nd

102J nd

nd nd

nd

0.02

94J h

0.01 0.05

0.02

98

0.05 0.05

0.79(82)8

f

h

97

96

nd

0.08 (Ζ,Ζ)

101

tr

0.02 (Ζ,Ζ)

96

tr

)

tr*

(*)

nd

}

nd

0

0.79Z(79)

J

)

e

1

3

Bal.

0.11

i

Ί

6

C H

Mat.

0.64Z(60)

0.02E^

0.65Z,

4

5

C

°(49) 0.05E^

3

(mmol) C H R(^)

0.29

0.19

Products

d

e

a

c

I n r e a c t i o n s c o n t a i n i n g 2 . 9 6 m m o l 1 - b r o m o p r o p e n e (95<£ Ζ a n d 54, E ) a n d 3 . 6 χ 1 0 " m m o l F e ( D B M ) i n 9 m l T H F at 25° f o r 1 h r . A l k e n e b y l o s s of $ - h y d r o g e n . C r o s s coupled product [Z is cis and Ε is t r a n s i s o m e r ] ; y i e l d s based on R M g X c o n s u m e d i n c l u d i n g 0.08 m m o l i n catalyst p r e p a r a t i o n . Based on R M g X c o n s u m e d (determined by h y d r o l y s i s ) . N o t d e t e r m i n e d , n d . < 0.01 m m o l d e t e c t e d . M i x t u r e of ( E ) a n d ( Z ) i s o m e r s . 0 . 0 4 ( Ζ , Ζ ) a n d 0.01 ( Z , E ) . J V a l u e a p p r o x i m a t e d u e to u n a v a i l a b i l ­ i t y of authentic p r o d u c t (see e x p e r i m e n t a l section).

3

h

nd

0.1

(CH ) C-

0.95

b

nd

0.04

2

n

cyclo-C H -

1.01

3

2

6

nd

0.13

CH CH CH (CH )CH-

1.00

3

2

3

0.03

0.04

CH CH (CH )CH-

1.01

3

2

0.02

0.07

(CH ) CH-

1.04

3

0.01

2

0.12

2

(CH ) CHCH -

1.09

3

nd

0.38

3

4

CH (CH ) -

1.13

2

0.03

0.45

2

CH CH CH -

1.04

2

0.12

0.32

1.02 CH3CH2-

3

RH

RMgBr (mmol)

C r o s s C o u p l i n g of P r i m a r y , S e c o n d a r y a n d T e r t i a r y A l k y l G r i g n a r d Reagents with 1- B r o m o p r o p e n e R(-H)b

T a b l e I.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

176

INDUSTRIAL AND

LABORATORY ALKYLATIONS

diates i s i m p r a c t i c a l . Any mechanistic formulation of the catalytic p r o c e s s must take into account the d i v e r s i t y of side products, as well as the isotopic labelling and s t e r e o c h e m i c a l results. In the following d i s c u s s i o n we wish to present a r e a c t i o n scheme which i s c o n s i s tent with the available data, while at the same time keeping the number of intermediates to a m i n i m u m . The C a t a l y s t i s best d e s c r i b e d as an iron(l) species formed by the f a c i l e reduction of the iron(lll) p r e c u r s o r by the G r i g n a r d reagent.(30) It i s a metastable species subject to deactivation on standing, probably by aggregation. F o r m a l l y , iron(l) species consist of a d electron configuration, i s o e l e c t r o n i c with manganese(O) and cobalt(ll). Only a few complexes of iron(l) have been isolated, but a p a r t i c u l a r l y relevant one i s the paramagnetic hydrido complex, HFe(dppe) , which i s stabilized by the b i s phosphine ligand, d p p e [ P h P C H C H P P h ] . A toluene solution shows a strong esr signal centered at = 2.085 with poorly r e s o l v e d fine structure.(31 ) A broad intense esr s p e c t r u m ( = 2.08) i s a l s o obtained i f F e ( D B M ) i s treated with excess ethylm a g n e s i u m b r o m i d e in T H F solutions at -40° to 0°C. A broad resonance i s a l s o observed when F e C l [ = 2.15] or F e ( a c a c ) [ = 2.07] a r e employed. The s p e c t r u m centered at = 2.00 retains the same general features when n-pentyl- or sec-butylm a g n e s i u m b r o m i d e s a r e employed as reducing agents.(l2) It i s destroyed immediately by m o l e c u l a r oxygen, and i s the dianionr a d i c a l of the ligand, P h C O C H C O P h - " . The M e c h a n i s m of the c r o s s coupling r e a c t i o n can be accommodated by an oxidative addition of 1-bromopropene to iron(l) followed by exchange with ethylmagnesium b r o m i d e and reductive elimination. Scheme 3 i s intended to f o r m a b a s i s for d i s c u s s i o n and further study of the catalytic mechanism. In order to maintain the stereospecificity, the oxidative addition of bromo-propene in step a should occur with retention. S i m i l a r s t e r e o c h e m i s t r y has been observed i n oxidative additions of platinum(O) and nickel(O) complexes.(32)(33) The metathesis of the iron(lll) intermediate i n step b is " e x p e c t e d to be rapid i n analogy with other alkylati on s. ( 34 ) The formation of a new carbon-carbon bond by the reductive elimination of a pair of carbon-centered ligands in step c has been demonstrated to occur 7

2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

2

2

2

2

3

3

2

Scheme 3

MgBr

2

RMgBr

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

3

10.

Transition

KOCHi

Metal

Catalysts

177

with organogold(lll), organonickel(ll), organoplatinum(lV) and o r g a n o r h o d i u m ( l l l ) c o m p l e x e s . ( 1 7)(35) The iron(lll) intermediates~in~Scheme 3 serve as focal points f o r the f o r m a t i o n of the side products. F o r example, metathetical exchange of propenyl-iron(lll) with G r i g n a r d reagent would afford propenylmagnesium bromide i n Equation 30.(36) Fe

m

-CH =CHCH

+ R - M g B r —+· F e ^ - R + C H C H = C H M g B r

3

[30]

3

F u r t h e r e x c h a n g e i n E q u a t i o n s 31 a n d 3 2 w o u l d p r o d u c e b i s - ( 1 propenyl)iron(lll) species w h i c h reductively eliminate to produce the 2 , 4 - h e x a d i e n e s stereospecifically.(37) mBr

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

F

e

CH=CHCH

ïïr

X : H = C H C H

3

+

C

H

3

C

H

=

C

H

g

M

B

mC H=CH C H F

e

+

r

^CH=CHCH

F

e

3

^CH=CHCH

3

^

M

+

B

r

P

2

1

!

τ

3

F

3

e

+

C

H

3

C

H

=

C

H

-

C

H

=

C

H

C

H

3

P 1 2

Disproportionation products a r e postulated to a r i s e f r o m alkyliron(lll) and/or dialkyliron(lll) species formed b y a n analo­ gous m e t a t h e s i s between i r o n ( l l l ) species a n d a l k y l m a g n e s i u m bromide. Thus, thedisproportionation processes m a y proceed as f o l l o w s (vide i n f r a ) : mCH CD ^ C H C D 2

F

e

2

τ

3

3

F

e

r +

C

H

2

=

C

D

2

+DCH CD

+

C

H

2

=

C

D

2

+CH CH=CHD

2

3

,

[33]

CH CD 2

F

e

X3H=CHCH

3

F

e

I

3

[34]

These disproportionations could proceed directly or b y a 2-step m e c h a n i s m involving p r i o r transfer of a β-hydrogen to i r o n f o l ­ lowed by reductive elimination. Similar disproportionation pro­ cesses have been described with organocopper(l), organomanganese(ll), and organoplatinum(ll) complexes.(38) The m e c h a n i s m i n Scheme 3 accommodates m u c h of the extant data on the i r o n - c a t a l y z e d c r o s s coupling r e a c t i o n of Grignard reagents andalkenyl halides. T h eside products derive naturally f r o m organoiron(lll) intermediates b y reason­ ably well-established pathways. However, there a r e a number of i n t e r e s t i n g o b s e r v a t i o n s w h i c h m e r i t f u r t h e r s c r u t i n y i n t h e light of this m e c h a n i s m . F o r e x a m p l e , i t i s c o m m o n l y h e l d that organometallic compounds such as thea l k y l - andp r o p e n y l - i r o n (III) s p e c i e s i n S c h e m e 3 u n d e r g o e l i m i n a t i o n o f | 3 - h y d r o g e n s i n the o r d e r ; tert.-R>sec.-R >prim.R. However, the results pre­ sented i n Table I r u ncounter to this expectation. Furthermore, if the oxidative addition of 1 - b r o m o p r o p e n e to iron(l) i s ratelimiting, thereactivities of the (Z)and (E) isomers should be

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL AND LABORATORY ALKYLATIONS

178

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

r e l a t i v e l y i n d e p e n d e n t of the G r i g n a r d r e a g e n t . It i s f o u n d , h o w ­ ever, the ( Z ) - b r o m o p r o p e n e i s m o r e r e a c t i v e than the (E) i s o m e r w i t h p r i m a r y a l k y l m a g n e s i u m b r o m i d e , but the c o n v e r s e i s t r u e of m e t h y l , s e c o n d a r y a n d t e r t i a r y a l k y l m a g n e s i u m b r o m i d e s . T h e d e g r e e of a s s o c i a t i o n a n d c o m p l e x f o r m a t i o n of the l a t t e r no doubt affect a q u a n t i t a t i v e e v a l u a t i o n , but even a q u a l i t a t i v e r a t i o n a l i z a t i o n of t h i s r e s u l t r e m a i n s o b s c u r e . C h a n g e s i n the c o n c e n t r a t i o n of the r e a c t a n t s a s w e l l a s the t e m p e r a t u r e of the r e a c t i o n c o u l d a f f e c t the r a t e s a n d e q u i l i b r i a of the v a r i o u s r e a c ­ t i o n s o u t l i n e d i n S c h e m e 3 and E q u a t i o n s 3 0 - 3 4 i n a m a n n e r to change the p r o d u c t d i s t r i b u t i o n . N o n e t h e l e s s , the a n o m a l i e s presented above u l t i m a t e l y m u s t be r e s o l v e d b e f o r e this m e c h a n ­ i s t i c f o r m u l a t i o n c a n be a c c e p t e d w i t h m o r e c o n f i d e n c e . F i n a l l y , the m e c h a n i s m i n S c h e m e 3 b e a r s a resemblance to that p r e s e n t e d a b o v e f o r the n i c k e l - c a t a l y z e d r e a c t i o n of m e t h y l m a g n e s i u m b r o m i d e and a r y l b r o m i d e s . However, there are outstanding differences between i r o n and n i c k e l in their a b i l i t i e s to e f f e c t c r o s s c o u p l i n g r e a c t i o n s . Iron is a catalyst w h i c h i s e f f e c t i v e at l o w e r t e m p e r a t u r e s a n d c o n c e n t r a t i o n s than used with nickel. E v e n m o r e i m p o r t a n t l y , c r o s s c o u p l i n g c a n be effected c o m p l e t e l y s t e r e o s p e c i f i c a l l y with an i r o n catalyst and no a l k y l i s o m e r i z a t i o n of the G r i g n a r d c o m p o n e n t has b e e n o b ­ s e r v e d , i n c o n t r a s t to the n i c k e l - c a t a l y z e d r e a c t i o n s . C. C r o s s C o u p l i n g of G r i g n a r d R e a g e n t s and A l k y l H a l i d e s with Copper(I) Catalysts. Copper(I) s p e c i f i c a l l y c a t a l y z e s the c r o s s c o u p l i n g ( E q u a t i o n 35) b e t w e e n G r i g n a r d r e a g e n t s a n d a l k y l b r o m i d e s w h e n c a r r i e d out i n T H F s o l u t i o n s at 0°C o r lower.(39) RMgX

4- R X

R-R

!

4- M g X

1

[35]

2

T h e y i e l d of h o m o d i m e r s , R - R a n d R - R , u n d e r t h e s e c o n d i t i o n s is negligibly s m a l l . This cross coupling reaction is most facile w i t h p r i m a r y a l k y l h a l i d e s , but u n l i k e s i l v e r ( l ) c a t a l y s i s , the secondary and tertiary a l k y l halides are generally inert and give p o o r y i e l d s of c o u p l e d p r o d u c t s and m a i n l y d i s p r o p o r t i o n a t i o n . T h e s t r u c t u r e of the G r i g n a r d r e a g e n t i s not as i m p o r t a n t , i n analogy with the c r o s s c o u p l i n g o b s e r v e d with l i t h i u m d i a l k y l cuprates.(40) The~c~oupling of e t h y l m a g n e s i u m b r o m i d e and e t h y l b r o m i d e to η - b u t a n e f o l l o w s o v e r a l l t h i r d - o r d e r k i n e t i c s , b e i n g f i r s t o r d e r i n each c o m p o n e n t and the copper(l) c a t a l y s t . T h e r e i s no evidence for a l k y l r a d i c a l s i n the c o p p e r ( l ) - c a t a l y z e d c o u p l i n g process, and w e p r o p o s e the f o l l o w i n g t w o - s t e p m e c h a n i s m : f

Scheme 4

RMgBr RCu

+ Cu Br + R'Br

!

RCu

S

l

°

w

>- R - R

1

+

MgBr

2

+ C u B r

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

[36] [37]

10.

KOCHI

Transition

Metal

179

Catalysts

T h e r a t e - l i m i t i n g s t e p 37 c a n be s h o w n i n d e p e n d e n t l y b y e x a m i n i n g the s t o i c h i o m e t r i c r e a c t i o n of a l k y l c o p p e r ( l ) d i r e c t l y with organic halides. H o w e v e r , the extent to w h i c h d e c o m p o s i ­ tion of the a l k y l c o p p e r ( l ) i n t e r m e d i a t e c o m p e t e s w i t h the c a t a l y tic c o u p l i n g r e a c t i o n i n t r o d u c e s d i s p r o p o r t i o n a t i o n p r o d u c t s . The latter involves a copper(0)-catalyzed sequence(41 ) s i m i l a r to that o b s e r v e d w i t h i r o n ( v i d e i n f r a ) , a n d i t i s e s p e c i a l l y important with secondary and tertiary alkyl systems. The e f f e c t s of s t r u c t u r a l v a r i a t i o n a r e c o n s i s t e n t w i t h a r a t e - l i m i t i n g step involving nucleophilic d i s p l a c e m e n t of halide i n E q u a t i o n 37.(40) T h e i n v o l v e m e n t of a n u c l e o p h i l i c c o p p e r ( l ) c e n t e r , i . e . , oxidative addition, followed by reductive elimination has direct analogy to the m e c h a n i s m w h i c h has been established with the analogous gold(l) catalyst. Organocopper(lII) intermediates

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

[38] [39] p r e s e n t e d i n E q u a t i o n 38 a r e f o r m a l l y r e l a t e d to t h e s p e c i e s f o r m e d i n the a s s o c i a t i o n of a l k y l r a d i c a l s w i t h copper(ll) c o m ­ p l e x e s , (4Z) w i t h b o t h s h o w i n g a m a r k e d p r o p e n s i t y f o r r e d u c t i v e elimination. A l t h o u g h the o b s e r v a t i o n of t h e s e h i g h l y m e t a s t a b l e i n t e r m e d i a t e s i s u n l i k e l y , the analogous organogold i n t e r m e ­ diates a r e m o r e stable and c a n be isolated or observed d i r e c t l y b y N M R . O x i d a t i v e a d d i t i o n of a l k y l h a l i d e s to a l k y l ( P P h ) gold(l) follows the expected pattern: C H I >EtI >i-PrI.(_3) T h e subsequent r e d u c t i v e e l i m i n a t i o n of t r i a l k y l g o l d ( l l l ) c o m p l e x e s to c o u p l e d d i m e r w a s d e s c r i b e d e a r l i e r ( E q u a t i o n 11). The parallel between copper(l) and gold(l) i s f u r t h e r shown i n the b e h a v i o r of the c o r r e s p o n d i n g c u p r a t e ( l ) a n d a u r a t e ( l ) c o m p l e x e s . Thus, a l k y l g o l d ( l ) r e a c t s w i t h a n e q u i m o l a r a m o u n t of a l k y l l i t h i u m to afford an isolable lithium dialkylaurate(l). The anionic dimethyla u r a t e ( l ) s p e c i e s f o r m e d i n this m a n n e r i s at l e a s t 1 0 times m o r e r e a c t i v e to o x i d a t i v e a d d i t i o n of m e t h y l i o d i d e than the neutral methyl(PPh )gold(l). The same pattern is qualitatively established with organocopper(l) species i n c o m p a r i n g the coup­ l i n g r e a c t i o n i n E q u a t i o n 3 7 w i t h that r e p o r t e d f o r l i t h i u m dialkylcuprates.(40) 3

3

6

3

D. Homo-Coupling with Silver(l). Silver is an effective catalyst for the c o u p l i n g of G r i g n a r d r e a g e n t s and a l k y l halides, and it i s e s p e c i a l l y useful when both a l k y l groups a r e the same.(43) When different alkyl groups a r e employed, a mixture of t h r e e c o u p l e d p r o d u c t s i s o b t a i n e d . Disproportionation becomes increasingly important with secondary and tertiary

RMgX + E X

·>- R-R + M g X

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

[40]

INDUSTRIAL AND LABORATORY ALKYLATIONS

180

g r o u p s , i n d e p e n d e n t l y of w h e t h e r they a r e d e r i v e d f r o m the G r i g n a r d r e a g e n t or the a l k y l h a l i d e . T h e r a t e of p r o d u c t i o n of butane f r o m e t h y l m a g n e s i u m b r o m i d e and ethyl b r o m i d e is r o u g h l y f i r s t o r d e r i n s i l v e r and e t h y l b r o m i d e , but z e r o o r d e r i n G r i g n a r d r e a g e n t . ( 4 4 ) T h e r e a c t i v i t y of a l k y l h a l i d e s f o l l o w s the o r d e r : t - b u t y l > i ^ p r o p y l > n - p r o p y l b r o m i d e i n the r a t i o 20:3:1, and s t r u c t u r a l v a r i a t i o n s i n the G r i g n a r d r e a g e n t s h o w no apparent systematic trend. T h e r e s u l t s c a n b e a c c o m m o d a t e d b y S c h e m e 5, i n w h i c h the c o u p l i n g a r i s e s f r o m a l k y l s i l v e r ( l ) i n t e r m e d i a t e s generated via two l a r g e l y independent pathways: Scheme

5 R'MgX

+ AgX

RAg , R ' A g

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

1

Ag°

+ R-X

R.

+ Ag°

—+· 1

TV A g

— [ R - R ,

—ν

[41]

2

R'-R, R -R ] !

!

+ 2 Ag°

AgX

R- +

—>- R A g

+ MgX

1

[42] [43]

etc.

[44]

The r a t e - l i m i t i n g step in this m e c h a n i s m is given by E q u a t i o n 43 i n w h i c h the a l k y l h a l i d e i s r e s p o n s i b l e f o r the r e o x i d a t i o n of s i l v e r ( O ) p r o d u c e d i n E q u a t i o n 4 2 . T h i s slow step is c l o s e l y a k i n to the p r o d u c t i o n of a l k y l r a d i c a l s b y the l i g a n d t r a n s f e r r e d u c t i o n of a l k y l h a l i d e s w i t h o t h e r r e d u c i n g m e t a l complexes.(45) M o r e d i r e c t evidence for the selective f o r m a t i o n of a l k y l r a d i c a l s f r o m the a l k y l h a l i d e i s s h o w n b y t r a p p i n g e x p e r i m e n t s as w e l l as s t e r e o c h e m i c a l s t u d i e s . Thus, the c a t a l y t i c r e a c t i o n of c i s - p r o p e n y l m a g n e s i u m b r o m i d e w i t h methyl bromide yielded cis-butene-2, i n a c c o r d w i t h the r e t e n ­ t i o n of s t e r e o c h e m i s t r y d u r i n g t h e r e d u c t i v e c o u p l i n g of v i n y l s i l v e r ^ ) c o m p l e x e s . ( 4 6 ) O n the other hand the r e v e r s e c o m b i n a ­ tion, c i s - p r o p e n y l b r o m i d e and m e t h y l m a g n e s i u m b r o m i d e , is c a t a l y t i c a l l y c o n v e r t e d to a m i x t u r e of c i s - a n d trans-butene-2, c o n s i s t e n t w i t h the f o r m a t i o n a n d r a p i d i s o m e r i z a t i o n of t h e 1 p r o p e n y l r a d i c a l i n S c h e m e 5.

[45] CH MgBr 3

E. C a t a l y s i s of A l k y l D i s p r o p o r t i o n a t i o n b y I r o n . Alkyl d i s p r o p o r t i o n a t i o n is the sole r e a c t i o n o b s e r v e d d u r i n g the i r o n c a t a l y z e d r e a c t i o n of e t h y l m a g n e s i u m b r o m i d e and e t h y l b r o ­ m i d e . (47) T h e c a t a l y s t i s a r e d u c e d i r o n s p e c i e s f o r m e d i n s i t u b y the r e a c t i o n of i r o n ( l I , I I l ) w i t h G r i g n a r d r e a g e n t , a n d e l f e c t i v e

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

10.

Transition Metal Catalysts

KOCHi

CH CH MgBr +CH CH Br 3

2

3

2

(

F

e

) »

181

CH CH 3

+CH =CH +MgBr

3

2

2

2

[46]

in c o n c e n t r a t i o n s as l o w as 1 0 " M . A l t h o u g h the r e a c t i o n has l i m i t e d synthetic utility, it m e r i t s study s i n c e it c a n p r o v i d e i n s i g h t i n t o s o m e of the c o m p l i c a t i o n s i n v o l v e d w i t h o r g a n o ­ metallic intermediates discussed above. T h e r a t e of r e a c t i o n s h o w s f i r s t o r d e r d e p e n d e n c e on t h e c o n c e n t r a t i o n of i r o n a n d e t h y l b r o m i d e , but i s i n d e p e n d e n t of the c o n c e n t r a t i o n of e t h y l m a g n e s i u m b r o m i d e . The rate, how­ e v e r , v a r i e s w i t h the s t r u c t u r e of the G r i g n a r d reagent, and d i s p r o p o r t i o n a t i o n u s u a l l y r e s u l t s except w h e n the a l k y l g r o u p is m e t h y l , neopentyl or b e n z y l w h i c h p o s s e s s no (3-hydrogens. The r e a c t i v i t i e s of the a l k y l b r o m i d e s ( t - b u t y l > i - p r o p y l > n - p r o p y l ) as w e l l as the k i n e t i c s a r e the s a m e as the s i l v e r - c a t a l y z e d coupling described above and suggest a s i m i l a r m e c h a n i s m :

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

5

Scheme

6 Fe

1

R. R'MgBr

+ RBr

—>

Fe^Br

+ pe

- >

RFe

1

+ FeBr

RFe , R'Fe 1

—•

[4 7] [48]

1

—+> R ' F e 1

+ R-

+ MgBr

1

[49]

2

[RH, R H , R - H , R - H ] + 2 Fe , !

!

1

etc.

[50]

A c c o r d i n g to t h i s p o s t u l a t e , the d i f f e r e n c e b e t w e e n c o u p l i n g w i t h s i l v e r and d i s p r o p o r t i o n a t i o n w i t h i r o n r e s t s on the d e c o m p o s i ­ t i o n of the a l k y l m e t a l i n t e r m e d i a t e i n E q u a t i o n 50. Indeed, it has b e e n s h o w n s e p a r a t e l y i n E q u a t i o n 42 t h a t t h e d e c o m p o s i t i o n of a l k y l s i l v e r ( l ) p r o c e e d s by r e d u c t i v e c o u p l i n g . U n f o r t u n a t e l y , the h i g h l y u n s t a b l e a l k y l i r o n i n t e r m e d i a t e i n S c h e m e 6 i s not yet a c c e s s i b l e to i n d e p e n d e n t s t u d y , but the s o m e w h a t a n a l o g o u s d i a l k y l m a n g a n e s e ( l l ) s p e c i e s i n E q u a t i o n 51 u n d e r g o e s s i m i l a r r e d u c t i v e d i s p r o p o r t i o n a t i o n b y a m e c h a n i s m ( £ 8 ) r e m i n i s c e n t of d i a l k y l p l a t i n u m ( l l ) c o m p l e x e s d e s c r i b e d i n E q u a t i o n 7. RjjMn

1

—• R H + R - H + M n °

[51]

S e l e c t i v e t r a p p i n g of a l k y l r a d i c a l s f r o m the a l k y l h a l i d e c o m p o n ­ ent d u r i n g the c o u r s e of the c a t a l y t i c d i s p r o p o r t i o n a t i o n i s t h e s a m e as the p r e v i o u s o b s e r v a t i o n w i t h s i l v e r , and it i n d i c a t e s that the p r i m e s o u r c e of r a d i c a l s i n the K h a r a s c h r e a c t i o n l i e s i n the o x i d a t i v e a d d i t i o n of a l k y l h a l i d e to r e d u c e d i r o n i n E q u a t i o n 47. S e p a r a t e p a t h w a y s f o r r e a c t i o n of i - p r o p y l g r o u p s d e r i v e d f r o m the o r g a n i c h a l i d e and the G r i g n a r d r e a g e n t a r e a l s o s u p ­ p o r t e d b y d e u t e r i u m l a b e l l i n g s t u d i e s w h i c h s h o w that they a r e not c o m p l e t e l y e q u i l i b r a t e d . ( 4 9 ) F u r t h e r m o r e , t h e o b s e r v a t i o n of C I D N P ( A E m u l t i p l e t effect) TrTthe l a b e l l e d p r o p a n e a n d p r o p e n e

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL AND LABORATORY ALKYLATIONS

182

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch010

d e r i v e d only f r o m the a l k y l halide component c a n be attributed to a b i m o l e c u l a r d i s p r o p o r t i o n a t i o n of i s o p r o p y l r a d i c a l s a r i s i n g f r o m diffusive displacements. However, the latter c a n only be a m i n o r fate of the a l k y l r a d i c a l s d e r i v e d f r o m the a l k y l halide, since the coupled d i m e r i s not f o r m e d i n amounts r e q u i r e d by the b i m o l e c u l a r r e a c t i o n of a l k y l r a d i c a l s p r e v i o u s l y d i s c u s s e d i n Equation 9·(48)(5£) C r o s s c o u p l i n g of G r i g n a r d reagents w i t h 1 - a l k e n y l halides, i n m a r k e d c o n t r a s t to a l k y l halides, o c c u r s r e a d i l y w i t h the r e d u c e d i r o n catalyst, a s d e s c r i b e d above. The ironc a t a l y z e d r e a c t i o n of G r i g n a r d reagents w i t h 1 - a l k e n y l h a l i d e s can, however, be differentiated f r o m the reaction with alkyl halides. T h u s , a m i x t u r e of p r o p e n y l b r o m i d e a n d ethyl b r o m i d e on r e a c t i o n w i t h m e t h y l m a g n e s i u m b r o m i d e a f f o r d e d b u t e n e - 2 but no c r o s s - o v e r p r o d u c t s s u c h a s p e n t e n e - 2 o r p r o p y l e n e . The latter certainly would have resulted if a propenyliron species per se w e r e i n v o l v e d i n the c a t a l y t i c p r o c e s s . C r o s s coupling under tïïese c i r c u m s t a n c e s c l e a r l y m e r i t s further study. Conclusions T h e c o m p l e x catalytic reactions leading to the coupling of organic substrates induced by metal complexes c a n be rationally d i s s e c t e d into a v a r i e t y of e l e m e n t a r y steps i n v o l v i n g o x i d a t i o n r e d u c t i o n reactions of o r g a n o m e t a l l i c i n t e r m e d i a t e s . Electron transfer interactions a r e important considerations i n differentia­ ting concerted f r o m stepwise processes, especially with regard to c h a i n p r o c e s s e s . C r u c i a l to the design of new synthetic p r o ­ cedures andthe understanding of catalytic p r o c e s s e s i s the i n f o r ­ m a t i o n to be gained f r o m the s c r u t i n y of transient a l k y l m e t a l species, w h i c h r e p r e s e n t a l a r g e p o t e n t i a l f o r a v a r i e t y of n o v e l reactions.

Literature Cited 1. 2.

3. 4. 5. 6.

Rice, G. W. and R. S. Tobias, J. Organometal. Chem. (1975), 86, C37. Clark, H. C., C. Jablonski, J. Halpern, A. Mantovani and T. A. Weil, Inorg. Chem. (1974), 13, 1541; A. J. Deeming, B. F. G. Johnson and J. Lewis, J. Chem. Soc. Dalton (1973), 1848. Kochi, J. K. and J. W. Powers, J. Am. Chem. Soc. (1970), 92, 137. Tamaki, A. and J. K. Kochi, J. Chem. Soc. Dalton (1973), 2620. Matteson, D. S., "Organometallic Reaction Mechanisms," Academic Press, New York, 1974; S. Komiya and J. K. Kochi, to be published. Whitesides, G. Μ., J. G. Gaasch and E. R. Stedronsky, J. Am. Chem. Soc. (1972), 94, 5258.

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10. 7. 8.

9· 10. 11.

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12. 13. 14.

15. 16.

17.

18.

20.

21.

183

Gibian, M. J. and C. Corley, Chem. Revs. (1973), 73, 441. The complex mixture of products resulting from free radi­ cals in Wurtz-type reactions have been described by J. F. Garst, "Chemically Induced Magnetic Polarization," A. R. Lepley and G. L . Closs, eds., Chapter 6, J. Wiley and Sons, New York, 1973. See also Chapter 7, Ibid., H. R. Ward, R. G. Lawler and R. A. Cooper. Dodd, D. and M. D. Johnson, J. Organometal. Chem. (1973), 52, 1; P. Abley, E . R. Dockal and J. Halpern, J. Am. Chem. Soc. (1972), 94, 659. Tamaki, A. and J. K. Kochi, J. Organometal. Chem. (1974), 64, 411. Kharasch, M. S. and O. Reinmuth, "Grignard Reagents of Nonmetallic Substances," Prentice-Hall, Inc. New York, 1954. (a) Tamao, Κ., K. Sumitani and M. Kumada, J. Am. Chem. Soc. (1972), 94, 4374. (b) Corriu, R. J. P. and J. P. Masse, J. Chem. Soc., Chem. Commun. (1972), 144. Kiso, Υ., K. Tamao and M. Kumada, J. Organometal. Chem. (1973), 50, C12. Similar species have been invoked in cross couplings effected with stoichiometric amounts of organonickel rea­ gents; see (a) Semmelhack, M. F., Org. Reactions (1972), 19, 155; (b) Baker, R., Chem. Revs. (1973), 73, 487; (c) Nakamura, A. and S. Otsuka, Tetrahedron Letters (1974), 463. Parshall, G. W., J. Am. Chem. Soc. (1974), 96, 2360. Cf. (a) Hidai, M . , T. Kashiwagi, T. Ikeuchi and Y. Uchida, J. Organometal. Chem. (1971), 30, 279; (b) Cundy, C. S., Ibid. (1974), 69, 305; (c) Fahey, D. R., J. Am. Chem. Soc. (1970), 92, 402; and (d) reference 15. (a) Tamaki, Α . , S. A. Magennis and J. Κ. Kochi, J. Am. Chem. Soc. (1974), 96, 6140; (b) Cf. also for Pt(lV): M. P. Brown, R. J. Puddephatt, C. Ε. E . Upton, J. Chem. Soc. Dalton (1974), 2457. For structural factors in equilibria involved in 4- and 5coordinate Ni(ll) complexes with monodentate phosphines: L N i X (n=2,3) see E. C. Alyea and D. W. Meek, J. Am. Chem. Soc. (1969), 91, 5761; Cf. also J. W. Dawson et al., Ibid. (1974), 96, 4428. Interestingly, reductive elimination from alkylgold(III) also proceeds from a 3-coordinate species (see ref. 17a). Cf. J. F. Garst in "Free Radicals," J. K. Kochi, ed., Chapter 9, Wiley-Interscience, Inc., New York, 1973; G.A. Russell, E . G. Janzen, A. G. Bemis, E . J. Geels, A. J. Moye, S. Mak, Ε. T. Strom, Adv. Chem. Ser. (1965), 51, 112. (a) Bank, S. and D. A. Juckett, J. Am. Chem. Soc. (1975), 97, 567; (b) Baizer, Μ. Μ., ed., "Organic Electrochemis­ try," M. Dekker, Inc., New York, 1973; (c) Rogers, R. J., n

19·

Transition Metal Catalysts

KOCHI

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

184

22.

23.

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24. 25. 26. 27. 28. 29· 30. 31. 32.

33.

34. 35. 36.

INDUSTRIAL AND LABORATORY ALKYLATIONS

H. L . Mitchell, Y. Fujiwara and G. M. Whitesides, J. Org. Chem. (1974), 39, 857. (a) House, H. O. and M. J. Umen, J. Am. Chem. Soc. (1972), 94, 5495; (b) Gardner, H. C. and J. K. Kochi, Ibid. (1975), 97, 1855; (c) Nugent, W. Α . , F. Bertini and J. K. Kochi, Ibid. (1974), 96, 4945; (d) Hegedus, L . S. and L. L . Miller, Ibid. (1975), 97, 459; (e) Ashby, E . C., I. G. Lopp and J. D. Buhler, Ibid. (1975), 97, 1964. (a) Halpern, J., M. S. Chan, J. Hanson, T. S. Roche and J. A. Topich, J. Am. Chem. Soc. (1975), 97, 1607; (b) Anderson, S. N . , D. H. Ballard, J. Z. Chrzastowski and M. D. Johnson, J. Chem. Soc., Chem. Commun. (1972), 685; (c) Kochi, J. Κ., Acc. Chem. Research. (1974), 7, 351; (d) Costa, G . , A. Puxeddu and E. Reisenhofer, Bio­ electrochem. and Bioenergetics. (1974), 1, 29· Oxidation numbers of nickel are included only as a book­ keeping device and are not necessarily intended to denote actual changes in oxidation states. A stable 5-coordinate σ-phenylnickel(II) species is described [P. DaPorto and L . Sacconi, Inorg. Chim. Acta (1974), 9, 62]. Cf. Η. Ο. House and M. J. Umen, J. Org. Chem. (1973), 38, 3893. Tamura, M. and J. K. Kochi, J. Am. Chem. Soc. (1971), 93, 1487. Neumann, S. M. and J. K. Kochi, J. Org. Chem. (1975), 40, 599. Braterman, P. S. and R. J. Cross, Chem. Soc. Revs. (1973), 2, 271. Kwan, C. L . and J. K. Kochi, J. Am. Chem. Soc., in press. Gargano, M., P. Giannocaro, M. Rossi, G. Vasapollo and A. Sacco, J. Chem. Soc. Dalton (1975), 9. (a) Osborn, J. A. in "Prospects in Organotransition Metal Chemistry," M. Tsutsui, ed., Plenum Press, New York, 1975; (b) Rajaram, J., R. G. Pearson and J. A. Ibers, J. Am. Chem. Soc. (1974), 96, 2103. (a) Tamao, K . , M. Zembayashi, Y. Kiso and M. Kumada, J. Organometal. Chem. (1973), 55, C91; (b) Semmelhack, M. F . , P. M. Helquist and J. D. Gorzynski, J. Am. Chem. Soc. (1972), 94, 9234; but see (c) Zembayashi, Μ., K. Tamao and M. Kumada, Tetrahedron Letters (1975), 1719. Chatt, J. and B. L . Shaw, J. Chem. Soc. (1960), 1718; J. R. Moss and B. L . Shaw, Ibid. (1966), 1793; G. Calvin and G. E . Coates, Ibid. (1960), 2008. (a) Parshall, G. W., J. Am. Chem. Soc (1974), 96, 2360; (b) Morrell, D. M. and J. K. Kochi, Ibid. (1975), 97, 7262. Propenylmagnesium bromide formed in this manner should retain the stereochemistry of the reactant bromopropene in contrast to that formed with magnesium metal. Cf. H. M.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

10.

37. 38.

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39· 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50.

KOCHI

Transition Metal Catalysts

185

Walborsky and M. S. Aronoff, J. Organometal. Chem. (1973), 51, 53; H. L . Goering and F. H. McCarron, J. Am. Chem. Soc. (1958), 80, 2287; R. J. Rogers, H. L . Mitchell, Y. Fujiwara and G. M. Whitesides, J. Org. Chem. (1974), 39, 857. Cf. G. M. Whitesides, C. P. Casey and J. K. Krieger, J. Am. Chem. Soc. (1971), 93, 1379. Whitesides, G. M . , E . R. Stedronsky, C. P. Casey and J. San Filippo, J r . , J. Am. Chem. Soc. (1970), 92, 1426; G. M. Whitesides, E . J. Panek and E . R. Stedronsky, Ibid. (1972), 94, 232; M. Tamura and J. K. Kochi, Ibid. (1971), 93, 1483; J. Organometal. Chem. (1972), 42, 205; Ibid. (1971), 29, 111. Tamao, Κ., Y. Kiso, K. Sumitani and M. Kumada, J. Am. Chem. Soc. (1972), 94, 9268; M. Tamura and J. K. Kochi, J. Organometal. Chem. (1972), 42, 205. Jukes, Α. Ε . , Adv. Organometal. Chem. (1974), 12, 215. Tamura, M. and J. K. Kochi, J. Am. Chem. Soc. (l 971), 93, 1485. Kochi, J. Κ., Pure App. Chem. (1971), 4, 3958. Tamura, M. and J. K. Kochi, Synthesis (1971), 303. Tamura, M. and J. K. Kochi, J. Am. Chem. Soc. (19 71), 93, 1483. Jenkins, C. L . and J. K. Kochi, J. Am. Chem. Soc. (1972), 94, 843, 856. Whitesides, G. M . , C. P. Casey and J. K. Krieger, J. Am. Chem. Soc. (1971), 93, 1379. Tamura, M. and J. K. Kochi, J. Organometal. Chem. (1971), 31, 289; Bull. Chem. Soc. Japan (1971), 44, 3063. Tamura, M. and J. K. Kochi, J. Organometal. Chem. (1971), 29, 111. Allen, R. B., R. G. Lawler and H. R. Ward, J. Am. Chem. Soc. (1973), 95, 1692. The large enhancement possible in CIDNP may not reflect its chemical importance until they are quantitatively related. A small amount of radical combination leading to CIDNP may have been overlooked in the chemical studies.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11 N e w Strong A c i d Catalyzed Alkylation and Reduction Reactions

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

M. SISKIN, R. H. SCHLOSBERG, and W. P. KOCSI Corporate Research Laboratories, Exxon Research and Engineering Company, P. O. Box 45, Linden, NJ 07036

Most of the work described in this paper was carried out using the strong acid system composed of tantalum pentafluoride and hydrogen fluo­ ride. Tantalum pentafluoride (TaF ) is a white solid which melts at ~97°C. It is an acidic metal fluoride because of its large metal atom, which is coordinatively unsaturated having only ten electrons around it. The posi­ tive nature of the tantalum atom is enhanced by five very electronegative fluorines. This allows the tantalum to accept an anion from a Brönsted acid, such as hydrogen fluoride and generate a proton active enough to protonate the weakly basic hydrogen fluoride solvent (eq. 1). 5

+

2HF + T a F ^ HF + H - - - F — T a F ^ ' ^ H F + TaFg 5

(1 )

2

+

The resultant concentration of [H F ] is responsible for the extraordinary acidity of the system. Furthermore, the TaF-6 anion is so weakly basic as to be essentially inert in a medium which thus allows the formation of stable, long-lived carbocations in hydrocarbon reactions. Tantalum pentafluoride is also very thermally stable (1) even at 300°C and resistant to reduction reactions, especially, by molecular hydrogen and hydrocarbon ions (2-5). This is in sharp contrast to antimony pentafluoride containing strong acid systems which are readily reduced to the antimony (III) state (6-8). Hydro­ gen fluoride is a colorless liquid boiling at ~19.5°C, which when anhydrous is itself a fairly strong acid with a Hammett acidity (Ho) of ~11 (9). It is a thermally stable and non-reducible Brönsted acid (10). When TaF and HF are mixed together, a colorless solution is formed which can be classified as a "super acid" having an Ho of -18.85 (11), or ~10 times stronger than anhydrous hydrogen fluoride. In addition to forming a very stable liquid phase strong acid Friedel-Crafts system, it is, because of its high acidity, and therefore its ability to protonate weak organic bases, a good hydrogena­ tion catalyst. We have shown that in the hydrogenation of benzene, in fact, it is protonated benzene, not benzene itself, which undergoes the initial hydrogenation (12). 2

5

8

186

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

SISKIN E T AL.

Strong Acid Catalyzed

Reactions

187

Introduction

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The direct and selective alkylation of benzene by alkanes has long been a desirable goal ( Ί 3 ) . The ability to ionize the lower alkanes to highly acidic cations in super acids has given further impetus to the challenge (14). Sacrificial species have even been added to the reaction mixture in order to provide a stoichiometric driving force to overcome the very unfavorable thermodynamics (Table I) for the reaction (15, Ί 6 ) . In sharp contrast, less attention has been given to carrying out the direct acid catalyzed alkylation of the lower alkanes with the lower alkenes, (17, 6) although such reactions are very thermodynamically favorable (Table I), especially at low temperatures ( 2 5 - 1 2 5 ° ) where antagonistic entropy effects are less important. TABLE I (18) THERMODYNAMICS OF ALKANE ALKYLATIONS A F ? (KCAL/MOLE) TK)

AROMATIC S CH

4

+C H —^C H CH 6

6

6

5

3

+H

2

CH3CH3+C H —^C H CH CH3 + H 6

6

6

5

2

2

300

400

500

+10.32

+10.36

+10.31

+8.08

+8.18

+8.15

- 9.70

- 6.43

- 3.17

-12.46

- 9.14

- 5.86

- 7.77

- 3.97

- 0.21

ALKENES CH

4

+C

2

H

4

— C

3

H

8

CH3CH3 + C H - ^ n - C H 2

CH

4

+ C

3

H

6

4

— Μ :

4

4

Η

1

(

)

1 0

Conventional alkane-alkene alkylation is an acid catalyzed reaction which involves the addition of a tertiary carbenium ion generated from an alkane to an alkene to yield (after hydride addition) a saturated hydro­ carbon of higher molecular weight. Mechanistically, as elucidated by Schmerling (19) and as illustrated for isobutane-ethylene (alkane-alkene) alkylation (Scheme 1), the reaction is initiated by protonation of the alkene (ethylene) to form a very acidic primary ethyl cation (step 1) which rapidly abstracts a hydride ion from an isobutane molecule to generate the chain carryings-butyl cation (step 2). This can then alkylate another molecule of ethylene to form the secondary 2-methyl-t-butyl carbenium ion (step 3). This cation rapidly undergoes a

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

188

INDUSTRIAL AND LABORATORY ALKYLATIONS

methyl shift to form the more stable (less acidic) tertiary-dimethylisopropyl carbenium ion which then abstracts a hydride ion from isobutane to form the 2,3-dimethylbutane alkylation product and generate a M>utyl cation which can then react with another ethylene in (step 3), e t c . , and thus make the reaction catalytic. SCHEME 1 ISOBUTANE-ETHYLENE ALKYLATION

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

INITIATION:

CH

2

—

CHg-CH

CH + H 2

®

0)

2

C

GENERATION O F REACTIVE SPECIES:

©

1

C-C-H + CH -CH 3

2

-

C - C ^ +ChL-CH,

(2)

C

CRUCIAL STEPS:

1

C-C

Θ W

+ CH.

ChL

C Η C Η I I I I ~c C - C - C - C H o ^ C-C-C-CH, :

I ©

3

(3)

C Η I

I

C - C - C - C H® I c J

C I C-C-H I C

C Η I

C - C - C - C Ho + C - C I I I H C C

®

(4)

The conditions required to carry out conventional alkane-alkene alkylation reactions selectively depends upon (a) the strength of the acid catalyst, (b) the acidity (reactivity) of the carbenium ion generated upon protonation of the alkene, e . g . , (the ethyl cation is so much more reactive than the t-butyl cation that it can be consumed in ways other than tertiaryhydride abstraction), and (c) the alkane reactant should have a tertiaryhydrogen because the hydride abstraction steps are easier. A turning point in the revival of interest in strong acid chemistry was a publication in 1968 in which ionization of the C - H bonds of the extraordi­ narily unreactive "lower paraffins" methane and ethane in HSU3F-SbF5 at 5 0 ° C was reported (14). The proposed mechanism (Scheme 2) proposes the existence, in super acid solution, of protonated alkanes or pentacoordinated ions, at least as possible transition states, and attempts quite logically to draw a parallelism between the presence of such species in solution chemistry

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

SISKIN E T AL.

Strong Acid Catalyzed

Reactions

189

in super acids and gaseous ion-molecule reactions which occur in the mass spectrometer. SCHEME 2 METHANE C O N D E N S A T I O N REACTION HS0 F-SbF

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

3

5

This parallelism is reflected in the proposed mechanism for the ionization of methane which shows that (a) the second step of the scheme involves attack of an ethyl cation on methane, but the reaction cannot stop there, and goes on to (b), the third step, which involves attack of a secondaryisopropyl cation on methane. The primary and secondary alkyl cations are very strongly acidic species and are unstable under the reaction conditions. The condensation reaction essentially terminates with the much more weakly acidic tertiary-butyl ion. Alkane polycondensation and olefin polymerization side reactions producing stable, less acidic, tertiary ions obscured the simple alkylation reactions of the primary and secondary alkyl cations. Implicit in this mechanism, however, is that it is possible to react an acidic energetic primary cation (such as the ethyl cation) with molecules as weakly basic as methane and thus, the door was opened to new chemistry through activation of the heretofore passive, weakly basic, "paraffins" (20-24). Results and Discussion Alkene-Alkane Alkylations. A logical approach to achieve the catalytic alkylation reaction of methane was to initiate electrophilic attack

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

190

INDUSTRIAL AND LABORATORY ALKYLATIONS

of its very unreactive C - H bonds by using a very energetic primary carbenium ion. The simplest way to generate such an ion is to dissolve ethylene in a large excess of a super acid at a moderate temperature (in which it would be as fully protonated as possible) to form the highly acidic and reactive primary ethyl cation. The ion is thus available to react with the strongest base available, i . e . , methane, in an alkene-alkane alkylation in contrast with the traditional alkane-alkene alkylations. We have now found that such simple addition reactions can be selectively carried out in the HF-TaF5 catalyst system (25). A methane:ethylene (85.9%: 14.1%) gas mixture was passed through an autoclave containing 50 cc of a 10:1 HF-TaF (2.0 mol/0.20 mol) system stirred at 1000 rpm at 4 0 ° and maintained at 40 psig. In order to minimize possible competition from ethylene oligomerization reactions a forty-fold excess of acid as well as efficient mixing was maintained and the temperature was not permitted to vary more than +1 ° . Gas samples were taken after 1 .5 and 2.5 hours and the selectivity to C3 in the product amounted to 58%.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

5

Mechanistically, two pathways are logical (Scheme 3). The ethyl cation can directly alkylate methane via a pentacoordinated carbonium ion (Olah) (path a), or alternatively, although a less favorable pathway (b), the ethyl cation could abstract a hydride ion from methane. The methyl cation thus formed, which is less stable by ^39 kcal/mole (26), could then react directly with ethylene. In the latter case, propylene and/or polymeric material would probably be formed since the hydrogen required for a catalytic reaction has been consumed by the formation of ethane. SCHEME 3 ETHYLENE-METHANE ALKYLATION AT 4 0 ° C HF-TaF

5

CH2 ~~ CH2

CH —

CH

3

CH -CH2~CH 3

3

*<-

CH -CH-CH + 3

3

3

+

+ CH -CH 3

^

3

CH -CH=CH 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2

11.

SISKIN E T A L .

Strong Acid Catalyzed

Reactions

191

Ethylene alone (15% diluted in helium) does not react in HF-TaF^ at 4 0 ° C to form any propane product but rather forms a complex mixture of unsaturated and higher molecular weight products. Methane also does not react at all under these conditions (27). It should be noted that unless a flow system is used, the propane product, which is a substantially better hydride donor than methane, reacts further with the intermediate ethyl cation to ultimately form ethane and propylene (eq. 2). CH -CH -CH 3

2

3

^CH -CH + 3

2

CH -CH-CH Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

3

I—^

3

(

+ CH -CH 3

2

)

3

>• C H - C H = C H 3

2

In our work, o n l y ^ l % of the propylene formed in the flow system reacted with another molecule of methane to form isobutane. Also, based upon the results of acid quenching and analysis of hydrocarbons, only traces of isopentane and isohexanes were present in the acid. No hydrogen or hydrocarbons above C could be detected in the product. In an attempt to generate primary (trivalent) cations and to simulate the ethylene-methane alkylation, ethyl chloride was reacted with methane (eq. 3) under alkylation reaction conditions (28). When no propane or propylene product was observed, the energetically more favorable reaction of methyl chloride with ethane was carried out (eq. 3a). These two reactions proceeded without any involvement of the alkane and provide evidence that the ethylene-methane alkylation proceeds through a more stabilized species such as a pentacoordinated carbonium ion. The behavior of these alkyl chlorides will be discussed separately after the alkylation chemistry. Q

HF-TaF ,

40°C

5

CH CH CI 3

2

Chi C H CH C H 3

2

3

CH CI 3

(3) (3a)

It should also be noted that the propane product is not being formed by degradation of polyethylene, because under similar reaction conditions,

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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192

INDUSTRIAL AND LABORATORY ALKYLATIONS

but in the presence of hydrogen, we have shown that the polymer (MW 800,000) reacts quantitatively to form C3-C6 paraffins with isobutanes and isopentanes constituting over 85% of the product. The polymer degradation products can be easily rationalized on the basis of known carbenium ion stabilities in acid media. Olah (29) observed t-butyl cation by reaction of polyethylene in "magic a c i d . " These results further substantiate that the direct alkene-alkane alkylation takes place in the ethylene/methane reaction. The reaction of ethylene with ethane is of major scientific significance. The only C4 product, formed in 78% selectivity, in this reaction is norma I butane (Scheme 4) which does not isomerize under these conditions with the HF-TaF5 catalyst (eq. 4) or under similar conditions with the HF-SbF5 catalyst (30). This means that the primary ethyl cation is alkylating a primary ethane position (path a) and that there is no classical free primary norma I-butyl cation formed (path b) because such a cation, as would be generated from n-butylchloride, would yield exclusively isobutane upon rearrangement as shown in one experiment carried out where n-butyl chloride with hydrogen in the acid yielded only isobutane (eq. 5). SCHEME 4 ETHYLENE-ETHANE ALKYLATION AT 4 0 ° C HF-TaFc

CH2~CH2

R CH3-CH3

+

CH -CH 3

2

+

CH2 ~ CH2

C H - C H - C H - C Η,η 0

0

0

CH3-CH2" CH

CH

3

3

+H^C-CHo. -2-> CH.

\ CH

/I 3

C-CHo 3

Η

CH3-CH2-CH2-CH3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

SISKIN E T A L .

Strong Acid Catalyzed

HF-TaF °

193

Reactions

5

CH CH CH CH 3

2

2

3

CHoCHoCH CH CI 9

3

2

2

9

2

N.R.

HF-TaFs, 2 0 ° C — ^ •—>H 0.13 mole ^ 2

(0.05 mole)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

>

(4)

C

H

3 ^

C-CHo cw*% I 3 H

(5)

C H

Of further interest is the fact that η - b u t y l chloride reacts in the pres­ ence of excess ethane, also at 4 0 ° C , to form b u t y l è n e s (85%) and some isobutane (15%)(eq. 6a). These products lead to the conclusion that rearrangement of the "free" trivalent carbenium ion is more rapid than hydride abstraction from another η - b u t y l chloride molecule. The t-butyl carbenium ion thus formed, being too weak an acid to abstract a hydride, deprotonates to form b u t y l è n e products. No isohexane alkylation products are formed (eq. 6). C H 6

CH CH CH CH CI 3

2

2

(0.05 mole)

2

1 4

's

(6)

HF-TaF , 4 0 ° C 5

0

CH3CH3 (0.13 mole) C

4 8' H

S

(85%)

+

r 4 c

H

io

^

(15%)

The secondary propyl carbenium ion formed in the reaction of propylene (3.4%) at 4 0 ° in 10:1 HF-TaF5, attacks methane (96.6%) to form isobutane (Scheme 5) with 60% selectivity. Olah (1 7a) has also reported the alkylation reactions (at - 1 0 ° with 1 :1 HS03F-SbF5) of η - b u t a n e with ethylene to yield 38 weight percent of hexanes and of η - b u t a n e with propylene to yield 29 weight percent of heptanes. The former reaction has also been reported by Parker (31 ) at 6 0 ° , but the product in this case more nearly resembles polyethylene degradation products. In our work with 10:1 HF-TaF5 at 4 0 ° , in a flow system, ethylene (14.1 wt.%) reacted with η - b u t a n e to form 3-methylpentane as the initial product of 94% selectivity (Scheme 6, path a). The alternative, i . e . , the direct reaction of ethylene with a secondary-butyl cation (path b), can be ruled out since butane does not ionize under these conditions (vide supra). The products of the reactions in schemes 4 and 6 suggest strongly that cations or tight ion pairs of the pentacoordinated type proposed by Olah are more stable than the classical type in these reactions. In pentacoordinated systems three center-two electron bonds help stabilize the system relative to a localized cation. This becomes more

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

194

INDUSTRIAL AND LABORATORY ALKYLATIONS SCHEME 5 A L K Y L A T I O N O F M E T H A N E WITH PROPYLENE

HF-TaF

5

CH3CH — C H

2

xsH CH3CHCH3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

+ I

CH

A

CH
\

(CH ) C4 3

3

+H~

CH-,

(CH ) CH 3

3

important as the carbocation type goes from tertiary to secondary to primary and thus we can rationalize the formation of η - b u t a n e rather than^-butane in the ethylene/ethane reaction and of 3-methylpentane rather than 2 , 3 dimethylbutane in the ethylene/butane reaction. Direct Alkyl Chloride Reductions. It was previously pointed out that at 4 0 ° in HF-TaF5 methyl- and ethyl-chloride do not form the expected a l k y l ­ ation product with alkanes, expected that is, assuming traditional carbenium ion chemistry, but rather underwent an independent reaction. The second part of this paper will describe in more depth what reactions do take place when alkyl chlorides react in the presence or absence of the lower alkanes under our reaction conditions of 4 0 ° C . A century ago, Friedel and Crafts (32) reported that "when a small amount of anhydrous aluminum chloride was added to amyl chloride an immediate vigorous evolution of gas was observed in the cold. The gas was composed of hydrogen chloride accompanied by gaseous hydrocarbons not absorbed by bromine." The precise nature of these saturated hydrocarbons has not been well understood. In the course of our mechanistic studies on alkene-alkane alkylations we observed the direct reduction products of several alkyl chlorides. While there exists an extensive literature on the b e -

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

SISKIN E T AL.

Strong Acid Catalyzed

195

Reactions

SCHEME 6 A L K Y L A T I O N O F N O R M A L - B U T A N E WITH ETHYLENE

HF-TaF

5

CH

2

= CH

2

V

f CH -CH 3

CH -CH -CH -CH 3

2

2

\ CH -CH -CH CH (b)\ 3

;

2

2

3

CH -CH-CH CH + CH CH

CHo Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

2

3

2

3

3

3

CH -CH -CH—; 3

2

CH CH 2

CHq 3

.C-CH CH

-H

x

3

+

3

CH CH 2

CHo

CHq

C H -CH2~CH-CH ~CH 3

2

—

2

CHq

"CHo

•CH -CH-CH-CH

3

3

CH

3

+CH-CH

3

CHo

3

havior or alkyl chlorides in acidic and super-acidic media, we believe that these results represent the first conversion of C] - C alkyl chlorides as determined by analysis of the primary gas phase products to the corresponding alkane. The reactions proceed in considerable yield (up to 34%), via a direct hydride transfer route. We have looked at the following systems in HF-TaF^ at 4 0 ° C (eq. 7-9): C H C I , C H ^ C I , and Î S O - C H T C I . The latter systems and n-C H7CI were also studied in HChAICf^ at 1 4 0 ° . In all cases the gas phase was analyzed and, where reaction occurred, the corresponding alkane was found to be the major product. The first conclusion is that the lower alkane does not participate in the reaction and the alkyl chloride reacts with a second molecule of alkyl chloride to form the direct reduction product which is observed in the gas phase. These gas phase products do not account for all of the alkyl chloride charged to the reactor. Upon quenching the acid, we can recover some alkyl halide and some higher molecular weight condensed-hydrocarbon products. 3

3

2

3

3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

196

INDUSTRIAL AND LABORATORY ALKYLATIONS

ANALYSIS OF G A S PHASE HF-TaF

5

CVU

CH3CH3

(7)

CH3CH3

(7a)

CH CH -CI 3

2

C t t o g ^ C H

(8)

4

CH3-CI (8a)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

CH,

CH, ;CH-CI

*

CH CH CH 3

2

(9)

3

CH,

Olah (33) has shown that alkyl fluorides undergo a self-condensation reaction (eq. 10) similar to that previously described for the ionization and condensation of methane so that this additional pathway is not an unexpected one. SELF C O N D E N S A T I O N O F ALKYL FLUORIDES IN HF-SbF^

FCH + • CH F-SbF " ,

3

3

5

00)

^ FCH — 2

XH

3

"RF-SbF " 5

FCH CH 2

( C H ) C , Etc. 3

3

3

Using the propyl chlorides as an example (eq. 11, Table II), after five minutes at 1 4 0 ° in a 45 cc Hastelloy C reactor charged with aluminum chloride and 2-chloropropane the pressure was 500 psig of which 71 % was propane by mass spectrometric analysis. CH3CHCH3 Cl

HCI-AICI3 140°C

C H3C H3C H3

CH CH CH CI J 2

2

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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11.

SISKIN ET AL.

Strong Acid Catalyzed

197

Reactions

TABLE II REACTION OF PROPYL CHLORIDES IN HCI-AICI3 Compound

% C Conv. to C^Hg

N^HTCI

5 15

34 24

n-C H7CI

5 15

18 17

3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

Time (Min.)

In other words, of the initial charge of isopropyl chloride, 34% of the carbon is converted to propane under these conditions. A comparable sample of 1-chloropropane under identical reaction conditions, of excess alkyl halide vs. Lewis acid, was converted after five minutes to the extent of 18% to propane. After 15 minutes the relative amount of "propane" had decreased as a result of further acid catalyzed polycondensation reactions. Similarly, isopropyl chloride reacts in HBr-AIBr3 at room temperature to give a gas product which is entirely propane after 2 min. In this system we again begin to see a buildup of heavier hydrocarbon species with time. The fact that the reaction proceeds so rapidly here can probably be attributed to a homogeneous hydrocarbon/acid liquid phase. This last result and additional experiments are summarized in Table IV. Since the ratio of acid to alkyl halide could conceivably affect the acidity of the medium and hence the reaction mechanism, these reactions were also carried out at widely varying ratios (Tables III and IV). The results indicate that in aluminum halide systems the stoichiometry does not alter the primary pathway. In the HF-TaF5 system at the higher acid :a Iky I chloride ratio there is a lower selectivity to the alkane with hydrogen the only other major product in the gas phase lending support to the conclusion that condensation is the major competing reaction. 2-Chloropropane undergoes a shift in reaction mechanism at low acid:alkyl chloride ratio to form the direct reduction product propane. The more acidic methyl cation, on the other hand, undergoes only slow polycondensation (^25% in 1 hr.) reaction and no direct reduction at the low acid:alkyl halide ratio. Mechanistically, alkane formation could be occurring via several pathways. 1 . Dialkylchloronium ions (Scheme 7): The existence of halogen substituted cations (34) is well documented in the literature as is the existence of dialkylhalonium ions (35). Support for this possibility in our studies comes from low temperature ( - 3 5 ° C ) 60 MHz pmr spectra of the acid layer of the methyl chloride reaction in HF-TaF5 which shows a sharp

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL AND LABORATORY ALKYLATIONS

TABLE III REACTIONS O F ALKYL CHLORIDES WITH STRONG ACIDS - RESULTS -

% RH on Total HC Gases % CH

%C iJ6

% 3 8

57

49

48

0

—

97

4

2

C

TaF :RCI(4:l)^ 5

HF-TaF

5

4 0 ° C , 2 hr. TaF :RCI(l -A) Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

5

R=CH ,C H i-C H 3

2

5 /

3

7

% C H g of HC Gases ?

i-PrCl AICI :RCI(4:1)^ = >3

HCI-AICI

n-PrCI

97

3

1 4 0 ° C , 5 min.

AICI :RCI(1 :4) 3

97

97

R—Î -Cg Hy, Π -Cg Hy

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

H

11.

SISKIN E T AL.

Strong Acid Catalyzed

199

Reactions

TABLE IV SUMMARY OF RESULTS OF THE REACTIONS OF ALKYL CHLORIDES WITH STRONG ACIDS % RH % RH in in Total Gas Phase HC Gase:

MXn/ RCI

CH3CI

4.0

10:1 HF-TaF ( )

40

30 60 120

6.6 7.5 8.9

CH3CI

0.2

10:1 HF-TaF

5

40

60

0.0

0.0

4.0

10:1 HF-TaF

5

40

30 60 120

9.7 10.0

25.7 32.2 49.3

0.2

1:1 HCI-AICI3

140

5 15

47.0^

97.2 93.0

5 15

70.7(°) 56.8< )

97.1 92.8

CH CH CI 3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

t

Alkyl Chloride (R-CI)

2

CH CH CH CI 3

2

2

(CH ) CHCI 3

2

0.2 4.0

Τ Acid

(mîn.) 5

1:1 HCI-AICI3 1:1 HCI-AICI3 10:1 HF-TaF

5

0.2

10:1 HF-TaF5

0.2

1 :1 HBr-AlBr

3

a

140

21.5< > 42.3 57.0 d

c

140

5

>90.0

96.8

40

30 60 120

30.1 32.5 33.4

43.0 46.0 47.8

40

5 60

55.5 61.8

97.0 96.7

20

2 18

~100.0 ~ 90.0

~ 100.0^ ~ 90.0

(a) HF-TaF5 (2.0 mole:0.2 mole) + RCI (0.05 mole) in a 300 cc Hastelloy C Autoclave Engineers autoclave stirred at 1000 rpm. (b) Yields: 9.5% and 9.0% in 5 and 15 min. respectively. (c) Yields: 34.2% and 23.6% in 5 and 15 m î n . respectively. (d) 21 .5% of the hydrocarbons in the gas phase is methane. (e) Analysis via gas chromatography.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

200

INDUSTRIAL AND LABORATORY ALKYLATIONS

singlet at 4.1 < S in HF solution relative to external TMS (36). This peak represents about 50% of the unreacted methyl chloride remaining in the acid layer. This also indicates that the formation of dimethylchloronium ion must be more rapid than displacement of chloride in methyl chloride by fluoride ion and that since fluoride is too electronegative to form fluoronium ion salts the fluoride does not displace chloride from the dimethylchloronium ion. SCHEME 7 Via Dialkylhalonium Ions:

+

2R CHCI + MXn (R CH) CI(MXnCI)~ + (R CH) CI(MXnClf + R CHCI ^R CH +

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

2

2

2

2

2

2

2

2

+ (R CHCICR CI)(MXnCI)" 2

2

2. Chloroalkyl carbenium ions (Scheme 8): The existence of simple halomethyl cations has as yet only been the subject of speculation and discussion (37). The stability of such species should become increasingly favorable as the size of the alkyl group and number of such groups is increased. Recent energy calculations by Hehre favor the 1 -haloethyl form of the cation (38). Based upon the temperature dependence of the observed nmr spectrum, Olah (39) has postulated the formation of the 1-fluoroethyl cation by the reaction of SbF5 with 1,1 -difluoroethane. He also observed the 1 chloroethyl and chlorine-bridged ethyl cation in the nmr by reaction of SbF5 in sulfuryl chloride and from ^ C nmr results predicts a significant contribution by the CH3-CH=CI resonance form. That part of these reactions are occurring through this type of species cannot be precluded. We have not as yet been successful, however, in identifying by nmr or quenching experiments with toluene possible chloroalkyl-halonium ions in the acid solution. 3

+

SCHEME 8 Via Haloalkyl Carbenium Ions:

+

R CHCI + M X n ^ = ^ R CH(MXnCI)" 2

2

+ R C H ( M X n C l f + R CHCI 2

2

+ ^ R C H + R CCI(MXnCI)" 2

2

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

11.

SISKIN E T AL.

Strong Acid Catalyzed

Reactions

201

For the reaction of the propyl chlorides, the possibility of dehydrohalogenation followed by hydride abstraction from propylene to produce propane, while remote, cannot be discounted (Scheme 9). We believe, however, that propylene formation would produce oligomerization and polymerization products and thus is not consistent with fully one-third of the product going to propane. SCHEME 9 For Propyl Chlorides: A.

Via Propenyl Cation Formation; CH CHCH +MXn

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

3

MCH3CHCH3) ( M X n C l f

3

Cl (CH3CHCH3) ( M X n C l f

>H (MXnClf +CH CH=CH +

3

2

+ C H C H = C H + (CH3CHCH3) MXnCI" 3

2

+ CH CH CH 3

2

3

+ (CH —CH—CH )MXnCI" 2

2

Or, B.

Via Di isopropyl Chloronium Ion; C H C H = C H + ([CH ] CH) CI(MXnCI)~ 3

2

3

CH CH CH 3

2

2

2

>.

+

3

+ (C H )-CI-(C H ) (MXnClf 3

5

3

7

In any case, the conversion of methyl or ethyl chlorides to methane and ethane, respectively, precludes the ally lie hydrogen donation pathway for these systems and lends support to a mechanism such as outlined in schemes 7 and 8. In a related experiment we looked at the chemistry of methanol in HCI-AICI3 at 1 5 0 ° C . We were interested in determining whether a reduction reaction of methanol to methane (eq. 12) could be competitive with conversion to methyl chloride (eq. 13). Mass spectral results show copious amounts of methyl chloride in the gas phase after 5 min. and 30 min. of reaction, with little or no methane, thus arguing that, if occurring, the

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

202

INDUSTRIAL AND LABORATORY ALKYLATIONS

reduction does not kinetically compete with the conversion to methyl chloride under our conditions. COMPETITIVE REDUCTION V S . CHLORINATION O F METHANOL — HCI-AICI3 CATALYST—

H+ 2CH OH ^

"

3

+ (CH ) OH 3

2

H ( C H ) O H + CH3OH

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

3

^CH

2

4

(,2)

+ HOCH -0-CH 2

3

I Versus |

CH OH^=^= C H 3

3

O H

2

^ = ^

(13)

CH3CI

Conclusions The complexity of the chemistry involved is apparent from the variety of plausible pathways which can be invoked to explain that part of the reaction we can measure. The work to date clearly indicates that differences in reaction products will result and should be expected in comparing the behavior of carbocations generated from the alkane versus the complex mixture of cationic species generated from the alkyl chloride in super acid media. REACTIONS IN STRONG FRIEDEL-CRAFTS ACIDS PROCEED VIA DIFFERENT STABILIZED SPECIES Via De localized PentaCoordinated Carbonium Ion

Via Localized Trivalent Carbenium Ions

C H 2

C H C\

6

2

C H CI 2

C

4 10 H

C H

C2H4

5

H" 4 10 C

H

2

C

4 10 H

5

C H CI 2

6

C H 2

6

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5

11.

SISKIN ET AL.

Strong Acid Catalyzed

Reactions

203

We believe much more work is needed before the true nature of species obtained via the acid catalyzed treatment of haloalkanes is well understood and we are loathe to extrapolate from alkane/acid systems to those involving carbon halogen bonds.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

Literature Cited 1. Fairbrother, F., Grundy, Κ. H. and Thompson, Α . , J. Chem. Soc., 765 (1965). 2. O'Donnell, Τ. Α . , "The Chemistry of Fluorine," Vol. 5, p. 1078, Pergamon Press, Oxford, England, 1973. 3. Canterford, J . H. and O'Donnell, Τ. Α., J. Inorg. Chem. 5, 1442 (1966). 4. Muetterties, E. L. and Castle, J . E., J. Inorg. Nucl. Chem., 18, 148 (1961). 5. Emeleus, H. J. and Guttmann, V . , J. Chem. Soc., 2115 (1950). 6. Oelderik, J. M . , Mackor, E. L., Platteeuw and van derWiel, Α . , U.S. Patent 3,201,494, August 17, 1965. 7. Olah, G. A. and Olah, J . A. in "Carbonium Ions," Vol. II, p. 761, Edited by G. A. Olah and P. v. R. Schleyer, Wiley - Interscience, New York, New York, 1970. 8. Olah, G. Α . , Schilling, P. and Grosse, I. M . , J. Amer. Chem. Soc., 96, 876 (1974). 9. Gillespie, R. J. and Peel, T. E., "Advances in Physical Organic Chemistry," Vol. 9, p. 16 and references cited therein, Edited by V. Gold, Academic Press, New York, New York, 1971. 10. Simons, J . H. in "Fluorine Chemistry," Vol. I, p. 225 and references cited therein, Edited by J. H. Simons, Academic Press, New York, New York, 1968. 11. Gillespie, R. J., personal communication. 12. Siskin, M . , J. Amer. Chem. Soc., 96, 3641 (1974). 13. Patinkin, S. H. and Friedman, B. S. in "Friedel Crafts and Related Reactions," pp. 254-255, Edited by G . A. Olah, Vol. II, Interscience Publishers, New York, New York 1964. 14. Olah, G. A. and Schlosberg, R. H., J. Amer. Chem. Soc., 90, 2726 (1968). 15. Olah, G. Α., Schilling, P., Staral, J. S., Halpern. Y. and Olah, J. Α., ibid., 97, 6807 (1975). 16a. Schmerling, L. and Vesely, J. Α., J. Org. Chem., 38, 312 (1973). b. Schmerling, L., J. Amer. Chem. Soc., 97, 6134 (1975). 17a. Olah, G. Α . , U.S. Patent 3,708,553, January 2, 1973. b. van Dijk, P., U.S. Patent 3,415,899, December 10, 1968. c. Pinkerton, R. D., U.S. Patent 2,177,579, October 24, 1939.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch011

204

INDUSTRIAL AND LABORATORY ALKYLATIONS

18. Calculated from values taken from D. R. Stull, E. F. Westrum, Jr. and G. C. Sinke, "The Chemical Thermodynamics of Organic Com­ pounds," John Wiley and Sons, Inc., New York, New York 1969. 19. Schmerling, L., J . Amer. Chem. Soc., 66, 1422 (1944). 20. Olah, G. Α., Klopman, G. and Schlosberg, R. H., J. Amer. Chem. Soc., 91, 3261 (1969). 21. Hogeveen H., Lukas, J. and Roobeek, C. F., Chem. Commun. 920 (1969). 22. Olah, G. A. and Mo, Y. K., J . Amer. Chem. Soc., 94, 6864 (1972). 23. Roberts, D. T., Jr. and Calihan, L. E., J. Macromol. Sci., Chem., 7, 1629 (1973). 24. Olah, G. Α . , Yoneda, N . and Parker, D. G., J. Amer. Chem. Soc., 98, 5261 (1976). 25. Siskin, M . , ibid, 98, 5413 (1976). 26. Field, F. H. and Franklin, J. L., "Electron Impact Phenomena and Properties of Gaseous Ions,", p. 87, Academic Press, Inc. New York, New York, 1957. 27. Results reported by Z. Vostroknutova and A. A. Shteinman in Kinet. Katal., 13, 324 (1972) indicate that even at 50°C in 1 :1 HSO F­ -SbF ,theionizationof methane is too slow to account for our results in terms of the traditional alkylation mechanism. 28. Schlosberg, R. H., Siskin, M . , Kocsi, W. P. and Parker, F. J., J. Amer. Chem. Soc., 98, 7723 (1976). 29. Olah, G. A. and Lukas, J. ibid., 89, 4739 (1967). 30. Brouwer, D. M. and Oelderik, J. M., Rec. Trav. Chim., 87, 721 31. Parker, P. T., U.S. Patent 3,636,129, January 18, 1972. 32. Friedel, C. and Crafts, J. M . , Compt. Rend., 84, 1450 (1877). 33. Olah, G. Α . , DeMember, J. R., Schlosberg, R. H. and Halpern, Y . , J. Amer. Chem. Soc., 94, 156 (1972). 34. Olah, G. Α., and Comisarow, M. B., J. Amer. Chem. Soc., 91, 2955 (1969). 35. Olah, G. A. and DeMember, J . R., ibid., 2113 (1969). 36. Farcasiu, D.A., personal communication. 37a. Ogata, Y. and Okano, M . , J. Amer. Chem. Soc., 78, 5123 (1956). b. Olah, G. A. and Yu. S. H., ibid., 97, 2293 (1975). 38. Hehre, W. J. and Hiberty, P. C., ibid., 96, 2665 (1974). 39a. Olah, G. Α . , Beal, D. A. and Westerman, P. W., ibid., 95, 3387 (1973). b. Olah, G. Α., Mo, Y. K. and Halpern. Y . , J . Org. Chem., 37, 1169 (1972). 3

5

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

12 Base-Catalyzed Carbon-Carbon Addition of Hydrocarbons and Related Compounds H E R M A N PINES

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

The Ipatieff Catalytic Laboratory, Department of Chemistry, Northwestern University, Evanston, IL 60201

The d i s c o v e r y that sodium in the p r e s e n c e of s m a l l amounts of organosodium compounds, produced in s i t u o r deposited on a l u m i n a , acts as an effective catalyst for double bond i s o m e r i z a t i o n of alkenes and cyclenes (1) t r i g g e r e d much r e s e a r c h in this field (2). It was subsequently d i s c o v e r e d that b a s e - c a t a l y z e d i s o m e r i z a t i o n of olefins m a y p r o c e e d i n homo­ geneous solutions using l i t h i u m ethylenediamine (3) o r potassium tert-butoxide ( t - B u O K ) in d i m e t h y l sulfoxide (DMSO) (4). B a s e - c a t a l y z e d c a r b o n - c a r b o n addition reactions are of synthetic interest because they afford hydrocarbons and r e l a t e d compounds in good yields by a s i m p l e one-step p r o c e d u r e . T h e s e reactions a r e made p o s s i b l e by the fact that hydrocarbons and r e l a t e d compounds having a benzylic or a l l y l i c hydrogen a r e carbon a c i d s , having a pK of about 35 to 37; they can donate a proton to a base and thus become carbanions. T h e s e carbanions can add to olefinic h y d r o c a r b o n s . The steps involved in the catalytic chain reactions a r e i l l u s t r a t e d by the following set of equations, using toluene and ethylene as reactants, and sodium as catalyst (5). a

P r o m o t e r + Na -4 B ~ N a

+

(1)

Initiation C H CH 6

5

+

3

B~Na

+

2

C H CH "Na 6

5

+

+ BH

2

(2)

Addition C H CH ~Na 6

5

2

+

+ CH =CH 2

2

^=^- C H CH CH CH ~Na 6

5

2

2

+

2

205

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

(3)

INDUSTRIAL AND LABORATORY ALKYLATIONS

206

Propagation C H CH CH CH "Na 6

5

2

2

2

+ C H CH

+

6

5

C H CH CH CH

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

6

5

2

2

3

3

+ C H CH "Na 6

5

2

+

(4)

Step 2, chain initiation, involves the metalation of toluene by an organosodium compound. Since the action of sodium on the reactants does not produce organosodium compounds, a " p r o m o t e r " is added to a c c o m p l i s h it. o - C h l o r o toluene and anthracene were found to be effective p r o m o t e r s since they r e a d i l y react with sodium to f o r m b e n z y l s o d i u m and disodium anthracene (6), r e s p e c t i v e l y . T h e p r o m o t e r s also facilitate the d i s p e r s i o n of s o d i u m into a v e r y fine black powder which can f o r m additional organosodium compounds as the reactions p r o g r e s s . Step 3, the addition r e a c t i o n , is e n e r g e t i c a l l y the least favorable step as it involves the f o r m a t i o n of an anion l a c k i n g resonance s t a b i l i z a t i o n f r o m a r e s o n a n c e - s t a b i l i z e d b e n z y l i c anion. However, once the anion adduct i s produced it i s i n s t a n taneously and i r r e v e r s i b l y protonated by the b e n z y l i c hydrogen of the toluene p r e s e n t . T h e f a c i l i t y with which addition o c c u r s depends to a great degree on the olefin used. A d d i t i o n of b e n z y l anion to propene r e q u i r e s m o r e d r a s t i c conditions than to ethylene, due both to s t e r i c and to inductive effects. The addition r e a c t i o n is greatly facilitated when conjugated alkadienes or styrenes are used as olefins s i n c e the anion adducts f o r m e d are resonance s t a b i l i z e d by conjugation with a double bond and benzene r i n g , r e s p e c t i v e l y . The ease of addition to olefins depends also on the acidity of the a l k y l a r e n e s used i n the r e a c t i o n . 4 - M e t h y l p y r i d i n e , having a p K of about 29 at - 4 0 ° , adds to isoprene at r o o m temperature i n the p r e s e n c e of t - B u O K i n D M S O . T o l u e n e , however, having a much higher p K does not add to isoprene i n the p r e s e n c e of this catalyst. Of the a l k a l i m e t a l s , p o t a s s i u m is a m o r e effective catalyst than s o d i u m , while lithium has only l i m i t e d applications as catalyst. Unlike s o d i u m , p o t a s s i u m also catalyzes c e r t a i n c y c l i a l k y l a t i o n r e a c t i o n s , and thus p r o v i d e s new methods for the synthesis of a v a r i e t y of c y c l i c compounds. a

a

O l i g o m e r i z a t i o n of O l e f i n s Propene.

T h e o l i g o m e r i z a t i o n of olefins by bases was

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

12.

PINES

Base-Catalyzed

Carbon-Carbon

Addition

207

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

r e p o r t e d i n 1956 u s i n g s i m p l e olefins o r olefin p a i r s i n the p r e s e n c e of s o d i u m as catalyst, and anthracene as a chain initiator (7). T h e olefins u s e d were ethylene, propene, i s o butylene, and cyclohexene. T h e d i m e r i z a t i o n of propene at about 2 1 0 ° i n the p r e s e n c e of potassium o r c e s i u m y i e l d e d 4 - m e t h y l - l - p e n t e n e as the predominant d i m e r (8). T h e d i m e r i z a t i o n proceeds through an i n i t i a l f o r m a t i o n of an organoalkali compound, followed b y metalation of the propene. T h e d i m e r i z a t i o n of propene i n a flow s y s t e m over supported p o t a s s i u m or s o d i u m on graphite o r potassium carbonate, at 1 5 0 ° and under p r e s s u r e , gave good y i e l d s of d i m e r s , and the c o p o l y m e r i z a t i o n of ethylene with propene on supported a l k a l i m e t a l catalysts gave 92$ pentenes (9). Isoprene. U s i n g benzene as solvent and sodium as catalyst isoprene undergoes o l i g o m e r i z a t i o n at 4 0 ° to y i e l d 47$ of d i m e r s and 20$ of t r i m e r s (10). T h e d i m e r f r a c t i o n contained 85$ m y r c e n e , 1, and the t r i m e r contained 76$ of 2. T h e f o r m a t i o n of these compounds involves an i n i t i a l metalation of the methyl group i n i s o p r e n e .

L i t h i u m naphthalene and sodium naphthalene (11) i n solvents such as T H F , d i g l y m e , o r aliphatic amines were found to be effective agents f o r the h y d r o d i m e r i z a t i o n of i s o p r e n e . Although this r e a c t i o n is not s t r i c t l y catalytic, it contributes to a better understanding of the b a s e - c a t a l y z e d o l i g o m e r i z a t i o n of unsaturated conjugated h y d r o c a r b o n s . In a t y p i c a l r e a c t i o n u s i n g T H F as solvent L i (0.1g.-at. ), naphthalene (0.03 mol), t r i e t h y l a m i n e (0.001 mol), and isoprene (0.1 mol) at 3 0 ° f o r 8 h r s , a 75$ y i e l d of h y d r o d i m e r s was obtained, consisting of 3 (43$), 4 (52$), and other products (5$).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL AND LABORATORY ALKYLATIONS

CHQ 3

CHQ 3

CHQ

CH C=CHCH CH C=CHCH 3

2

CHQ

I

(

2

3

I

CH C=CHCH CI|CH=CCH 3

2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

3

3

4

Styrenes. D i m e r i z a t i o n and c y c l i d i m e r i z a t i o n of styrene and of a - and β-methylstyrene have been a c c o m p l i s h e d i n the p r e s e n c e of b a s e s . T h e type of product depends greatly on the styrene and on the s p e c i f i c catalyst u s e d . The p o l y m e r i z a t i o n of styrene to f o r m m a c r o m o l e c u l e s using a l k a l i metal catalysts has been known and extensively u s e d . The d i m e r i z a t i o n of styrene i s , however, a novel reaction (12). D i m e r s of styrene, α - m e t h y l s t y r e n e and a c o d i m e r of the above two s t y r e n e s are obtained by heating the olefins at about 1 6 0 ° i n the p r e s e n c e of catalytic amounts of anhydrous _ t - B u O K . a - M e t h y l s t y r e n e yields 93$ d i m e r 5, while styrene f o r m s 11$ of 6. When a mixture c o n s i s t i n g of 1 m o l of styrene and 0. 5 m o l of α - m e t h y l s t y r e n e i s r e a c t e d , " d i m e r i c " m a t e r i a l composed of 7$ 5, 48$ 6, 32$ 7, and 13$ 8 r e s u l t s . The i n i t i a l

5

6

7

8

step probably involves the f o r m a t i o n of an i o n i z e d compound through the addition of _t-BuOK to the m o n o m e r . In the next step, through a concerted addition and e l i m i n a t i o n reaction an intermediate d i m e r , 9, i s produced which by the u s u a l b a s e catalyzed i s o m e r i z a t i o n is converted to 5.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

12.

PINES

Base-Catalyzed f H

Carbon-Carbon

209

Addition

8

v^CH -OC H 2

4

>CH JCH

2

K

-> _ t - B u O K

9

+

+

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

8

The intermediate d i m e r 9 could also be f o r m e d by a D i e l s - A l d e r condensation of the "monomers (13), followed by t - B u O K catalyzed i s o m e r i z a t i o n of the double bond (14). α -Methylstyrene, on r e f l u x i n g i n the p r e s e n c e of s o d i u m b e n z y l s o d i u m , produces a c y c l i c d i m e r 10 i n a 32$ y i e l d based on the r e a c t e d olefin (15). The other products are i s o p r o p y l benzene, a t r i m e r , and s m a l l amounts of p - t e r p h e n y l . The following m e c h a n i s m was p r o p o s e d for the~formation of the c y c l i c d i m e r 10. ^ C H

2

C H C 6

+ Β Na

5

+

-4


2

CH

2

+ BH

C H C^ 6

5

Na

n

Β ^ C H H C^ Q ^ C ^ ^CC H CH CH 2

A

+ Β

3

6

2

5

CH,

C H ,

C H -^ 6

Na

5

C H 6

Na

2

5

C 6H5

BH

R

+ Β Na

n

10 (B = b e n z y l s o d i u m o r any organosodium compound f o r m e d i n the reaction)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

210

INDUSTRIAL A N D LABORATORY A L K Y L A T I O N S

β -Methylstyrene undergoes d i m e r i z a t i o n to 1, 5 - d i p h e n y l 4 - m e t h y l - l - p e n t e n e , 11, i n 80-90$ y i e l d s , when heated at 1001 5 5 ° i n the p r e s e n c e of sodium (16), In the p r e s e n c e of the m o r e electropositive p o t a s s i u m , " h y d r o d i m e r i z a t i o n was the p r i n c i p a l r e a c t i o n , r e s u l t i n g i n the f o r m a t i o n of compound 12. CHo

CHQ

I CgE^CH^CHCHCI^CgH^

I

CgH5CH=CHCH CHCH C6H5 2

2

CH

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

11

3

12

T h e two reactions are m e c h a n i s t i c a l l y different: d i m e r i z a t i o n to f o r m 1^ is a t y p i c a l c a r b a n i o n - c a t a l y z e d chain r e a c t i o n , whereas h y d r o d i m e r i z a t i o n leading to compound 12 i s a non-catalytic r e a c t i o n . D i m e r 11. may undergo f u r t h e r reaction leading to the f o r m a t i o n of toluene, 1 , 3 - d i p h e n y l - 2 - m e t h y l p r o p a n e , 13_, and 3-methyl-4-phenylcyclobutene, 14: -

11

?

+

-

M

V

/Λ

Hs

[C H CH=CHCH'-CH^CH C H ] M 6

5

2

e

5

-,

+

RH C H CH=CHCH=CHCH 6

5

3

+ C H CH ~M e

5

2

R

J

+

L

R"M

^

C H CH 6

5

CH C H CH 6

5

2

M

+

1

+ C H CH=CHCH 6

5

^

3

RH

3

-

Η

C H CH CHCHC H M 6

5

2

6

5

? CgHsCHgCHCHgCgHs Η 3

^ R"M

3

+

+

13

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

12.

A

PINES

^

R

Base-Catalyzed

-

M

Carbon-Carbon

211

Addition

[C H CH--CH*-CH"-CH"-CH ]" M 6

5

2

+

RH CgHsCH Ç H — C H

2

M

C

+

6

H

CH=CH

5

Ç H - Ç H - C H

2

~

M

+

C H = C H ^

R

^

H

C

6

H

5

C H - C H C H

3

CH=CH

M

14

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

ο: , β - U n s a t u r a t e d E s t e r s and N i t r i l e s E t h y l crotonate undergoes fast and selective d i m e r i ­ zation at 1 1 0 i n the p r e s e n c e of p o t a s s i u m and a p r o m o t e r to f o r m the diethyl e s t e r of d i a c i d 1^5 with a high y i e l d (16). u

ÇH

3

CjH C H

3

Et(X)CCC~CHCH CCX)Et 2

15 C r o t o n o n i t r i l e undergoes o l i g o m e r i z a t i o n at 1 1 0 ° i n the p r e s e n c e of p o t a s s i u m - b e n z y l p o t a s s i u m catalyst to afford a m i x t u r e consisting 20-23$ of d i m e r and 67-75$ of a t r i m e r 18, and 5-15$ of high boiling product. T h e d i m e r was composed of 67$ c i s - , 16, and 33$ t r a n s - 2 - e t h y l i d e n e - 3 - m e t h y l - g l u t a r o n i t r i l e , 17. CHQ

I CHCH CN

H C 3

H

2

H

CN

CHQ ι

CHCH CN 2

H C

16

CN

3

17

T h e t r i m e r consisted of 75-80$ of 18.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

212

INDUSTRIAL AND LABORATORY ALKYLATIONS

H C 3

CH

N C

CN

3

18

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

Reaction of A l k y l a r o m a t i c H y d r o c a r b o n s with Olefins T h e b a s e - c a t a l y z e d r e a c t i o n of a l k y l a r o m a t i c s with olefins is unique i n that it allows the s i z e of the a l k y l group of an arylalkane to be i n c r e a s e d . A r y l a l k a n e s suitable for this r e a c t i o n are those which contain a b e n z y l i c hydrogen. T h e olefins most useful for this reaction are ethylene, p r o p y l e n e , conjugated alkadienes, and styrene and its d e r i v a t i v e s . Sodium and potassium are v e r y effective catalysts. Sodium u s u a l l y r e q u i r e s the p r e s e n c e of a chain p r e c u r s o r to initiate the reaction. Ethylation of alkylbenzene p r o c e e d s at 1 5 0 ° to 2 0 0 ° with ethylene p r e s s u r e ranging f r o m 1 to 70 atm. T h e r e a c t i o n involves the replacement of b e n z y l i c hydrogens by ethyl groups, i . e . , toluene f o r m s n-propylbenzene as the p r i m a r y product of r e a c t i o n , further ethylation produces 3-phenylpentane and 3ethyl-3-phenylpropane (5). T h i s reaction can also be extended to the ethylation of cycloalkylbenzenes, indan, and tetrahydronaphthalene. P o t a s s i u m also catalyzes c y c l i a l k y l a t i o n r e a c t i o n r e s u l t i n g i n the f o r m a t i o n of indans. T h e ratio of indans to monoalkylbenzenes f o r m e d depends on the extent of substitution on the a - c a r b o n atom, and in the case of isopropylbenzene the concentration of 1 , 1 - d i m e t h y l i n d a n amounted to 49$. Potassium hydride or K - B u L I s e e m to be m o r e effective catalysts for cycliethylation (20). Sodium i n the p r e s e n c e of o-chlorotoluene p r o m o t e r i s a selective catalyst for the ethylation of alkylnaphthalenes at 1752 0 0 ° (21):

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

12.

PINES

Base-Catalyzed

Carbon-Carbon

213

Addition

R

—

CH2CH2CH3

CH(C H ) 2

5

C(C H ) 2

5

2

3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

Only on prolonged heating and s t i r r i n g a s m a l l amount of the heptyltoluene is obtained. P o t a s s i u m - c a t a l y z e d ethylation of alkylnaphthalenes proceeds at 90-160° and, besides the n o r m a l s i d e - c h a i n ethylation, a c y c l i a l k y l a t i o n also o c c u r s . F r o m 1-methylnaphthalene compounds 19 and 20 are obtained, and f r o m 2methylnaphthalene compound 2 f T s obtained.

19 R = H 20

21

R = CoH 2 5 n

P r o p y l a t i o n of alkylbenzene with propene r e q u i r e s m o r e d r a s t i c conditions than that of ethylation. T h e m a i n product of s i d e - c h a i n propylation of toluene was isobutylbenzene. A l k e n y l a t i o n of A l k y l b e n z e n e s The m e c h a n i s m of alkenylation i s s i m i l a r to that of sidechain alkylation of a l k y l a r o m a t i c s and can be i l l u s t r a t e d as follows: C H CH 6

5

+ B*Na

3

C H CH "Na 6

5

2

^

+

+

^

+

C H CH "Na 6

5

2

CH =CHCH=CH 2

+

2

[C H CH CH CH -CH*-CH ]"Na 6

5

2

e

2

2

+

C H CH 6

C H CH "Na 6

5

2

+

+ C H CH CH CH=CHCH 6

5

2

2

5

3

3

The alkenylation r e a c t i o n proceeds at 100° or below. Y i e l d s of 80-91$ of monobutenylated alkylbenzene were obtained f r o m toluene, o - and p - x y l e n e , and ethylbenzene u s i n g sodium deposited on c a l c i u m oxide (23).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

214

INDUSTRIAL AND LABORATORY ALKYLATIONS

T h e pentenvlation of alkylbenzenes with isoprene was c a r r i e d out at 1 3 5 ° u s i n g d i s p e r s e d s o d i u m or p o t a s s i u m as catalyst (24). T w o monoadducts were obtained, A and B , with a r a t i o of A / B ranging f r o m 2 to 3.

CgH5ÇCH CH=CCH3

CgH5CCH Ç—CHCH3 2

2

R-i

R^

CH3

CH3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

A

Β R

= Ri = Η

R

—

R

— R| = CH3

H,

R| — CH3

In the p r e s e n c e of a catalyst c o m p o s e d of s o d i u m n a p h ­ thalene i n T H F , the pentenylation o c c u r s at 2 0 ° (25). A r a l k y l a t i o n of A l k y l b e n z e n e s M o n o - and diadducts have been p r o d u c e d i n r e l a t i v e l y good y i e l d s i n r e a c t i n g alkylbenzenes with s t y r e n e and a - and β -substituted s t y r e n e i n the p r e s e n c e of either s o d i u m or p o t a s s i u m at 1 0 0 - 1 2 0 ° (26). Toluene and ethylbenzene r e a c t with s t y r e n e to f o r m monoadducts 22_ and 2S_ and diadducts 24 and 25

CeHjCHjCI^CI^CeHs

/CH CgH CH^

3

5

CH CH CeH5 2

22

23

C6H CH(CH CH C6H ) 5

2

2

2

5

2

/ C H Cg^CT^

3

(CH CH CgH ) 2

24

2

25

Isopropylbenzene produces with styrene m o n o - and diadducts 26 and 27

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

5

2

12.

PINES

Base-Catalyzed

^(CH ) 3

Carbon-Carbon

^(CH )

2

3

CH CH CgHg 2

215

Addition

2

26

2

CH CHCH CH CgH5 2

2

2

27

α - M e t h y l s t y r e n e r e a c t s r e a d i l y with n-alkylbenzenes i n the p r e s e n c e of potassium to f o r m 1,3-diphenylalkanes i n y i e l d s ranging f r o m 73 to 82$. β - A l k y l b e n z e n e s on r e a c t i o n with toluene f o r m 1 , 3 - d i p h e n y l - 2 - a l k y l p r o p a n e s i n 60-95$ y i e l d s .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

Reaction of A l k y l p y r i d i n e s with O l e f i n s T h e p i c o l y l hydrogens of 2- and 4 - a l k y l p y r i d i n e s are m o r e acidic than the c o r r e s p o n d i n g benzylic hydrogens. For that r e a s o n , the reactions of a l k y l p y r i d i n e s with olefins o c c u r under m i l d conditions, and with conjugated dienes, s t y r e n e s , and v i n y l p y r i d i n e s at below r o o m t e m p e r a t u r e s . T h e mechanism of s i d e - c h a i n addition of a l k y l p y r i d i n e s to olefins is v e r y s i m i l a r to that d e s c r i b e d for alkylbenzenes. 2- A n d 4 - a l k y l p y r i d i n e s undergo r e a c t i o n with ethylene under p r e s s u r e at 1 4 0 - 1 5 0 ° i n the p r e s e n c e of s o d i u m to f o r m the c o r r e s p o n d i n g 2 - n - p r o p y l - and (3-pentyl)-2- and 4p y r i d i n e s . Y i e l d s of"86-94$ of monoethylated products are obtained f r o m higher 2- and 4 - a l k y l p y r i d i n e s (28). The relative ethylation of 4 - a l k y l p y r i d i n e s i s 3. 5 to 7. 0 t i m e s g r e a t e r than that of 2 - a l k y l p y r i d i n e s , and is a s s o c i a t e d with g r e a t e r acidity of the 4 over the 2 i s o m e r s . 3- A l k y l p y r i d i n e s . T h e r e a c t i o n between ethylene and 3a l k y l p y r i d i n e s i n the p r e s e n c e of a l k a l i m e t a l is m u c h m o r e complicated than s i m i l a r r e a c t i o n s made with the c o r r e s p o n d i n g 2 and 4 i s o m e r s (29). The two p r i m a r y products f r o m the r e a c t i o n of 3-ethylpyridine with ethylene i n the p r e s e n c e of either sodium or potassium are 3 - s e c - b u t y l p y r i d i n e and c y c l i c compound 28. F u r t h e r ethylation o c c u r s with a longer r e a c t i o n time to f o r m 29.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

216

INDUSTRIAL AND LABORATORY ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

28 C H —CH 2

2

7

29 2 - A n d 2- A l k y l p y r i d i n e with D i o l e f i n s , Styrenes, and V i n y l p y r i d i n e s . T h e r e a c t i o n of a l k y l p y r i d i n e s with i s o p r e n e , s t y r e n e s , and v i n y l p y r i d i n e s o c c u r s at 0 - 2 5 ° . The yields of adducts are high, and the compounds f o r m e d are those p r e dicted f r o m s i m i l a r reactions made with alkylbenzenes (30). T h e r e l a t i v e rate of alkenylation of 4 - a l k y l p y r i d i n e s with either butadiene o r i s o p r e n e i s about 8 to 20 t i m e s greater than that of 4 - m e t h y l p y r i d i n e , and therefore the alkenylation of 4methylpyridine is always accompanied by dialkenylation (31). Homogeneous C a r b o n - C a r b o n A d d i t i o n Reactions T h e use of aprotic solvents promotes anionic reactions of v e r y weak organic acids under m i l d conditions. A v a r i e t y of a l k y l a r o m a t i c compounds undergo alkenylation and a r a l k y l a t i o n i n a homogeneous aprotic s o l vent - t - B u O K s y s t e m (32). The reactions can be r e p r e s e n t e d by the following equations.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

12.

PINES

Base-Catalyzed

Carbon-Carbon

217

Addition

ArCH CH CH=CCH R' 2

ArCH

f + CH =CHC=CHR

3

2

2

t-BuOK T

2

and

solvent

R'R I I ArCH CHC=CHCH 2

t-BuOK

R

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

ArCH

3

+ C H C=CHR' 6

5

s

o

l

y

e

n

t

3

' ArCH CHCHC H R

>

R

2

Ar

6

5

or

R , R ' = Η or C H

3

T h e rate of r e a c t i o n i s greatly influenced by the type of solvents u s e d . A p r o t i c solvents s u c h as N M - 2 - P , 30a, and N M - 2 - P i , 30b, may react almost quantitatively with olefins containing an activated double bond, at r o o m temperature and i n the p r e s e n c e of _ t - B u O K (33). T h e g e n e r a l scope of the r e a c t i o n i s presented by R ι " i C=0 + CH,=C-R'

(CHj). CH

3

η = 2 = NM-2-P

= 30a

η = 3 = NM-2-Pi

= 30b

CHR (CH K n\

c=o

2

Ν I CH

C(R )

2

2

and

(CH ) 2

2

c=o

3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

218

INDUSTRIAL AND LABORATORY ALKYLATIONS

R=

H ; R* = C H = C H ;

R=

H; R ^

2

R =

CH CH=CHCH

2

2

C(CH )=CH ; 3

R =

CH CH CH(CH )

2

2

3

2

2

3

CH CH(CH )C H 2

3

2

2

5

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

(after h y d r o g é n a t i o n ) R=

H; R

R=

H ; R*=

R=

C H ; R* = C H ;

1 =

CgH ;

2

Si(CH ) ; 3

3

CH CH C6H

R =

5

6

R = 2

3

R = 2

5

2

2

5

CH CH Si(CH )

3

CH CH(CH )C H

5

2

2

3

2

3

6

Although D M S O i s u s e d extensively as an aprotic solvent, the hydrogens i n D M S O a r e quite l a b i l e . D M S O under the influence of base can r e a c t with a v a r i e t y of conjugated d i e n i c h y d r o c a r b o n s , a r y l a l k e n e s , and a r o m a t i c and h e t e r o a r o m a t i c r i n g compounds (34). The net r e s u l t of these reactions i s the f o r m a t i o n of methylated analogs of the s t a r t i n g h y d r o c a r b o n s . R e a c t i o n of Olefins with M i s c e l l a n e o u s Compounds Ethylene r e a c t s with s a l t s of saturated c a r b o x y l i c a c i d s containing at least one hydrogen atom attached to the α - c a r b o n atom (35). T h e ethylation which i s catalyzed by a l k a l i m e t a l s and t h e i r d e r i v a t i v e s and which o c c u r at 1 5 0 - 2 5 0 ° under ethylene p r e s s u r e , can be p r e s e n t e d as f o l l o w s : /C H

M

RCH CC"

+CH =CH

2

2

2

OM (R = H , a l k y l , c y c l o a l k y l .

2

5

RCH ^C0 M 2

.(C H ) +RC^ C0 M 2

5

2

M = a l k a l i metal)

A l d i m i n e s , w h i c h can be s y n t h e s i z e d i n good y i e l d s by the condensation of p r i m a r y amines with aldehydes, undergo a f a c i l e r e a c t i o n with i s o p r e n e and v i n y l a r o m a t i c h y d r o c a r b o n s i n the p r e s e n c e of a l k a l i metals (36). The alkenylation of a l d i m i n e s with isoprene is made at a t m o s p h e r i c p r e s s u r e i n benzene solvent. A l m o s t quantitative y i e l d s of m o n o - and diadducts are obtained. T h e alkenylation with i s o p r e n e can be p r e s e n t e d as f o l l o w s .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2

12.

PINES

Base-Catalyzed

RN=CHCHR'

Carbon-Carbon

+ CH =CHC=CH 2

R"

3

CH

Addition

219

Na

3

R' RN=CHÇCH Ç=CHCH 2

R

tT

3

CH3

When R is hydrogen the monoadducts can undergo further reaction with isoprene to form dialkenylated aldimines. f

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

Intramolecular Cyclization Reactions Potassium hydride catalyzes cyclization of cyclooctadienes at 190° to form 84-94$ of 31 (37), while 1,4, 7-cyclononatriene undergoes in the presence"©! potassium tert-butoxide in dimethyl sulfoxide double cycloisomerization to 32.

31

32

ω -Phenylalkenes undergo cyclization and cyclialkylation at 185° in the presence of either potassium or cesium, i . e . ,

Κ

cis and trans

12$

66$

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

220

INDUSTRIAL AND LABORATORY ALKYLATIONS

6 - ( 3 - P y r i d y l ) - l - h e x e n e i n the p r e s e n c e of either sodium or potassium f o r m s 33^ and 34 i n good y i e l d s . 33 Is the p r e ­ f e r r e d t r i c y c l i c compound (30).

33

34

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch012

Conclusion B a s e - c a t a l y z e d c a r b o n - c a r b o n addition reactions a r e of synthetic importance as they p e r m i t the production of difficult to p r e p a r e hydrocarbons and r e l a t e d compounds i n good y i e l d s by a one-step p r o c e d u r e . The reactions p r o c e e d under r e l a t i v e l y m i l d conditions and i n the p r e s e n c e of either d i s p e r s e d a l k a l i metals o r a l k a l i metals deposited on supports. In the case of olefins containing an activated double bond the use of t - B u O K i n D M S O c an be used as an effective catalyst.

Literature Cited (1) (a) Pines, Η . , Vesely, J . A., and Ipatieff, V. Ν., J . Amer. Chem. Soc. (1955) 77, 347; (b) Pines, H. and Eschinazi, Η. Ε., ibid. (1955) 77, 6314; (c) Pines, H. and Haag, W. Ο . , J. Org. Chem. (1958) 23, 328. (2) (a) Pines, Η . , Acct. Chem. Research (1974) 7, 155; (b) Pines, Η . , Synthesis (1974), 309. (3) Reggel, L., Friedman, S., and Wender, I., J . Org. Chem. (1958) 23, 1136. (4) Schriesheim, A . , Hofmann, J . Η . , and Rowe, C. A . , J. Amer. Chem. Soc. (1961) 83, 3731. (5) Pines, Η . , Vesely, J . A., and Ipatieff, V. Ν . , J . Amer. Chem. Soc. (1955) 77, 554.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Base-Catalyzed Carbon-Carbon Addition

221

(6) For general discussion of sodium anthracene complexes see K. Tamaru, Advan. Catal. Relat. Subj. (1969) 20, 327. (7) Mark, V. and Pines, H . , J . Amer. Chem. Soc. (1956), 78, 5946. (8) Shaw, A. W . , Bittner, C. W . , Bush, W. V., and Holzman, G . , J . Org. Chem. (1965) 30, 3286. (9) Hambling, J . Κ., Chem. Brit. (1969) 5, 354. (10) Takabe, Κ . , Katagiri, Τ . , and Tanaka, J . Bull. Chem. Soc. Japan (1972) 45, 2662. (11) (a) Suga, K . , Watanabe, S., Watanabe, Τ . , and Kuniyoshi, Κ., J . Appl. Chem. (London) (1969) 19, 318; (b) Watanabe, S., Suga, Κ., and Fujita, Τ . , Synthesis (1971) 375. (12) Zwierzak, A. and Pines, Η., J . Org. Chem. (1963) 28, 3392. (13) Brown, W. G., J . Amer. Chem. Soc. (1968) 90, 1916. (14) Zwierzak, A. and Pines, Η . , J . Org. Chem. (1962) 27, 4084. (15) Kolobielski, M. and Pines, H . , J. Amer. Chem. Soc. (1957) 79, 1698. (16) Shabtai, J . and Pines, Η., J . Org. Chem. (1964) 29, 2408. (17) Shabtai, J . and Pines, Η . , J . Org. Chem. (1965) 30, 3854. (18) Shabtai, J., Ney-Igner, Ε., and Pines, Η . , J . Org. Chem. (1975) 40, 1158. (19) Pines, H. and Schaap, L., J . Amer. Chem. Soc. (1958) 80, 3076. (20) Eberhardt, G. G., J . Org. Chem. (1964) 29, 643. (21) Stipanovic, B. and Pines, Η., J . Org. Chem. (1969) 34, 2106. (22) Pines, H. and Mark, V., J . Amer. Chem. Soc. (1956) 78, 4318. (23) Eberhardt, G. G. and Petersen, J . J., J . Org. Chem. (1965) 30, 82. (24) Pines, H. and Sih, N. C., J . Org. Chem. (1965) 30, 280. (25) Watanabe, S., Suga, Κ., and Fujita, Τ . , Synthesis (1971) 3, 375. (26) (a) Pines, H. and Wunderlich, D., J . Amer, Chem. Soc. (1958) 80, 6001; (b) Shabtai, J . and Pines, Η., J . Org. Chem. (1961) 26, 4225; (c) Shabtai, J., Lewicki, Ε., and Pines, Η . , J . Org. Chem. (1962) 27, 2618.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL AND LABORATORY ALKYLATIONS

(27) (a) Profft, E . and Schneider, F., Arch. Pharm. (1955) 289 99. (b) Pines, H. and Wunderlich, D . , J . Amer. Chem. Soc. (1959) 81, 2568. (28) Pines, H.andNotari, B . , J . Amer. Chem. Soc. (1960) 82, 2209. (29) (a) Pines, H. and Kannan, S. V., Chem. Commun. (1969) 1360. (b) Kannan, S. V. and Pines, Η . , J . Org. Chem. (1971) 36, 2305. (30) (a) Pines, H. and Notari, Β . , J. Amer. Chem. Soc. (1960) 82, 2209. (b) Chumakov, Y. I. and Ledovskikh, Ukr. Chim. Zh. (1965) 31, 506. (c) Pines, H. and Oszczapowicz, J . Org. Chem. (1967) 32, 3183. (d) Stalick, W. M. and Pines, Η . , J . Org. Chem. (1970) 35, 415. (e) Pines, H. and Sartoris, Ν. E., J . Org. Chem. (1969) 34, 2113. (f) Sartoris, Ν. E . and Pines, Η . , J. Org. Chem. (1969) 34, 2119. (g) Oszczapowicz, J . and Pines, Η . , J . Org. Chem. (1972) 37, 2799. (31) Stalick, W. M. and Pines, Η . , J. Org. Chem. (1970) 35, 422. (32) (a) Pines, H. and Stalick, W. Μ . , Tetrahedron Lett. (1968) 3723. (b) Pines, Η . , Stalick, W. M., Holford, T. G . , Golab, J., Lazar, Η . , and Simonik, J., J . Org. Chem. (1971) 36, 2299. (33) Pines, Η . , Kannan, S. V., and Simonik, J., J. Org. Chem. (1971) 36, 2311. (34) (a) Argabright, P. A., Hofmann, J . E., and Schriesheim, A., J. Org. Chem. (1965) 30, 3233. (b) Feldman, M., Danischefsky, S., and Levine, R . , J. Org. Chem., (1966) 31, 4322. (c) Russell, G. A. and Weiner, S. A., J. Org. Chem. (1966) 31, 248. (d) Nozaki, Η . , Yamamoto, Υ . , and Noyori, R . , Tetrahedron Lett. (1966) 1123. (35) Schmerling, L . and Tockelt, W. G . , J. Amer. Chem. Soc., (1962) 84, 3694.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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223

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(36) (a) Martirosyan, G. Τ., Kazaryan, A. T s . , and Mirsaryan, So., Arm. Khim. Zh. (1973) 26, 569. (b) Kazaryan, A. Ts. and Martirosyan, G.Τ.,Arm. Khim. Zh. (1972) 25, 861. (37) Slaugh, L., J . Org. Chem. (1967) 32, 108. (38) Wathley, J . W. H. and Winstein, S., J . Amer. Chem. Soc. (1963) 85, 3716. (39) Pines, H., Sih, N. C., and Lewicki, Ε., J . Org. Chem. (1965) 30, 1457. (40) Pines, Η . , Kannan, S. V., and Stalick, W. Μ . ,J.Org. Chem. (1971) 36, 2309.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

13 M i x i n g in Emulsion-Reaction Types of L i q u i d - L i q u i d Processes

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

J. Y. OLDSHUE Mixing Equipment Co., Inc., 135 Mt. Read Blvd., Rochester, NY 14611

This discussion is aimed primarily at alkylation processes, which are characterized by two-phase emulsions. The traditional process includes a hydrocarbon phase in contact with a sulfuric acid catalyst to form the environment for proper alkylation. In the petroleum industry, the desired product is a high octane alka­ late, but other alklation processes have other desired products. There are several different ways of running full scale alkyl­ ation processes. One of the earlier systems was the use of a "cascade reactor", there was a sulfuric acid catalyst in each stage, which did not flow between stages, and the hydrocarbon was allowed to flow in each stage in series. A mixing device was used to form a two-phase emulsion, which then must settle in each stage so that clear hydrocarbon can flow into the next stage. Mixers used included jets, submerged pumps, and mixing impellers. Another type of cascade continuous flow system did not try to settle in each stage, but allowed emulsion to flow co-currently through the system. A third type used a high energy side entering propeller unit, which carried out the process in a single stage. This paper analyzes the role that mixing can play in this reaction, and tries to divide "mixing" down into its several com­ ponent fluid mechanic parts, which is helpful in analyzing process results. In order to orient the reader, Table I illustrates the steps that are desirable in designing a fluid mixer. Under I, we look at the mechanics of a flow from impellers, what kind of fluid re­ gimes are required by the alkylation process, and how do we scale up and scale down the operation. Under II, impeller power characteristic curves hold true whether we are doing the desired process job or not. It is es­ sential to have data on various impellers in these areas, but this data is largely available and it is primarily a matter of specifying the specific gravity and viscosity of the various 224

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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TABLE I ELEMENTS OF MIXER DESIGN I PROCESS DESIGN

1 - FLUID MECHANICS OF IMPELLERS 2 - FLUID REGIME REQUIRED BY PROCESS 3 - SCALE UP; HYDRAULIC SIMILARITY

II IMPELLER POWER CHARACTERISTICS III

M E C H A N I C A L DESIGN

4 - RELATE IMPELLER HP, SPEED & DIAMETER 5 - IMPELLERS

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6 - SHAFTS 7 - DRIVE ASSEMBLY

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INDUSTRIAL AND LABORATORY ALKYLATIONS

226

phases and emulsion that the impeller will see during various parts of the process operation. In III, mechanical design is essential for a satisfactory operation, but this part of the design is not treated in this pro­ cess oriented paper. Fluid Mechanics of Flow From Impeller By way of review, all the power that we apply to the mixing impeller produces a pumping capacity, Q, and a velocity head, H, within the discharge from the impeller, such that power P, is pro­ portional as shown below. Ρ « QH

Other relationships, such as:

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

Ρ « Ν

D

3

5

where Ν is impeller speed and D is impeller diameter, as well as: Q « ND allow us to calculate the way that we can vary the flow to impel­ ler head ratio at a given power level with various impeller sizes and speed. It turns out that i f we combine the previous three equations, that we arrive at a fourth, Q/H « D 4/3 This equation essentially tells us that the large diameter impel­ ler running at slow speed at a given power level gives us a high volume of fluid pumped, and a relatively low impeller head, while a small impeller running at high speed gives us less flow and a higher level of impeller head. The impeller head is related to various fluid shearing phe­ nomena going on in the tank, and as such, is an important element of emulsion and reaction processing. In general, every process has an optimum combination of flow and impeller head. For many processes, the particular impeller type used to generate that flow and impeller head is relatively unimportant, and two impellers will achieve the same process re­ sult when operated at their optimum geometry to give this flow to head ratio for the particular process requirement. Fig. 1 i l l u s ­ trates this phenomena with two different impellers producing the best process result at different actual impeller diameters. The whole question of impeller shear effects has been devel­ oping rapidly in the last few years, and it will be helpful to summarize the role that these play in the alkylation process. Using for illustration the radial flow impeller, Fig. 2 shows the velocity profile based on average velocities at a point coming off the blades of an impeller. As shown in the diagram, by taking the slope at any point, we obtain the velocity gradient, which is the shear rate that exists at that point. This shear rate can be cal­ culated at any point in the mixing tank i f we will make various velocity measurements and establish the velocity profile at any point. Actually, the fluid shear rate must be multiplied by the vis3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Liquid-Liquid TABLE

Processes

II

SHEAR RATE TO RUPTURE A GIVEN DROPLET SIZE JUL' = 80 Cp JUL CP

SHEAR RATE SEC. -1

SHEAR STRESS IN CONTIN. PHASE g/cm

80

93

0.08

240

38

0.09

370

22

0.08

745

16

0.12

1175

14

0.17

2

JUL = continuous phase viscosity

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

JUL' = discontinuous phase viscosity

SHEAR RATE = -ffi

Figure 2. Schematic of velocity flow pattern from radial flow turbine, showing shear rate calculation

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL AND LABORATORY ALKYLATIONS

cosity, to give the fluid shear stress which carries out our pro­ cess result, in accordance with the equation below. Fluid shear stress = μ (fluid shear rate) An article by Karam (1) gives typical data to illustrate the difference between shear rate and shear stress. Table II is ex­ tracted from cross plots of their data, showing the shear rate re­ quired with different continuous phase viscosities and one dis­ persed phase viscosity to break up a second fluid of the same size droplet. This shows that the shear stress in grams per cen­ timeter squared is the basic parameter and the viscosity and shear rate are inversely proportional to give the required shear stress. Looking at the profile from the average velocity at a point, there are 4 regions in the tank which are of particular interest. These give us the following points of pertinent definitions: 1. The average impeller zone shear rate. 2. The maximum impeller zone shear rate. 3. The average tank zone shear rate. 4. The minimum tank zone shear rate. The average velocity gradients throughout the tank have been defined by several different methods. Estimates from our labora­ tory indicate that these velocity gradients are an order of magni­ tude less than the average velocity gradient around the impeller zone. The minimum velocity gradient of the tank has been estimated as 1/4 to 1/3 of the average velocity gradient throughout the en­ tire tank. If a flow in the tank is turbulent, either because of high power levels or low viscosity, then a typical velocity pattern at a point would be illustrated by Fig. 3. The velocity fluctuation μ" can be changed into a root mean square value (RMS), which has great utility in estimating the intensity of turbulence at a point. So in addition to the definitions above, based on average velocity point, we also have the same quantities based on the root mean square fluctuations at a point. We're interested in this value at various rates of power dissipation, since energy dissipation is one of the major contributors to a particular value of RMS μ " . Looking at the average velocity at a point, Fig. 4 gives the result that the maximum shear rate around an impeller increases with impeller diameter at a given RPM, while the average shear rate around the impeller remains essentially a constant with impel­ ler diameter. This yields a further relationship, as shown in Fig. 5, which shows that typically on scaleup, maximum shear rates increase, while average shear rates decrease. These now are shear rates that affect large scale particle, variously estimated at 100 to 200 microns and larger. It is impossible to keep the ratio of all the pertinent mixing parameters constant in scaleup, so that we must pick and choose the mixing parameters and shear rates that are important for a given type of process.

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4.0 CONSTANT SPEED

lxj

2.0

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

1.0

AVERA( 3E

.75 IMPELLER DIAMETER

TANK DIA.

RATIO

Figure 4. Data showing that maximum shear rate around an impeller increases, while average shear rate remains constant with different diameters having the same RPM

Figure 5. Effect of scale-up on maximum and average impellers zone shear rates

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL AND LABORATORY ALKYLATIONS

On the other hand, the turbulent velocity fluctuations RMS affect microscale processes, again variously estimated at 100 to 200 microns or less, on down to possibly the mixing length or possibly on down to the scale of molecular reaction.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

Turbulent Velocity Fluctuations Experimental data reported by J . Y. Oldshue, (6) were obtain­ ed with a hot wire velocity meter. Details of that equipment are included in the appendix to this report. Additional data from this equipment are shown on Figs. 6, 7 and 8. Fig. 6 shows some of the data which give the ratio of the RMS velocity fluctuation to the average velocity at that point as a function of position above and below the impeller centerline. These data are for a 4" diameter, 6 flat blade turbine at 259 RPM. This indicates the ratio of fluctuating velocity to average velocity at a point can be as high as 0.75 and is generally in the range of 0.5 to 0.7. These measurements were made approximately 3/4" from impeller periphery. Additional measurements made in other parts of the tank are shown in Fig. 7. These indicate that the velocity fluc­ tuation in other parts of the tank in the range of 0.05 to 0.15 of the average velocity which is more typical of the turbulence behind grids and in pipelines. Other background on turbulent velocity parameters is given by Cutter (3) who calculated several parameters from photographs of flow patterns in a mixing vessel. He found that the RMS veloc­ ity fluctuation was primarily related to energy dissipation. His measurement scale in making these photographic studies could be quite different from the scale velocities from the hot wire veloc­ ity meter reported here, so that a direct comparison of these re­ sults with those of Cutter has not been made in this paper. It since appears that the frequency and size of the turbulent velocity fluctuations are more compatible with phenomena on a mo­ lecular micron size scale in a mixing vessel. For example, in a publication Paul & Treybal (4) shows the yield of a given reac­ tion which had several alternate paths was determined by the RMS velocity fluctuations at the feed point. Paul used data from Schwartzberg & Treybal (5) and Cutter to calculate RMS velocity at the feed point. Another parameter which can be measured by the hot wire ve­ locity meter technique is a dissipation length. λ

DISSIPATION LENGTH

2

υ

VELOCITY

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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231

r

0.7

0.6

|3

0.5

0.4

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

0.3 INCHES A B O V E (+) OR B E L O W (-) TURBINE DISC

0.2

+1/2

-1/2

Figure 6. The ratio of RMS velocity fluctuations to average velocity at different distances above and below the impeller centerline

0.2

6 FBT 33 RPM

KEY

M

0.15

&l» L o.i

SURFACE

6"

η 11" ο 11 χ

ο

• X χ •

0.01

· 2-3/8 Β :LOW χ

χ

o

X

° χ

ο

•

ο

χ

·

0 χ

ο *

ο

•

4

•

ο

ο

χ •

χ

•

6

INCHES, F R O M SHAFT

Figure 7.

Effect of distance from impeller shaft on the ratio of RMS velocity fluc­ tuation to the average velocity at a point

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

232

INDUSTRIAL AND LABORATORY ALKYLATIONS

This is helpful in indicating the size of the turbulent eddies, λ is a measure of, although not equal to, the mean size of the smaller eddies which are dissipated Into energv. Fig. 8 gives some experimental values. At the moment, λ values are not being used to quantitatively analyze processes in the mixing vessel.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

Some Practical Concerns On Scaleup Of Alkylation Alkylation needs pumping capacity to maintain a uniform mix­ ture of components within each phase as well as a uniform d i s t r i ­ bution of dispersed phase in the continuous, and the dispersion step itself requires a certain amount of shear stress to create interfacial area for mass transfer. There is no way of knowing what levels of each are needed without running some experiments. If this is coupled with the various kinds of continuous flow phenomena, and the requirement for settling of the various phases in one or more stages of the system, there comes out to be some very definite optimum mixer combinations for a given process. For example, i f the emulsion must settle in each stage, so that a clear hydrocarbon phase can be passed on to the subsequent stage, then the optimum requirement for mixer variables becomes quite unique. As the speed of the given impeller is increased, the interfacial area is increased, better mass transfer is pro­ duced, possibility of better uniformity is available, but d i f f i ­ culty in settling a clear hydrocarbon phase is increased. There is a definite optimum power level, D/T ratio and other parameters, that have been found to exist in these kinds of-processes. In general, the relatively large diameter mixing impellers with relatively high pumping capacity and lower levels of fluid shear have been found to be more effective than higher shear de­ vices, such as high speed pumps or high velocity jet nozzles. If the emulsion is to flow unsettled from stage to stage, then there is no concern about settling until the final product settler is reached. This means that at various power levels, dif­ ferent combinations of variables are optimum. For example, at a low total hp level, large D/T ratios are required to achieve the pumping and blending required to maintain a uniform emulsion. As power levels are increased, the total productivity of the process usually increases, and smaller D/T's are more important because a level of pumping action at a higher power level can be achieved with smaller D/T ratios and s t i l l give adequate blending. As power levels are increased further, more of the energy can be put into shear rates, since a smaller proportion of the power is needed to achieve uniformity of blending and emulsification. At some point, the improvement in process yield with power begins to reach a peak and fall off, and at that point, economic conditions enter into the picture and dictate practical levels of power. If consideration is being given to a single stage reactor, then high power levels are used to go along with coil and jacket type cooling, and power levels are often dictated by the necessi-

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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ty for heat transfer and mass transfer, rather than subsequent settling and stage operation.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

Some Considerations In Scaling Up Or Scaling Down Alkylation Studies Table III gives the change in various mixing parameter ratios for 4 different scaleup calculations. What this shows is that we cannot control the ratio of every individual fluid mechanics parameter. It also indicates that it is better to use correlating parameters to find out how they change on scaleup, rather than searching for a constant scaleup parameter for every conceivable mixing process. There is no assurance that there is a constant scaleup parameter for any given process job we are studying. Therefore, pilot plant studies should be directed toward establishing a controlling factor in the process, so that its control on scaleup can be more closely monitored. Referring to this table, it is seen that i f constant power per unit volume is used as a parameter, then maximum impeller zone shear rates go up while the pumping capacity system goes down. Another column shows that a constant impeller tip speed, the power per unit volume goes down drastically and the pumping capacity goes down s t i l l further. In general, small scale models have too much pumping capacity and too l i t t l e impeller zone shear rate to be typical of the performance to be expected in a full scale prototype. Thus, it is normally necessary to purposely scale down the pumping capacity, and increase the shear rate on small scale equipment to more closely duplicate the performance which will be expected on full size units. In alkylation, this means that the large size tank will normally have higher shear stresses, and finer bubbles produced around the impeller, but also a much greater tendency for coalescense to occur in the lower shear zones in the tank. The pumping capacity per unit volume of the full size unit will tend to be much less than it is in the small size unit and therefore, the uniformity of reagents, the blending of these materials, and the stability of the emulsion will be less than it would be on the pilot scale. Non-geometric designs must often be used. Some Considerations About Pilot Plants There is a minimum size pilot plant for two phase processes. For example, Fig. 9 shows an impeller that, let's say, is 2 centimeters in blade width. The jet from the impeller gives a macroscale shear rate of 10 at a given speed, while the shear rate across a quarter centimeter distance is 9-1/2, across a 0.5 centimeter distance is 7.0, across half the blade width is 5, and across the entire impeller is zero. Thus, a bubble that is 2-1/2 centimeters in size will see no shear rate, while a micron sized

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

234

INDUSTRIAL AND LABORATORY ALKYLATIONS

.01 ο ζ

" Ζ

I

I

6 " FBT

ο c>

0

.005

ο ο

0 ο ο

ο

0

ο ο

ïï!

ο

.001 ο

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

.005 50

500

100 RPM

Figure 8. The effect of RPM on the dissipa­ tion length in a mixing vessel

TABLE

III

PROPERTIES OF A FLUID MIXER ON SCALE UP

PROPERTY

PILOT SCALE 5 GALLONS

PLANT SCALE 625 GALLONS

POWER (P)

1.0

125

3125

25

0.2

P/VOL.

1.0

1.0

25

0.2

0.0016

SPEED(N)

1.0

0.34

1.0

0.2

0.04

TURBINE DIA(D)

1.0

5.0

5.0

5.0

5.0

PUMPING CAPACITY (0)

1.0

42.5

125

25

5.0

0/VOL.

1.0

0.34

1.0

0.2

0.04

ND

1.0

1.7

5.0

1.0

0.2

1.0

8.5

25.0

5.0

1.0

2

ND/>

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

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bubble will see a shear rate of 10. We cannot let the physical size of the impeller blade in the pilot scale get out of proportion to the particle we are trying to disperse and the bubble we are trying to create. A way to evaluate the effect of macroscale maximum and average impeller zone shear rates, and the microscale fluctuating turbulent intensity forces, is to build a series of different impellers as shown in Table IV. Merely for illustration, 5 impellers are shown. The first impeller is a standard blade width, run at a diameter of 1 and a speed of 1, to yield a maximum shear rate of 1, an average shear rate of 1, and a fluctuating shear rate of 1 on a relative basis. There is no relationship between the values of 1 for the three shear rate quantities. This impeller would be run and the process result evaluated. Then impeller number 2 would be used, which is a smaller diameter, higher speed impeller of the same blade proportions. It gives the shear rate properties as shown on the table. A 3rd, 4th and 5th impeller are used, which vary the various shear quantities. By observing the effect on process result, this allows a general interpretation of the role of various macro and micro scale shear rates in the process to be evaluated, and give some idea of the kind of scaleup performance to be expected with various kinds of scaleup parameters. Some Comments About Liquid-Liquid Dispersion One of the key points is to know which phase is continuous. If there is an ambivalent range, which means that either phase can be continuous, then the phase that the impeller starts in will normally be the continuous phase and it will suck in the dispersed phase into the zone. Fig. 10 illustrates the ways the different phases can be dispersed, and also shows the method of dispersing a heavy phase and light phase with the impeller s t i l l being at the bottom portion of the tank. Emulsion break time can be a measure of the degree of tightness of the emulsion, and Figs. 11 and 12 show data obtained under various kinds of experiments illustrating the effect of different mixing variables on emulsion break time for a particular two phase system. This kind of data does give an indication of the settling times to be expected in the settling stage following a continuous system. A general truism says that the f i r s t phase will settle with more clarity than will the continuous phase. The continuous phase normally has a haze that is very difficult to settle, while the dispersed phase, once it settles, is usually much more clear. Some Considerations About Instantaneous Concentrations At The Feed Point Figs. 13 and 14 show the average velocity at a point as de-

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

Figure 9. Schematic of different shear rates as a function of different size particles in the flow stream

ADD

HEAVY

Ι

tit

•h» M -

Μ­ LIGHT DISP.

Figure 10.

HEAVY DISP.

Θ

Ο

HEAVY DISP.

ADD LIGHT

Method of controlling which phase is dispersed in batch extractions

SHEAR

IMPELLER

RATE

D

Ν

Du>/D

MAX

AVG

FLUC

1 0.7 1 1 0.8

1 1.3 1.3 1 1.3

S S Ν Ν S

1.0 1.3 1.3 1.0 1.0

1. 0 1. 8 1. 3 1. 0 1. 3

1. 0 1. 0 1. 0 0. 5 0. 7

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

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OLDSHUE

Emulsion-Reaction

Liquid-Liquid

) 20 40 60 TIME O F M I X I N G - S E C O N D S

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Figure 11. Effect of mixing time and RPM on break time for a liquid-liquid emulsion

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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90°

^TURBINE BLADE

Figure 14. Effect on the angle between the blades on the average velocity at a particular position in the discharge stream from a radialflowimpeller

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

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termined by the angle between the blades. What this shows is that the velocity at a point fluctuates about 50% from the average, as is also shown by the RMS values discussed previously. If a chemical is injected at a constant rate, then the molar concentration ratio at that point is actually fluctuating over a factor of 2. If reaction rates are fast enough so that this would affect the path that a reaction would take, this could affect the distribution of reaction products in a way that would be either good or bad, depending upon circumstances. For example, in neutralizing a sensitive chemical or biological product, adding acid or base at a constant rate into the eye of the impeller, can cause the pH to fluctuate markedly at that point, and is thought to be one of the reasons for the decrease in yield from a theoretical value when trying different types of introduction. If a uniform concentration of a miscible liquid is more desirable than the high intensity turbulent dispersion of these materials in the stream, then it may be well to have injection points out in a more uniform, less fluctuating environment. Thus evaluation of injection point conditions can be very critical in reactions that may take different paths, depending upon chemical concentrations and fluid mechanics variables. In the paper by Paul & Treybal ,thev showed that the reaction products of a competitive, consecutive second order reaction do depend on the RMS fluctuation value at the injection point. Summary Mixers can be designed to increase pumping capacity at a constant level of impeller shear rate, which would increase the total horsepower of the system, they can be designed to increase pumping capacity at the expense of fluid shear rate variables, or they can be designed to increase fluid shear rate variables at the expense of pumping capacity. To determine which of these would be more advantageous, there has to be some information or speculation on where a given process result stands relative to these variables. On a full scale unit, it is usually very difficult to make significant changes in mixing variables, so that i t is seldom possible to assess possible improvements in increasing horsepower, level, the torque in the mixer drive to change other variables, or whether it is worth making major changes in geometry, feed introduction, etc. If small scale experiments are to be used for evaluation purposes, then they must be designed to have blend time, pumping capacity and shear rate levels relatively similar to full scale installation. This normally means a non-geometric model of scaledown to control various mixing parameters. The small scale model must be of the same general type as full scale with regards staging, continuous flow and other variables. The impeller must not be allowed to get out of proportion

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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in terms of physical size to the bubbles and droplets involved in the full scale process. To shed most light on the effect of mixing, the usual order of variables includes the following: 1.

Vary mixer speed, which varies both pumping capacity and all of the shear rates. If this does not change the process result, then the probability of other variables affecting it are relatively small. Making a change in impeller size to tank size ratio of a given type impeller will normally tell whether pumping cap­ acity or the entire variety of shear rates is significant in the process result. If i t is desired to separate out macroscale and microscale shear rate effects, then a change in the internal geometry of an impeller is necessary to change the relative propor­ tions of these two quantities.

2.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

3.

Symbols Used U

Impeller diameter

D/T

Impeller diameter-to-tank diameter ratio.

Deo

Impeller blade width.

^jjj- "

Reynolds number, ratio of inertia force to viscosity force, dimensionless.

Ρ

Total power.

2

Pq N

3 5 D

p

Power number, ratio of applied force to graviation force, dimensionless.

Q

Volumetric fluid displacement of impeller.

RMS

Root mean square, / y

Τ

Tank diameter

u

Velocity in χ direction.

û

Mean velocity, ft./sec.

2

Fluctuating velocity.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Ζ

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Liquid depth. Γ 1

>

Dissipation length.

μ

Continuous phase viscosity.

χΤ

1 /duV"

ΰ \~3χ)

y

Discontinuous phase viscosity

ρ

Density of fluid or solid.

A

2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch013

Literature Cited 1 Karam, H. J., and Bellinger, J . C.: "Deformation and Break-up of Liquid Droplets in a Simple Shear Field", Ind. Engng. Chem., Fundamentals 7 (4), 576 (1968) . 2 Oldshue, J . Y . : "Fermentation Mixing Scale-up Techniques", Biotech, and Bioeng. VIII (1),3 (1966). 3 Cutter, L.A.: "Flow and Turbulence in a Stirred Tank", Α.I.Ch.E.J 12 (1), 35 (1966). 4 Paul, E.L., and Treybal, R.E.: "Mixing and Product Distribution for a Liquid-Phase, Second-Order, Competitive-Consecutive Reaction", presented at 62nd Annual Meeting A.I.Ch.E., Washington, D. C. (November 1969). 5 Schwartzberg, H.E., and Treybal, R. E. : "Fluid and Particle Motion in Turbulent Stirred Tanks", Ind. Engng. Chem. Fundamentals 7 (1), (1968). 6 Oldshue, J . Y . : "The Spectrum of Fluid Shear in a Mixing Vessel", Chemeca '70, Butterworth (1970).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

14 Improved M i x i n g i n Alkylation

D. E. ALLAN and R. H. CAULK

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch014

Exxon Research and Development Laboratories, P. O. Box 2226, Baton Rouge, LA 70821

Turbulent transfer processes are important in many petroleum and petrochemical operations. For example, turbulent mixing in stirred tanks affects both yield and product quality in such chemical conversions as alkylation and vinyl chloride polymerization; i t influences the rate in physical conversions such as crystallization by dilution chilling. Mixing efficiency, as measured by process results, is tied to the type and degree of turbulence present in the reactor. This paper will show that the efficiency of mixing may be improved through a better understanding of turbulent flow field coupled with an understanding of how flow affects the process. This study was an attempt at combining turbulent flow studies, studies on model systems and pilot plant data in order to understand the mixing processes involved. The paper is in two parts. First is a study of turbulent flows generated by radially discharging impellers. It has been asserted that mixing is a flowphenomenonhence, the f i r s t step in gaining an understanding of mixing is to catalog flow characteristics generated by common impellers. The second part is a detailed comparison of the performance of two impellers that generated significantly different flows in a pilot plant test which studied the alkylation of butylenes. Summary T h i s paper d i s c u s s e s a way t o improve m i x i n g , hence product q u a l i t y , i n a c i d catalyzed a l k y l a t i o n without i n c r e a s i n g t h e power consumption. I t i s e s s e n t i a l l y d i v i d e d i n t o two p a r t s : (1) a b a s i c s t u d y o f t h e f l u i d mechanics o f i m p e l l e r d r i v e n f l o w s which has y i e l d e d a new i m p e l l e r d e s i g n , and (2) an a l k y l a t i o n m i x e r comparison w i t h s u l f u r i c a c i d c a t a l y s t done i n an a l k y l a t i o n p i l o t p l a n t . L o o k i n g a t m i x i n g as a t u r b u l e n t f l o w g e n e r a t e d by an i m p e l l e r , a s t u d y o f t h e f l o w s g e n e r a t e d by c o n v e n t i o n a l and n o v e l r a d i a l l y d i s c h a r g i n g i m p e l l e r s t y l e s was done a t E x x o n s 1

242

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch014

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C o r p o r a t e Research L a b o r a t o r i e s . Modern l a s e r v e l o c i m e t r y t e c h n i q u e s were employed. L o c a l average v e l o c i t i e s and t u r b u l e n t i n t e n s i t i e s were o b t a i n e d i n the d i s c h a r g e from t h e i m p e l l e r s . Average v e l o c i t i e s v a r i e d w i t h power number f o r the v a r i o u s s t y l e s as e x p e c t e d and t h i s means the most commonly used f l a t b l a d e t u r b i n e g e n e r a t e d t h e h i g h e s t average v e l o c ities. The s i g n i f i c a n t r e s u l t was t h a t t u r b u l e n t i n t e n s i t i e s were s i m i l a r f o r a l l c o n v e n t i o n a l i m p e l l e r s . One n o v e l i m p e l l e r g e n e r a t e d i n t e n s i t i e s o v e r t w i c e as h i g h i n t h e f l u i d n e a r the i m p e l l e r . M i x i n g l i t e r a t u r e s u g g e s t s an improvement i n p r o c e s s e s such as a l k y l a t i o n based on t h i s f l o w d i f f e r e n c e . A m i x e r comparison w i t h s u l f u r i c a c i d c a t a l y s t was c a r r i e d out i n the Exxon Research and Development L a b o r a t o r i e s a l k y l a t i o n p i l o t p l a n t . The n o v e l i m p e l l e r was compared t o the c o n v e n t i o n a l f l a t b l a d e d t u r b i n e at c o n s t a n t power l e v e l s u s i n g r e f i n e r y o l e f i n and i s o b u t a n e streams. A n a l y s i s o f t h e p r o d u c t q u a l i t y - a c i d c o m p o s i t i o n d a t a f o r the p i l o t p l a n t comparison showed t h a t the o c t a n e i n c e n t i v e f o r the new m i x e r was r e l a t e d t o a c i d s t r e n g t h and v a r i e d between 0.4 and 0.25 MON i n the commercial o p e r a t i n g r e g i o n (96-90% H2SO4). In a d d i t i o n t o the q u a l i t y comparison, c a t a l y s t l i f e e f f e c t s were c a l c u l a t e d and compared f o r b o t h m i x e r s . These d a t a showed t h a t the n o v e l i m p e l l e r r e q u i r e d somewhat lower a c i d r e p l a c e ment r a t e than t h e f l a t b l a d e d t u r b i n e at h i g h a c i d s t r e n g t h s (98-94% H2SO4). C a l c u l a t e d a c i d replacement r a t e s f o r b o t h m i x e r s were e q u i v a l e n t a t lower a c i d s t r e n g t h s (94-90% H2SO4). I n t e r p r e t a t i o n of these p i l o t p l a n t r e s u l t s i n l i g h t of the m i x i n g s t u d i e s i n d i c a t e s t h a t t h e key r o l e o f t h e n o v e l i m p e l l e r i n a l k y l a t i o n i s t o generate a d d i t i o n a l emulsion surface area. The

I m p e l l e r s and The

Flows They Generate

Flow c h a r a c t e r i s t i c s i n a m i x i n g v e s s e l can i n f l u e n c e p r o c e s s performance. The i m p e l l e r i s a d e v i c e which imparts m o t i o n t o the medium i n which i t o p e r a t e s . The c h a r a c t e r i s t i c s o f t h e f l o w w h i c h a r e o f g r e a t e s t i n t e r e s t are the mean f l u i d v e l o c i t y at a l l p o i n t s w i t h i n t h e f l u i d and t h e t u r b u l e n t f l u c t u a t i o n s superimposed on the mean v e l o c i t y . P a u l and T r e y b a l (1) have d i s c u s s e d how t h e d e t a i l e d f l o w c h a r a c t e r i s t i c s can i n f l u e n c e p r o c e s s performance. T h i s paper w i l l show how i m p e l l e r s t y l e can i n f l u e n c e the f l o w c h a r a c t e r i s t i c s . The i m p e l l e r s used i n t h i s study are shown i n F i g u r e 1. They are b o t h o f t h e r a d i a l l y d i s c h a r g i n g t y p e which i s c h a r a c t e r i z e d by a s t r o n g r a d i a l j e t o f f l u i d t h a t moves out t o t h e v e s s e l w a l l s w h i l e e n t r a i n i n g f l u i d from above and below. Near the w a l l i t s p l i t s i n t o two c i r c u l a t i o n zones. The f l a t b l a d e t u r b i n e (FBT) i s commonly used i n i n d u s t r y and c o n s i s t s o f a d i s c w i t h s e v e r a l p a d d l e s f i x e d normal t o t h e d i s c which s e r v e t o generate the r a d i a l f l o w . The n o v e l i m p e l l e r d e s i g n

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch014

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(HIT)* has two d i s c s t h a t l i m i t t h e f l o w i n t o t h e i m p e l l e r . I t a l s o has s e v e r a l p a i r s o f p a d d l e s f i x e d normal t o t h e d i s c s w h i c h generate t h e r a d i a l f l o w . E a r l i e r work has used s e v e r a l methods t o measure t u r b u l e n t f l o w parameters i n t h e d i s c h a r g e stream o f an i m p e l l e r and t h e s e a r e summarized by Gunkel and Weber ( 2 ) . Only t h e FBT i m p e l l e r s t y l e was used i n a l l e a r l i e r s t u d i e s . In t h i s work, measurements o f t h e mean v e l o c i t y and t h e t u r b u l e n t f l u c t u a t i o n s i n t h e f l o w s generated by t h e two i m p e l l e r s were c o n f i n e d t o t h e c e n t e r l i n e o f t h e r a d i a l j e t s i n c e t h i s i s t h e zone where t h e f l o w i s most s t r o n g l y i n f l u e n c e d by t h e i m p e l l e r s t y l e . T u r b u l e n t f l o w parameters were d e t e r mined u s i n g a DISA E l e c t r o n i c s L a s e r Anemometer System. As t h e name i m p l i e s , t h i s i s an o p t i c a l d e v i c e t h a t measures t h e i n s t a n t a n e o u s v e l o c i t y a t a p o i n t . The t e c h n i q u e i s l i n e a r w h i c h a l l o w s a c c u r a t e f l o w measurements a t v e r y h i g h t u r b u l e n c e l e v e l s such as found i n m i x i n g v e s s e l s . S i n c e t h e r e i s no p r o b e , t h e r e a r e no f l o w d i s t u r b a n c e s and t h e measurement i s independent o f f l u i d p r o p e r t i e s . The anemometer used i n t h i s work was s e n s i t i v e t o the d i r e c t i o n o f the instantaneous v e l o c i t y . A g l a s s m i x i n g v e s s e l o f 0.20 m d i a m e t e r was used f o r t h e study. I t was e n c l o s e d i n a square p l e x i g l a s s tank t h a t was a l s o f i l l e d w i t h t h e same l i q u i d as used i n t h e m i x i n g v e s s e l i n o r d e r t o m i n i m i z e r e f r a c t i o n o f t h e l i g h t beams. The l i q u i d l e v e l was 0.20 m and t h e i m p e l l e r s were 0.10 m from t h e bottom. I m p e l l e r s o f a p p r o x i m a t e l y 0.064 m d i a m e t e r were used t o m i n i m i z e w a l l feedback e f f e c t s . Water was t h e w o r k i n g f l u i d f o r the r e s u l t s reported here. The i n s t a n t a n e o u s v e l o c i t y , Vj_, i n a t u r b u l e n t f l o w can be expressed as Vi = V i + U

±

( i = 1,2,3)

where i s t h e t i m e mean v e l o c i t y and i s the instantaneous f l u c t u a t i n g v e l o c i t y i n the i d i r e c t i o n . By d e f i n i t i o n , t h e average f l u c t u a t i n g v e l o c i t y , U^, i s z e r o . The r e l a t i v e i n t e n s i t y o f t u r b u l e n c e , I , i s d e f i n e d as

where i s t h e mean o f t h e square o f t h e f l u c t u a t i n g v e l o c i t y . F i g u r e s 2 and 3 a r e measurements o f t h e r a d i a l component o f v e l o c i t y along the center l i n e o f the strong r a d i a l j e t i s s u i n g from t h e d i f f e r e n t i m p e l l e r s t y l e s v e r s u s t h e r a d i a l p o s i t i o n ( r ) n o r m a l i z e d by t h e i m p e l l e r r a d i u s ( R ) . *High i n t e n s i t y t u r b i n e

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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The v a r i a t i o n o f mean r a d i a l v e l o c i t y w i t h d i s t a n c e from t h e i m p e l l e r t i p i s shown i n F i g u r e 2. When t h e v e l o c i t y i s n o r m a l i z e d u s i n g t h e i m p e l l e r t i p speed ( V t i p ) a r e l a t i o n i s o b t a i n e d f o r each i m p e l l e r s t y l e f o r v a r i o u s r o t a t i o n a l speeds. The mean r a d i a l v e l o c i t y i s a measure o f i m p e l l e r pumping c a p a c i t y . As e x p e c t e d , t h e v a r i o u s s t y l e s show g r o s s l y d i f f e r e n t c h a r a c t e r i s t i c s i n terms o f pumping c a p a c i t y . In a l l cases t h e mean r a d i a l v e l o c i t y d e c r e a s e s w i t h i n c r e a s i n g r a d i a l d i s t a n c e (except f o r t h e HIT i m p e l l e r n e a r the t i p ) . T h i s i s due t o two t h i n g s : (a) i n a c y l i n d r i c a l geometry, t h e c r o s s s e c t i o n a l a r e a f o r f l o w i n c r e a s e s w i t h r a d i a l d i s t a n c e , and (b) t h e r a d i a l j e t e n t r a i n s f l u i d from above and below, hence v e l o c i t y must d e c r e a s e t o conserve momentum. The d i s t r i b u t i o n o f t h e t u r b u l e n t i n t e n s i t i e s f o r t h e r a d i a l component o f v e l o c i t y i s p l o t t e d i n F i g u r e 3 as a f u n c tion of radial position. T u r b u l e n t i n t e n s i t y i s a measure o f t h e energy p a r t i t i o n i n g between t h e f l u c t u a t i n g v e l o c i t y t o which l o c a l m i x i n g i s a t t r i b u t e d and mean v e l o c i t y which r e l a t e s t o pumping o r b l e n d i n g . The FBT ranges from 0.35 n e a r t h e i m p e l l e r t o 0.60 toward t h e w a l l . The i n c r e a s e i n i n t e n s i t y w i t h d i s t a n c e i s due t o t h e mean v e l o c i t y d e c r e a s i n g more r a p i d l y than t h e f l u c t u a t i n g v e l o c i t y . I n t e n s i t y i s seen t o be independent o f i m p e l l e r speed. That i s , once f u l l y d e v e l o p e d t u r b u l e n t f l o w i s a c h i e v e d , a d d i t i o n a l energy i n p u t i s d i v i d e d i n a c o n s t a n t manner between f l o w and t u r b u l e n c e . The new i m p e l l e r s t y l e (HIT) g e n e r a t e s a d i f f e r e n t p r o f i l e and i s c h a r a c t e r i z e d by a zone o f v e r y h i g h t u r b u l e n t i n t e n s i t y , up t o 0.95, n e a r t h e i m p e l l e r t i p . These h i g h e r t u r b u l e n c e l e v e l s mean more energy i s b e i n g p u t i n t o f l u c t u a t i o n s ( l o c a l m i x i n g ) a t t h e expense o f pumping. The v e r y h i g h l e v e l s a l s o i n d i c a t e that instantaneous flow r e v e r s a l s are occurring ( t h i s c o n d i t i o n c o u l d o n l y be observed u s i n g a L a s e r Anemometer). N e g a t i v e i n s t a n t a n e o u s v e l o c i t i e s , when made p a r t o f an average v e l o c i t y , reduce t h e t i m e mean near t h e i m p e l l e r t i p . T h i s e x p l a i n s t h e d e c r e a s i n g p o r t i o n o f t h e mean v e l o c i t y p r o f i l e f o r t h e HIT i m p e l l e r as we move toward t h e i m p e l l e r . That i s , t h e new i m p e l l e r g e n e r a t e s a "washing-machine" a c t i o n where some o f t h e f l u i d e j e c t e d i s p e r i o d i c a l l y sucked back i n t o t h e impeller. R e s u l t s on t h e FBT agree w i t h e a r l i e r s t u d i e s o f Mujumdar e t a l (3) who used a h o t w i r e anemometer f o r t h e i r measurements. Recent m i x i n g l i t e r a t u r e (]^, 4) suggests t h a t t h e t u r b u l e n t f l o w c h a r a c t e r i s t i c s o f t h e n o v e l HIT i m p e l l e r s h o u l d be o f value i n a l k y l a t i o n . Experimental

Alkylation

Equipment

The e x p e r i m e n t a l equipment used t o o b t a i n t h e m i x e r a l k y l a t i o n d a t a d e s c r i b e d i n t h i s paper i s a p i l o t p l a n t a t t h e Exxon

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Research and Development L a b o r a t o r i e s (ERDL) i n Baton Rouge, La. T h i s u n i t was d e s i g n e d t o be s i m i l a r i n performance t o t h e s t i r r e d a l k y l a t i o n u n i t s c u r r e n t l y i n commercial use. Although i t was n o t p o s s i b l e t o m a i n t a i n e x a c t m i x i n g s i m i l a r i t y , t h i s u n i t m a i n t a i n e d s i m i l i t u d e i n t h e more i m p o r t a n t scale-down parameters. A condensed v e r s i o n o f t h e ERDL a l k y l a t i o n p i l o t p l a n t f l o w p l a n i s shown i n F i g u r e 4. O l e f i n and i s o b u t a n e f e e d streams a r e s e p a r a t e l y pumped t o t h e u n i t from l a r g e f e e d s t o r a g e v e s s e l s w i t h Lapp P u l s a f e e d e r diaphragm pumps and metered w i t h t u r b i n e f l o w meters. The streams a r e t h e n combined, c a u s t i c s c r u b b e d , water washed and d r i e d w i t h m o l e c u l a r s i e v e s b e f o r e b e i n g s e n t t o t h e r e a c t o r . The combined f e e d stream i s t h e n i n j e c t e d i n t o the a c i d - h y d r o c a r b o n e m u l s i o n i n t h e s t i r r e d reactor vessel. I n o r d e r t o m a i n t a i n a c o n s t a n t temperature environment b o t h r e a c t o r and s e t t l e r a r e c o o l a n t j a c k e t e d . A f t e r r e a c t i o n , t h e a c i d - h y d r o c a r b o n e m u l s i o n passes from t h e r e a c t o r t o a b a f f l e d s e t t l e r where a phase s e p a r a t i o n t a k e s p l a c e and s e t t l e d a c i d i s pumped back t o t h e r e a c t o r . The s e t t l e d hydrocarbon phase i s c a u s t i c scrubbed t o remove any e n t r a i n e d a c i d and sent e i t h e r t o a m a t e r i a l b a l a n c e a c c u m u l a t o r or t o a p r o d u c t a c c u m u l a t i o n system. I n f o r m a t i o n t h a t has been o b t a i n e d from t h i s p i l o t p l a n t i n c l u d e s : (1) a l k y l a t e q u a l i t y a t s i m u l a t e d commercial o p e r a t i n g c o n d i t i o n s , (2) a l k y l a t e y i e l d , (3) i s o b u t a n e consumption, (4) c a t a l y s t l i f e , (5) maintenance o f p r o d u c t q u a l i t y w i t h c a t a l y s t l i f e , and (6) s e l e c t i v i t y d a t a (which c o n t r i b u t e s t o the determination o f r e a c t i o n r a t e c o n s t a n t s ) . M i x e r A l k y l a t i o n Comparison - P i l o t P l a n t

Parameters

In o r d e r t o get t h e most m e a n i n g f u l comparison between t h e two m i x e r s t y l e s i n an a l k y l a t i o n environment, two backto-back d y i n g a c i d r u n s * (each o f about two weeks d u r a t i o n ) were made i n t h e ERDL a l k y l a t i o n p i l o t p l a n t a t t h e nominal t e s t c o n d i t i o n s shown below. Reactor

Parameters

R e a c t o r Temperature - 40°F O l e f i n Space V e l o c i t y - 0.15 v o l . o l e f i n / h r / v o l . H2SO4 H2SO4 i n E m u l s i o n - 60 v o l . % *In a d y i n g a c i d r u n one b e g i n s w i t h f r e s h a c i d i n t h e r e a c t o r and w i t h o u t spent a c i d w i t h d r a w a l o r f r e s h a c i d makeup a l l o w s t h e c a t a l y s t d i l u e n t s ( a c i d s o l u b l e o i l and water) t o b u i l d up w i t h t i m e . T h i s t y p e o f r u n can be c o n t r a s t e d t o a s t e a d y s t a t e r u n where spent a c i d i s purged and f r e s h a c i d added so as t o keep t h e d i l u e n t l e v e l c o n s t a n t .

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M i x i n g Parameters - F l a t bladed turbine, novel high i n t e n s i t y turbine M i x e r Speed - 170 RPM (FBT), 245 RPM (HIT) ( i . e . , c o n s t a n t power) Mixer Size - Both m i x e r s a r e 7" i n d i a m e t e r J e t Reynolds No. - 3245

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Mixing Devices

The r e a c t o r parameters shown above a r e t y p i c a l f o r commercial s t i r r e d a l k y l a t i o n u n i t s i n H2S04-butylene s e r v i c e . I t i s i m p o r t a n t t o emphasize t h a t t h e m i x e r comparison was made a t c o n s t a n t power. The o l e f i n and i s o b u t a n e f e e d streams used i n t h e m i x e r a l k y l a t i o n comparison were o b t a i n e d from Exxon Company USA's Baton Rouge R e f i n e r y . The o l e f i n s t r e a m was c a t a l y t i c a l l y c r a c k e d butènes w h i l e t h e i s o b u t a n e stream was o b t a i n e d as t h e overhead from a d e i s o b u t a n i z e r tower. The c o m p o s i t i o n o f t h e s e streams i s shown below: Feed Stream

Olefin

Composition, V o l . % Isobutane Olefin

37.1

c

=

3 C= C" Total Other P a r a f f i n s 4

5

Isobutane 85.6

1

°28.0 3.6 31.7 31.2

}·• 0.1 14.3

A l k y l a t i o n P i l o t Plant Results P r e v i o u s i n v e s t i g a t o r s such as A l b r i g h t e t a l (5) have shown t h a t a l k y l a t i o n c a t a l y s t c o m p o s i t i o n has a p r o f o u n d e f f e c t on p r o d u c t q u a l i t y and t h a t q u a l i t y comparisons must be made a t c o n s t a n t c a t a l y s t c o m p o s i t i o n . I n a d d i t i o n t o measurement o f p r o d u c t q u a l i t y d i f f e r e n c e s , one o f t h e o b j e c t i v e s o f t h e m i x e r comparison was t o l o o k a t p o s s i b l e d i f f e r e n c e s i n c a t a l y s t c o m p o s i t i o n between t h e two m i x e r s t y l e s and t h e subsequent e f f e c t on c a t a l y s t l i f e . The e f f e c t o f c a t a l y s t age (measured as hours on o l e f i n ) on t h e c o n c e n t r a t i o n o f H2SO4* i n t h e c a t a l y s t phase i s shown i n t h e t o p p a r t o f F i g u r e 5. The H2SO4 c o n c e n t r a t i o n f o r b o t h m i x e r s d e c r e a s e d smoothly and n e a r l y l i n e a r l y w i t h i n c r e a s i n g c a t a l y s t age and t h e r e seemed t o be no s i g n i f i c a n t d i f f e r e n c e s *H2S04 c o n c e n t r a t i o n i n t h e c a t a l y s t was d e t e r m i n e d by NaOH titration.

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0

100 CATALYST AGE,

Figure 5.

200 HRS.

Catalyst composition vs. age. O , HIT mixer; A , FBT mixer.

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between them. The s t a r t i n g a c i d f o r the HIT m i x e r s t u d y was 97.9% H S 0 w h i l e the d i s c h a r g e a c i d was 86.0% H S 0 . The f r e s h o r s t a r t i n g a c i d f o r t h e FBT s t u d y was 97.3% H2SO4 w h i l e the d i s c h a r g e a c i d s t r e n g t h was 89.6% H2SO4. The r e a s o n f o r the d i f f e r e n c e i n d i s c h a r g e s t r e n g t h s was t h a t t h e FBT s t u d y was t e r m i n a t e d at a lower c a t a l y s t age. The second p a r t o f F i g u r e 5 shows the e f f e c t o f c a t a l y s t age on the c a t a l y s t w a t e r c o n c e n t r a t i o n ^ f o r b o t h m i x e r s . These d a t a show t h a t the w a t e r c o n t e n t v a r i e d smoothly from about 2 wt. % f o r the f r e s h a c i d t o about 3-3.5 wt. % f o r t h e d i s c h a r g e c a t a l y s t . A l t h o u g h t h e r e was a s l i g h t d i f f e r e n c e i n water c o n t e n t between the m i x e r s i n i t i a l l y , the w a t e r d a t a f o r the most p a r t are q u i t e s i m i l a r . S i n c e the t o t a l f e e d t o the ERDL p i l o t p l a n t was d r i e d t o a l e v e l o f 1-2 ppm H2O, t h i s w a t e r b u i l d u p was due t o hydrocarbon o x i d a t i o n by the s u l f u r i c a c i d . F i n a l l y , the e f f e c t o f c a t a l y s t age on a c i d s o l u b l e o i l ^ l e v e l i n the c a t a l y s t f o r the m i x e r comparison i s shown i n F i g u r e 6. These d a t a show t h a t , as a n t i c i p a t e d , a c i d s o l u b l e o i l b u i l t up s t e a d i l y w i t h i n c r e a s i n g c a t a l y s t age r e a c h i n g a l e v e l o f 10 wt. % f o r t h e HIT m i x e r d i s c h a r g e a c i d and ^7 wt. % f o r the FBT m i x e r d i s c h a r g e a c i d . For a l l p r a c t i c a l purposes b o t h m i x e r s showed about the same v a r i a t i o n o f a c i d s o l u b l e o i l c o n t e n t w i t h c a t a l y s t age. There are two i n t e r e s t i n g f e a t u r e s w i t h r e g a r d t o the d a t a i n F i g u r e 6 t h a t s h o u l d be n o t e d . The f i r s t p o i n t i s t h a t b o t h r u n s show a f i n i t e a c i d s o l u b l e o i l l e v e l i n the a c i d b e f o r e the o l e f i n stream was s t a r t e d (as measured by c a t a l y s t age). This low l e v e l was due t o f e e d i n g i s o b u t a n e o v e r the f r e s h H2SO4 p r i o r t o s t a r t i n g o l e f i n f e e d and shows t h a t s i g n i f i c a n t a c i d s o l u b l e o i l components can be formed from compounds o t h e r t h a n d i e n e s , o l e f i n s and/or s u l f u r a t low t e m p e r a t u r e s . The o t h e r i n t e r e s t i n g p o i n t w i t h r e g a r d t o the F i g u r e 6 d a t a i s t h a t the HIT d a t a become n o n - l i n e a r a f t e r about 225 hours on o l e f i n s . T h i s seems t o i n d i c a t e an " a c i d runaway" c o n d i t i o n * and more w i l l 2

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4

2

4

(|>Water c o n c e n t r a t i o n i n the c a t a l y s t was d e t e r m i n e d by w i t h fuming H S04 (oleum) a f t e r A l b r i g h t e t a l ( 5 ) .

titration

2

M c i d d i l u e n t commonly r e f e r r e d t o as r e d o i l i s formed p r i m a r i l y i n t h e r e a c t o r (emulsion i n the s e t t l e r i s an o r d e r o f magnitude l e s s A l t h o u g h f e e d contaminants such as d i e n e s o r i m p o r t a n t r e d o i l p r e c u r s o r s , i t can a l s o be o l e f i n , i s o b u t a n e and a l k y l a t e .

or sludge which residence time than the r e a c t o r ) . s u l f u r are formed from the

* " A c i d runaway" i s a term commonly used i n commercial a l k y l a t i o n o p e r a t i o n s and i s c h a r a c t e r i z e d by a c o n d i t i o n o f low a c i d s t r e n g t h and r a p i d b u i l d up o f d i l u e n t s . In c e r t a i n s i t u a t i o n s an a c i d runaway may f o r c e o l e f i n f e e d t o be cut out s i n c e f r e s h a c i d u s u a l l y cannot be added f a s t enough t o c o u n t e r a c t the r a p i d d i l u e n t f o r m a t i o n .

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Figure 6.

Acid-soluble oil vs. catalyst age

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be s a i d about i t i n t h e d i s c u s s i o n on c a t a l y s t l i f e . The c o n s i s t e n c y o f t h e raw c a t a l y s t c o m p o s i t i o n d a t a can be seen by l o o k i n g a t t h e bottom p a r t o f F i g u r e 5. T h i s i s a p l o t on t h e sum o f wt. % H S04, wt. % H 0 and wt. % a c i d s o l u b l e o i l f o r each o f t h e a c i d a n a l y s e s i n t h e mixer comparison s t u d y . The a b s o l u t e d i f f e r e n c e between t h i s sum and 100 g i v e s a measure o f t h e c o n s i s t e n c y o f t h e a c i d a n a l y s e s . Except f o r t h e one p o i n t a t about 250 h r s . (and t h e a n a l y s e s t h a t were r e r u n at ^75-100 h r s . ) , t h e sums i n F i g u r e 5 f o r t h e mixer comparison runs v a r y between 99% and 101% w i t h most sums b e i n g c l o s e r t h a n 1%. I f i t i s c o n s i d e r e d t h a t t h e s e sums a r e formed from t h e r e s u l t s o f t h r e e independent a n a l y s e s , i t can be s a i d t h a t the q u a l i t y o f t h e a c i d c o m p o s i t i o n d a t a i s v e r y good. One o f the most i m p o r t a n t f a c e t s o f t h e m i x e r comparison was t h e e f f e c t o f t h e m i x e r type on a l k y l a t e q u a l i t y . As mentioned p r e v i o u s l y , s i n c e a c i d c o m p o s i t i o n does have a p r o f o u n d e f f e c t on q u a l i t y i t i s n e c e s s a r y t o compare m i x i n g e f f e c t s a t c o n s t a n t a c i d c o m p o s i t i o n . For t h i s s t u d y , t h e a c i d component which seemed t o p l a y t h e key r o l e i n t h i s c o m p o s i t i o n / q u a l i t y e f f e c t i s the a c i d s o l u b l e o i l . T h i s component, which i s c h a r a c t e r i s t i c o f s t r o n g a c i d p r o c e s s e s , i s a complex m i x t u r e i n which c y c l i c c o n j u n c t polymers predominate ( 6 ) . S i n c e a l k y l a t e q u a l i t y does v a r y markedly w i t h a c i d s o l u b l e o i l c o n t e n t , many t h e o r i e s on i t s r o l e i n q u a l i t y enhancement have been proposed such as a h y d r i d e t r a n s f e r agent, s u r f a c t a n t , o r agent to i n c r e a s e i s o b u t a n e s o l u b i l i t y . T h e r e f o r e , s i n c e t h e c a t a l y s t water c o n t e n t was r e l a t i v e l y c o n s t a n t , a c i d s o l u b l e o i l l e v e l has been used as a p r i m a r y i n d i c a t o r o f a c i d c o m p o s i t i o n t o compare t h e p r o d u c t q u a l i t i e s of t h e two m i x e r s . A comparison o f octane p r o d u c t q u a l i t y f o r t h e two m i x e r s i s i l l u s t r a t e d i n F i g u r e 7 where t h e d a t a a r e p l o t t e d as GC c a l c u l a t e d C MON ( c l ) * v e r s u s wt. % a c i d s o l u b l e o i l i n t h e c a t a l y s t . A l t h o u g h i n i t i a l p r o d u c t q u a l i t y was poor* F i g u r e 7 shows t h a t t h e MON went t h r o u g h a broad maximum f o r b o t h mixers from 2 t o 4 wt. % a c i d s o l u b l e o i l . These d a t a show t h a t t h e HIT m i x e r gave a p r o d u c t q u a l i t y i n c e n t i v e o v e r t h e f l a t b l a d e d t u r b i n e and t h a t the magnitude o f t h i s i n c e n t i v e v a r i e d between 0.4 and 0.25 MON i n t h e commercial o p e r a t i n g r e g i o n (2-7 wt. % a c i d s o l u b l e o i l o r 96-90 wt. % H S 0 ) . As f a r as t h e g e n e r a l shape o f t h e curves i s concerned, t h e p r e s e n c e o f maxima i n d i c a t e s t h a t a t low c o n c e n t r a t i o n s a c i d soluble o i l s i n t e r a c t d i r e c t l y with the a l k y l a t i o n r e a c t i o n s and have a b e n e f i c i a l e f f e c t toward p r o d u c t q u a l i t y w h i l e at h i g h c o n c e n t r a t i o n s the d i l u e n t e f f e c t on a c i d s t r e n g t h outweighs any p o s s i b l e b e n e f i t s . 2

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A N D

2

+

6

2

4

* C l e a r motor octane number

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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OS

ο <3 S Ο

ε s CO

δ* "α cr

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ν.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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In a d d i t i o n t o p r o d u c t q u a l i t y t h e economics o f t h e a l k y l a t i o n p r o c e s s d i c t a t e t h a t c a t a l y s t d e a c t i v a t i o n must be f u l l y c o n s i d e r e d when e v a l u a t i n g p o t e n t i a l p r o c e s s improvements. C a t a l y s t d e a c t i v a t i o n i n a l k y l a t i o n i s c h a r a c t e r i z e d by t h e f o r m a t i o n o f d i l u e n t s t h a t lower a c i d s t r e n g t h and have a d e l e ­ t e r i o u s e f f e c t on p r o d u c t q u a l i t y beyond a c e r t a i n l e v e l . These d i l u e n t s can e i t h e r be absorbed d i r e c t l y i n t h e a c i d such as water i n t h e h y d r o c a r b o n f e e d o r be formed from f e e d components. The p r i m a r y d i l u e n t f o r m a t i o n r o u t e i s p o l y m e r i z a t i o n o f t h e s e f e e d components ( e s p e c i a l l y d i e n e s and s u l f u r compounds) t o a c i d soluble o i l s . I n a d d i t i o n , o x i d a t i o n o f t h e f e e d and/or a l k y l a t e hydrocarbons by t h e a c i d may o c c u r w h i c h forms w a t e r and tends t o d i l u t e t h e a c i d . I n a commercial a l k y l a t i o n opera­ t i o n t h e d i l u e n t s formed a r e c o n t i n u o u s l y purged by w i t h d r a w i n g spent a c i d and s e n d i n g i t f o r r e g e n e r a t i o n . Fresh or replace­ ment a c i d i s added back a t a r a t e t h a t r e p l a c e s t h e a c i d l o s t by p u r g i n g and compensates f o r any i n t e r n a l l o s s e s such as oxidation. Due t o t h e importance and c o s t s a s s o c i a t e d w i t h c a t a l y s t l i f e , d e a c t i v a t i o n r a t e s f o r b o t h m i x e r s were measured and a r e d i s c u s s e d i n t h e f o l l o w i n g p a r a g r a p h s . The q u a n t i t a t i v e measure o f c a t a l y s t l i f e i n a l k y l a t i o n i s t h e pounds o f d i l u e n t ( i . e . , a c i d s o l u b l e o i l and Η 0 ) g e n e r a t e d p e r g a l l o n o f o l e f i n (pure) f e d . T h i s f a c t o r when a p p r o p r i a t e l y combined w i t h a c i d l o s s e s ( i . e . , o x i d a t i o n ) and f r e s h and spent a c i d c o n c e n t r a t i o n s , g i v e s t h e f r e s h a c i d replacement r a t e which i s a d i r e c t measure o f t h e r e g e n e r a t i o n c o s t f o r any p a r t i c u l a r a l k y l a t i o n p r o c e s s . I n o r d e r t o c a l c u ­ l a t e v a l u e s f o r t h e a c i d replacement r a t e s , i t was n e c e s s a r y t o f o r m u l a t e a " d y i n g a c i d " model f o r t h e p i l o t p l a n t r e a c t o r s e t t l e r system.* T h i s model assumed t h e r e a c t o r - s e t t l e r system t o be a p e r f e c t l y mixed t a n k and t o o k i n t o account a c i d s o l u b l e o i l g e n e r a t i o n and H2SO4 o x i d a t i o n . U s i n g d a t a on a c i d composi­ t i o n , a d d i t i o n s / d e l e t i o n s (sampling and l o s s e s ) and c a t a l y s t i n v e n t o r i e s , t h e model was a p p l i e d i n c r e m e n t a l l y t o t h e d a t a t o c a l c u l a t e d i l u e n t and o x i d a t i o n p a r a m e t e r s . These parameters were t h e n used t o c a l c u l a t e e q u i v a l e n t a c i d replacement r a t e s f o r each m i x e r . The c a l c u l a t e d e q u i v a l e n t a c i d replacement r a t e s f o r each m i x e r a r e shown i n F i g u r e 8 as f u n c t i o n s o f a c i d s t r e n g t h 2

* I n a " d y i n g a c i d " t y p e o f experiment w i t h no a d d i t i o n s / w i t h ­ d r a w a l s , t h e f r e s h a c i d replacement r a t e has no r e a l meaning. V a l u e s c a l c u l a t e d f o r t h e m i x e r comparison d a t a a r e c a l l e d e q u i v a l e n t replacement r a t e s . These e q u i v a l e n t replacement r a t e s a r e t h e r a t e s n e c e s s a r y ( i . e . , f o r a g i v e n d i l u e n t forma­ t i o n rate) t o maintain e q u i l i b r i u m i n a h y p o t h e t i c a l steady s t a t e a l k y l a t i o n u n i t w h i c h uses f r e s h a c i d a t 98% t i t r a t a b l e a c i d i t y and spends i t s a c i d a t t h e a c i d s t r e n g t h i n q u e s t i o n .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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and as e x p e c t e d decrease w i t h d e c r e a s i n g H2SO4 c o n c e n t r a t i o n down t o about 90 wt. % FUSC^. These d a t a i n d i c a t e t h a t t h e HIT m i x e r showed a lower a c i d replacement r a t e i n t h e h i g h a c i d s t r e n g t h p o r t i o n o f t h e commercial o p e r a t i n g r e g i o n ( i . e . , 98-94 H2SO4).* The d i f f e r e n c e i n a c i d replacement r a t e s seemed t o be t h e g r e a t e s t w i t h t h e f r e s h a c i d and p r o g r e s s i v e l y narrowed w i t h d e c r e a s i n g a c i d s t r e n g t h . In t h e lower a c i d s t r e n g t h p o r t i o n o f t h e commercial o p e r a t i n g r e g i o n ( i . e . , 9490% H2SO4), t h e a c i d replacement r a t e s f o r b o t h m i x e r s were e s s e n t i a l l y e q u i v a l e n t . Below 90% H2SO4, d a t a from t h e HIT m i x e r r u n g r a p h i c a l l y showed how q u i c k l y replacement r a t e s can r i s e when t h e a c i d s t r e n g t h gets below a c r i t i c a l v a l u e ( i . e . , " a c i d runaway").

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch014

I n t e r p r e t a t i o n o f M i x i n g and A l k y l a t i o n R e s u l t s S i n c e d a t a a r e a v a i l a b l e on t h e f l o w s g e n e r a t e d by t h e two i m p e l l e r s , as w e l l as on p r o c e s s performance some s p e c u l a t i o n s can be made on t h e r o l e o f t h e n o v e l HIT i m p e l l e r i n a l k y l a t i o n . A summary o f t h e r e l a t i v e f l o w c h a r a c t e r i s t i c s and a l k y l a t e q u a l i t y a r e g i v e n i n t h e t a b l e below.

Impeller FBT

HIT

Power

Flow Turbulence at O l e f i n Addition Point

1.0 2.0 3.0 1.0

1.0 1.26 1.45 0.59

1.0 1.26 1.45 1.45

Emulsion Surface Area 1.0 1.3 1.6 1.2

Δ MON @ 3% A c i d Soluble (

0.3 0.7 0.25

R e s u l t s on o p e r a t i n g t h e FBT a t h i g h e r power l e v e l s a r e from o t h e r p i l o t p l a n t r u n s . The Δ MON i s a t t h e optimum a c i d s o l u b l e o i l l e v e l o f about 3.0 wt. %. High f l o w o f e m u l s i o n g e n e r a t e d by t h e i m p e l l e r s h o u l d d i s p e r s e t h e o l e f i n f e e d more q u i c k l y throughout t h e r e a c t o r and t h e r e b y improve q u a l i t y . Comparing t h e FBT and HIT i m p e l ­ l e r s a t c o n s t a n t power, t h e f l o w i s 40% lower f o r t h e HIT i m p e l l e r . C o n v e n t i o n a l wisdom would p r e d i c t t h e p r o d u c t q u a l i t y t o be lower. Hence i m p e l l e r pumping i s not t h e key v a r i a b l e . M i c r o m i x i n g and t h e subsequent r a p i d d i s p e r s i o n o f t h e o l e f i n s h o u l d be i n c r e a s e d by i n c r e a s i n g t h e t u r b u l e n c e a t t h e p o i n t o f i n j e c t i o n o f o l e f i n . A t c o n s t a n t power t h e HIT i m p e l l e r has t u r b u l e n c e l e v e l s t h a t a r e 1.45 times as h i g h . F o r the FBT t o r e a c h t h e s e l e v e l s , i t s power must be i n c r e a s e d by a *This d i f f e r e n c e t o : (1) a s m a l l acid soluble o i ference i n a c i d

i n replacement r a t e s f o r t h e two m i x e r s i s due d i f f e r e n c e i n t h e e f f e c t o f c a t a l y s t age on l l e v e l (see F i g . 6) and (2) about a 10% d i f ­ i n v e n t o r i e s f o r t h e two r u n s .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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f a c t o r o f t h r e e . A t t h e s e h i g h power l e v e l s t h e p r o d u c t q u a l i t y i s improved b y 0.7 MON. S i n c e t h i s i s t w i c e t h e improvement o b t a i n e d b y t h e HIT i m p e l l e r , t h i s s u g g e s t s t h a t t u r b u l e n c e a l o n e (and i t s i n f l u e n c e i n d i s p e r s i n g o l e f i n ) i s n o t t h e key variable. The c o m b i n a t i o n o f r e d u c i n g t h e f l o w and i n c r e a s i n g t h e t u r b u l e n c e l e v e l has been shown by Brown and P i t t (4_) t o decrease e m u l s i o n drop s i z e and, i n systems as we have h e r e w i t h a f i x e d amount o f d i s p e r s e d phase, i n c r e a s e t h e e m u l s i o n s u r f a c e a r e a . The HIT i m p e l l e r has been shown t o g e n e r a t e emulsions w i t h 20% more s u r f a c e a r e a t h a n d i d t h e FBT when compared a t t h e same i n p u t power l e v e l . T h i s i s i n l i n e w i t h Brown and P i t t s c o r ­ r e l a t i o n s i f t h e observed f l o w c h a r a c t e r i s t i c s f o r t h e HIT i m p e l l e r a r e used. To i n c r e a s e t h e e m u l s i o n s u r f a c e a r e a by t h i s amount u s i n g t h e FBT, t h e power l e v e l must be a p p r o x i m a t e l y doubled. When t h e FBT power l e v e l i s d o u b l e d , t h e improvement i n p r o d u c t q u a l i t y i s i n l i n e w i t h t h a t o b t a i n e d w i t h t h e HIT i m p e l l e r . T h i s suggests t h e key r o l e o f t h e i m p e l l e r i n a l k y l a t i o n i s t o generate emulsion s u r f a c e area. The b i g g e r i n c r e a s e s i n a l k y l a t e q u a l i t y a t h i g h e r a c i d s t r e n g t h s due t o improved m i x i n g i s l i k e l y due t o an i n c r e a s e d importance o f m i x i n g i n s t r o n g e r a c i d environments. A t p r e s e n t i n s u f f i c i e n t d a t a e x i s t t o be s u r e i f t h e r o l e o f t h e i m p e l l e r i s t h e same i n t h i s r e g i o n .

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1

Literature Cited 1. 2. 3.

Paul, E. L. and Treybal, R. E., AIChEJ (1971), 17, 718. Gunkel, A. A. and Weber, M. E., AIChEJ (1975), 21, 931. Mujumdar, A. S., Huany, B., Wolf, D., Weber, M. E., and Douglas, W. J. M., Can. J. Chem. Eng. (1970), 48, 475. 4. Brown, D. E. and Pitt, Κ., Chem. Eng. Sci. (1974), 29, 345. 5. Albright, L. F., et a l , Ind and Eng Chem-Proc Des and Dev. (1972), 11 (No. 3), 446. 6. Miron, S. and Lee, R. J., J. Chem. Eng. Data (1963), 8 (No. 1), 150.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

15 C o m p u t e r M o d e l i n g of A l k y l a t i o n U n i t s J. C. KNEPPER* and R. D. KAPLAN Amoco Research Center, Naperville, IL 60540

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

G. Ε. TAMPA** Amoco Oil Refinery, Whiting, IN 46394

Computer simulation (1,2) is a powerful tool for improving the design and operation of process units. Such techniques have been used to design units, to evaluate proposed process modifica­ tions, to compare operations between units, to identify declining unit performance, to optimize current performance, and ultimately to control unit operation. Within the petroleum industry, a cata­ lytic cracking simulation model (3) is being used to predict and guide unit operation. Amoco has now applied this approach to sulfuric acid alkyla­ tion units. Gilmour (4) had previously developed an alkylation unit model, using PACER, a general purpose simulator. He present­ ed no quantitative results of model applications, however, Sauer et a l . (5) also developed an alkylation unit simulation, but they did not use a rigorous approach and indicated that "the similar­ ity to alkylation is not complete because several simplifying assumptions are made in describing the process and in using the correlations (6)." In contrast, the Amoco model is more fundamental and is based on extensive laboratory and commercial test data that accurately reflect unit operations. Because Stratco and cascade units ac­ count for over 80% of the alkylation capacity of Amoco refineries, we developed complete computer models for each type. Unit Description Blow diagrams o f S t r a t c o and cascade a l k y l a t i o n u n i t s , t h e two w h i c h were modeled, a r e shown i n F i g u r e s 1 and 2. B o t h t y p e s

^ P r e s e n t address i s R i o B l a n c o O i l S h a l e P r o j e c t , 9725 E. Hampden Ave., Denver, C o l o r a d o 80231. * * P r e s e n t address i s S t a n d a r d O i l ( I n d i a n a ) , 200 E. Randolph D r i v e , C h i c a g o , I l l i n o i s 60680. 260

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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E T A L .

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Deisobutanizer

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^

Figure 1.

* η-Butane + alkylate

Stratco effluent-refrigeration alkylation unit

Propane

A

Depropanizer

Compressor

Refrigerant Isobutane

(^Olefin

,1

,1

1

I I

D

Recycle acid Isobutane recycle Deisobutanizer

Ί 1 .

Butane + alkylate

Figure 2.

Cascade alkyhtion unit

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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t y p i c a l l y contain multiple reactors. I n t h e S t r a t c o e f f l u e n t r e f r i g e r a t i o n u n i t , mixed o l e f i n s and i s o b u t a n e f l o w i n p a r a l l e l t o the s h e l l s i d e o f each r e a c t o r , where the e x o t h e r m i c a l k y l a t i o n r e a c t i o n s t a k e p l a c e i n a h y d r o c a r b o n - i n - a c i d e m u l s i o n . The r e a c t o r e f f l u e n t f l o w s t o a s e t t l e r where a c i d and h y d r o c a r b o n phases a r e s e p a r a t e d . The a c i d i s t h e n r e c y c l e d t o t h e s h e l l s i d e o f the r e a c t o r s . A back p r e s s u r e v a l v e i n t h e h y d r o c a r b o n e f f l u e n t l i n e from the s e t t l e r i s used t o m a i n t a i n t o t a l l i q u i d o p e r a t i o n i n the r e a c t o r and s e t t l e r . Downstream o f t h e v a l v e , the p r e s s u r e i s reduced. Some hydrocarbon v a p o r i z e s , c o o l i n g the remaining m a t e r i a l . This s t r e a m i s t h e n f l a s h e d through h e a t exchange tubes t o c o n t r o l r e a c t i o n temperature. The l i q u i d - v a p o r h y d r o c a r b o n e f f l u e n t t h e n f l o w s t o a p r e s s u r e - c o n t r o l l e d f l a s h drum. L i q u i d from t h e drum i s s e n t t o a d e i s o b u t a n i z e r , which produces an i s o b u t a n e r e c y c l e s t r e a m overhead and a crude a l k y l a t e bottoms p r o d u c t . F l a s h drum vapors a r e compressed and condensed. Then a p a r t o f t h i s s t r e a m i s d e p r o p a n i z e d . The d e p r o p a n i z e r bypass and bottoms p r o duct form t h e l i q u i d r e f r i g e r a n t r e c y c l e s t r e a m , w h i c h r e t u r n s t o the r e a c t i o n zone. The u n i t a l s o i n c l u d e s i n t e r s t r e a m h e a t exchangers t h a t improve the energy e f f i c i e n c y o f t h e p r o c e s s . I n t h e cascade u n i t , the o l e f i n f e e d f l o w s i n p a r a l l e l t o s e v e r a l mixed zones w i t h i n each r e a c t o r s h e l l , w h i l e r e f r i g e r a n t i s o b u t a n e , i s o b u t a n e r e c y c l e and a c i d f l o w i n s e r i e s t h r o u g h t h e s e zones. Compared w i t h s i n g l e - s t a g e r e a c t o r s h a n d l i n g e q u i v a l e n t f e e d s t r e a m s , t h i s s e r i e s of s t i r r e d r e a c t o r s a c h i e v e s a h i g h e r average i s o b u t a n e c o n c e n t r a t i o n . Temperature i s d e t e r m i n e d by r e a c t o r pressure c o n t r o l , which s e t s the extent of v a p o r i z a t i o n of the hydrocarbons i n t h e r e a c t i o n zones. The i s o b u t a n e r e c y c l e and r e f r i g e r a n t i s o b u t a n e streams a r e produced s i m i l a r l y i n b o t h S t r a t c o and cascade u n i t s . Need F o r Models S i m u l a t i o n models a r e needed t o e v a l u a t e commercial u n i t p e r formance because o f the s t r o n g emphasis on r e c y c l e w i t h i n t h e proc e s s , as i s shown i n F i g u r e s 1 and 2. A n a l y s i s o f such f l o w p a t t e r n s r e q u i r e t e d i o u s , time-consuming, t r i a l - a n d - e r r o r c a l c u l a t i o n s t h a t a r e b e s t done by computer. Models can be used t o b a l a n c e t h e key elements of p r o f i t a b i l i t y , energy v e r s u s p r o d u c t q u a l i t y . For example, good r e a c t o r performance i s f a v o r e d by low t e m p e r a t u r e s and h i g h i s o b u t a n e c o n c e n t r a t i o n s i n the r e a c t i o n zones. R e f r i g e r a t i o n systems s e r v e the d o u b l e r o l e of c o n t r o l l i n g r e a c t o r temperature and k e e p i n g i s o b u t a n e c o n c e n t r a t i o n h i g h t h r o u g h e f f i c i e n t removal o f propane from t h e system. These r e s u l t s a r e o b t a i n e d a t t h e expense o f compressor energy. The d e i s o b u t a n i z e r a l s o maximizes the c o n c e n t r a t i o n of isobutane i n the r e a c t o r system, but only a t t h e expense of energy. S i m u l a t i o n models a r e a l s o p a r t i c u l a r l y u s e f u l f o r a s s e s s -

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i n g t h e economics o f u n i t maintenance and proposed m o d i f i c a t i o n s . D e i s o b u t a n i z e r condenser performance i s a good example. As t h e s e u n i t s age and t h e i r h e a t t r a n s f e r c a p a b i l i t y d e c r e a s e s , t h e r e i s a d e c l i n e i n t h e r a t e and/or p u r i t y o f t h e i s o b u t a n e r e c y c l e stream. W i t h a comprehensive s i m u l a t i o n model, t h e e v a l u a t i o n o f t h e economics o f a t u r n a r o u n d c a n be made w i t h i n a m a t t e r o f days by u s i n g a c t u a l measured and d e s i g n h e a t t r a n s f e r c o e f f i c i e n t s .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

D e s c r i p t i o n of Models The o p t i o n s o f u s i n g a v a i l a b l e g e n e r a l purpose p r o c e s s f l o w sheet s i m u l a t o r s , o r f o r m u l a t i n g s p e c i a l purpose models were cons i d e r e d . The l a t t e r was chosen t o s a t i s f y t h e need f o r d e t a i l e d , a c c u r a t e , and f l e x i b l e models, which a r e s u i t a b l e f o r r o u t i n e use. The components of our models a r e :

• Data input • Vapor-liquid equilibrium constant and enthalpy value calculation routines • Dew point, bubble point, and flash calculations • Stream enthalpy and temperature from enthalpy routines • Heat exchanger and distillation column simulations • Convergence techniques for trial-and-error calculations • Reaction correlations • Process economics • Optimization routine • Data output

Thermodynamic c a l c u l a t i o n s a r e used t o e v a l u a t e v a p o r - l i q u i d e q u i l i b r i u m c o n s t a n t s , e n t h a l p y v a l u e s , dew p o i n t s , b u b b l e p o i n t s , and f l a s h e s . E s t a b l i s h e d t e c h n i q u e s s i m u l a t e t h e h e a t exchangers and d i s t i l l a t i o n columns, and h a n d l e convergence and o p t i m i z a tion. R e a c t i o n c o r r e l a t i o n s r e l a t e a l k y l a t e o c t a n e and y i e l d , a c i d usage, and i s o b u t a n e consumption t o f e e d c o m p o s i t i o n and p r o c e s s v a r i a b l e s . These c o r r e l a t i o n s , determined from p i l o t p l a n t and

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commercial t e s t s , a r e o f t h e form:

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

Response = f ( o l e f i n f e e d c o m p o s i t i o n , temperat u r e , space v e l o c i t y , i s o b u t a n e c o n c e n t r a t i o n , acid strength, mixing conditions, e t c . ) F i g u r e s 3 and 4 show t y p i c a l c o r r e l a t i o n s . The e f f e c t o f p r o p y l e n e c o n c e n t r a t i o n i n t h e o l e f i n f e e d on a c i d consumption i s shown i n F i g u r e 3. There i s a c r i t i c a l p r o p y l e n e c o n c e n t r a t i o n below which a c i d consumption i n c r e a s e s a t a low, l i n e a r r a t e and above which t h e i n c r e a s e i s more d r a s t i c . The v a r i o u s symbols r e f l e c t a number o f d i f f e r e n t p i l o t p l a n t and commercial t e s t r e s u l t s . F i g u r e 4 p r e s e n t s p i l o t p l a n t d a t a showing t h e e f f e c t o f i s o b u t a n e i n t h e r e a c t o r e f f l u e n t on r e s e a r c h o c t a n e number. A number o f o t h e r a l k y l a t i o n c o r r e l a t i o n s have appeared i n t h e l i t e r a t u r e ( 2 , S, 9., 10, 1 1 , 12 ) . Model s t r u c t u r e i s shown i n F i g u r e 5. P r o c e s s v a r i a b l e s , u n i t c o n s t a n t s (such as h e a t t r a n s f e r c o e f f i c i e n t s ) , and f e e d streams a r e d e s c r i b e d on i n p u t o r as s e l e c t e d by t h e o p t i m i z a t i o n r o u t i n e . Then, h e a t and m a t e r i a l b a l a n c e s a r e performed u s i n g an assumed a l k y l a t e y i e l d and i s o b u t a n e consumption. These r e s u l t s form a s e t o f r e a c t i o n c o n d i t i o n s w h i c h a r e used i n c o r r e l a t i o n s t o c a l c u l a t e r e a c t o r performance. The h e a t and m a t e r i a l b a l a n c e c a l c u l a t i o n s a r e r e p e a t e d i f r e a c t o r performance d i f f e r s s i g n i f i c a n t l y from t h a t used i n t h e p r e v i o u s c a l c u l a t i o n . O p e r a t i n g i n c e n t i v e s a r e t h e n computed and may be used i n t h e o p t i m i z a t i o n r o u t i n e t o s e l e c t new v a l u e s o f t h e o p t i m i z a t i o n v a r i a b l e s . The a c c u r a c y o f t h e models has been v a l i d a t e d by comparison w i t h commercial o p e r a t i n g d a t a . U n i t performance d a t a a r e used t o a d j u s t r e a c t i o n c o r r e l a t i o n s t o base p o i n t l e v e l s . Examples o f Model A p p l i c a t i o n s The models have been a p p l i e d t o a n a l y z e v a r i o u s Four examples o f model usage a r e : 1) 2) 3) 4)

To To To To

operations.

identify profitable unit modifications. compare performance between u n i t s . evaluate optimal u n i t capacity. determine optimal d e i s o b u t a n i z e r operation.

Unit Modifications. Model s i m u l a t i o n s a r e u s e f u l f o r e v a l u a t i n g t h e b e n e f i t s o f proposed c o n f i g u r a t i o n a l changes i n u n i t s . F o r example, s i m u l a t i o n s s u g g e s t e d t h a t m o d i f i c a t i o n s t o t h e i n t e r n a l s o f cascade u n i t s would improve performance. A f t e r t h e s e changes had been made i n an Amoco commercial u n i t , weekly average a c i d consumptions as low as 0.2 l b / g a l o f a l k y l a t e were r e c o r d e d .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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I Ατ· •

Commercial tests Pilot plant tests

/ J

As'

Propylene, % of olefins

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

Figure 3. Effect of propylene con­ centration on acid consumption

fdsobutane concentration in effluent)

Figure 4. Effect of isobutane concentration on research octane number

Input Independent variables Unit constants Feeds

Reactor simulation

Heat and material balances

±

I Economics |

I

±

Output

I

é Figure 5.

Model structure

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Comparison of Performance. The models may be used t o compare performance between s e v e r a l u n i t s or u n i t t y p e s . For example, a week of p r o d u c t i o n d a t a from the above-mentioned m o d i f i e d cascade u n i t was compared w i t h s i m u l a t e d S t r a t c o performance. The agreement between Amoco s S t r a t c o s i m u l a t i o n model p r e d i c t i o n s and m a t e r i a l b a l a n c e and p e r formance p r e d i c t i o n s p r o v i d e d by the S t r a t f o r d E n g i n e e r i n g C o r p o r a t i o n had been c o n f i r m e d e a r l i e r . Model adjustments a l l o w e d a comparison a t c o n s t a n t o p e r a t i n g c o n d i t i o n s t o be made. T a b l e I compares the performance o f the m o d i f i e d cascade u n i t w i t h the S t r a t c o s i m u l a t i o n model p r e d i c t i o n s . A c i d consumption i s 36% lower i n t h e m o d i f i e d cascade u n i t . The S t r a t c o u n i t does show a s l i g h t r e s e a r c h octane advantage over the cascade. However, o v e r a l l economics f a v o r the m o d i f i e d cascade i n t h i s case. Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

1

Optimal Unit Capacity. The s i m u l a t i o n models can e a s i l y be used t o i d e n t i f y o p t i m a l u n i t c a p a c i t y . I n t h i s example, f e e d r a t e s t o t h e cascade u n i t were v a r i e d i n such a way t h a t c o m p o s i t i o n remained c o n s t a n t . Maximum r e f r i g e r a t i o n and d e i s o b u t a n i z e r r e b o i l e r duty were a l s o s p e c i f i e d . V a r i a t i o n i n o l e f i n f e e d c o m p o s i t i o n w i t h changes i n f e e d r a t e c o u l d a l s o have been s i m u l a t e d . F i g u r e 6 shows the e f f e c t of i n c r e a s i n g f e e d r a t e on average r e a c t o r i s o b u t a n e c o n c e n t r a t i o n and temperature, and on u n i t o p e r a t i n g i n c e n t i v e s ( p r o f i t ) . The average i s o b u t a n e c o n c e n t r a t i o n decreases s i g n i f i c a n t l y as feed r a t e i n c r e a s e s ; but t h e average r e a c t o r temperature remains r e l a t i v e l y c o n s t a n t a t 4 6 F u n t i l a b u t a n e - b u t y l e n e s f e e d r a t e of about 1000 B/H i s reached. T h e r e a f t e r , temperature r i s e s s h a r p l y . T h i s temperature p a t t e r n r e s u l t s from the i m p o s i t i o n of d u a l l i m i t a t i o n s : f i r s t , minimum a l l o w a b l e r e a c t o r zone temperature, then minimum p e r m i s s i b l e compressor s u c t i o n p r e s s u r e . As f e e d r a t e i n c r e a s e s , the c o m b i n a t i o n of h i g h e r space v e l o c i t y , lower i s o b u t a n e c o n c e n t r a t i o n and, e v e n t u a l l y , h i g h e r temperature r e s u l t s i n lower octanes and a l k y l a t e y i e l d per b a r r e l of o l e f i n f e e d , and i n h i g h e r a c i d consumption. However, the lower p a r t o f the f i g u r e shows t h a t t h e v a l u e o f the a d d i t i o n a l p r o d u c t o v e r comes these d i s a d v a n t a g e s u n t i l the o p t i m a l f e e d r a t e of 1050 B/H i s reached. A l k y l a t i n g i n c r e m e n t a l f e e d above t h i s p o i n t i s not economical. e

Optimal Deisobutanizer

Operation

D e i s o b u t a n i z e r o p e r a t i o n i s a key f a c t o r i n t h e performance of an a l k y l a t i o n u n i t . The d e i s o b u t a n i z e r f u l f i l l s two main f u n c t i o n s ; s e p a r a t i n g a l k y l a t e from l i g h t e r components, and m a i n t a i n i n g a h i g h c o n c e n t r a t i o n of i s o b u t a n e i n the r e a c t o r . The S t r a t c o model was used t o s e a r c h f o r the c o m b i n a t i o n of energy c o s t s and a l k y l a t e q u a l i t y g i v i n g maximum p r o f i t . S i m u l a t i o n model p r e d i c -

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Table I Comparison of modified cascade operation with Stratco performan Modified Cascade

Conditions

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Average isobutane concentration in reactor, vol %

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Space velocity, V/V/hr

0.27

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50.0

Spent acidity, Wt%H S0 2

91.5

4

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Research octane

95.0

95.2

Acid consumption, lb 98.5-91.5 wt% H S 0 / 2

gal. C + alkylate 5

4

0.369

0.580

Butane-butylene feed rate, B/H

Figure 6.

Capacity study

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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t i o n s were made f o r g i v e n o l e f i n and make-up i s o b u t a n e s t r e a m r a t e s and c o m p o s i t i o n s t o show the e f f e c t t h a t d e i s o b u t a n i z e r r e b o i l e r duty and r e f l u x r a t i o have on r e l a t i v e p r o f i t . The r e s u l t s a r e shown i n F i g u r e 7, where the e l l i p t i c a l curves a r e cons t a n t p r o f i t contours. The l a r g e r the p r o f i t , the s m a l l e r the ellipse. I n c r e a s i n g r e c y c l e r a t e a t c o n s t a n t r e b o i l e r duty i n i t i a l l y l e a d s t o improved performance because of h i g h e r r e a c t o r i s o b u t a n e concentrations. Further increases i n r e c y c l e r a t e w i l l eventua l l y have a n e g a t i v e e f f e c t on performance because o f d e c r e a s e d i s o b u t a n e c o n c e n t r a t i o n i n the r e c y c l e as w e l l as o t h e r e f f e c t s . I n c r e a s i n g r e b o i l e r duty a t c o n s t a n t r e c y c l e l e a d s t o i n c r e a s e d r e c y c l e p u r i t y and a h i g h e r r e a c t o r i s o b u t a n e c o n c e n t r a t i o n . As a r e s u l t , performance improves. F u r t h e r i n c r e a s e s i n r e b o i l e r duty w i l l c o n t i n u e t o improve o c t a n e and d e c r e a s e a c i d .consumption. E v e n t u a l l y , t h e v a l u e of these improvements w i l l not be s u f f i c i e n t t o pay f o r the i n c r e a s e d r e b o i l e r energy usage. A s e c t i o n drawn through F i g u r e 7 a t a c o n s t a n t i s o b u t a n e r e c y c l e r a t e i s shown i n F i g u r e 8, f o r which the a b s c i s s a i s now r e f l u x r a t i o ( r e f l u x / i s o b u t a n e r e c y c l e ) . The optimum c o r r e s p o n d s to the v a l u e of r e b o i l e r duty g i v i n g the maximum p r o f i t f o r the s p e c i f i e d r e c y c l e r a t e . As the r e b o i l e r d u t y ( o r r e f l u x r a t e ) d e c r e a s e s , the p r o f i t drops s h a r p l y . No r e f l u x corresponds t o the o p e r a t i o n o f the d e i s o b u t a n i z e r as an " i s o s t r i p p e r " . Figure 8 shows t h a t " i s o s t r i p p e r " o p e r a t i o n s i g n i f i c a n t l y reduces u n i t profitability. The e f f e c t of reduced r e f l u x r a t e on Motor octane i s shown i n F i g u r e 9. As " i s o s t r i p p e r " o p e r a t i o n i s approached, o c t a n e drops markedly because of s h a r p l y reduced r e a c t o r i s o b u t a n e c o n c e n t r a tion. Conclusions Complete s i m u l a t i o n models have been f o r m u l a t e d f o r cascade and S t r a t c o s u l f u r i c a c i d a l k y l a t i o n u n i t s ; and s t u d i e s have c o n f i r m e d the a c c u r a c y of the models. A p p l i c a t i o n s t u d i e s i n c l u d e cases i n w h i c h model usage i d e n t i f i e d p r o f i t a b l e u n i t m o d i f i c a t i o n s , d e t e r m i n e d o p t i m a l u n i t c a p a c i t y and o p t i m a l d i s t i l l a t i o n tower o p e r a t i o n , and compared the performance of cascade and Stratco units. " I s o s t r i p p e r " d e i s o b u t a n i z e r o p e r a t i o n was d e t e r mined t o be r e l a t i v e l y u n p r o f i t a b l e f o r s u l f u r i c a c i d a l k y l a t i o n u n i t s ; and a c i d consumption on a m o d i f i e d cascade u n i t was found to be 36% below t h a t e x p e c t e d f o r a S t r a t c o u n i t . The examples p r e s e n t e d s u g g e s t the b r o a d a p p l i c a b i l i t y of the s i m u l a t i o n models f o r i m p r o v i n g a l k y l a t i o n u n i t o p e r a t i o n . Use of the models not o n l y p i n p o i n t s a r e a s where s i g n i f i c a n t improvements a r e poss i b l e , but a l s o q u a n t i f i e s i n c e n t i v e s needed t o get them i m p l e mented q u i c k l y .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

K N E P P E R

Computer

E T A L .

Modeling

! Optimum

•

ξ 2000 §

ω

ίοοο

/

Isostripper operation

0 Deisobutanizer reflux ratio

Figure 8.

Effect of deisobutanizer reflux ratio on profita­ bility at a given isobutane recycle rate

Optimum profitability

/

I Isostripper operation Deisobutanizer reflux ratio

Figure 9. Effect of deisobutanizer reflux ratio on motor octane number

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Acknowledgement We g r a t e f u l l y acknowledge c o n s t r i b u t i o n s made toward t h e development o f t h e s e models by Β. E. Brown, G. W. Elmer, B. S. Kennedy, S. J . C h o i , and the l a t e W. F. P a n s i n g .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch015

Abstract Computer simulation models have been formulated for cascade and Stratco s u l f u r i c acid a l k y l a t i o n units. These complete models incorporate mathematical descriptions of all the i n t e r a c t ­ ing parts of the units, including reactors, d i s t i l l a t i o n columns, compressors, condensers, and heat exchangers. Examples illusstrate diverse model applications. These include i d e n t i f y i n g p r o f i t a b l e unit modifications, comparing cascade to Stratco per­ formance, evaluating optimal unit capacity and determining o p t i ­ mal deisobutanizer operation. Literature Cited 1)

Crowe, C.M., Hamielec, A.E. Hoffman, T.W. Johnson, A.I. and Woods, D.R., "Chemical Plant Simulation," Prentice-Hall, Inc., Englewood Cliffs, N.J. (1971). 2) Franks, R.G.E., "Modeling and Simulation i n Chemical En­ gineering," Wiley-Interscience, New York (1975). 3) Wollaston, E.G., H a f l i n , W.J. Ford, W.D., and D'Souza, G.J., O i l and Gas Journal (1975) 73, (38), p. 87. 4) Gilmour, R.H., B r i t i s h Chemical Engineering, (March 1969), 14, p. 315. 5) Sauer, R.N., C o l v i l e , A.R., J r . , and, Burwick, C.W., Hydro­ carbon Processing and Petroleum Refiner (February 1964), 43, p. 84. 6) Ibid, p. 86. 7) The P h i l l i p s Petroleum Company, "Hydrofluoric Acid A l k y l a ­ tion", p. 117-128 (1946). 8) Mrstik, Α. V., Smith, K.A., and Pinkerton, R.D., "Advances i n Chemistry Series, V," p. 97, American Chemical Society. 9) Payne, R.E., Petroleum Refiner (September 1958), 37, p. 316. 10) Putney, D.H., i n "Advances i n Petroleum Chemistry and Refin­ ing I I , " p. 315, Kobe, K.A., and McKetta, J . J . , J r . , Editors, Interscience Publishers, Inc., New York (1959). 11) Jernigan, E.C., Gwyn, J.E., and Claridge, E.L., Chem. Eng. Prgr. (1965), 61, p. 94. 12) Van Zoonen, D., World Petroleum Congress, Mexico C i t y , Paper No. P.D. 17 (1967)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

16 Sulfuric

Acid

R e q u i r e m e n t s for Industrial

Alkylation

Plants

ORLANDO WEBB

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Rt. 4, F-12,Lee'sSummit, MO 64063

The most common u t i l i z a t i o n o f the l i g h t o l e f i n s produced from c a t a l y t i c c r a c k i n g and c o k i n g o p e r a t i o n s i s as f e e d s t o c k f o r a l k y l a t i o n u n i t s f o r r e a c t i o n w i t h i s o b u t a n e . The a l k y l a t e p r o d u c t has h i g h r e s e a r c h and motor o c t a n e numbers and i s used i n motor g a s o l i n e b l e n d i n g o r , to a l i m i t e d e x t e n t , r e r u n and used as t h e base s t o c k f o r m a n u f a c t u r i n g a v i a t i o n g a s o l i n e . Of the 125 commercial a l k y l a t i o n u n i t s o p e r a t i n g i n the U n i t e d S t a t e s t o d a y , 59 employ c o n c e n t r a t e d s u l f u r i c a c i d as the c a t a l y s t . T o t a l a l k y l a t e p r o d u c t i o n i s over 850,000 b a r r e l s p e r s t r e a m day, and of t h i s d o m e s t i c t o t a l the d a i l y c a p a c i t y o f the s u l f u r i c a c i d a l k y u n i t s i s i n excess o f 500,000 b a r r e l s ( 1 ) . To produce a s a t i s f a c t o r y p r o d u c t and a v o i d c o r r o s i o n and o t h e r problems the t i t r a t a b l e a c i d i t y o f the a c i d c a t a l y s t must be m a i n t a i n e d a t a r e l a t i v e l y h i g h l e v e l , n o r m a l l y above 88% ( e q u i v a l e n t wt. % H2SO4). I n most p l a n t s t h i s i s a c c o m p l i s h e d by c o n t i n u o u s a d d i t i o n o f f r e s h s u l f u r i c a c i d o f 98.0 t o 99.5% H2SO4 s t r e n g t h and c o n t i n u o u s d i s c a r d o f spent a c i d o f the m i n i mum a c c e p t a b l e s t r e n g t h . F i g u r e 1 i s a b l o c k d i a g r a m showing the g e n e r a l p r o c e s s arrangement. The d i s c a r d a c i d i s e i t h e r r e t u r n e d t o the a c i d s u p p l i e r , o r t o a much l e s s e r e x t e n t , u t i l i z e d e l s e where i n the r e f i n e r y . P u r c h a s e d a c i d c o s t s have i n c r e a s e d i n r e c e n t y e a r s from n o m i n a l l y $20/ton t o $30-40/ton i n many l o c a t i o n s . Typically, the c u r r e n t c o s t of make-up a c i d ranges from a low o f about $0.10 t o h i g h s of over $1.00 p e r b a r r e l o f a l k y l a t e . I t i s one o f t h e major o p e r a t i n g expenses f o r a s u l f u r i c a c i d a l k y l a t i o n u n i t . The purpose of t h i s paper i s t o d i s c u s s the f a c t o r s t h a t a f f e c t f r e s h a c i d r e q u i r e m e n t s and t o p o i n t o u t areas t h a t w a r r a n t close operator a t t e n t i o n . Plant Evaluation Considerations B e f o r e c o n s i d e r i n g s p e c i f i c a c i d r e a c t i o n s and t h e o r i e s , one s h o u l d pause b r i e f l y and t a k e n o t e o f the o p e r a t i n g p r o c e d u r e used on a t y p i c a l commercial u n i t and the e f f e c t t h i s can have on 271

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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the apparent p l a n t p e r f o r m a n c e , i r r e s p e c t i v e o f f e e d i m p u r i t i e s , s i d e r e a c t i o n s , e t c . F i r s t , r e c o g n i z e t h a t the volume of the a c i d c a t a l y s t i n the r e a c t i o n s e c t i o n o f the p l a n t i s v e r y l a r g e compared t o b o t h the f r e s h a c i d make-up and the d i s c a r d a c i d flow rates. For example, t h e r e may be as much as 1,800 barrels o f a c i d i n v e n t o r y i n a 17,000 b a r r e l per day u n i t , and the f r e s h and d i s c a r d a c i d f l o w r a t e s may be o n l y r o u g h l y 30 b a r r e l s p e r h o u r . The c o n f i g u r a t i o n o f the l a r g e s e t t l e r s used f o r s e p a r a t i n g and r e c y c l i n g the a c i d u s u a l l y i s such t h a t even a s m a l l change i n the a c i d l e v e l , say one i n c h , may r e p r e s e n t 45 minutes of t o t a l f r e s h a c i d f l o w . Thus the m a i n t a i n i n g of a c o n s t a n t i n v e n t o r y i n the p l a n t i s a d i f f i c u l t o p e r a t i n g g o a l t o s a t i s f y . P l a n t performance e v a l u a t i o n s s h o u l d t a k e i n t o account the p o s s i b l e e f f e c t o f i n v e n t o r y changes. Second, even assuming t h a t an e s s e n t i a l l y c o n s t a n t volume o f a c i d c a t a l y s t i s m a i n t a i n e d , the o p e r a t o r must d e c i d e what the optimum d i s c a r d a c i d i t y s h o u l d be and attempt t o m a i n t a i n i t by making a d j u s t m e n t s i n f r e s h a c i d and d i s c a r d a c i d f l o w r a t e s . If the d i s c a r d a c i d i t y i s allowed to i n c r e a s e , excessive f r e s h a c i d i s used. I f i t i s a l l o w e d t o d e c r e a s e , a l k y l a t e q u a l i t y d e c l i n e s , u n d e s i r a b l e s i d e r e a c t i o n s i n c r e a s e , and a c i d usage increases-. A decrease i n average s y s t e m a c i d i t y o f 1% t y p i c a l l y reduces a l k y l a t e q u a l i t y by about 0.4 octane numbers. I n c e r t a i n s i t u a t i o n s , a c i d i t y may drop below the p o i n t where the a c i d i s no l o n g e r an e f f e c t i v e a l k y l a t i o n c a t a l y s t but c o n t i n u e s t o absorb olefins. C h a i n p o l y m e r i z a t i o n r e a c t i o n s can a l s o be i n i t i a t e d . T h i s i s accompanied by r a p i d t e m p e r a t u r e r i s e and a sharp f u r t h e r d e c l i n e i n t i t r a t a b l e a c i d i t y . In such s i t u a t i o n s , o p e r a t o r s commonly r e s o r t to v e r y l a r g e a c i d a d d i t i o n s i n an e f f o r t t o b r i n g the e n t i r e volume of a c i d up i n s t r e n g t h . R e c o g n i z i n g the enormous a c i d i n v e n t o r y i n the s y s t e m , i t i s o b v i o u s t h a t such u p s e t s , i n a d d i t i o n t o changes i n a c i d i t y at the b e g i n n i n g and end of an o p e r a t i n g p e r i o d , must a l s o be t a k e n i n t o account i n making a f a c t u a l p l a n t performance e v a l u a t i o n o f average a c i d usage. T h i r d , and now assuming e s s e n t i a l l y c o n s t a n t volume and a c i d i t y are m a i n t a i n e d , t h e r e i s the problem o f d e t e r m i n i n g an a c c u r a t e d i s c a r d a c i d a n a l y s i s . D i s c a r d a c i d samples a r e v i s c o u s and can c o n t a i n a p p r e c i a b l e e n t r a i n e d h y d r o c a r b o n . The h y d r o carbon phase must be c o m p l e t e l y removed by c e n t r i f u g i n g the sample i f the a n a l y s i s i s t o have any meaning o r r e p r o d u c i b i l i t y . Most a n a l y t i c a l l a b o r a t o r i e s r e p o r t the t i t r a t a b l e a c i d i t y o f the a c i d p o r t i o n o f the sample. T h i s i s c a l c u l a t e d from the amount of sodium h y d r o x i d e used i n n e u t r a l i z i n g t h e sample i n a s t a n d a r d t i t r a t i o n p r o c e d u r e . W h i l e the r e s u l t i s e x p r e s s e d as wt.% H2SO4 i t i s i m p o r t a n t t o r e c o g n i z e t h a t the d i s c a r d l i q u i d i s not a s i m p l e s u l f u r i c a c i d s o l u t i o n , but i s a c t u a l l y a v e r y complex m i x t u r e o f s u l f u r i c a c i d , weak o r g a n i c a c i d s , s u l f o n i c a c i d s , s u l f i d e s , a c i d s o l u b l e p o l y m e r i c o l e f i n compounds, c a r b o n , w a t e r , and p r o b a b l y o t h e r compounds depending on f e e d c o m p o s i t i o n and

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Requirements

273

i m p u r i t i e s . The n a t u r e and r e l a t i v e amounts of t h e a c i d d i l u t i n g compounds can v a r y and have a pronounced e f f e c t on the make-up a c i d r e q u i r e m e n t and the c a t a l y t i c b e h a v i o r o f the a c i d i n the reactor. W i t h the a c i d i n v e n t o r y c o n t r o l , a c i d i t y c o n t r o l , and anal y t i c a l l i m i t s i n mind, and r e s p e c t i n g t h e i r p o t e n t i a l e f f e c t on r e p o r t e d a c i d make-up r e q u i r e m e n t s f o r any g i v e n o p e r a t i o n , p a r t i c u l a r l y o v e r o p e r a t i n g p e r i o d s o f l e s s t h a n t h i r t y d a y s , l e t us now t u r n t o some of t h e s p e c i f i c f a c t o r s a f f e c t i n g a c i d usage.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Feed I m p u r i t y

Effects

The most s i g n i f i c a n t i m p u r i t i e s i n the f e e d streams t o a t y p i c a l a l k y l a t i o n u n i t are e t h y l e n e , d i o l e f i n s , s u l f u r compounds and w a t e r . C o r r o s i o n i n h i b i t o r s and o t h e r c h e m i c a l s used i n ups t r e a m p r o c e s s i n g can a l s o be p r e s e n t i n some c a s e s , and t h e s e can have h a r m f u l e f f e c t s . The amount o f each i m p u r i t y t h a t r e a c h e s the a l k y l a t i o n r e a c t o r v a r i e s c o n s i d e r a b l y from r e f i n e r y to r e f i n e r y . I f a c c u r a t e l y determined and p r o p e r l y accounted f o r , t h e s e i m p u r i t i e s can e x p l a i n an a p p r e c i a b l e p e r c e n t a g e o f the a c i d make-up r e p o r t e d by v a r i o u s o p e r a t i n g u n i t s . The impur i t y d a t a shown i n T a b l e I can be used t o e v a l u a t e the m e r i t of improved upstream p r o c e s s c o n t r o l and/or more e f f i c i e n t f e e d p r e t r e a t m e n t methods. Table I .

Feed I m p u r i t y E f f e c t s

Compound

S u l f u r i c A c i d D i l u t i o n Rates ( B a s i s 98.5% F r e s h , 90.0% D i s c a r d )

Ethylene Butadiene S u l f u r Compounds Water

3952 Lbs. per B a r r e l 2465 Lbs. per B a r r e l 15-60 Lbs. p e r Pound of 4116 L b s . per B a r r e l

Sulfur

Ethylene I f s u f f i c i e n t i s o b u t a n e i s a v a i l a b l e , most r e f i n e r s today are c h a r g i n g a f u l l C3-C4 cut t o a l k y l a t i o n . In t h e s e o p e r a t i o n s the c o n t r o l of the f e e d d e e t h a n i z e r can have a n o t i c e a b l e e f f e c t on the amount of f r e s h a c i d needed f o r the a l k y u n i t , and y e t the c o n c e n t r a t i o n o f e t h a n e - e t h y l e n e i n the f e e d may appear t o be i n s i g n i f i c a n t . E t h y l e n e r e a c t s w i t h s t r o n g s u l f u r i c a c i d t o form e t h y l s u l f u r i c a c i d , r a t h e r than combining w i t h i s o b u t a n e t o form an a l k y l a t e . The e t h y l s u l f u r i c a c i d becomes a p a r t o f the d i s c a r d a c i d m i x t u r e and t i t r a t e s as a weak a c i d , t h e r e b y d e c r e a s i n g the c a l c u l a t e d d i s c a r d a c i d i t y and r e q u i r i n g the a d d i t i o n o f more f r e s h a c i d f o r c o n t r o l . On a mole f o r mole b a s i s , and assuming an a c i d d i l u t i o n range of from 98.5 t o 90.0% ( w t . ) , the f r e s h a c i d make-up r a t e i s 3952 pounds of a c i d per b a r r e l of e t h y l e n e

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i n the f e e d . T h i s c a l c u l a t e d f i g u r e i s c o n s i s t e n t w i t h r a t e s r a n g i n g from 2940 t o 4620 pounds p e r b a r r e l , w h i c h t h e w r i t e r has found i n common i n d u s t r i a l use. The a l k y l a t i o n a c i d p e n a l t y f o r e t h y l e n e i s so l a r g e i t makes c l o s e c o n t r o l o f t h e f e e d d e e t h a n i z e r a b s o l u t e l y mandatory f o r e c o n o m i c a l o v e r a l l o p e r a t i o n . The ethane and l i g h t e r c o n t e n t o f the C3-C4 c u t s h o u l d be m a i n t a i n e d n i l as measured by c o n t i n u o u s chromatography. Even a t r a c e amount o f C 2 s may r e p r e s e n t seve r a l b a r r e l s o f e t h y l e n e p e r day. I n a d d i t i o n , i f a s l u g o f e t h y l e n e i s a c c i d e n t a l l y charged t o the a l k y l a t i o n r e a c t o r i t can a l s o have t h e e f f e c t o f suddenly r e d u c i n g t h e s t r e n g t h o f t h e a c i d c a t a l y s t t o the p o i n t t h a t a l k y l a t i o n c e a s e s , o l e f i n a b s o r p t i o n r a p i d l y d i l u t e s t h e a c i d , and c h a i n p o l y m e r i z a t i o n o f o l e f i n s ( " a c i d runaways") can o c c u r . f

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Diolefins D i o l e f i n s a l s o occur i n r e l a t i v e l y s m a l l concentrations i n o l e f i n f e e d streams. T h e i r c o n c e n t r a t i o n i n c r e a s e s as c r a c k i n g s e v e r i t y i n c r e a s e s , such as i n f l u i d c o k i n g . As i n the case o f e t h y l e n e , t h e b u t a d i e n e s do n o t appear t o r e a c t w i t h i s o b u t a n e i n the presence o f s t r o n g s u l f u r i c a c i d . The d i e n e s a r e b e l i e v e d t o form r e a c t i o n p r o d u c t s , most o f w h i c h a r e a c i d s o l u b l e , and i f t h i s g e n e r a l p r e m i s e i s a c c e p t e d t h e f r e s h a c i d make-up r a t e f o r a d i l u t i o n range o f 98.5 t o 90.0% (wt.) can be c a l c u l a t e d t o be 2465 pounds o f a c i d p e r b a r r e l o f b u t a d i e n e . Industry p r a c t i c e i s t o use r a t e s i n t h e range o f 1890 t o 4200 pounds p e r b a r r e l . S e l e c t i v e hydrogénation has been s u c c e s s f u l l y employed comm e r c i a l l y t o convert the butadienes t o mono-olefins. Current s u l f u r i c a c i d p r i c e s give considerable j u s t i f i c a t i o n f o r adding these f a c i l i t i e s i n cases where s e v e r e c r a c k i n g c o n d i t i o n s a r e employed. S u l f u r Compounds B e f o r e b e i n g charged t o an a l k y l a t i o n u n i t , o l e f i n streams are n o r m a l l y t r e a t e d f o r removal o f s u l f u r compounds. The type o f t r e a t i n g used depends f o r t h e most p a r t on the amount and k i n d o f s u l f u r compounds p r e s e n t . Q u a n t i t i e s a r e n o r m a l l y r e p o r t e d i n parts per m i l l i o n u n i t s . According to industry sources, estimates o f t h e amount o f s u l f u r i c a c i d d i l u t e d l i e i n a range o f 15 t o 60 pounds p e r pound o f s u l f u r i n t h e f e e d . A v e r y commonly used f a c t o r i s 20 pounds p e r pound. I n t h e case o f m e t h y l m e r c a p t a n , i f one assumes a mole f o r mole r e a c t i o n o c c u r s and t h a t t h e r e a c t i o n p r o d u c t s a r e s o l u b l e i n t h e a c i d and do n o t t i t r a t e , then t h e c a l c u l a t e d amount o f a c i d d i l u t e d i s 53.7 pounds p e r pound o f mercapt a n s u l f u r ( d i l u t i o n range 98.5 t o 90.0%). This i s a very severe assumption however: commercial t e s t s i n d i c a t e about 45 pounds p e r pound and t h i s i s p r o b a b l y more r e a l i s t i c . Somewhat lower d i l u t i o n r a t e s a r e n o r m a l l y assumed f o r H2S and COS, t y p i c a l l y r a n g i n g between 15 and 18 pounds p e r pound o f s u l f u r p r e s e n t .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

16.

W E B B

Sulfuric Acid

Requirements

275

In a d d i t i o n t o the d i l u t i o n e f f e c t , the p r e s e n c e o f the s u l f u r r e a c t i o n p r o d u c t s i n the a c i d c a t a l y s t promote p o l y m e r i z a t i o n and o t h e r u n d e s i r a b l e s i d e r e a c t i o n s . I t i s t h e r e f o r e o b v i o u s t h a t o p e r a t i n g companies s h o u l d check t r e a t e r performance f r e q u e n t l y and make w h a t e v e r changes are n e c e s s a r y t o a c c o m p l i s h a h i g h degree of d e s u l f u r i z a t i o n o f the a l k y l a t i o n f e e d s t o c k .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Water Water i n f e e d s t o c k s , p a r t i c u l a r l y t h a t i n excess o f s a t u r a t i o n , i s an i m p o r t a n t p o t e n t i a l a c i d d i l u e n t . There are s e v e r a l types o f s e p a r a t o r s and d r i e r s i n commercial use on a l k y l a t i o n u n i t s . The s i m p l e s t are c o a l e s c e r d e v i c e s packed w i t h e x c e l s i o r , o r o t h e r k i n d s of p a c k i n g m a t e r i a l . W i t h p r o p e r maintenance, these d e v i c e s can c o a l e s c e and remove s i g n i f i c a n t amounts o f f i n e l y d i v i d e d and e n t r a i n e d w a t e r d r o p l e t s i n the o l e f i n and i s o b u t a n e s t r e a m s . F o r b e s t r e s u l t s the f e e d streams are c h i l l e d by h e a t exchange w i t h the c o l d h y d r o c a r b o n e f f l u e n t b e f o r e they are charged t o the c o a l e s c e r s . I n one p l a n t t e s t , a 5 5 - g a l l o n drum o f w a t e r was drawn o f f such a d e v i c e every 12 h o u r s . The p l a n t was o p e r a t i n g a t an a l k y l a t e p r o d u c t i o n r a t e o f about 2,000 b a r r e l s per day. A problem w i t h these s e p a r a t o r s , however, i s t h a t they develop c h a n n e l i n g i n t i m e and t h e i r w a t e r removal e f f i c i e n c y d e c l i n e s r a p i d l y , u n f o r t u n a t e l y t h i s performance d e t e r i o r a t i o n and need f o r p a c k i n g replacement o f t e n goes u n d e t e c t e d , s i n c e t h e r e i s no s i g n i f i c a n t change i n p r e s s u r e d r o p , o r o t h e r d a t a t o a l e r t the o p e r a t o r . The r e s u l t i s t h a t f r e s h a c i d usage s t e a d i l y i n c r e a s e s i n many l o c a t i o n s . A more r e l i a b l e type o f s e p a r a t o r w h i c h i s sometimes used i s a guard chamber packed w i t h r o c k s a l t . These u n i t s can be b u i l t l a r g e enough so t h a t onstream time can be q u i t e l o n g . F i e l d d a t a i n d i c a t e e s s e n t i a l l y complete removal o f f r e e w a t e r and, i n some c a s e s , even a p o r t i o n o f the s o l u b l e w a t e r . The c o a l e s c e d w a t e r i s w i t h d r a w n as a b r i n e s o l u t i o n . Maintenance c o n s i s t s o f s i m p l y r e s t o r i n g s a l t l e v e l w h i l e the u n i t i s b e i n g by-passed f o r a s h o r t time. The i s o b u t a n e r e c y c l e from f r a c t i o n a t i o n can a l s o c o n t a i n a p p r e c i a b l e e n t r a i n e d f r e e w a t e r . I f the r e c y c l e c o n t a i n s no o l e f i n s (from o u t s i d e make-up s t r e a m s , f o r example) t h i s s t r e a m can be c h e m i c a l l y d r i e d by c o n t a c t i n g i t w i t h t h e d i s c a r d a c i d f r o m the u n i t . T h i s i s an e f f i c i e n t and a r e l a t i v e l y i n e x p e n s i v e p r o cedure . The most e f f i c i e n t d e v i c e s a v a i l a b l e f o r complete w a t e r removal employ m o l e c u l a r s i e v e s . These are w i d e l y used on h y d r o f l u o r i c a c i d u n i t s but have been d i f f i c u l t t o j u s t i f y f o r s u l f u r i c p l a n t s . They can a l s o be u t i l i z e d to remove any s u l f u r compounds r e m a i n i n g i n the f e e d a f t e r p r e t r e a t m e n t ( 2 ) . I f s u l f u r i c a c i d p r i c e s continue t o i n c r e a s e , f u r t h e r c o n s i d e r a t i o n of molecular s i e v e s seems w a r r a n t e d . The f r e s h a c i d make-up r a t e f o r w a t e r d i l u t i o n i s 4116 pounds

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

276

INDUSTRIAL

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

o f a c i d p e r b a r r e l o f w a t e r i n t h e f e e d , a g a i n assuming an a c i d s p e n d i n g range o f 98.5 t o 90.0% ( w t . ) . F u r t h e r m o r e , i n t h e v i e w o f many t e c h n o l o g i s t s , i n c r e a s i n g t h e w a t e r content o f t h e a c i d i n the r e a c t o r has t h e a d d i t i o n a l u n d e s i r a b l e e f f e c t o f r e d u c i n g i t s e f f e c t i v e n e s s as an a l k y l a t i o n c a t a l y s t ( 3 ) . I f t r u e , t h i s c o u l d r e s u l t i n t h e f o r m a t i o n o f more a c i d s o l u b l e r e a c t i o n p r o d u c t s and t h e r e f o r e a f u r t h e r i n c r e a s e i n t h e a c i d make-up. Water a l s o i n c r e a s e s t h e c o r r o s i v e n a t u r e o f t h e a c i d i n t h e r e a c t i o n s e c t i o n . Metal l o s s e s i n the t u r b u l e n t high v e l o c i t y s e c t i o n s o f r e a c t o r s can be q u i t e r a p i d i n u n i t s c i r c u l a t i n g h i g h w a t e r content a c i d s .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Reactor Operating

Conditions

The p r e v i o u s d i s c u s s i o n has been concerned w i t h i m p u r i t i e s i n f e e d streams and t h e i r e f f e c t s on a c i d make-up r e q u i r e m e n t . A l l o f t h e a c i d d i l u t i o n r a t e s a r e l a r g e and t h e r e s u l t i n g f r e s h a c i d c o s t s a r e adequate t o support e f f i c i e n t feed f r a c t i o n a t i o n and t r e a t i n g f a c i l i t i e s , f r e q u e n t maintenance and c l o s e o p e r a t o r o b s e r v a t i o n and c o n t r o l o f upstream o p e r a t i o n s . Assuming t h i s i s done, t h e major r e m a i n i n g concern i s t h e o p e r a t i o n o f t h e a l k y l a t i o n u n i t proper, p a r t i c u l a r l y the reactor s e c t i o n . In making a l l o p e r a t i n g and d e s i g n d e c i s i o n s , i t i s i m p o r t a n t to keep i n mind t h e d e f i n i t i o n o f t h e t r u e r e a c t i o n zone. Fundam e n t a l l y , t h i s i s t h e i n t e r f a c i a l a r e a between t h e i m m i s c i b l e h y d r o c a r b o n and a c i d c a t a l y s t l i q u i d phases i n the r e a c t o r . React a n t s and p r o d u c t s f l o w a c r o s s t h i s boundary. The o l e f i n s i n t h e feed stream react instantaneously w i t h the s u l f u r i c a c i d c a t a l y s t and combine w i t h t h e r e l a t i v e l y s m a l l amount o f i s o b u t a n e p r e s e n t i n s o l u t i o n i n t h e a c i d c a t a l y s t t o form a l k y l a t e . A l k y l a t e p a s s e s o u t through t h e i n t e r f a c i a l s u r f a c e r e a c t i o n boundary i n t o the h y d r o c a r b o n phase w h i l e i s o b u t a n e passes i n t o r e s a t u r a t e t h e c a t a l y s t . To s u p p r e s s u n d e s i r a b l e p o l y m e r i z a t i o n and o t h e r r e a c tions i t i s necessary t o : a. o p e r a t e t h e r e a c t o r and s e t t l e r i n such a manner as t o produce a f i n e l y d i v i d e d h y d r o c a r b o n - i n a c i d emulsion; b. m a i n t a i n v i g o r o u s and r e p e t i t i v e c o n t a c t between the h y d r o c a r b o n and a c i d c a t a l y s t phases and t h e r e b y a c c o m p l i s h continuous r e s a t u r a t i o n o f t h e a c i d as t h e o l e f i n s r e a c t and i s o b u t a n e i s consumed; c. keep t h e c o n c e n t r a t i o n o f o l e f i n u n i f o r m l y low i n the a c i d c a t a l y s t phase; d. m a i n t a i n a h i g h c o n c e n t r a t i o n o f i s o b u t a n e i n t h e h y d r o c a r b o n phase; and e. keep t h e t e m p e r a t u r e u n i f o r m l y low throughout t h e reactor.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

16.

W E B B

Sulfuric Acid

Requirements

277

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Emulsification Perhaps the most d i f f i c u l t o f the r e q u i r e m e n t s i s t h e e m u l s i f i c a t i o n and c o n t a c t i n g . F o r e f f i c i e n t o p e r a t i o n s the e m u l s i o n c h a r a c t e r i s t i c s must be u n i f o r m throughout the r e a c t o r . An e x c e s s of a c i d i s p r e f e r r e d , since t h i s r e s u l t s i n a hydrocarbon-in-acid e m u l s i o n . I n t h e s e m i x t u r e s t h e v i s c o s i t y and s u r f a c e t e n s i o n o f the c o n t i n u o u s a c i d phase are e f f e c t i v e i n m i n i m i z i n g t h e tendency of t h e d i s p e r s e d h y d r o c a r b o n d r o p l e t s t o c o a l e s c e and s e p a r a t e , a c t i n g under t h e i n f l u e n c e o f the v e r y l a r g e s p e c i f i c g r a v i t y d i f f e r e n t i a l between the l i g h t and heavy phases. The e f f l u e n t h y d r o c a r b o n - a c i d m i x t u r e i s s e p a r a t e d e i t h e r i n a s e t t l i n g zone i n t h e r e a c t o r o r i n a s e p a r a t e a c i d s e t t l e r v e s s e l . The o p e r a t i o n o f the a c i d s e t t l e r s e c t i o n can have a marked e f f e c t on t h e o v e r a l l performance o f t h e r e a c t o r . A v e r y s u c c e s s f u l o p e r a t i n g t e c h n i q u e i n v o l v e s o p e r a t i n g w i t h an a c i d e m u l s i o n i n the a c i d s e t t l e r and r e c y c l i n g the e m u l s i o n r a t h e r t h a n a s e p a r a t e d a c i d phase ( 4 ) . To a c c o m p l i s h t h i s t h e i n v e n t o r y o f a c i d i n the r e a c t o r s e t t l e r s e c t i o n i s l o w e r e d and t h e r e c y c l e r a t e i s i n c r e a s e d t o the p o i n t t h a t as much as 20 t o 30 p e r c e n t h y d r o c a r b o n i s e n t r a i n e d i n t h e a c i d as an e m u l s i o n r e c y c l e . Large improvements i n a c i d r e q u i r e m e n t s have been o b s e r v e d on b o t h butylène and mixed p r o p y l e n e - b u t y l e n e feeds when e m u l s i o n r e c y c l e has been employed. To m i n i m i z e a c i d make-up r e q u i r e m e n t s t h e i n t e r f a c i a l a r e a o f the c i r c u l a t i n g e m u l s i o n i n t h e r e a c t o r must a l s o be maximized. E m u l s i o n s e t t l i n g r a t e s a r e n o r m a l l y used*to measure t h e amount o f d i s p e r s e d h y d r o c a r b o n phase i n the e m u l s i o n . A sample i s t r a p p e d i n a t r a n s p a r e n t gauge g l a s s and t h e time i s r e c o r d e d as the hydrocarbons c o a l e s c e and s e p a r a t e i n a c o n t i n u o u s l a y e r on top o f the h e a v i e r a c i d e m u l s i o n l a y e r . E l e c t r i c a l c o n d u c t i v i t y measurements have a l s o been made c o n f i r m i n g the s e t t l i n g c u r v e d a t a . The e m u l s i o n s e t t l i n g c u r v e s p u b l i s h e d by C u p i t , Gwyn and J e r n i g a n (5) are t y p i c a l o f those o b s e r v e d on commercial r e a c t o r s . An example of a d e s i r a b l e homogenous a c i d - c o n t i n u o u s e m u l s i o n s e t t l i n g curve i s i l l u s t r a t e d i n F i g u r e 2. I n c r e a s i n g e m u l s i f i c a t i o n has t h e e f f e c t o f i n c r e a s i n g t h e a r e a a v a i l a b l e f o r mass t r a n s f e r o f i s o b u t a n e i n t o t h e a c i d c a t a l y s t phase. A l k y l a t e q u a l i t y improves and a c i d consuming s i d e r e a c t i o n s d e c r e a s e . Other i n v e s t i g a t o r s (5) have r e p o r t e d a l a r g e i n c r e a s e i n the r a t i o o f C8 compounds t o o t h e r 05+ compounds i n the p r o d u c t a l k y l a t e was o b s e r v e d when a homogeneous e m u l s i o n was produced. In t h e w r i t e r ' s e x p e r i e n c e , changing commercial r e a c t o r o p e r a t i o n t o produce t h e d e s i r e d t y p e o f e m u l s i o n h a s , i n some c a s e s , had the e f f e c t o f i m p r o v i n g a l k y l a t e q u a l i t y by 1.5 RON o r more, and r e d u c i n g a c i d make-up by 20 p e r c e n t w i t h o t h e r o p e r a t i n g v a r i a b l e s e s s e n t i a l l y unchanged.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

A N D L A B O R A T O R Y

A L K Y L A T I O N S

PROPANE.

NEUT.

EFFLUENT

REF'G.

REACTOR

TREATING

j SETTLER I

N-BUTAN^

RECYCLE

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

ACID

ALKYLATE

DRYING 0LEF1NIC ISOBUTANE SULFURIC

DISCARQ

FEEDS

ACID RECYCLE

FEED

ISOBUTANE

ACID

Figure 1.

10

20

Simplifiedflowdiagram

30 SETTLING TIME,

Figure 2.

40

50

MINUTES

Preferred emuhion settling characteristics

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

*

16.

W E B B

Sulfuric Acid

Requirements

279

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Contacting The o p e r a t i o n o f t h e m i x e r used i n t h e r e a c t o r can have a l a r g e e f f e c t on t h e degree o f e m u l s i f i c a t i o n . I t c o n t r o l s t h e r a t e o f c i r c u l a t i o n o f t h e e m u l s i o n w i t h i n t h e r e a c t o r , and t h e r e f o r e t h e average number o f passes t h e f e e d s t o c k s make through t h e m i x i n g i m p e l l e r d u r i n g t h e i r r e s i d e n c e t i m e i n t h e r e a c t o r . Most commercial r e a c t o r s have motor d r i v e n m i x e r s , and m i x e r speed cannot be v a r i e d . Some, however, a r e equipped w i t h t u r b i n e and gear d r i v e s , and some range o f speed v a r i a t i o n i s a v a i l a b l e t o t h e operator. I m p e l l e r speeds o f 620 RPM have been r e p o r t e d t o be v e r y e f f e c t i v e i n i m p r o v i n g a l k y l a t e q u a l i t y i n mixed f e e d o p e r a t i o n s ( 4 ) . Improved d i s p e r s i o n has been c r e d i t e d by K n o b l e and Hebert w i t h r e d u c i n g a c i d make-up from 1.85 t o 0.659 pounds p e r g a l l o n on t h i s commercial u n i t . Use o f e f f i c i e n t o l e f i n f e e d d i s t r i b u t o r s i s a l s o e f f e c t i v e i n r e d u c i n g a c i d consumption. The c o n d i t i o n s a t t h e p o i n t o f i n i t i a l o l e f i n contact w i t h the c i r c u l a t i n g c a t a l y s t are very i m p o r t a n t because o f t h e e x t r e m e l y r a p i d r a t e o f t h e i n i t i a l r e a c t i o n . P e r f o r a t e d s p a r g e r r i n g s a r e f r e q u e n t l y employed, and a c o n c e n t r i c f e e d n o z z l e i s a l s o a common f e a t u r e ( 6 ) . Space V e l o c i t y As a p p l i e d t o a l k y l a t i o n , space v e l o c i t y i s d e f i n e d as t h e g a l l o n s p e r h o u r o f o l e f i n i n t h e f e e d d i v i d e d by t h e g a l l o n s o f a c i d i n t h e r e a c t o r . T h i s t e r m i s s i m p l y a measure o f t h e concent r a t i o n o f o l e f i n i n t h e a c i d phase o f t h e r e a c t o r . As o l e f i n space v e l o c i t y i s i n c r e a s e d , t h e r e i s a g r e a t e r tendency f o r p o l y m e r i z a t i o n and o t h e r u n d e s i r a b l e r e a c t i o n s t o o c c u r and a c i d makeup r e q u i r e m e n t s i n c r e a s e . There i s a l s o an i n c r e a s e i n t h e h i g h e r b o i l i n g compounds i n t h e a l k y l a t e p r o d u c t . Space v e l o c i t y , i n one form o r a n o t h e r , e n t e r s i n t o almost a l l p r o c e s s performance c o r r e l a t i o n s and i s i m p o r t a n t t o n o t e i n any p l a n t e v a l u a t i o n s t u d i e s . F o r a g i v e n p l a n t i t i s sometimes used s i n g l y i n p r e d i c t i n g p l a n t behavior. F i g u r e 3 i s a t y p i c a l example o f t h e combined e f f e c t s of space v e l o c i t y and o t h e r v a r i a b l e s on a butylène o p e r a t i o n . Note c a r e f u l l y however t h a t space v e l o c i t y i s i n t i m a t e l y a s s o c i a t e d w i t h e m u l s i f i c a t i o n , c o n t a c t i n g , and m i x i n g horsepower. I t can be v e r y m i s l e a d i n g t o compare r e a c t o r s o r p l a n t s o f d i f f e r e n t d e s i g n s u s i n g space v e l o c i t y as a p r i m a r y c r i t e r i o n . Isobutane

Concentration

The d r i v i n g f o r c e t o complete t h e a l k y l a t i o n p r o c e s s i s t h e c o n c e n t r a t i o n o f i s o b u t a n e i n t h e h y d r o c a r b o n phase i n t h e r e a c t o r ( i . e . i n the hydrocarbon e f f l u e n t ) . This i s the source o f the i s o b u t a n e needed t o r e s a t u r a t e t h e a c i d c a t a l y s t as t h e a l k y l a t i o n r e a c t i o n p r o c e e d s . The η-paraffins i n t h e h y d r o c a r b o n phase a r e i n e r t and i f they a r e a l l o w e d t o b u i l d i n c o n c e n t r a t i o n they can

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c o n s t i t u t e a h a r m f u l d i l u e n t i n the r e a c t i o n zone. T h e i r e f f e c t i s n o t always r e c o g n i z e d , p a r t i c u l a r l y by those who, f o r the sake o f c o n v e n i e n c e , o v e r s i m p l i f y r e a c t o r b e h a v i o r by u s i n g the e x t e r n a l i s o b u t a n e t o o l e f i n r a t i o i n performance c o r r e l a t i o n . To c o n t r o l an o p e r a t i n g p l a n t f o r minimum a c i d make-up, the i s o b u t a n e c o n c e n t r a t i o n i n the r e a c t o r must be m a i n t a i n e d a t the maximum p o s s i b l e l e v e l . T h i s means o p e r a t i n g b o t h the depropani z e r and the d e i s o b u t a n i z e r under optimum c o n d i t i o n s . The opera t o r s h o u l d a d j u s t tower f e e d r a t e s and o p e r a t i n g c o n d i t i o n s , always u s i n g the i s o b u t a n e c o n c e n t r a t i o n i n e i t h e r the t o t a l e f f l u e n t h y d r o c a r b o n o r the n e t e f f l u e n t h y d r o c a r b o n f r o m the r e a c t o r as h i s p r i m a r y r e f e r e n c e . I s o b u t a n e - t o - o l e f i n r a t i o * d e i s o b u t a n i z e r overhead p u r i t y , d e p r o p a n i z e r r e c y c l e p u r i t y , and r e f r i g e r a n t r e c y c l e p u r i t y a r e s i g n i f i c a n t o n l y as they r e l a t e t o r e a c t i o n zone i s o b u t a n e c o n c e n t r a t i o n . The c o r r e l a t i o n s p u b l i s h e d by Putney (7) show the e f f e c t s o f i s o b u t a n e c o n c e n t r a t i o n on octane number, and o c t a n e number on a c i d consumption. These a r e f o r butylène f e e d s t o c k s . By comb i n i n g the d a t a i t i s p o s s i b l e t o c o n s t r u c t the curve shown i n F i g u r e 4 i l l u s t r a t i n g the i n f l u e n c e o f i s o b u t a n e c o n c e n t r a t i o n on a c i d make-up r e q u i r e m e n t , w i t h a l l o t h e r v a r i a b l e s c o n s t a n t . The p o t e n t i a l a c i d s a v i n g s p r o v i d e an o b v i o u s i n c e n t i v e f o r o p t i m i z i n g f r a c t i o n a t i o n o p e r a t i o n i n b o t h butylène and mixed f e e d o p e r a tions . Propane i s e l i m i n a t e d from the p l a n t by c h a r g i n g a p o r t i o n o f the s t r e a m c o n t a i n i n g the h i g h e s t p e r c e n t a g e o f propane, u s u a l l y the r e f r i g e r a n t s t r e a m , t o a d e p r o p a n i z e r tower. In some p l a n t s propane b u i l d - u p has been reduced and i s o b u t a n e c o n c e n t r a t i o n i n c r e a s e d by revamping and c h a r g i n g the d e p r o p a n i z e r tower at a h i g h e r f e e d r a t e , u t i l i z i n g the f u l l l i q u i d h a n d l i n g c a p a c i t y o f the tower e f f e c t i v e l y . I n the case o f η-butane the o p e r a t o r must f i n d the optimum mode o f o p e r a t i o n o f the d e i s o b u t a n i z e r , o r i s o s t r i p p e r column. For r e f l u x e d columns t h i s i n v o l v e s d e t e r m i n i n g the b e s t f e e d p o i n t l o c a t i o n , and the b e s t d i v i s i o n between r e f l u x and overhead r e c y c l e t o the r e a c t o r s e c t i o n . I n some cases i t has been found t h a t i s o b u t a n e c o n c e n t r a t i o n i n the r e a c t o r c o u l d be i n c r e a s e d by moving the f e e d p o i n t up, r e d u c i n g the r e f l u x and i n c r e a s i n g the r e c y c l e t o the maximum t h a t the r e a c t o r l o o p c o u l d h a n d l e . R e a c t i o n Temperature R e l a t i v e l y low temperatures a r e r e q u i r e d i n a l k y l a t i o n r e a c ­ t o r s u s i n g s u l f u r i c a c i d c a t a l y s t . They a r e n e c e s s a r y i n o r d e r t o s l o w down p o l y m e r i z a t i o n r e a c t i o n s and reduce the f o r m a t i o n o f u n d e s i r a b l e a c i d s o l u b l e and h y d r o c a r b o n s o l u b l e b y - p r o d u c t s . T y p i c a l l y , most commercial u n i t s o p e r a t e w i t h r e a c t i o n tempera­ t u r e s i n the range o f 35°F. t o 65°F. D e s i g n temperatures are u s u a l l y s e t at 50°F. F o r minimum a c i d make-up the r e a c t o r s e c ­ t i o n s h o u l d be o p e r a t e d as c o l d as p o s s i b l e . T h i s means o p e r a t i n g

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the r e f r i g e r a t i o n compressor f o r peak performance and t a k i n g maximum advantage o f a v a i l a b l e c o o l i n g w a t e r . The c o s t o f the i n c r e m e n t a l u t i l i t i e s r e q u i r e d f o r l o w e r temperature o p e r a t i o n i s cons i d e r a b l y l e s s than the c o s t o f t h e i n c r e m e n t a l a c i d make-up. Some o p e r a t o r s have e x p r e s s e d concern o v e r the p o s s i b i l i t y o f a c i d f r e e z i n g and have r e s t r i c t e d o p e r a t i o n t o 45°F. Others howe v e r , have r e p o r t e d e x c e p t i o n a l l y low a c i d make-up r e q u i r e m e n t s at 32°F. t o 35°F. and have n o t r e p o r t e d any f r e e z i n g o r o t h e r o p e r a t i n g problems. V a r i a t i o n s i n the w a t e r c o n t e n t o f the a c i d c a t a l y s t may e x p l a i n why p l a n t e x p e r i e n c e v a r i e s .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Fresh A c i d Composition Make-up a c i d f o r a l k y l a t i o n u n i t s t y p i c a l l y c o n t a i n s from 98.0 t o 99.5 wt. p e r c e n t H2SO4. R e c o g n i z i n g the d e s i r a b i l i t y o f m a i n t a i n i n g the l o w e s t p o s s i b l e w a t e r c o n t e n t ( 8 ) , some compan i e s s p e c i f y f r e s h a c i d i s t o be 99.0 t o 99.9 % H2SO4 but cont a i n i n g no f r e e SO3. Others s p e c i f y 98.0 t o 99.0 % based on the assumption t h a t t h i s s p e c i f i c a t i o n w i l l a s s u r e t h e r e i s , i n f a c t , no f r e e SO3 p r e s e n t . I n the w r i t e r ' s o p i n i o n , t h e f r e s h a c i d c o n c e n t r a t i o n s h o u l d be s p e c i f i e d as 99.0 t o 99.5 % H2SO4 and c o n t a i n i n g no f r e e SO3. F r e s h a c i d samples s h o u l d be s p o t checked r o u t i n e l y and c a r e f u l l y a n a l y z e d f o r t i t r a t a b l e a c i d i t y and SO3. Summary The o p e r a t o r o f a commercial s u l f u r i c a c i d a l k y l a t i o n u n i t can reduce t h e amount o f make-up s u l f u r i c a c i d he must charge i f he: 1. improves f e e d t r e a t m e n t f o r removal o f s u l f u r compounds and i n h i b i t o r s ; 2. m o n i t o r s f e e d s t o c k c o m p o s i t i o n and e l i m i n a t e s ethane and l i g h t e r compounds from the f e e d ; 3. o p e r a t e s f e e d d r i e r s f o r maximum w a t e r r e m o v a l ; 4. checks d i s c a r d a c i d i t y f r e q u e n t l y and c o n t r o l s i t at the optimum l e v e l d i c t a t e d by p l a n t e x p e r ience; 5. o p e r a t e s t h e a c i d s e t t l e r as a d e c a n t e r , maint a i n i n g an e m u l s i o n i n the a c i d s e t t l e r and r e c y c l i n g an e m u l s i o n t o t h e r e a c t o r ; 6. maintains a hydrocarbon-in-acid emulsion i n the r e a c t o r w i t h as h i g h an a c i d c o n t e n t as possible, consistent with s e t t l e r limitations; 7. i n c r e a s e s the speed of t h e r e a c t o r m i x e r t o as h i g h an RPM as i s p o s s i b l e , l i m i t e d by d r i v e r and s e t t l e r c a p a b i l i t y ; 8. o p e r a t e s t h e d e i s o b u t a n i z e r and d e p r o p a n i z e r as n e c e s s a r y t o a c c o m p l i s h a maximum c o n c e n t r a t i o n of i s o b u t a n e i n the h y d r o c a r b o n e f f l u e n t from the r e a c t o r s e c t i o n ;

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l o w e r s t h e r e a c t i o n temperature t o t h e minimum consistent w i t h the a v a i l a b l e c o o l i n g water and r e f r i g e r a t i o n equipment l i m i t a t i o n s ; and uses f r e s h a c i d o f maximum s t r e n g t h and con­ t a i n i n g no f r e e SO3.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch016

Abstract One of the largest operating costs of a s u l f u r i c acid alky­ l a t i o n unit for reacting l i g h t o l e f i n s with isobutane i s the cost of the fresh s u l f u r i c acid make-up needed to maintain the a c i d i t y of the catalyst at, or above, the required minimum l e v e l . Factors a f f e c t i n g fresh acid requirement are c l a s s i f i e d i n two categories: feed contaminants and their e f f e c t s ; and the reaction conditions that contribute to acid d i l u t i o n . Estimates of acid make-up are presented when the feed impurities are ethylene, butadiene, s u l ­ fur compounds, and water. The importance of proper sampling, analysis, and control of the t i t r a t a b l e a c i d i t y of the acid cata­ l y s t and potential r e s u l t i n g operating problems are emphasized. Reaction conditions which a f f e c t acid make-up are: o l e f i n space v e l o c i t y i n the acid c a t a l y s t ; isobutane and n-paraffin concen­ tration i n the hydrocarbon phase; the amount of surface area at the hydrocarbon-acid catalyst i n t e r f a c e ; the degree of contacting between the two immiscible phases; and the reaction temperature. These conditions a f f e c t the formation of undesirable side reaction products; such products r e s u l t i n increased fresh acid require­ ments, lower aklylate product q u a l i t y , and more downstream oper­ ating problems. Methods of obtaining improved plant operation are considered. Literature Cited (1) (2) (3)

(4) (5) (6)

(7) (8)

"Gas Processing Refining and Worldwide Directory" (34th E d i t i o n ) , The Petroleum Publishing Company, Tulsa, (1976-77) C o l l i n s , J . J . , presented at NPRA annual meeting, San Antonio, Texas, (1962), Tech. 62-9 A l b r i g h t , Lyle F., Houle, Lawrence, Sumutka, Andrew Μ., and Eckert, Roger Ε. , Ind. Eng. Chem, Process Des. Develop., (1972), Vol I I , (No. 2). Knoble, W. S. and Hebert, F. E., Petroleum Refiner, (1959) Dec. Cupit, C. R., Gwyn, J . E., and Jernigan, E. C., Petro/Chem Engineer, (1961-1962), Dec. Jan. Kobe, Kenneth A. and McKetta, John J . , J r . , "Advances i n Petroleum Chemistry and Refining", Vol. 2, pages 315-355, Interscience Publishers, Inc., New York, (1959) Webb, Orlando, U. S. Patent 3,027,242 (1962) Goldsby, A. R., U. S. Patent 3,683,041 (1972)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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SARP:

Chemical

Recovery

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Used

Sulfuric

Acid

Alkylation Catalyst

ARTHUR R. GOLDSBY

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

76 Marcourt Drive, Chappaqua, NY 10514

In the early days, in the late 1930's and early 1940's, of the alkylation of isobutane with olefins using a s u l f u r i c acid c a t a l y s t , the acid catalyst was low in cost, the production of alkylate was l i m i t e d , and the discarded or used catalyst could be used in other processes, such as naphtha and lube o i l treating (1). Therefore, there was little incentive for the development of a recovery process unique to the alkylation c a t a l y s t . In addition, i t was confirmed early in the development of a l k y l a t i o n that the current, conventional processes for the recovery or conversion of s u l f u r i c acid containing hydrocarbons from t r e a t ing processed could be used for converting the used a l k y l a t i o n catalyst to fresh s u l f u r i c acid of any desired strength. As the production of alkylate increased in the 1940's, largely because of World War I I , a great deal more of the used catalyst became available for recovery. Most of it continues to be used merely as a source of s u l f u r , and is charged to conventional sludge conversion processes for recovery. To most chemists this did not seem to be a good solution to the problem, and i t still does not. The used catalyst has a t i t r a t a b l e a c i d i t y of about 90% H S0 , and a water content of about 2-5%. The fresh charge acid to a l k y l a t i o n is usually white s u l f u r i c acid of about 98.0-99.5% concentration. Currently a large amount of the used catalyst on the order of 5,000 tons per day in the United States is available for recovery, since t y p i c a l l y about 0.5 pound of s u l f u r i c acid i s required for each gallon of alkylate produced. 2

4

In view o f t h e f o r e g o i n g , i t i s not s u r p r i s i n g t h a t many attempts have been made by many companies a l m o s t from t h e s t a r t o f a l k y l a t i o n t o d e v e l o p a r e c o v e r y p r o c e s s unique t o t h e used s u l f u r i c acid alkylation catalyst. Most o f t h e e a r l y attempts were n o t i n t e n s i v e and c o n t i n u o u s . Most o f t h e work i s unpubl i s h e d , s i n c e i t was o f a p r e l i m i n a r y n a t u r e and n o t v e r y successful. An added i n c e n t i v e was p r o v i d e d f o r t h e u s e r s and l i c e n s o r s o f t h e S u l f u r i c A c i d A l k y l a t i o n P r o c e s s when i t was d i s c o v e r e d t h a t h y d r o f l u o r i c a c i d was a l s o a good a l k y l a t i o n

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catalyst. S i n c e h y d r o f l u o r i c a c i d u s u a l l y c o s t s on t h e o r d e r o f twenty times t h a t o f s u l f u r i c a c i d , a r e c o v e r y system by d i s t i l l a t i o n was i n c o r p o r a t e d i n the HF d e s i g n . Hence, the f i g u r e s g i v e n f o r a c i d consumption i n HF a l k y l a t i o n are u s u a l l y n e t figures after recovery. The f i g u r e s g i v e n i n H2SO4 a l k y l a t i o n are u s u a l l y g r o s s f i g u r e s w i t h o u t r e c o v e r y . S i n c e t h e hydrocarbons o r c o n j u n c t polymers i n the used s u l f u r i c a c i d c a t a l y s t are u n s a t u r a t e d , attempts have been made t o hydrogenate t h e c a t a l y s t i n an e f f o r t t o s a t u r a t e t h e p o l y m e r s , and thus make them i n s o l u b l e i n t h e a c i d . Attempts have a l s o been made t o conduct t h e a l k y l a t i o n under hydrogen p r e s s u r e . V a r i o u s s o l v e n t s have been used t o t r y t o e x t r a c t the s o l u b l e o r c h e m i c a l l y bound c o n j u n c t polymers from t h e used c a t a l y s t . Attempts have been made t o s e p a r a t e t h e a c i d from the c o n j u n c t polymers by c r y s t a l l i z a t i o n o f t h e a c i d , and washing o f t h e polymers from t h e a c i d c r y s t a l s . T h i s work was p r o m i s i n g and a l a r g e p i l o t u n i t was o p e r a t e d . A paper on t h e p r o c e s s by Mr. S. Robert S t i l e s i s s c h e d u l e d f o r t h i s Symposium ( 2 ) . Background f o r SARP One l i n e o f a t t a c k , which i s the s u b j e c t o f t h i s p a p e r , i s t o c o n v e r t t h e s u l f u r i c a c i d i n the used c a t a l y s t t o d i a l k y l s u l f a t e s , which a r e s o l u b l e i n h y d r o c a r b o n s , and then e x t r a c t the d i a l k y l s u l f a t e s from the c o n j u n c t polymers and w a t e r . Cons i d e r a b l e background i n f o r m a t i o n was a v a i l a b l e p r i o r t o the l a t e 1950's when a s t u d y was s t a r t e d w i t h t h e s p e c i f i c o b j e c t i v e o f d e v e l o p i n g such a r e c o v e r y p r o c e s s . When i t i s c o n s i d e r e d t h a t s u l f u r i c a c i d had a net c o s t o f not o v e r about one c e n t per pound, o r $20.00 per t o n , and a n e t c o s t i n a l k y l a t i o n o f about 0 . 4 t o 0 . 6 c e n t s per g a l l o n o f a l k y l a t e , and t h a t o n l y 5% o r l e s s o f the a c i d was l o s t i n c o n v e n t i o n a l r e c o v e r y p r o c e s s e s , i t was r e a l i z e d t h a t any new r e c o v e r y p r o c e s s would have t o have low c a p i t a l and o p e r a t i n g c o s t s , and h i g h y i e l d s , i f i t were t o be c o m p e t i t i v e s t r i c t l y on a s a v i n g s i n a c i d c o s t . Some o f the background i n f o r m a t i o n gave hope t h a t not o n l y c o u l d such a p r o cess be i n t e g r a t e d w i t h an a l k y l a t i o n u n i t , b u t by u s i n g such a p r o c e s s , an improved a l k y l a t e o f h i g h e r octane v a l u e and lower end p o i n t c o u l d be made. S i n c e t h i s g e n e r a l l i n e o f a t t a c k i s an e x c i t i n g and c h a l l e n g i n g f i e l d f o r c h e m i s t s and c h e m i c a l e n g i n e e r s , and s i n c e such a p r o c e s s i s o f i n t e r e s t t o most o i l companies and many chemical companies f o r commercial o p e r a t i o n , some o f t h e background i n f o r m a t i o n w i l l be d i s c u s s e d b r i e f l y . S u l f u r i c a c i d and o l e f i n s a r e an i n t r i g u i n g p a i r i n t h a t v a s t l y d i f f e r e n t r e s u l t s may be o b t a i n e d depending on the r e a c t i o n c o n d i t i o n s , the p a r t i c u l a r a c i d s t r e n g t h and the o l e f i n involved. Up t o about 1932 one o f t h e most w i d e l y used a n a l y t i c a l methods f o r t h e a n a l y s i s o f o l e f i n m i x t u r e s was the O r s a t

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analysis. The o l e f i n m i x t u r e i n gaseous form was passed through progressively stronger s u l f u r i c a c i d . T h u s , i s o b u t y l e n e was removed by 62.5% a c i d , p r o p y l e n e and n-butenes by 82.5% a c i d , and e t h y l e n e by 8% fuming a c i d . C o n s i d e r a b l e work was done by many o i l companies on the s o c a l l e d 2-stage a l k y l a t i o n process ( 3 ) . T h i s p r o c e s s had c o n s i d e r a b l e a p p e a l , s i n c e i t o f f e r e d a p o s s i b l e means o f r e d u c i n g t h e amount o f f r a c t i o n a t i o n r e q u i r e d i n a l k y l a t i o n , and f r a c t i o n a t i o n was the most e x p e n s i v e p a r t o f a l k y l a t i o n . In a d d i t i o n t o p i l o t u n i t work, s e v e r a l p l a n t t r i a l s were made. In t h i s p r o c e s s o l e f i n was absorbed i n used o r r e c y c l e a l k y l a t i o n a c i d , the i n e r t s and p a r a f f i n hydrocarbons e l i m i n a t e d i n the a b s o r p t i o n s t e p , and the a c i d - o l e f i n m i x t u r e c o n t a i n i n g t h e c a t a l y s t contaminants charged t o a l k y l a t i o n . The e l i m i n a t i o n o f i n e r t s r e s u l t e d i n a h i g h e r o c t a n e p r o d u c t and a r e d u c t i o n i n t h e amount o f f r a c t i o n a t i o n r e q u i r e d f o r the r e c y c l e o f i s o b u t a n e . However, a weakness i n the p r o c e s s was t h a t i t r e s u l t e d i n a c o n s i d e r a b l y h i g h e r a c i d consumption. One o t h e r weakness o r c o m p l i c a t i o n was t h a t when t h e a b s o r p t i o n s t e p was c a r r i e d o u t a t a f a i r l y h i g h c o n v e r s i o n o f the a c i d to e s t e r s i n the l i q u i d phase, a c o n s i d e r a b l e amount o f the n e u t r a l e s t e r s o r d i a l k y l s u l f a t e s ended up i n t h e h y d r o c a r b o n l i q u i d , r a t h e r than i n t h e a c i d . Fractionation is s t i l l an e x p e n s i v e p a r t o f a l k y l a t i o n i n c a p i t a l and o p e r a t i n g costs. However, i t i s n o t as e x p e n s i v e as o r i g i n a l l y , s i n c e t h e i n t r o d u c t i o n o f e f f l u e n t r e f r i g e r a t i o n ( 4 , 5 ) i n about 1953 and i s o s t r i p p i n g i n about 1956. Both o f t h e s e schemes r e s u l t i n a s m a l l e r d e i s o b u t a n i z e r and a lower o p e r a t i n g c o s t f o r f r a c t i o n a t i o n to f u r n i s h r e c y c l e isobutane. I t was found i n the e a r l y a l k y l a t i o n work t h a t v a r i o u s o l e f i n e s t e r s c o u l d be used i n p l a c e o f o l e f i n s t o a l k y l a t e i s o butane w i t h a s t r o n g H2SO4 c a t a l y s t . I t was a l s o known t h a t d i e t h y l s u l f a t e was an a c c e p t e d e t h y l a t i n g agent i n the c h e m i c a l industry. B e f o r e the days o f t h e s o p h i s t i c a t e d mechanisms such as t h o s e b e i n g p r e s e n t e d i n t h i s Symposium, i t was t h o u g h t t h a t p r o b a b l y t h e o l e f i n f i r s t formed an a l k y l s u l f a t e b e f o r e r e a c t i n g with isobutane. In a l k y l a t i o n , r e a c t i o n c o n d i t i o n s were s e l e c t e d so as t o keep t h e c o n c e n t r a t i o n o f t h e a l k y l s u l f a t e s low. It was s t a n d a r d p r o c e d u r e i n b a t c h l a b o r a t o r y work t o have a f i n i s h i n g p e r i o d , t h a t i s , a p e r i o d a t t h e end o f a run under a l k y l a t i o n c o n d i t i o n s e x c e p t t h a t no o l e f i n was c h a r g e d . E s p e c i a l l y w i t h p r o p y l e n e as t h e o n l y o l e f i n , o r i n a h i g h c o n c e n t r a t i o n i n the o l e f i n f e e d , i t was d i f f i c u l t t o g e t good enough a l k y l a t i o n c o n d i t i o n s so t h a t the a l k y l s u l f a t e c o n c e n t r a t i o n would not become t o o h i g h i n t h e r e a c t i o n m i x t u r e . And even today sometimes i n commercial a l k y l a t i o n n e u t r a l e s t e r s end up i n t h e a l k y l a t e l e a v i n g the r e a c t o r . T h i s has been shown by a n a l y s i s , and i n some c a s e s by a t e m p e r a t u r e r i s e i n t h e s e t t l e r , d e c o m p o s i t i o n i n the f r a c t i o n a t i o n s y s t e m , and poor l e a d s u s c e p t i b i l i t y o f the a l k y l a t e . N e u t r a l e s t e r s are n o t removed from

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a l k y l a t e by the u s u a l c a u s t i c washing t r e a t m e n t , and t h a t i s t h e main r e a s o n some p l a n t s use b a u x i t e t r e a t i n g o f a l k y l a t e . Numerous p a t e n t s have been i s s u e d on v a r i o u s phases o f an a c i d r e c o v e r y p r o c e s s i n v o l v i n g the a b s o r p t i o n o f o l e f i n s i n r e c y c l e o r used a l k y l a t i o n c a t a l y s t , e x t r a c t i o n o f t h e d i a l k y l s u l f a t e s , and c h a r g i n g o f t h e d i a l k y l s u l f a t e e x t r a c t , a f t e r treatment with H S 0 , to a l k y l a t i o n . R e f e r e n c e w i l l be made t o t h o s e o f p a r t i c u l a r i n t e r e s t i n l a t e r s e c t i o n s o f the p a p e r . The o t h e r s w i t h which t h e a u t h o r i s f a m i l i a r a r e i n c l u d e d i n the L i t e r a t u r e C i t e d f o r convenience ( 6 - 1 6 ) . In t h e November 1965 Hydrocarbon P r o c e s s i n g and P e t r o l e u m R e f i n e r (17)» i t was i n d i c a t e d t h a t the f i r s t commercial p l a n t f o r such a p r o c e s s was b e i n g i n s t a l l e d by C i t i e s S e r v i c e f o r s t a r t - u p i n l a t e 1966, under l i c e n s e from Texaco Development C o r p o r a t i o n . A s t a f f a r t i c l e on the p r o c e s s i n t h e J a n u a r y 2, 1967 O i l and Gas J o u r n a l , (18), was a p p a r e n t l y based on t h r e e p a t e n t s i s s u e d up t o t h a t t i m e ( 1 9 - 2 1 ) . A second commercial p l a n t by Humble O i l & R e f i n i n g Co. went i n t o o p e r a t i o n i n 1969 ( 2 2 ) . To c o n f i r m some o f the above t y p e s o f i n f o r m a t i o n and t o get some q u a n t i t a t i v e d a t a on the a b s o r p t i o n o f p r o p y l e n e and b u t y l è n e s i n r e c y c l e a l k y l a t i o n a c i d , and t h e s o l u b i l i t y o f d i i s o p r o p y l s u l f a t e and d i i s o b u t y l s u l f a t e s i n h y d r o c a r b o n s , some fundamental work, u n p u b l i s h e d , was done by Midwest Research I n s t i t u t e i n Kansas C i t y , M i s s o u r i , i n t h e e a r l y I 9 6 0 ' s f o r Texaco Development C o r p o r a t i o n . I t seemed q u i t e c l e a r from the a l k y l a t i o n p r o c e s s i t s e l f , and some o f the attempts t o e x t r a c t the c o n j u n c t polymer from t h e used a l k y l a t i o n c a t a l y s t , t h a t t h e polymers c o u l d n o t be ext r a c t e d from the s t r o n g s u l f u r i c a c i d , such as used a l k y l a t i o n catalyst. However, t h e r e was no a s s u r a n c e t h a t t h i s would be the case when the a c i d became weak as a r e s u l t o f most o f t h e a c i d being converted to d i a l k y l s u l f a t e . A number o f d i f f e r e n t p r o c e s s e s i n v o l v i n g t h e a b s o r p t i o n o f olefin in recycle sulfuric acid alkylation catalyst, extraction o f t h e d i a l k y l s u l f a t e , t r e a t m e n t o f the e x t r a c t i n some manner, and a l k y l a t i o n o f t h e t r e a t e d d i a l k y l s u l f a t e have been c o n sidered. One such p r o c e s s which has become known i n t h e i n d u s t r y as SARP i s the s u b j e c t o f t h i s p a p e r . SARP s t a n d s f o r S u l f u r i c A c i d Recovery P r o c e s s , which o b v i o u s l y has a r a t h e r g e n e r i c c o n notation. The p r o c e s s i s r a t h e r s p e c i f i c . The w r i t e r p r e f e r s t h e name o r i g i n a l l y g i v e n t o t h e p r o c e s s , namely, E x t r a c t y l a t i o n . However, SARP has t h e advantage o f b e i n g known and i s s h o r t , so SARP w i l l p r o b a b l y p r e v a i l . The i n f o r m a t i o n m a r s h a l l e d and a c q u i r e d i n c o n n e c t i o n w i t h the development o f SARP has been q u i t e h e l p f u l i n g e t t i n g a b e t t e r understanding of H S 0 a l k y l a t i o n i t s e l f . This i s part i c u l a r l y t r u e f o r such a r e a s as r u n - a w a y s , poor l e a d s u s c e p t i b i l i t y o f a l k y l a t e , t r e a t i n g p r o c e d u r e s f o r crude a l k y l a t e , the importance o f low w a t e r c o n t e n t c a t a l y s t and what c o n s t i t u t e s good m i x i n g o r a g i t a t i o n . 2

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From e a r l y work done f o r o t h e r p u r p o s e s , i t seemed c e r t a i n t h a t a t l e a s t q u a l i t a t i v e l y o l e f i n s c o u l d be absorbed i n r e c y c l e s u l f u r i c a c i d a l k y l a t i o n c a t a l y s t , the r e s u l t i n g d i a l k y l s u l f a t e s e x t r a c t e d w i t h i s o b u t a n e and a l k y l a t e d . E v i d e n c e as t o what would happen t o t h e c o n j u n c t polymer p r e s e n t i n t h e r e c y c l e a c i d and t h e a d d i t i o n a l c o n j u n c t polymer formed i n t h e a b s o r p t i o n s t e p when t h e a c i d phase o f t h e a b s o r p t i o n m i x t u r e was e x t r a c t e d w i t h i s o b u t a n e was m i s s i n g . T h e r e was some c o n c e r n t h a t the c o n j u n c t p o l y m e r , o r a t l e a s t p a r t o f i t , would a l s o be e x t r a c t e d by t h e isobutane. I t was c o n f i r m e d i n t h e work a t Midwest Research t h a t p r o p y l e n e c o u l d be r e a c t e d w i t h r e c y c l e a l k y l a t i o n a c i d t o g i v e a h i g h y i e l d o f d i i s o p r o p y l s u l f a t e ( D I P S ) , and t h a t t h e DIPS c o u l d be e x t r a c t e d w i t h hydrocarbon s o l v e n t s , i n c l u d i n g i s o butane. The i s o p r o p y l a c i d s u l f a t e (IPS) i s q u i t e i n s o l u b l e i n h y d r o c a r b o n s and o n l y a s m a l l amount i s e x t r a c t e d a l o n g w i t h t h e DIPS. S i n c e t h e r e a c t i o n o f p r o p y l e n e w i t h s u l f u r i c a c i d i s an e q u i l i b r i u m r e a c t i o n , some IPS i s always p r e s e n t . I t was found t h a t some o f t h e c o n j u n c t polymer i s a l s o e x t r a c t e d w i t h t h e DIPS. I t was a n t i c i p a t e d t h a t t h e water would s t a y i n t h e a c i d phase o r r a f f i n a t e , and t h i s was found t o be t h e c a s e . I t was f a i r l y o b v i o u s t h a t some method had t o be d i s c o v e r e d t o remove t h e c o n j u n c t polymer from t h e i s o b u t a n e - D I P S e x t r a c t i f i t were t o be charged t o an a l k y l a t i o n u n i t . I t was found t h a t t h e polymer r e a c t s q u a n t i t a t i v e l y w i t h s t r o n g s u l f u r i c a c i d (19,21 ),such as f r e s h 98% a c i d o r r e c y c l e a l k y l a t i o n c a t a l y s t . About an equal w e i g h t o r 50% by volume o f t h e a c i d i n r e l a t i o n t o t h e c o n j u n c t polymer i s r e q u i r e d . The a c i d - p o l y m e r complex forms e a s i l y and q u i c k l y m e r e l y by hand s h a k i n g i n a c e n t r i f u g e tube a t room t e m p e r a t u r e . The complex i s a heavy but f a i r l y f r e e f l o w i n g , v i s c o u s l i q u i d a t room t e m p e r a t u r e . I t may be s e p a r a t e d by g r a v i t y s e t t l i n g . I t i s i n s o l u b l e i n hydrocarbons such as i s o b u t a n e , and s o l u b l e i n H0SO4. DIPS a p p a r e n t l y i s not s o l u b l e i n the complex. However, i f e x c e s s a c i d i s used, some DIPS w i l l d i s s o l v e i n t h e a c i d and a c i d complex. IPS i s a l s o s o l u b l e i n t h e e x c e s s a c i d and a c i d complex. T h u s , the t h r e e s t e p p r o c e s s o f a b s o r p t i o n , e x t r a c t i o n and a l k y l a t i o n became a f o u r s t e p p r o c e s s o f a b s o r p t i o n , e x t r a c t i o n , a c i d t r e a t m e n t o f t h e e x t r a c t , and a l k y l a t i o n . I t was c o n c l u d e d from the r e s u l t s o f t h e work a t Midwest Research and t h e l a t e r work on the removal o f c o n j u n c t polymer from t h e e x t r a c t w i t h H S 0 t h a t a l l f o u r s t e p s were o p e r a b l e . An economic s t u d y i n d i c a t e d t h a t t h e p r o c e s s would be a t t r a c t i v e i f about 90% o f the a c i d i n t h e used a l k y l a t i o n c a t a l y s t c o u l d be c o n v e r t e d t o DIPS, and about 90% o f the DIPS e x t r a c t e d and alkylated. T h i s amounted t o an 80% r e c o v e r y o f t h e a c i d , and a corresponding r e d u c t i o n i n a c i d consumption. In o r d e r t o o b t a i n q u a n t i t a t i v e d a t a on t h e i n d i v i d u a l s t e p s 2

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and o v e r a l l y i e l d s , a b r i e f p i l o t u n i t s t u d y was c a r r i e d out by Texaco Development C o r p o r a t i o n and S t r a t f o r d E n g i n e e r i n g C o r p o r a t i o n i n Kansas C i t y , M i s s o u r i . To e x p e d i t e t h e s t u d y , a v a i l a b l e S t r a t c o C o n t a c t o r s were used f o r the a b s o r p t i o n , a c i d t r e a t i n g and a l k y l a t i o n s t e p s . U s i n g Texaco Development's s o l v e n t r e f i n i n g e x p e r i e n c e , a R o t a t i n g D i s c C o n t a c t o r (RDC) was used f o r the e x t r a c t i o n s t e p . The SARP f l o w i n s i m p l i f i e d form i s shown i n F i g u r e 1. The SARP f l o w as used i n t h e p i l o t u n i t i s shown i n F i g u r e 2. and d e s c r i b e d i n d e t a i l i n U . S . P a t . 3 , 8 0 3 , 2 6 2 ( 2 3 ) . In the f o l l o w i n g example, t h e f e e d s t o c k s shown i n T a b l e 1 were employed i n t h e a p p a r a t u s o f F I G . 2. TABLE I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

Feed S t o c k s In w e i g h t

Isobutane Ethane Propylene Propane Isobutane n-Butane Isobutylene Butylene-1 Butylene-2 Pentanes Total

6.9 91.1 2.0

100.0

percent

Propanepropylene

Butanebutylène

0.4 62.3 33.7 3.6

100.0

0.1 2.7 34.6 11.0 15.9 9.5 22.9 3.3 100.0

10 c c . p e r minute o f used a l k y l a t i o n a c i d from the s e t t l e r 39 t i t r a t i n g 91.0% was c h a r g e d t o a b s o r b e r 12 a t about 25° F. F r e s h p r o p a n e - p r o p y l e n e f e e d a t t h e r a t e o f 4 5 . 0 c c . per minute was c h a r g e d t o a b s o r b e r 11 a t about 30° F. U n r e a c t e d propanep r o p y l e n e from a b s o r b e r 11 s e p a r a t e d i n s e t t l e r 23 was c h a r g e d t o a b s o r b e r 12. The h y d r o c a r b o n phase o r u n r e a c t e d propanep r o p y l e n e from a b s o r b e r 12 s e p a r a t e d i n s e t t l e r 14 c o m p r i s e d 11.8% d i p r o p y l s u l f a t e . The a c i d phase from a b s o r b e r 11 s e p a r a t e d i n s e t t l e r 23 c o m p r i s i n g 80.6% d i p r o p y l s u l f a t e and 15.3% p r o p y l a c i d s u l f a t e was passed a t a r a t e o f 2 4 . 2 c c . per minute t o a r o t a t i n g d i s c c o n t a c t o r e x t r a c t o r 33 near t h e t o p . 315.0 c c . p e r m i n u t e o f t h e i s o b u t a n e f e e d was c h a r g e d t o t h e r o t a t i n g d i s c c o n t a c t o r near the bottom. A temperature g r a d i e n t was m a i n t a i n e d i n t h e e x t r a c t o r , t h e bottom temperature b e i n g about 55° F and the top t e m p e r a t u r e about 65° F. Overhead from t h e e x t r a c t o r c o m p r i s i n g 83.8% i s o b u t a n e , 5.7 d i p r o p y l s u l f a t e , and

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Olefin Feed

Used Alkylation Add ^

Xi

iscard dd

Alkylate

Settler

Used Alkvlatlon Add

Fresh Add

Flowsheet for SARP (simplified)

R

ο ο ε

Recycle Add

Alkylatlon Reactor

Isobutane Dialkyl Sulfate

Add Trbater

Figure 1.

Isobutane

<:

ο «Λ

Off Gas

Olefin-Isobutane Feed

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

Figure 2.

Detailedflowsheetof SARP

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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0.3% p r o p y l a c i d s u l f a t e was passed t o a 600 c c . m e c h a n i c a l l y a g i t a t e d r e a c t o r a t about 80° F a l o n g w i t h 0 . 2 c c . p e r minute o f used a l k y l a t i o n a c i d o f 91.0% c o n c e n t r a t i o n . The a c i d t r e a t e d p r o d u c t was passed t o a s e t t l e r 41 s e p a r a t i n g a h y d r o c a r b o n phase a t t h e r a t e o f 341.2 c c . p e r minute c o m p r i s i n g 84.2% i s o b u t a n e , 5.8% d i p r o p y l s u l f a t e and 0.1% p r o p y l a c i d s u l f a t e . 105.5 c c . p e r minute o f the butane b u t y l è n e f e e d i n l i n e 2 9 , 315.4 c c . per minute o f t h e i s o b u t a n e f e e d i n l i n e 3 0 , and 0 . 4 pound p e r hour o f 97.5% s u l f u r i c a c i d i n l i n e 43 were c h a r g e d t o g e t h e r w i t h the h y d r o c a r b o n phases from s e t t l e r s 14 and 4 1 , r e c y c l e a c i d i n l i n e 21 and r e c y c l e i s o b u t a n e i n l i n e 34 t o a S t r a t c o a l k y l a t i o n r e a c t o r 31 w i t h e f f i c i e n t m i x i n g h e l d a t 40 t o 45° F. R e a c t i o n m i x t u r e was passed c o n t i n o u s l y t o a s e t t l e r 3 9 . The h y d r o c a r b o n phase produced a t a r a t e o f 749 c c . per minute was c a u s t i c and water washed and s t a b l i z e d t o remove most o f t h e butane and l i g h t e r h y d r o c a r b o n p r o d u c i n g a p p r o x i m a t e l y 50 g a l l o n s p e r day o f d e s i r e d a l k y l a t e p r o d u c t . Spent a c i d from t h e a c i d t r e a t e r 38 was produced a t t h e r a t e o f 1.3 c c . per m i n u t e . The spent a c i d from e x t r a c t o r 33 a t the r a t e o f 3 . 8 c c . per minute c o r r e s p o n d s t o an a c i d consumption o f 0.18 pound per gallon of a l k y l a t e . A c o r r e s p o n d i n g c o n t r o l run w i t h o u t a c i d r e c o v e r y gave an a c i d consumption o f 0.88 pound per g a l l o n o f alkylate. A p p r o x i m a t e l y 90% o f the used a l k y l a t i o n a c i d was c o n v e r t e d t o d i p r o p y l s u l f a t e and a p p r o x i m a t e l y 90% o f t h e d i p r o p y l s u l f a t e formed was s e n t back t o a l k y l a t i o n wherein t h e s u l f u r i c a c i d was regenerated or r e c o v e r e d . O v e r a l l , a p p r o x i m a t e l y 80% o f t h e used a l k y l a t i o n a c i d was r e c o v e r e d . The r e a c t i o n s o f s u l f u r i c a c i d w i t h p r o p y l e n e i s an e q u i l i b r i u m r e a c t i o n , and by t h e method o f o p e r a t i o n d e s c r i b e d i t i s not p o s s i b l e to convert a l l o f the a c i d t o e x t r a c t a b l e d i a l k y l s u l f a t e s ; some w i l l remain as a l k y l a c i d sulfate. In a d d i t i o n , w i t h the e x t r a c t i o n c o n d i t i o n s used i t i s not p o s s i b l e t o e x t r a c t a l l o f the d i a l k y l s u l f a t e s f o r m e d . The spent a c i d from e x t r a c t o r 33 had an a n a l y s i s o f a p p r o x i m a t e l y 2.5% w a t e r , 10% a c i d - p o l y m e r i c o i l complex ( p r o b a b l y a c t u a l l y c o n s i d e r a b l y h i g h e r ) , 10% d i p r o p y l s u l f a t e and 77.5% propyl a c i d s u l f a t e . The r e s e a r c h o c t a n e o f the t o t a l a l k y l a t e from t h e a c i d r e c o v e r y run was 9 5 . 5 c l e a r and 107.0 w i t h 3 . 0 c c . o f T e l . The motor octane was 92.6 c l e a r and 106.8 w i t h 3 c c . T e l . The a l k y l a t e from t h e c o n t r o l run w i t h o u t a c i d r e c o v e r y had a r e s e a r c h o c t a n e c l e a r o f 94.7 and 105.9 w i t h 3 . 0 c c . o f T e l . A f t e r a l i t t l e e x p e r i e n c e , the o p e r a t i o n o f t h e p i l o t u n i t was smooth and e a s y . In g e n e r a l the o p e r a t i o n was s t a b l e and e a s i e r t o c o n t r o l than i n a c o n v e n t i o n a l a l k y l a t i o n u n i t . In one run some water was a c c i d e n t a l l y i n t r o d u c e d i n t o the a l k y l a t i o n system. The system a c i d r a p i d l y dropped t o about 80% t i t r a t a b l e a c i d i t y w i t h o u t c a u s i n g a run-away ( 2 4 ) , as would have been t h e case in conventional a l k y l a t i o n .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

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The r e s u l t s o f the p i l o t u n i t s t u d y were about as e x p e c t e d and p r e d i c t e d . However, t h e a l k y l s u l f a t e s were much more s t a b l e t o time and t e m p e r a t u r e than a n t i c i p a t e d . Aà a r e s u l t , t h e r e was c o n s i d e r a b l e l a t i t u d e f o r t h e c o n d i t i o n s i n t h e e x t r a c t i o n and acid treating steps. A commercial u n i t was d e s i g n e d based on t h e p i l o t u n i t r e sults. The d e s i g n was e s s e n t i a l l y the same as i n t h e p i l o t u n i t . A p l a n t was o p e r a t e d by C i t i e s S e r v i c e f o r s e v e r a l y e a r s . Some y e a r s ago t h e e n t i r e r e f i n e r y where the SARP u n i t was l o c a t e d was discontinued. As was the c a s e w i t h the p i l o t u n i t , t h e SARP u n i t was easy t o o p e r a t e , and i n g e n e r a l a s t e a d i e r o p e r a t i o n was obtained. Upsets and poor o p e r a t i o n o f u n i t s not d i r e c t l y a p a r t o f the r e c o v e r y s e c t i o n , such as t h e f e e d s p l i t t e r , butane i s o m e r i z a t i o n u n i t , and d e i s o b u t a n i z e r were n o t as s e r i o u s when SARP was i n o p e r a t i o n . The g e n e r a l f e e l i n g was t h a t an o c t a n e i n c r e a s e was o b t a i n e d , as w e l l as a demonstrated two t h i r d s t o three f o u r t h s r e d u c t i o n i n a c i d consumption. S u f f i c i e n t l y prec i s e runs under s t a b l e c o n d i t i o n s were not made i n the p i l o t u n i t o r i n e i t h e r o f two commercial p l a n t s t o be c e r t a i n t h a t an i n c r e a s e i n o c t a n e was o b t a i n e d . Up u n t i l some time a f t e r t h e commercial o p e r a t i o n o f SARP i n 1966, i t was assumed t h a t t h e d i s c a r d SARP a c i d would o r c o u l d be d i s p o s e d o f i n t h e same manner as d i s c a r d a l k y l a t i o n a c i d , namely, by s e n d i n g i t back f o r c r e d i t t o the a c i d s u p p l i e r . This was based on i n f o r m a t i o n from a c i d s u p p l i e r s a f t e r samples o f a c i d had been s e n t t o them. L a t e r , i t developed that although the a c i d c o u l d be r e c o v e r e d i n a s l u d g e c o n v e r s i o n u n i t , i t d e c r e a s e d the c a p a c i t y o f t h e u n i t by about 50%, because o f the h i g h hydrocarbon c o n t e n t o f t h e a c i d . As a r e s u l t , t h e d i s c a r d SARP a c i d as f a r as t h e a c i d s u p p l i e r was c o n c e r n e d , had a minor o r n e g a t i v e v a l u e as a s o u r c e o f s u l f u r f o r a s l u d g e c o n v e r s i o n unit. I t was found t h a t a second SARP commercial u n i t o f about t h e same d e s i g n as t h e f i r s t o n e , a l t h o u g h c o n s i d e r a b l y l a r g e r , was a l s o e a s y t o o p e r a t e , and i n g e n e r a l gave l i t t l e t r o u b l e . Using an o v e r a l l o l e f i n f e e d o f about 35% p r o p y l e n e and 65% b u t y l è n e s , t h e a c i d consumption was reduced t o about one t h i r d . The r e s e a r c h o c t a n e v a l u e o f t h e t o t a l a l k y l a t e o f about 375° F . E . P . was about 94 c l e a r and 105 w i t h 3 c c . T E L . The water c o n t e n t on t h e SARP d i s c a r d a c i d was about 1.9% whereas w i t h o u t SARP i t was about 4-5%, and i n each case w i t h make-up a c i d o f 99.0-99.5%. O r i g i n a l l y , i t was thought t h a t q u i t e s i m p l e and low c o s t equipment c o u l d be and would be used f o r SARP c o m m e r c i a l l y . Howe v e r , more s o p h i s t i c a t e d and e x p e n s i v e equipment was a v a i l a b l e f o r the p i l o t u n i t , so i t was u s e d . To be as s u r e as p o s s i b l e about the s c a l e - u p , t h e same type o f equipment was used c o m m e r c i a l l y . As a r e s u l t , the c o s t o f t h e r e c o v e r y s e c t i o n ( a b s o r p t i o n , e x t r a c t i o n and a c i d t r e a t m e n t o f e x t r a c t ) was c o n s i d e r a b l y h i g h e r than o r i g i n a l l y p r o j e c t e d . T h i s became even more pronounced when a l l o y s had t o be used f o r c e r t a i n p a r t s o f the equipment t o t a k e

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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care of c o r r o s i o n . With t h i s as b a c k g r o u n d , and i n a d d i t i o n , the r e l a t i v e l y low c o s t o f f r e s h s u l f u r i c a c i d and low v a l u e o f d i s c a r d a c i d , i t became a p p a r e n t a l o n g about 1969 t h a t SARP c o u l d n o t be a s u c c e s s c o m m e r c i a l l y j u s t on a c i d s a v i n g s a l o n e , e s p e c i a l l y w i t h f r e s h a c i d a t about $20.00 per t o n . SARP would have to r e s u l t i n o t h e r s a v i n g s , such as i n a h i g h e r o c t a n e p r o d u c t , o r lower o p e r a t i n g c o s t s . I t s h o u l d be made c l e a r t h a t t e c h n i c a l l y from a chemical and chemical e n g i n e e r i n g viewpoint the process i s a s u c c e s s . Each o f t h e t h r e e s t e p s o f the r e c o v e r y s e c t i o n works q u i t e w e l l , and the i n d i c a t i o n s a r e t h a t t h e o p e r a t i o n o f the a l k y l a t i o n s e c t i o n i s more s t a b l e and improved because o f t h e r e c o v e r y s e c t i o n . Because o f t h e above t y p e s o f f a c t o r s , and t h e u n c e r t a i n t y r e g a r d i n g t h e r o l e o f Government i n f u e l s , SARP has been dormant f o r several years. A l k y l a t i o n a l s o has been r a t h e r q u i e t . Howe v e r , w i t h t h e p h a s i n g o u t o f l e a d i n g a s o l i n e , and i n c r e a s e d p r e s s u r e f o r l e s s p o l u t i o n from f u e l s , i t l o o k s as i f a l k y l a t i o n may have y e t a n o t h e r s u r g e i n p r o d u c t i o n . And, with the r i s i n g c o s t o f s u l f u r i c a c i d , and t h e i n c r e a s i n g need f o r h i g h o c t a n e , c l e a r a l k y l a t e a t a reduced c o s t , perhaps SARP may a l s o have a renewal o f i n t e r e s t . Problems i n SARP w i t h s u g g e s t e d s o l u t i o n s and areas f o r improvement may perhaps be d i s c u s s e d i n a l a t e r paper. A b r i e f d i s c u s s i o n o f the f o u r s t e p s o f SARP o r E x t r a c t y l a t i o n w i l l be g i v e n . Absorption. In t h e a b s o r p t i o n s t e p as much as p o s s i b l e o f t h e o l e f i n s h o u l d be c o n v e r t e d t o d i a l k y l s u l f a t e . The d i a l k y l s u l f a t e s a r e q u i t e s o l u b l e i n h y d r o c a r b o n s above about 40° F, whereas the a l k y l a c i d s u l f a t e s a r e n o t . Propylene i s the pref e r r e d o l e f i n , and n - b u t y l e n e s may be u s e d . P r o p y l e n e has been used c o m m e r c i a l l y . A l t h o u g h an e x h a u s t i v e s t u d y was not made, t h e use o f a b u t y l è n e f e e d c o n t a i n i n g i s o b u t y l e n e gave poor r e s u l t s . I s o b u t y l e n e r e s u l t s i n a c o n s i d e r a b l e l o s s o f a c i d and a l s o i s o butylene. About 10-25% o f t h e t o t a l o l e f i n used i n SARP i s r e a c t e d i n t h e a b s o r b e r , assuming a n e t a c i d consumption o f about 0.2-0.5%. The e x a c t amount w i l l depend on t h e n e t a c i d consumpt i o n o r the amount o f f r e s h make-up a c i d charged t o the a l k y l a t i o n section. The a c i d charge t o t h e a b s o r b e r i s the used s u l f u r i c a c i d c a t a l y s t from the a l k y l a t i o n s e t t l e r . I t u s u a l l y i s o f about 90% t i t r a t a b l e a c i d i t y w i t h about 3-5% w a t e r and 3-6% c o n j u n c t p o l y mer. The a l k y l a t i o n c a t a l y s t i s no l o n g e r a c t i v e as an a l k y l a t i o n c a t a l y s t when the a c i d i t y drops t o about 80% due t o the p i c k up o f c o n j u n c t polymer and a l k y l s u l f a t e s . However, i t i s s t i l l a c t i v e f o r the a b s o r p t i o n o f propylene u n t i l s u b s t a n t i a l l y a l l of the a c i d i s converted to a l k y l s u l f a t e s . Since the formation of a l k y l s u l f a t e s from o l e f i n s and s u l f u r i c a c i d are e q u i l i b r i u m r e a c t i o n s , c o n d i t i o n s s h o u l d be used which w i l l s h i f t t h e e q u i l i b r i u m t o t h e r i g h t , o r to the d i a l k y l s u l f a t e , w i t h minimum f o r m a t i o n o f alkyl acid s u l f a t e .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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C H 36

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Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

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°4

°4

As may be seen i n F i g u r e 2, the S t r a t c o C o n t a c t o r s were o p e r a t e d so as t o g e t p a r t o f the advantage o f c o u n t e r c u r r e n t flow. The c o n t a c t o r s g i v e good m i x i n g and c o n t a c t o f the o l e f i n feed with the a c i d . I n t i m a t e m i x i n g o f t h e o l e f i n f e e d and a c i d is desirable. An e x c e s s o f o l e f i n , low water c o n t e n t o f a c i d , and removal o f d i a l k y l s u l f a t e from the a c i d phase o f the a b s o r p t i o n r e a c t i o n m i x t u r e f a v o r a h i g h c o n v e r s i o n o f the a c i d t o d i a l k y l sulfate. T h i s p r o b a b l y can be a c c o m p l i s h e d b e s t i n a t r u l y c o u n t e r c u r r e n t o p e r a t i o n i n l i q u i d p h a s e , such as i n a t o w e r . I t w i l l be noted from t h e f l o w o f F i g u r e 2 t h a t t h e u n ­ r e a c t e d o l e f i n stream from t h e weaker a c i d a b s o r b e r 11 i s sent to the s t r o n g e r a c i d a b s o r b e r 12. Then t h e u n r e a c t e d o l e f i n stream from s t r o n g e r a c i d a b s o r b e r 12 i s s e n t d i r e c t l y t o a l k y l a t i o n . T h i s f l o w under t h e p r o p e r c o n d i t i o n s p r o b a b l y i n s u r e s t h a t no c o n j u n c t p o l y m e r , or v e r y l i t t l e , i s s e n t t o a l k y l a t i o n i n the u n ­ reacted o l e f i n stream. I t a l s o e n a b l e s a l l o f the o l e f i n not r e ­ a c t e d i n the a b s o r p t i o n s t e p t o be u t i l i z e d i n a l k y l a t i o n . However, t h e u n r e a c t e d o l e f i n stream from weaker a c i d a b s o r b e r 11 may be s u b s t a n t i a l l y s a t u r a t e d w i t h DIPS, and when t h i s stream i s s e n t t o s t r o n g e r a c i d a b s o r b e r 1 2 , i t tends t o r e t a r d t h e e x t e n t o f c o n v e r s i o n o f a c i d and/or a c i d p r o p y l s u l f a t e t o DIPS. Ignor­ i n g the p o s s i b i l i t y t h a t the u n r e a c t e d o l e f i n stream from weaker a c i d a b s o r b e r 11 may c o n t a i n c o n j u n c t p o l y m e r , and j u s t c o n s i d e r ­ i n g the c o n v e r s i o n o f a c i d t o DIPS, i t would be b e t t e r t o send the unreacted o l e f i n d i r e c t l y to a l k y l a t i o n . E i t h e r l i q u i d phase o r vapor phase a b s o r p t i o n , or a com­ b i n a t i o n o f the two may be u s e d . L i q u i d phase was used commer­ cially. As i n a l k y l a t i o n , t h e time r e q u i r e d f o r t h e a b s o r p t i o n s t e p i s d e t e r m i n e d l a r g e l y by t h e c o o l i n g r e q u i r e d and the e f f i c i e n c y of the c o n t a c t i n g . The two c o n t a c t o r s used i n the p i l o t u n i t gave a c o n t a c t or r e s i d e n c e time o f about one hour i n each c o n t a c t o r , which i s p r o b a b l y f a r i n e x c e s s o f what i s needed. A temperature o f 35-40° F was used c o m m e r c i a l l y . In some l a t e r p i l o t u n i t work b e t t e r r e s u l t s were o b t a i n e d a t 50° F. However, the s o l u b i l i t y o f DIPS i n hydrocarbons i s much h i g h e r a t 50° F than a t 35° F, and t h i s may a c c o u n t f o r a h i g h e r c o n v e r s i o n a t 50° F. Conjunct p o l y m e r i z a t i o n s h o u l d be kept t o a minimum, as i t r e p r e s e n t s a l o s s o f o l e f i n and a c i d . Retardation of conjunct p o l y m e r i z a t i o n i s f a v o r e d by a low t e m p e r a t u r e , as i n a l k y l a t i o n , e s p e c i a l l y i n t h a t p o r t i o n o f the a b s o r b e r w i t h t h e s t r o n g e s t

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a c i d , such as t h e upper p o r t i o n o f a c o u n t e r c u r r e n t t o w e r . A s h o r t r e s i d e n c e time and e f f i c i e n t m i x i n g p r o b a b l y a l s o f a v o r minimum c o n j u n c t p o l y m e r i z a t i o n . U s u a l l y t h e r e i s no d i f f i c u l t y i n s e p a r a t i n g t h e a c i d and hydrocarbon phases i n a g r a v i t y s e t t l e r , e s p e c i a l l y i f the temp e r a t u r e o f the s e t t l e r i s c o n t r o l l e d . I f any d i f f i c u l t y i s e n c o u n t e r e d , i t may be s o l v e d by a d d i n g i s o b u t a n e t o the a b s o r p t i o n m i x t u r e , or by c o o l i n g t h e a b s o r p t i o n m i x t u r e t o about 4 0 - 5 0 " F. I f c o o l i n g i s n o t p r o v i d e d i n t h e s e t t l e r , the t e m p e r a t u r e may r i s e , a p p a r e n t l y due t o c o n t i n u e d r e a c t i o n , as o f t e n i s the c a s e in the a l k y l a t i o n s e t t l e r s in propylene a l k y l a t i o n . Extraction. Solvent e x t r a c t i o n processes are u s u a l l y f a i r l y e x p e n s i v e because o f the c o s t i n r e c o v e r i n g t h e s o l v e n t , such as by h e a t i n g or c h i l l i n g , and u s u a l l y w i t h some l o s s o f s o l v e n t . In SARP we have a u n i q u e and q u i t e f a v o r a b l e s i t u a t i o n . The s o l v e n t i s a r e c y c l e stream o f i s o b u t a n e from t h e a l k y l a t i o n s e c t i o n , w h i c h , a f t e r i t i s used t o e x t r a c t DIPS, i s r e t u r n e d a l o n g w i t h t h e DIPS t o a l k y l a t i o n , where t h e i s o b u t a n e i s p r o c e s s e d as u s u a l in a l k y l a t i o n . As w i l l be n o t e d i n F i g u r e 2 , i s o b u t a n e from the p r o d u c t r e c o v e r y f a c i l i t i e s o r d e i s o b u t a n i z e r was used c o m m e r c i a l l y . This i s a v e r y l a r g e stream and i s adequate i n q u a n t i t y . C o u n t e r c u r r e n t o p e r a t i o n and e f f i c i e n t c o n t a c t i n g w i t h i n t h e e x t r a c t o r , a h i g h s o l v e n t d o s a g e , and a t e m p e r a t u r e above about 40° F f a v o r complete e x t r a c t i o n o f the d i a l k y l s u l f a t e . DIPS i n creases in s o l u b i l i t y in isobutane with i n c r e a s i n g temperature. A temperature o f about 50° F was used c o m m e r c i a l l y w i t h a R o t a t i n g D i s c C o n t a c t o r (RDC). The optimum RPM o f the e x t r a c t o r was n o t determined. The volume r a t i o o f i s o b u t a n e t o DIPS s h o u l d be 6 o r higher. A h i g h s o l v e n t dosage a l s o f a v o r s a good s e p a r a t i o n o f the e x t r a c t from the r e a f f i n a t e i n t h e s e t t l e r . A l t h o u g h t h e DIPS seems q u i t e s t a b l e i n i s o b u t a n e s o l u t i o n , i t i s p r o b a b l y a d v a n tageous t o o p e r a t e a t about 50° F r a t h e r than a t about 100° F. The aim o r i d e a l i n the e x t r a c t i o n s t e p i s t o remove a l l o f t h e a v a i l a b l e HpSO, i n the used a l k y l a t i o n c a t a l y s t as DIPS and I P S , and t o l e a v e a l l o f the c o n j u n c t polymer and water i n t h e raffinate. J u s t how near t h e i d e a l i s r e a l i z e d depends on the e f f i c i e n c y o f t h e a b s o r p t i o n s t e p , as w e l l as the e x t r a c t i o n s t e p . I t was o r i g i n a l l y a n t i c i p a t e d t h a t s u b s t a n t i a l l y a l l o f t h e water would s t a y i n the r a f f i n a t e , and no e v i d e n c e o r d a t a have been developed to i n d i c a t e o t h e r w i s e . In g e n e r a l , a low water c o n t e n t and a low c o n v e r s i o n o f a c i d to DIPS f a v o r r e t e n t i o n o f the p o l y mer i n t h e r a f f i n a t e . A r e l a t i v e l y h i g h water c o n t e n t and a h i g h c o n v e r s i o n o f the a c i d t o DIPS f a v o r removal o f polymer i n t h e extract. The r a f f i n a t e o r s p e n t a c i d from t h e e x t r a c t i o n s t e p comp r i s e s w a t e r , a l k y l a c i d s u l f a t e , d i a l k y l s u l f a t e , and t h e c o n j u n c t polymers ( p r o b a b l y a s s o c i a t e d w i t h a c i d ) formed i n t h e a l k y l a t i o n , a b s o r p t i o n and a c i d t r e a t i n g s t e p s . The e x t r a c t comp r i s e s t h e i s o b u t a n e s o l v e n t , d i a l k y l s u l f a t e , a r e l a t i v e l y small

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amount o f a l k y l a c i d s u l f a t e , and p a r t o f t h e c o n j u n c t p o l y m e r . The c o m p o s i t i o n o f the SARP r e j e c t a c i d or e x t r a c t o r bottoms w i l l v a r y depending on a l o t o f f a c t o r s , but f o r most o f the work w i t h l e s s than optimum c o n d i t i o n s i n t h e a b s o r p t i o n , e x t r a c t i o n and a c i d t r e a t i n g s t e p s , a f a i r l y t y p i c a l a n a l y s i s i s shown i n T a b l e 2, below. For o r i e n t a t i o n purposes an a n a l y s i s o f used a l k y l a t i o n a c i d i s a l s o shown. TABLE

II

SARP R e j e c t

Acid Weight

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

Alkylation O i l ( c o n j u n c t polymer) Water Sulfuric acid Isopropyl a c i d s u l f a t e Diisopropyl sulfate Total Sulfur Hydrocarbon i n a c i d - o i l complex and a l k y l s u l f a t e s Equivalent H S0 2

4

Acid

Percent SARP A c i d

6.0 3.0 91.0 0.0 0.0

15.0 4.6 28.0 44.8 7.6

100.0

100.0

29.7

20.7

6.0 91.0

31.9 63.5

There i s some q u e s t i o n as t o whether t h e r e i s a c t u a l l y any f r e e s u l f u r i c a c i d i n the SARP a c i d . P r o b a b l y i n most c a s e s t h e r e i s n ' t and p r e f e r a b l y t h e r e s h o u l d not be any. In most c a s e s i t i s b e l i e v e d t h a t a p p r o x i m a t e l y an equal w e i g h t o f a c i d and c o n j u n c t polymer a r e l o o s e l y t i e d up as a complex. Under more n e a r l y optimum c o n d i t i o n s i n a l l f o u r s t e p s o f the p r o c e s s , and a f t e r e q u i l i b r i u m o r s t e a d y s t a t e c o n d i t i o n s have been r e a c h e d , the water c o n t e n t p r o b a b l y would be n e a r e r 2%, o r l e s s , and t h e amount o f a l k y l s u l f a t e s would be c o n s i d e r a b l y l o w e r . The i d e a l or u l t i m a t e would be j u s t c o n j u n c t polymer and w a t e r . It should be noted t h a t t h e hydrocarbon c o n t e n t o f the SARP a c i d i s much h i g h e r than t h a t o f a l k y l a t i o n a c i d . Acid Treatment. Under most c o n d i t i o n s , some o f the c o n j u n c t polymer i s removed by the i s o b u t a n e i n the e x t r a c t i o n s t e p . Just how much and whether i t w i l l be removed depends on the s p e c i f i c c o m p o s i t i o n o f t h e a b s o r p t i o n m i x t u r e and t h e e x t r a c t i o n c o n ditions. In t h e p i l o t u n i t , r e l a t i v e l y weak make-up a c i d o f 97.5% was charged t o the a l k y l a t i o n s t e p , so the r e c y c l e a c i d charged t o t h e a b s o r b e r was r e l a t i v e l y h i g h i n w a t e r . I f f r e s h make-up a c i d o f 99.5% c o n c e n t r a t i o n , the u s u a l o r b e t t e r d r y i n g o f a l k y l a t i o n s t r e a m s , and a s t r i c t l y c o u n t e r c u r r e n t a b s o r b e r were

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u s e d , i t might v e r y w e l l not be n e c e s s a r y t o a c i d t r e a t t h e isobutane-DIPS e x t r a c t . C o m m e r c i a l l y the e x t r a c t was t r e a t e d w i t h used a l k y l a t i o n c a t a l y s t t o remove c o n j u n c t p o l y m e r , s i n c e i t was a n t i c i p a t e d t h a t q u i t e l i k e l y under the c o n d i t i o n s used some c o n j u n c t polymer would be i n the e x t r a c t . I t was shown c o n c l u s i v e l y i n a p i l o t u n i t t h a t when t h e e x t r a c t was not t r e a t e d , the f r e s h make-up a c i d o r a c i d consumption i n a l k y l a t i o n w i t h SARP was no lower than w i t h o u t SARP. F o r t u n a t e l y , used o r d i s c a r d a l k y l a t i o n c a t a l y s t i s s a t i s f a c t o r y f o r the a c i d t r e a t m e n t , and o n l y a s m a l l amount i s r e quired. U s u a l l y about 0 . 0 5 pound p e r g a l l o n o f a l k y l a t e was a r b i t r a r i l y used c o m m e r c i a l l y . S i n c e o p e r a t i n g c o n d i t i o n s i n comm e r c i a l o p e r a t i o n v a r y from day t o d a y , and a n a l y t i c a l t e s t s a r e o f t e n slow and i n f r e q u e n t , an e x c e s s o f a c i d was u s u a l l y u s e d . As i n d i c a t e d e a r l i e r , an e x c e s s o f a c i d causes s o l u t i o n o f DIPS i n the a c i d . T h u s , t o r e c o v e r the DIPS i n the e x c e s s a c i d , the r a f f i n a t e o r a c i d phase from the a c i d t r e a t m e n t s t e p was s e n t t o the extractor. In r e f i n e r i e s o r a r e a s i n which two o r more a l k y l a t i o n u n i t s are o p e r a t e d , one SARP u n i t l a r g e enough t o p r o c e s s the used a l k y l a t i o n a c i d from a l l o f the a l k y l a t i o n u n i t s c o u l d be i n s t a l l e d . The r e c o v e r e d a c i d i n t h e form o f i s o b u t a n e - D I P S e x t r a c t c o u l d be s e n t t o t h e v a r i o u s a l k y l a t i o n u n i t s as needed o r d e s i r e d . Such a l a r g e r SARP u n i t would not o n l y have a lower c o s t per u n i t o f c a p a c i t y , b u t would a l s o have a d d i t i o n a l advantages i f f u r t h e r p r o c e s s i n g o f t h e SARP r e j e c t a c i d were c a r r i e d o u t p r i o r to c o n ventional recovery. Alkylation. In g e n e r a l t h e c o n d i t i o n s f o r a l k y l a t i o n a r e , o r may b e , the same w i t h o r w i t h o u t SARP. A good d i s c u s s i o n o f t h e c o n d i t i o n s and v a r i a b l e s i n a l k y l a t i o n i s g i v e n i n t h e paper by Mr. O r l a n d o Webb ( 2 5 ) s c h e d u l e d f o r t h i s Symposium. Only t h o s e c o n d i t i o n s which have some unique o r p e c u l i a r r e l a t i o n t o SARP w i l l be d i s c u s s e d h e r e i n . About t h r e e f o u r t h s o f the make-up a c i d charged t o a l k y l a t i o n i s i n the form o f a l k y l s u l f a t e s , and o n l y a minor p o r t i o n o r about one f o u r t h o f t h e usual 99.5% c o n c e n t r a t i o n . The c a t a l y s t i s , o r may b e , somewhat d i f f e r e n t w i t h SARP, e s p e c i a l l y as t o i t s w a t e r and c o n j u n c t polymer c o n t e n t . W i t h o u t SARP the c a t a l y s t u s u a l l y c o n t a i n s about 2.5-5.0% w a t e r . With SARP the water c o n t e n t s h o u l d u s u a l l y be i n t h e 0.5-2.0% r a n g e . A low w a t e r c o n t e n t o f t h e c a t a l y s t i s b e l i e v e d t o be d e s i r a b l e ( 2 6 ) . If less drying o f f e e d s t o c k s i n SARP were p r a c t i c e d , the w a t e r c o n t e n t o f the c a t a l y s t might be as h i g h as w i t h o u t SARP. A l a r g e excess o f i s o b u t a n e i s u s e d , e . g . , as much as 60-80% by volume o f t h e h y d r o c a r b o n s i n the a l k y l a t i o n r e a c t i o n m i x t u r e . C o n s e q u e n t l y , a l a r g e q u a n t i t y o f i s o b u t a n e must be r e c o v e r e d and recycled. I t i s a l s o a v a i l a b l e f o r SARP. The i s o b u t a n e c o n c e n t r a t i o n i s one o f the most i m p o r t a n t v a r i a b l e s , as f a r as q u a l i t y o f p r o d u c t and a c i d consumption are c o n c e r n e d . A high c o n c e n t r a t i o n o f i s o b u t a n e tends t o promote a l k y l a t i o n and

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suppress conjunct p o l y m e r i z a t i o n . The i s o b u t a n e c o n c e n t r a t i o n can be i n c r e a s e d by a d d i n g more i s o b u t a n e , o r by r e d u c i n g t h e amount o f i n e r t s , such as propane and n - b u t a n e . In a d d i t i o n t o the p a r t i c u l a r d e s i g n o f t h e a l k y l a t i o n r e a c t o r and the amount o f horsepower g o i n g i n t o t h e m i x i n g , t h e m i x i n g and a l k y l a t i o n r e s u l t s a r e u s u a l l y improved by having 50% o r more by volume o f a c i d c a t a l y s t i n the e m u l s i o n so t h a t the a c i d i s i n the c o n t i n u o u s p h a s e . Recycle o f emulsion c o n t a i n i n g 20-35% hydrocarbon r a t h e r than f l a t a c i d from t h e s e t t l e r t o t h e r e a c t o r a l s o h e l p s t h e m i x i n g and g i v e s improved r e s u l t s , as would be e x p e c t e d . T h i s i s e s p e c i a l l y t r u e a t h i g h t h r o u g h put o r space v e l o c i t y * , e . g . , 0.5 or h i g h e r , or w i t h high p r o p y l e n e c o n tent feeds. I t w i l l be r e c o g n i z e d t h a t r e c y c l e o f e m u l s i o n a l s o i s i n e f f e c t a way o f r e t u r n i n g i s o b u t a n e t o the a l k y l a t i o n r e a c t o r w i t h o u t r e s o r t i n g to f r a c t i o n a t i o n . Lower temperatures down t o about 30° F f a v o r l o w e r a c i d c o n sumption and h i g h e r q u a l i t y p r o d u c t . Most commercial u n i t s a r e o p e r a t e d i n the 40-50 F, w i t h an i n c r e a s e d a c i d c o n s u m p t i o n . T h i s i s n ' t so s e r i o u s i f the used c a t a l y s t from a l k y l a t i o n i s s e n t to t h e SARP r e c o v e r y s e c t i o n . In some c a s e s , t h e s i z e o f t h e r e a c t o r i s determined by the amount o f c o o l i n g s u r f a c e r e q u i r e d f o r the design temperature. With SARP not as much c o o l i n g i s r e q u i r e d i n t h e a l k y l a t i o n r e a c t o r , s i n c e p a r t o f the heat o f the a l k y l a t i o n r e a c t i o n i s evolved in the absorption s e c t i o n . I t has been e s t i m a t e d t h a t 50% o r more o f the heat o f a l k y l a t i o n i s i n the a b s o r p t i o n s t e p . E f f i c i e n t m i x i n g o f the hydrocarbon and a c i d i s d e s i r a b l e t o keep t h e a c i d c a t a l y s t as n e a r l y s a t u r a t e d as p o s s i b l e w i t h i s o b u t a n e , and i n as high a c o n c e n t r a t i o n as p o s s i b l e . The s o l u b i l i t y of isobutane i n the a c i d c a t a l y s t increases with decreased water c o n t e n t (26) and i n c r e a s e d polymer c o n t e n t . Thus, i t should be p o s s i b l e t o have a h i g h e r c o n c e n t r a t i o n o f i s o b u t a n e i n t h e SARP a l k y l a t i o n c a t a l y s t f o r a g i v e n t i t r a t a b l e a c i d i t y , and i t s h o u l d be p o s s i b l e t o m a i n t a i n a h i g h e r c o n c e n t r a t i o n o f i s o b u t a n e i n the c a t a l y s t . Based on a s t u d y o f commercial p l a n t s some y e a r s a g o , i t was c o n c l u d e d t h a t o f t e n t h e m i x i n g was q u i t e poor i n t h a t the e m u l s i o n was not u n i f o r m . T h e r e was u s u a l l y a small amount o f good e m u l s i o n and a l o t o f poor e m u l s i o n . A major p o r t i o n o f t h e r e a c t i o n m i x t u r e was l o o s e , f a s t b r e a k i n g e m u l s i o n , and even l a r g e amounts o f u n e m u l s i f i e d hydrocarbon were p r e s e n t . The d e s i g n and o p e r a t i o n i n many c a s e s a r e s t i l l about t h e same t o d a y , and hence the m i x i n g and e m u l s i o n p r o b a b l y a r e t o o . Although p r o o f i s not a v a i l a b l e , i t i s b e l i e v e d the use o f t h e i s o b u t a n e DIPS stream as p a r t o f the hydrocarbon f e e d i n SARP h e l p s improve the m i x i n g . The p r o p y l e n e r e p r e s e n t e d by t h e DIPS amounts to

* G a l l o n s per hour o f o l e f i n alkylation reactor.

i n f e e d d i v i d e d by g a l l o n s

of acid

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

in

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10-25% o f t h e t o t a l o l e f i n f e e d t o a l k y l a t i o n . The r e s t o f t h e o l e f i n f e e d may be p r o p y l e n e , b u t y l è n e s , amylenes o r p o l y m e r s . The a c i d r e p r e s e n t e d by t h e DIPS amounts t o about 65-75% o f t h e t o t a l make-up a c i d . The a l k y l a t i o n r e a c t o r s used i n t h e p i l o t u n i t o p e r a t i o n and a l s o t h e commercial o p e r a t i o n were S t r a t c o C o n t a c t o r s . However, t h e w r i t e r knows o f no r e a s o n , and no e v i d e n c e i s a v a i l a b l e , t o i n d i c a t e t h a t any o t h e r t y p e r e a c t o r , such as t h e cascade and pump and time t a n k , would n o t be s a t i s f a c t o r y . It i s believed t h a t t h e y would g i v e a t l e a s t as good r e s u l t s w i t h SARP as w i t h o u t SARP f o r t h e same o p e r a t i n g c o n d i t i o n s and o l e f i n f e e d s t o c k , and o f c o u r s e w i t h a much lower a c i d c o n s u m p t i o n .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

Summary and C o n c l u s i o n s A p r o c e s s termed SARP has been d e v e l o p e d f o r t h e r e c o v e r y o f t h e used o r d i s c a r d e d c a t a l y s t from t h e a l k y l a t i o n o f i s o b u t a n e w i t h o l e f i n s u s i n g s t r o n g s u l f u r i c a c i d as t h e c a t a l y s t . The p r o c e s s was used c o m m e r c i a l l y f o r s e v e r a l y e a r s by two companies, b u t c u r r e n t l y i s n o t i n commercial o p e r a t i o n . The used c a t a l y s t i s r e a c t e d w i t h p r o p y l e n e t o c o n v e r t t h e acid to diisopropyl sulfate. The d i i s o p r o p y l s u l f a t e i s e x t r a c t e d w i t h i s o b u t a n e , t h e e x t r a c t t r e a t e d w i t h a s m a l l amount o f used c a t a l y s t , l e a v i n g a weak a c i d c o n t a i n i n g t h e c o n j u n c t polymer and w a t e r . The i s o b u t a n e e x t r a c t f r e e o f c o n j u n c t p o l y mer and w a t e r i s charged t o a l k y l a t i o n , a l o n g w i t h a d d i t i o n a l o l e f i n and f r e s h make-up a c i d . A d i s c u s s i o n o f the r e a c t i o n cond i t i o n s r e q u i r e d and t h e v a r i a b l e s i n v o l v e d i n t h e f o u r s t e p s o f the process are g i v e n . With SARP t h e n e t a c i d consumption i s reduced by about 65 t o 75%, o r t o about 0 . 2 o f a pound o f s u l f u r i c a c i d p e r g a l l o n o f alkylate. The a l k y l a t e p r o d u c t i s o f about t h e same q u a l i t y , o r perhaps somewhat b e t t e r , as a l k y l a t e produced w i t h o u t SARP. A 375° F . E . P . t o t a l a l k y l a t e had a c l e a r o c t a n e o f about 94 and 105 with 3.0 c c . o f TEL. Literature 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Cited

Goldsby, A. R., U.S. Pat. 2,267,458 (Dec. 23, 1941). S t i l e s , R. S., This Book, Chapter 18, 1977. Goldsby, A. R., U.S. Pat. 2,420,369 (May 13, 1947). Goldsby, A. R. and VanGundy, J . C., U.S. Pat. Re 22,146 (July 28, 1942). Goldsby, A. R. and Putney, D. H., Pet. Ref., Sept. 1955. Goldsby, A. R., U.S. Pat. 3,422,164 (Jan. 14, 1969). Goldsby, A. R., U.S. Pat. 3,428,705 (Feb. 18, 1969). Goldsby, A. R., U.S. Pat. 3,448,168 (June 3, 1969). Goldsby, A. R., U.S. Pat. 3,691,252 (Sept. 12, 1972). Goldsby, A. R., U.S. Pat. 3,742,081 (June 26, 1973). Massa, Η. Ε., U.S. Pat. 3,442,972 (May 6, 1969).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

17.

12. 13. 14.

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15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26.

GOLDSBY

SARP

301

Goldsby, A. R. and Pevere, E. F., U.S. Pat. Re. 22,510 (July 4, 1944). Goldsby, A. R., Pevere, E. F., Clarke, L. A. and Hatch, G. C., U.S. Pat. 2,348,467 (May 9, 1944). Goldsby, A. R. and Clarke, L. Α., U.S. Pat. 3,000,991 (Sept. 19, 1961). Goldsby, A. R. and Gross, Η. H., U.S. Pat. 3,083,247 (March 26, 1963). DeJong, U.S. Pat. 2,381,041 (1945). Hydrocarbon Processing and Petroleum Refiner 14, (1965). O i l and Gas Journal, Jan. 2, 48 (1967). Goldsby, A. R., U.S. Pat. 3,227,774 (Jan. 4, 1966). Goldsby, A. R., U.S. Pat. 3,227,775 (Jan. 4, 1966). Goldsby, A. R., U.S. Pat. 3,234,301 (Feb. 9, 1966). Oil and Gas Journal, Jan. 2, 54 (1967). Goldsby, A.R., U.S. Pat. 3,803,262 (April 9, 1974). Goldsby, A. R., U.S. Pat. 3,683,041 (Aug. 8, 1972). Webb, O., This Book, Chapter 16, 1977. Albright, L. F., Houle, H., Sumutka, A. M. and Eckert, R. E., Ind. Eng. Chem. Proc. Dev. 11, 446, No. 3 (1972).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

18

Recovery of Sulfuric Acid Alkylating Catalyst by Crystallization

S. ROBERT STILES

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

Westinair Associates, P. O. Box 2091, Morristown, NJ 07960

A l k y l a t i o n of isobutane with o l e f i n i s accomplished by the carbonium ion mechanism when the s u l f u r i c acid catalyst p u r i t y i s maintained at a high l e v e l — generally above 90-92% t i t r a t a b l e a c i d i t y . At lower concentrations o l e f i n polymerization to the dimer i s accelerated and a l k y l a t i o n to tri-methyl-pentanes retarded. Alkylate product q u a l i t y i s effected. The free uncombined s u l f u r i c acid+ester+water composition of a t y p i c a l a l k y l a t i o n acid, present i n a commercial a l k y l a t i o n r e point data plotted i n the actor, is i l l u s t r a t e d by the check three component diagram of Figure 1. Water content ranges between 2-3% and ester diluents between 5-9%. Normally a continuous purge stream of reactor acid i s withdrawn, processed through an acid plant f o r r e j e c t i o n of hydrocarbon esters, and the regenerated acid a t 98.5-99.5% H SO purity returned to the reactor to control the c a t a l y s t a c i d i t y within t h i s range. A l k y l a t i o n c a t a l y s t a c t i v i t y can be maintained more economica l l y by concentrating these esters to 30-40% content l e v e l i n a small purge stream, p r i o r to being processed through the acid regeneration system. Savings i n acid regeneration and a l k y l a t e processing costs that r e s u l t are i l l u s t r a t e d by Figure 2. To accomplish these objectives recycle alky-acid is c h i l l e d , to freeze and extract 100% H SO crystals from the purge acid, according to procedures patented by S t i l e s , S k e l l y and F e l t e r (1-6). The s u l f u r i c acid i s returned to the a l k y l a t i o n reactor and the quantity of ester concentrate purge i s reduced to approximately 1/6th of its normal quantity. Operating data obtained from a commercial i n s t a l l a t i o n i s reported by 0 point composition data p l o t ted i n Figure 1. 2

4

2

4

Discussion

During a l k y l a t i o n a small quantity of reactants and impurit i e s remain trapped i n the acid phase as acid soluble esters. The term ester, as employed here, refers to any compound formed by the replacement of a t l e a s t one of the acid-hydrogen by a hydrocarbon 302

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

18.

STILES

Recovery by Crystallization

303

ς>

e

ο ο

1 ο

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I §| i t • f i

&S ν. -Κ " S -ta

'§§ §1 1^

^ s ^ s Ο

•a

•S

I

Ο

3)

Ε

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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r a d i c a l . Hydrocarbon r a d i c a l s may also contain s u l f u r , oxygen and/or nitrogen often found i n feed contaminants, such as amines, carbonyl s u l f i d e , carbamates, thio-carbamates and mercaptides. Being polar, esters are p r e f e r e n t i a l l y soluble i n the acid phase and accumulate to d i l u t e or contaminate the acid; and being a high molecular weight d i l u e n t , they have a temperature depressant e f f e c t on the freezing point of the acid l i q u i d phase. Generally these esters e x i s t only i n acids a t low water content, and r e a d i l y dissociate or hydrolyze when the water concent r a t i o n i s increased. Mono-esters with the HG-radical replacing only one hydrogen illustrated, by s C^Hg

+

HgSO^

-

(C^H )HS0^ 9

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

dissociate r e a d i l y a t r e l a t i v e l y low temperatures, whereas the dimer-ester i l l u s t r a t e d by the equations G^Hq

+

(C^H )HS0 9

(G4H ) S0^

4

9

2

requires higher temperatures and longer time f o r d i s s o c i a t i o n to occur. Trimer-esters, often c a l l e d t r i a l k y l esters, are formed from higher molecular weight r a d i c a l s such as:

These trimer-esters are extremely slow to dissociate and r e quire elevated temperatures a t b o i l i n g - a c i d conditions to complete the reactions. Tars are produced with release of s u l f u r dioxide. Differences i n hydrolysis c h a r a c t e r i s t i c s are used i n analyti c a l t e s t procedures to i d e n t i f y the e a s i l y dissociated esters by polymer and t i t r a t a b l e a c i d i t y , and the less reactive by t o t a l a c i d i t y procedures. Total hydrocarbon content i s determined by carbon analysis,and uncombined H^SO^ by the a n i l i n e sulfate procedure. Hydrolysis has been used i n some acid regeneration systems but the accumulation of excessive amounts of trimer-esters and tars have an adverse e f f e c t on alkylate q u a l i t y . Regeneration by combustion to t o t a l l y decompose the acid and esters to COp, SO^and H^O i s generally preferred. This decomposi t i o n i s performed i n an acid plant where the r e s u l t i n g SO^ i s then c a t a l y t i c a l l y converted to SOo n d regenerated to the 9 8 . 5 - 9 9 . 5 ^ HgSO^ that i s returned to the reactor system. a

A l k y l a t i o n and Ester Reaction Mechanism I t i s well known ( 7 » 8 , 9 ) that on start-up with f r e s h acid, the s u l f u r i c acid must be "'conditioned"" by adding the acid r a p i d l y to c i r c u l a t i n g isobutane containing less than 2% o l e f i n s to generate the carbonium-ion. Mixing acid with o l e f i n - f r e e isobutane w i l l not generate t h i s ion. However i f the acid i s added too slowly, to be overwhelmed by the o l e f i n , production of " r e d - o i l " r e s u l t s . I t i s also known that o l e f i n feed can be stopped a t any time without causing any problems, but i n t e r r u p t i o n of isobutane recycle

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

18.

Recovery by

STILES

Crystallization

305

flow — without immediate cut-off of o l e f i n feed flow — w i l l deteriorate the alkylate q u a l i t y which, i f carried on f o r any period of time, w i l l r e s u l t i n a disastrous "acid run-away . A reactor system can be kept on "stand-by" conditions f o r several days o r weeks, as long as isobutane r e c i r c u l a t i o n i s maintained. Alkylate i s slowly but continuously released from the a c i d phase into the isobutane l i q u i d during such operation and the catalyst " a c i d i t y " increases. A l k y l a t i o n , ester formation, polymerization, cracking, isomeri z a t i o n and other r e f i n e r y operations depend on the carbonium-ion. Whitmore (10) suggests that the carbonium-ion i s formed by the addi t i o n of hydrogen ion, from an a c i d , to an o l e f i n double bonds 11

H

Ç 3 H C-G=GH Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

3

2

+

+ H

H

+

Χ

Ç 3 H C-£-GH

β

3

3

+ Χ

which then performs the basic r e f i n e r y reactions 1. Addition of negative ion s R-Î-G 2.

+

X"

—

R-Ç-C

Elimination of proton to produce olefins G-Î-G

G-G=G

+

H

+

3. Migration of proton (order of s t a b i l i t y : t e r t i a r y - secondary primary):

4.

C-Ç-Î-C - — - C-$-C-C C ~ C Migration of methyl group:

C-çL-î-C-C C-Ç-Ç-C-C e ce 5 . Addition of o l e f i n ; reverse reaction occurs by s c i s s i o n , two carbon atoms removed from charge: -

C-Î-C

6.

+

G=G-G

- — — "

G-Ç-G-Î-G C

Hydrogen t r a n s f e r reaction with t e r t i a r y hydrogens

C-Ç + G-G-G — G-Ç+ + G-G-G e û Any non-reversible reaction that terminates the e q u i l i b r i a by forming dimer o r trimer esters d i l u t e the acid and hinder the r e action of the carbonium i o n . Ideal reaction conditions of high isobutane concentration, and isobutane d i f f u s i o n into the a c i d phase a t a rate greater than the o l e f i n d i f f u s i o n rate, r e s u l t i n high q u a l i t y alkylate product. Ester formation, exclusive of those formed from feed contaminants,

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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306

INDUSTRIAL

A N D

L A B O R A T O R Y

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l.3h

89

90

91

92

CLEAR RESEARCH

93 OCTANE

94

95

O F TOTAL

96

97

98

99

100

ALKYLATE

Figure 3. Ester production from olefin and isobutane reactants as a function of reaction conditions related to alkylate quality as measured by Research Octane Number

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

18.

STILES

Recovery by

Crystallization

307

i s n i l . As reaction conditions deteriorate and a l k y l a t e qualitydecreases, the rate of dimer and trimer ester formation increases. Ester production, r e l a t i v e to alkylate q u a l i t y , i s shown by Figure 3 & ^. Generally ester production from feed contaminants i s more d i f f i c u l t to p r e d i c t . Data obtained from commercial operations and plotted i n Figure ^, show the combined e f f e c t of ester production from these two sources. Y i e l d of trimer or t r i a l k y l esters o s c i l l a t e s as data of F i g ­ ure 5 i n d i c a t e s . They are d i f f i c u l t to analyze and do not show i n the a c i d i t y t e s t s . However t h e i r e f f e c t on acid make-up require­ ments i s appreciable. Variations i n " f r e e " HpSCV content of acid are plotted as dotted lines i n the top of t h i s figure and show os­ c i l l a t i o n s that are t y p i c a l of most commercial operations. An ester concentrator that can extract these esters as they are gen­ erated to remove them from the reactor system, w i l l accomplish a valuable s e r v i c e . Smoother operation producing better q u a l i t y a l k ­ ylate w i l l r e s u l t . Ester Concentrator - Process Description In t h i s process as shown by Figure 6, a portion of the A l k y l a t i o n Reactor acid recycle, that i s separated from the isobutaner i c h alky-reactor e f f l u e n t , i s c h i l l e d by d i r e c t contact with countercurrent flowing isobutane l i q u i d i n an agitated c h i l l e r v e s s a l or c r y s t a l l i z e r . Crystals of H^SO^ are formed. Referring to data points i n Figure 1, we have the alky-acid of composition "A" i n the area of the check (t/) point data, c h i l l e d to form c r y s t a l s of com­ p o s i t i o n "C" that are e s s e n t i a l l y 100^ H^SO^. As these c r y s t a l s form, the free H^SO^ content of the l i q u i d i s reduced and i t s ester plus water content increases along t i e - l i n e "CAB". This mixture of c r y s t a l s i n alky-acid l i q u i d flows downward thru colder upflowing isobutane l i q u i d and more c r y s t a l s are formed. The freezing point of the l i q u i d i s lowered as i t s ester plus water concentration i n ­ creases, u n t i l at point "Β" the freeze-point temperature equals the temperature of the incoming c h i l l e d isobutane l i q u i d and no f u r t h e r c r y s t a l l i z a t i o n occurs. C r y s t a l l i z a t i o n i s performed i n ir-obutane l i q u i d to remove heat of fusion, but more important - to maintain a high isobutane concentration, so that-as the ester and water concentration i s i n ­ creased, isobutane w i l l continue to react with the mono ester. The a l k y l a t e released from the acid phase, w i l l be absorbed by the isobutane l i q u i d and removed from the c r y s t a l l i z e r . Without t h i s removal of a l k y l a t e , c r y s t a l s i z e growth control i s d i f f i c u l t . A portion of the a l k y l a t i o n reactor auto-refrigerant recycle from the bottom of the depropanizer tower i s used f o r t h i s purpose. This stream i s free of o l e f i n s and moisture and i s c h i l l e d by ex­ change with evaporating propane before entering the bottom of the crystallizer. A portion of t h i s c h i l l e d isobutane l i q u i d flows upward to c h i l l the downflowing acid, remove the heat of fusion and convey the a l k y l a t e back to the a l k y l a t i o n reactor. The remainder conveys the a c i d c r y s t a l s plus ester concentrate mixture to the c e n t r i f u g a l

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

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308

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Figure 5.

AUGUST 2

Operating data showing effect of trimer esters on acid consumption and free H SO^ content

JULY

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

00

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

OLEUM

(0>

SOj

MIXER

-I

_|

cry/zs τ/911 /ΖΕ/?

REGENERATEA

-

r

.1 ,t ,T

r

Figure 6.

Γ

ι

* ESTER CONCENTRATE

R YY

1

Sulfuric acid type alkylation plant with acid purifier

ι )

r—;

/e&/e/a£/e/?T/os/

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

I

x

TRIMER

Ο

CO H-»

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

18.

Recovery by

STILES

Crystallization

311

f i l t e r . Here the acid crystals "C" are separated from ester concentrate "B" as the s l u r r y enters the apex of the spinning c o n i c a l screening centrifuge. Crystals larger than the screen openings are retained on the screen, while the ester concentrate and isobutane l i q u i d , containing smaller c r y s t a l s , pass thru the screen and flow into the decanter v e s s e l . Isobutane l i q u i d separate from the ester concentrate and i s returned to the a l k y l a t i o n reactor. Crystals "C" s l i d e across the surface of the c o n i c a l screen propelled by the angular force r e s u l t i n g from c e n t r i f u g a l force and the increasing diameter of the spinning c o n i c a l screen. The angle of the cone i s selected to allow c r y s t a l slippage while subjecting the c r y s t a l s to c e n t r i f u g a l force to remove adherent mother l i q u o r . Continuous flushing of isobutane i s maintained to a s s i s t i n t h i s l i q u i d - s o l i d separation. As the crystals reach the outer-diameter of the spinning cone, they are discharged into acid recycle flowing thru the c r y s t a l r e c e i v e r and are returned to the alky reactor. E s t e r concentrate "B" that decants from the isobutane, i s sent to acid regeneration f a c i l i t i e s f o r removal of hydrocarbons and water, The regenerated 9 8 . 5 - 9 9 . 5 ^ H^SO^ i s returned to the reactor. A portion of the ester concentrator i s continuously r e c i r c u l a t e d from the decanter to the c r y s t a l l i z e r i n l e t and mixed with incoming alky-acid, to provide "seed" crystals of the small crystals that had passed thru the screen. Freezing point temperature of ester concentrate i s lowered by depressant e f f e c t of both esters and water. Higher concentration of esters "B " can be obtained at a given c r y s t a l l i z a t i o n temperature, i f the water content i s reduced. Closed ft data points of Figure 1 show results of operations where oleum was mixed with alky a c i d , reacted with water: e

S0

3

+

H0 2

H S0 2

4

so that the r e s u l t i n g concentrate, obtained a f t e r subsequent c r y s t a l l i z a t i o n and separation of H^SO^ c r y s t a l s , had a higher ester content. Complete reaction must be accomplished before c h i l l i n g since oleum freezes at c r y s t a l l i z a t i o n temperatures, see Figure 7 . Water reaction with oleum "niaybe accomplished with incoming acid or with recycle acid-ester concentrate as shown i n Figure 6. Warmer c r y s t a l l i z a t i o n temperatures can be used to obtain a given ester concentrate l e v e l , i f the system i s operated on "block-flow" or intermittent procedure. In t h i s procedure ester concentrate c o l l e c t e d from alky acid i s accumulated i n the decanter f o r a time without discharging any to the acid p l a n t . Flow of alky-acid i s then stopped and the accumulated inventory run-off v i a the oleum contactor with HgSO^ c r y s t a l s returned to the reactor i n normal manner. For example ester concentrate of composition "B" obtained from alky acid "A" i s f o r t i f i e d to composition "A " and c r y s t a l s " C " séparated^to r e s u l t i n ester concentrate "Β'" that i s then sent to acid regeneration. A smaller quantity of concentrate r e s u l t s and processing costs are reduced. 1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

312

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

INDUSTRIAL

Figure 7.

Freezing point temperature of sulfuric acid-water-oleum system

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

18.

STILES

Recovery by

Crystallization

313

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch018

CONCLUSION Today d u r a b l e l a m i n a t e d 200 mesh s c r e e n s a r e a v a i l a b l e t h a t can o p e r a t e i n c o n i c a l s c r e e n i n g c e n t r i f u g e s w i t h e x c e l l e n t s e r v i c e f a c t o r t o r e t a i n c r y s t a l s as s m a l l a s 75 microns · The c e n t r i f u g e a v a i l a b l e i n the e a r l i e r p l a n t r e q u i r e d a more rugged 40 mesh s i e v e t h a t c o u l d o n l y r e t a i n c r y s t a l s l a r g e r t h a n 400 m i c r o n s . G r e a t l y improved y i e l d o f c r y s t a l s p e r p a s s r e s u l t . This f a c t o r combined w i t h a c r y s t a l l i z e r d e s i g n t h a t c o n t r o l s a l k y l a t e r e l e a s e more e f f i c i e n t l y , g r e a t l y improves the performance and economics of the process. C o n s i d e r a b l e r e d u c t i o n i n a c i d r e q u i r e m e n t s and a l k y l a t i o n p r o d u c t i o n c o s t a r e o b t a i n e d by e s t e r c o n c e n t r a t i o n , a s shown by Figure 2. The o p e r a t i o n o f t h e e a r l i e r p l a n t demonstrated t h e p r o c e s s o p e r a b i l i t y o f t h e s y s t e m , b u t d i s c l o s e d m e c h a n i c a l and o p e r a t i o n a l l i m i t a t i o n s o f equipment a v a i l a b l e t h a t made the p r o cess uneconomical a t t h a t t i m e . Today e n e r g y c o s t s have changed and s u l f u r i c a c i d i s no l o n g e r worth $ 2 0 / t o n . This process, i n s t a l l e d i n an a l k y l a t i o n u n i t w i t h the equipment a v a i l a b l e t o d a y , can be a n i n t e g r a l p a r t o f t h e a l k y l a t i o n system t o s u b s t a n t i a l l y reduce a l k y l a t e p r o d u c t i o n c o s t s . LITERATURE

CITED

(1) (2) (3) (4) (5) (6) (7) (8)

F e l t e r , R.H., US Patent 2,593,128 (1952) S k e l l y , J.F. and S t i l e s , S.R., US Patent 2,716,592 (1955) S t i l e s , S.R., US Patent 2,831,043 (1958) S t i l e s , S.R., US Patent 2,862,791 (1958) S k e l l y , J.F. and S t i l e s , S.R. US Patent 2,863,724 (1958) S t i l e s , S.R., US Patent 2,903,339 (1959) S t i l e s , S.R., World Petroleum, Annual Refinery Review (1956) Durrett, L.R., Taylor, L.M., Wantland, C.F., Dvoretzky, I . , J.Am.Chem.Soc. 84 (1962) (9) Cupit, C.R., Gwyn, J.E., Jernigan, E.,PetroChem.Engr., 203 Dec (1961), 207 Jan. (1962) (10) Whitmore, F.,Chem.Eng.News, 26, 668 (1948): Ind.Engr.Chem. 26, 94 (1934)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19

Alkylation: Its Possible Impact on the Sulfuric Acid Industry

WARD A. GRAHAM

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

Stratford/Graham Engineering Corp., 4520 Madison Avenue, Kansas City, MO 64111

I. P r e s e n t world alkylation capacity and the proportion thereof that i s based on s u l f u r i c acid, broken down by r e g i o n (North A m e r i c a , W. Europe, etc.). Approximate annual consumption of s u l f u r i c acid. P r o p o r t i o n of this that is r e c o v e r e d and regenerated. A l k y l a t i o n is here defined as the p r o c e s s of alkylating isobutane with light olefins, which i s the m a j o r petroleum r e f i n e r y p r o c e s s for producing both aviation gasoline and motor c a r gasoline blending iso-octanes. Combining published data (1) with our own job r e c o r d s , the estimated alkylation capacity of the free world refining industry is 1, 098, 000 BPSD. T h e two p r i n c i p a l catalysts used a r e s u l f u r i c acid and h y d r o f l u o r i c acid; the above worldwide capacity i s approximately 5 5 % s u l f u r i c and 4 5 % h y d r o f l u o r i c , as tabulated i n T a b l e I. TABLE I H2SO4

North A m e r i c a Europe Other TOTAL

554,440 7,200 43,460 605,100

HF

436,925 30,200 25, 775 492,900

A c i d consumed i n the p r o c e s s i s also i n need of d e f i n i tion. H y d r o f l u o r i c acid i s l i t e r a l l y consumed; it reacts to f o r m heavy p o l y m e r s and ultimately i s pumped f r o m the s y s t e m to a combustion chamber o r to a neutralization stage where the products of neutralization a r e hauled off to a dump o r used as landf i l l . Sulfuric acid i s consumed i n a s i m i l a r manner but only as a s m a l l f r a c t i o n of that charged to the p r o c e s s . T h e p r i m a r y effect upon s u l f u r i c a c i d is that of dilution, r a t h e r than actual consumption. T h e f r e s h s u l f u r i c a c i d catalyst i s typically 98. 0-

314

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19.

Impact on Sulfuric Acid Industry

G R A H A M

9 9 . 5% t i t r a t a b l e a c i d i t y .

315

W h e n the a c i d e n t e r s the a l k y l a t i o n

s y s t e m it i s g r a d u a l l y d i l u t e d b o t h w i t h w a t e r a n d h y d r o c a r b o n p o l y m e r s a n d e s t e r s t o a s p e n d i n g s t r e n g t h of a b o u t 9 0 % table acidity.

titra­

A l t h o u g h t h e a l k y l a t i o n r e a c t i o n s w i l l o c c u r at

lower acidities, c o r r o s i v i t y of

the u s u a l 90% c u t - o f f s t r e n g t h i s d i c t a t e d by the

carbon steel with weaker acid.

In a N a t i o n a l

Petroleum Refining Association Question and Answer session in Philadelphia(2),

we r e p o r t e d l a b o r a t o r y data showing

successful

a l k y l a t i o n at a s l o w a s 82% t i t r a t a b l e a c i d i t y w h e r e t h e

water

d i l u e n t w a s l o w a n d the g r e a t e s t d i l u e n t w a s h y d r o c a r b o n p o l y ­ mers.

Some w a t e r is n e c e s s a r y ,

but o n l y a f e w p e r c e n t .

This

c o n f i r m s p r e v i o u s l a b o r a t o r y w o r k at P u r d u e U n i v e r s i t y ^ ) . E c o n o m i c s a r e c o m p l i c a t e d but c o n s t i t u t e t h e f i n a l a n s w e r

in

d e t e r m i n i n g the o p t i m u m a c i d s p e n d i n g s t r e n g t h f o r a g i v e n

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

plant.

T h i s w i l l be d i s c u s s e d i n m o r e d e t a i l b e l o w . K e e p i n g i n m i n d t h e s u l f u r i c a c i d d i l u t i o n r a t e a n d the

actual consumption rate, t i o n i s 0. 5 l b s .

a typical acid dilution rate for a l k y l a ­

a c i d / U . S. g a l l o n of a l k y l a t e p r o d u c e d .

p l a n t p r o d u c i n g 1, 500

Thus,

a

B P S D of a l k y l a t e w o u l d r e q u i r e a f r e s h

a c i d f e e d r a t e o f a b o u t 16 s h o r t t o n s o f a c i d p e r d a y w h i c h w o u l d be d i l u t e d to about 90% b e f o r e r e g e n e r a t i o n . that o n l y 2 - 5 %

It i s

estimated

of this a c i d is a c t u a l l y c o n s u m e d by side

reac­

tions,

t h e r e m a i n d e r i s p u m p e d to s t o r a g e a n d t h e n t o

tion.

T h e e f f i c i e n c y o f r e g e n e r a t i o n v a r i e s b e t w e e n 98. 0 a n d

9 9 . 5%(4).

Thus,

regenera­

i f t h e a c i d d i l u t i o n r a t e i s a s s u m e d at 0. 5 l b s . /

g a l l o n a n d 5% i s a s s u m e d to b e c o n s u m e d i n t h e a l k y l a t i o n a n d regeneration steps,

the w o r l d w i d e a c i d c o n s u m p t i o n i n s u l f u r i c

a c i d a l k y l a t i o n a n d r e g e n e r a t i o n i s j O . 05 (0. 5 χ 605, 100 χ 2 0 0 0 ) ] o r 318

short tons/day.

However,

p l a n t c a p a c i t y m u s t be 20 t i m e s t h i s ,

42/

the a c i d r e g e n e r a t i o n

o r 6, 360 t o n s / d a y to p r o ­

v i d e the total a l k y l a t i o n a c i d r e q u i r e m e n t .

This is,

of

course,

i n a d d i t i o n to t h e a c t u a l a c i d p r o d u c t i o n c a p a c i t y f o r o t h e r u s e s . II.

L i k e l y t r e n d s i n a l k y l a t i o n c a p a c i t y i n view of

lead regulations,

demand patterns,

Likely trends in alkylation capacity are almost b l e to p r e d i c t .

gasoline

etc. impossi­

T h e e n t r y of f e d e r a l a n d l o c a l g o v e r n m e n t s

the c o n t r o l of m o r e a n d m o r e a s p e c t s of i n d u s t r y , the p e t r o l e u m r e f i n i n g i n d u s t r y ,

into

especially

is a l a r m i n g and renders

d e c i s i o n - m a k i n g on t e c h n i c a l a n d e c o n o m i c b a s e s v i r t u a l l y meaningless.

T h e p e l l - m e l l r u s h to " c o n t r o l " h a s

g r a v e m i s g i v i n g s i n e v e r y s e c t o r of s o c i e t y . a r t i c l e ( 5 ) that " . . .

prompted

It i s s t a t e d i n o n e

p o l i c i e s m a y be a d o p t e d by p o w e r p o l i t i c s

that c o u l d b r i n g o n unknown,

possibly catastrophic

results".

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

316

INDUSTRIAL

O t h e r headlines(6i) a n c e to a n g e r ,

include:

A N D L A B O R A T O R Y

A L K Y L A T I O N S

" F e e l i n g s went f i r s t f r o m

a n d n o w to r a g e . . . , M

annoy­

" G o v e r n m e n t bungling

h e l p e d b r i n g t h e U . S. e n e r g y c r i s i s " ,

" T h e r e is an energy

p o l i c y s t a l e m a t e i n W a s h i n g t o n . . . a n d it s t e m s f r o m t h e f a c t that . . . c r i t i c a l o i l a n d g a s i s s u e s partisan politics".

the a l k y l a t i o n p r o c e s s government

. . . a r e bogged down i n

In t h i s a t m o s p h e r e ,

p r e d i c t i o n of t r e n d s i n

m u s t be b a s e d f i r s t upon m o s t

probable

d e c i s i o n s and then upon t e c h n i c a l / e c o n o m i c

consid­

erations. M a n y excellent a r t i c l e s have a d d r e s s e d various

facets

of the t e c h n i c a l / e c o n o m i c a s p e c t s of a l k y l a t i o n i n r e c e n t

years.

D a t a s h o w n i n T a b l e II w e r e a b s t r a c t e d f r o m a n a r t i c l e p u b ­ l i s h e d i n 1971 (7^ ; t h e s e d a t a i n d i c a t e t h a t r e d u c i n g g a s o l i n e

lead

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

l e v e l s f r o m 3. 0 to 0. 0 c c T E L / U . S. g a l . , h o l d i n g a c o n s t a n t Μ . Ο. N . o f 86. 0,

could increase alkylation charge rates

from

47 to 6 8 % i n r e f i n e r i e s w i t h c a p a c i t i e s r a n g i n g f r o m 60, 000 t o 240, 000 B P S D ,

a s s u m i n g u n l i m i t e d butane a v a i l a b i l i t y .

refinery process

Other

c h a r g e r a t e s a r e a l s o changed; the r e a d e r i s

r e f e r r e d to the o r i g i n a l a r t i c l e f o r c o m p l e t e

details.

From

T a b l e II, i t c a n b e s e e n that p r e s e n t - d a y r a t i o o f a l k y l a t i o n t o c r u d e o f a b o u t 6% c o u l d i n c r e a s e to a b o u t 9% i n t h e s m a l l e r r e f i n e r i e s a n d about 10% i n the l a r g e r . TABLE Refinery Size, Gasoline

BPSD

II

60,000

120,000

240,000

Properties

Μ . Ο. N .

86. 0 8 6 . 0

86. 0 86. 0

86. 0 8 6 . 0

R. Ο. N .

94. 0 9 6 . 7

94. 0 97. 3

94. 0 96. 3

Lead level,

cc. T E L /

U . S. G a l .

3.0

0.0

0. 0

3.0

0.0

13. 4 19. 7

13.4

22.4

3. 0

Gasoline Pool, % Alkylate

13. 4 19. 7

Alkylation Unit Charge, MBPSD

4. 5

6. 6

9. 0 13. 2

17. 9 30. 0

% I n c r e a s e d at 0 cc T E L In 1 9 7 4 ,

47

47

68

i t w a s r e p o r t e d ( 8 ) that " f o r m e e t i n jg t h e c h a l l e n g e o f un-

leaded gasoline,

U . S. r e f i n e r s h a v e b u i l t u p t h e i r o c t a n e

i n g c a p a b i l i t y to the h i g h e s t l e v e l i n h i s t o r y .

mak­

A r o u g h i n d e x of

t h i s i s the c o m b i n e d c a t a l y t i c r e f o r m i n g a n d a l k y l a t i o n c a p a c i t y as a p e r c e n t of c r u d e c a p a c i t y .

That number has r i s e n f r o m

a b o u t 2 5 % t e n y e a r s a g o to 3 0 % i n 1 9 7 4 " .

It i s u n d e r s t o o d t h a t

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19.

G R A H A M

Impact on Sulfuric Acid Industry

m o s t of this i n c r e a s e i s i n r e f o r m i n g .

317

However,

reformate has

a l o w e r m o t o r o c t a n e r a t i n g a n d a l k y l a t e r e m a i n s the b e s t b l e n d ­ ing stock for i m p r o v i n g motor In t h i s a r t i c l e (8),

octane.

it is stated,

" A t y p i c a l b l e n d to m a k e

a n u n l e a d e d g a s o l i n e o f 93 R O N a n d 85 M O N c o u l d c o n t a i n t h e following: Vol. Reformate

31

(100 R O N )

15

Alkylate Cat-cracked

32

gasoline

15

Light h y d r o c r a c k a t e naphtha

7

Butane

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

%

T h e u n l e a d e d g a s o l i n e o f 93 R O N 85 M O N w a s p r e d i c t e d a s a p r o b a b l e r e q u i r e m e n t of 1976-1980 c a r s with c a t a l y t i c ers.

convert­

T h e o r i g i n a l u n l e a d e d r e q u i r e m e n t o f 91 R O N w a s p r e ­

d i c t e d (Ί) to b e i n a d e q u a t e f o r l o n g t e r m u s e i n t h e 1 9 7 4 - 1 9 7 5 m o d e l c a r s i n t h e U . S. a higher percentage

I n i t i a l p r e l i m i n a r y d a t a (9) i n d i c a t e t h a t

of these c a r s w i l l be " n o t s a t i s f i e d "

with

91 R O N , b u t t h e d i f f e r e n c e i s b e l i e v e d t o b e s m a l l . Obviously, stant change.

t h e g a s o l i n e s u p p l y p i c t u r e i s s u b j e c t to c o n ­

T h e E u r o p e a n P a r l i a m e n t h a s r e p o r t e d l y (10)

" u r g e d the C o m m o n M a r k e t C o m m i s s i o n to p o s t p o n e i t s p l a n s f o r r e d u c i n g the l e a d content i n g a s o l i n e . . . " . the U . S. E P A a l t e r e d t h e l e a d p h a s e d o w n

In O c t o b e r ,

1976,

schedule.

If t h e l e a d i s p h a s e d o u t o r r e d u c e d ,

the n e w m a n g a n e s e

a n t i k n o c k c o m p o u n d (11) c o u l d b e c o m e w i d e l y u s e d a n d , i n t h i s event,

the g a s o l i n e b l e n d i n g s c h e d u l e s

The response

w o u l d be r e v i s e d a g a i n .

of a l k y l a t e to the m a n g a n e s e c o m p o u n d i s s i m i l a r

to i t s r e s p o n s e

to l e a d ,

so it appears alkylate would r e m a i n as a

p r i m e octane blending ingredient.

T h e percentage

the f i n i s h e d g a s o l i n e w o u l d u n d o u b t e d l y v a r y .

of a l k y l a t e i n

However,

this

p r o d u c t i s n o w b e i n g i n v e s t i g a t e d to d e t e r m i n e i f i t c a n s a t i s ­ factorily replace lead.

T h e s e a r e but two of m a n y e x a m p l e s

new i n f l u e n c e s w h i c h w i l l enter into future d e c i s i o n s

of

concerning

alkylation. In a r e p o r t (12) d a t e d A u g u s t 1 1 ,

1976,

one f i r m

esti­

m a t e d that new o c t a n e - p r o d u c i n g f a c i l i t i e s w o u l d be r e q u i r e d f o r 1978 a n d 1 9 7 9 ,

as

follows:

C a t a l y t i c R e f o r m i n g 540, 000 B P D ; A l k y l a t i o n 2 9 8 , 000 B P D ; I s o m e r i z a t i o n 3 3 2 , 000 B P D ; a n d C r a c k i n g 8 9 9 , 000 B P D .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

318

INDUSTRIAL

III.

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

D i s c u s s i o n of the b a s i c p r i n c i p l e s of c u r r e n t s u l f u r i c

a c i d a n d H F a l k y l a t i o n t e c h n o l o g y a n d of any l i k e l y

developments

w h i c h c o u l d l e a d to a c h a n g e i n t h e p r e s e n t b a l a n c e b e t w e e n

the

two. T h e b a s i c p r i n c i p l e s of s u l f u r i c a n d h y d r o f l u o r i c a c i d catalyzed alkylation reactions have been d e s c r i b e d in m a n y different a r t i c l e s and books, b i b l i o g r a p h y (13-23).

s o m e of w h i c h a r e t a b u l a t e d i n the

T h e c o m p l e x i t y o f the r e a c t i o n i s

such

that m a n y d e t a i l s c o u l d not be i s o l a t e d u n t i l the advent of ticated analytical equipment and techniques.

sophis-

T h e fact that

c o m m e r c i a l r e f i n e r y a l k y l a t i o n units a l m o s t always

receive

f e e d s of v a r y i n g r a t e a n d / o r c o m p o s i t i o n m a k e s the a n a l y s i s of such plants' performance v e r y difficult.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

feed,

E v e n with a

constant

the n u m b e r of o l e f i n i c c o m p o u n d s u s u a l l y p r e s e n t i n the

feed promotes

different reactions and s i d e - r e a c t i o n s ,

the p r o -

d u c t s o f w h i c h g e n e r a l l y e n d up i n t h e a l k y l a t e p r o d u c t .

Lab-

o r a t o r y s t u d i e s o f a l k y l a t i o n of i s o b u t a n e w i t h i n d i v i d u a l p u r e olefins have p r o v i d e d significant data on r e a c t i o n rates

and

y i e l d s a s i n f l u e n c e d by the c o m m o n r e a c t i o n v a r i a b l e s

(24).

T h e b a s i c c h e m i c a l r e a c t i o n i n v o l v e d i s b e l i e v e d to be that of c a r b o n i u m i o n p r o d u c t i o n b y the a d d i t i o n of a p r o t o n to a n o l e f i n w h e r e the p r o t o n i s s u p p l i e d by the p r o t o n i c a c i d catalyst,

in this case either sulfuric o r hydrofluoric acid(20).

A f u r t h e r s t a t e m e n t i n t h i s s a m e a r t i c l e e x p l a i n s the i m p o r t a n t addition m a d e by m o d e r n a n a l y t i c a l equipment: development of s p e c t r o s c o p i c a l methods nuclear magnetic resonance portant,

11

. . . the

of a n a l y s i s ,

rapid

of w h i c h

s p e c t r o s c o p y w a s the m o s t i m -

h a s e n a b l e d D e n o (25)

a n d m a n y o t h e r s to show that

c a r b o n i u m i o n s c a n now b e d i r e c t l y o b s e r v e d i n s o l u t i o n .

This

h a s m a d e it p o s s i b l e to d e t e r m i n e the s t r u c t u r e o f s u c h i o n s . D e n o s t a t e s that the H S O 4 s a l t s of s u b s t i t u t e d c y c l o p e n t e n y l c a t i o n s f o r m the s l u d g e i n c o m m e r c i a l a l k y l a t i o n a c i d .

H e d i d not

e n c o u n t e r a n y c a t i o n s p o s s e s s i n g l e s s t h a n 10 c a r b o n a t o m s .

"

A l t h o u g h the b a s i c c h e m i c a l r e a c t i o n s h a v e b e e n thought, for many years,

to b e s i m i l a r w i t h e i t h e r s u l f u r i c o r h y d r o -

fluoric acid catalyst,

extensive work with sulfuric a c i d d e s c r i b -

e d b y A l b r i g h t et a l (24) not the c a s e .

h a s d e m o n s t r a t e d that t h i s i s p r o b a b l y

The need for m o r e detailed w o r k with h y d r o -

fluoric acid is cited.

T h e following s u m m a r i z e s

their report:

" T h e reaction mechanism for hydrogen fluoride alkylation also s e e m s to be r a d i c a l l y different t h a n that f o r s u l f u r i c a c i d a l k y l a tion.

T h e alkylation m e c h a n i s m w h i c h has been widely

accepted

i n the past s e e m s to be s o m e w h a t m o r e s a t i s f a c t o r y f o r h y d r o g e n f l u o r i d e a l k y l a t i o n e v e n t h o u g h it i s not f o r s u l f u r i c a c i d

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19.

Impact on Sulfuric Acid Industry

G R A H A M

alkylations. "

319

T h e a n n o u n c e m e n t of t h i s A l k y l a t i o n S y m p o s i u m

c o n t a i n e d the f o l l o w i n g :

" S o m e i m p o r t a n t new

developments

h a v e r e c e n t l y c l a r i f i e d to a s i g n i f i c a n t e x t e n t the m e c h a n i s m

of

the a l k y l a t i o n o f b o t h i s o b u t a n e a n d a r o m a t i c s . " O n e p o s s i b l e a d v a n t a g e o f the H F p r o c e s s

in propylene/

b u t y l è n e a l k y l a t i o n i s the p r o d u c t i o n of i s o b u t y l e n e f r o m

iso-

b u t a n e e f f e c t e d b y the h y d r i d e - i o n t r a n s f e r to p r o p y l e n e .

Iso-

b u t y l e n e i s the C 4 o l e f i n i c i s o m e r w h i c h p r o d u c e s a s i g n i f i c a n t l y higher octane alkylate with H F .

T h i s shift,

however,

converts

a s m u c h a s 22% of the p r o p y l e n e to p r o p a n e a n d i s a d e b i t . S o m e n o r m a l b u t a n e i s a l s o p r o d u c e d f r o m b u t y l è n e s but t h i s i s e s t i m a t e d at o n l y 4 - 6 % .

T h e higher octane isobutylene

alkylate

and a c l a i m e d y i e l d i n c r e a s e m u s t be c o n t r a s t e d with n o r m a l

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

paraffin p r o d u c t i o n f r o m olefins and a h i g h e r isobutane r e q u i r e ment.

The typical mixed 03 = ^ 4 =

f e e d c a n be m a d e to p r o d u c e

a h i g h o c t a n e a l k y l a t e with e i t h e r a c i d c a t a l y s t by the o p t i m i z a t i o n of o t h e r v a r i a b l e s .

T h e highest alkylate octane

r e p o r t e d a r e p r o d u c e d with s u l f u r i c a c i d catalyst,

numbers

alkylating

with a t y p i c a l cat c r a c k e r butylène olefin. T h e c o s t of the a c i d s ,

the r e l a t i v e h a z a r d s of e a c h ,

the

a c t u a l a l k y l a t e y i e l d a n d q u a l i t y a l l m u s t be c o n s i d e r e d w h e n s e l e c t i n g the a l k y l a t i o n p r o c e s s

to u s e .

T h e i n s t a l l e d c o s t of

the p l a n t a n d o p e r a t i n g c o s t s a l s o m u s t b e c o n s i d e r e d . s a v i n g s c a n be r e a l i z e d i f o c t a n e q u a l i t y i s Supplemental processes

Cost

lowered.

w h i c h c a n be o p e r a t e d i n c o n -

junction with a l k y l a t i o n a n d / o r s u l f u r i c a c i d p r o d u c t i o n can i n f l u e n c e the o v e r a l l e c o n o m i c s .

E x a m p l e s a r e (1) the i n t e g r a -

t i o n of n o r m a l b u t a n e - t o - i s o b u t a n e

i s o m e r i z a t i o n with alkylation,

u t i l i z i n g c o m m o n f r a c t i o n a t i o n e q u i p m e n t a n d (2),

u t i l i z i n g 65%

s u l f u r i c a c i d e x t r a c t i o n of i s o b u t y l e n e o r i s o a m y l ë n e f r o m

ole-

f i n s f e d to a l k y l a t i o n , j u s t i f i e d b y m o n e t a r y r e t u r n o n s a l e o f the h i g h p u r i t y i s o - o l e f i n as a p e t r o c h e m i c a l f e e d s t o c k ,

which r e -

d u c e s q u a n t i t y of a l k y l a t e p r o d u c e d a n d r e d u c e s i s o b u t a n e

re-

q u i r e d while p r o d u c i n g s t i l l higher quality alkylate with s u l f u r i c acid

catalyst. A t the p r e s e n t t i m e ,

the t r e n d s e e m s to be t o w a r d r e -

d u c e d a l k y l a t e p r o d u c t i o n a n d r e d u c t i o n o r e l i m i n a t i o n of p r o p y l e n e as a f e e d s t o c k . gasoline demands cal.

In a n y e v e n t ,

creases,

T h i s is based upon c u r r e n t l y r e d u c e d

a n d h i g h v a l u e of p r o p y l e n e a s a p e t r o c h e m i i f the p e r c e n t a g e

of b u t y l è n e s i n the f e e d i n -

sulfuric acid alkylation will assume a more

a d v a n t a g e o n the b a s i s of b a r r e l - o c t a n e

clear-cut

superiority.

N u m e r o u s factors have always r e q u i r e d c o n s i d e r a t i o n in a t t e m p t i n g to e v a l u a t e w h i c h a l k y l a t i o n p r o c e s s

to u s e .

New

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

320

INDUSTRIAL

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

r e a c t i o n e q u i p m e n t h a s b e e n p a t e n t e d (27, 28) w h i c h r e p o r t e d l y promotes

i n t i m a t e m i x i n g w i t h r e d u c e d p o w e r input;

c l a i m s a r e m a d e f o r a l k y l a t i o n of i s o p e n t a n e w i t h

some

isopentene

u s i n g e i t h e r s u l f u r i c o r h y d r o f l u o r i c a c i d as the c a t a l y s t . duced plant a n d operating costs would obviously i m p r o v e r e l a t i v e p o s i t i o n of a l k y l a t i o n i n t h e r e f i n e r y ' s scheme.

processing

A r e c e n t v e r b a l r e p o r t f r o m one r e f i n e r i n d i c a t e d H F

acid consumption over a two-year

period was

extremely

p e r h a p s o n l y o n e - t e n t h of that n o r m a l l y r e p o r t e d . ments

Rethe

i n s u l f u r i c a c i d effluent

New

low, develop-

refrigerated alkylation indicate

r e d u c t i o n s in o p e r a t i n g c o s t s c a n be m a d e .

Another verbal r e -

port indicates s t i l l higher octane alkylate is being p r o d u c e d in a p i l o t plant t h a n r e p o r t e d at a n y t i m e i n the

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

D:>GM-S;OH o f effluent

existh.M

p.ants

is

an î n t e r e s i . Î M u

refrigeration alkylation process

aco Development oration features

past.

Corporation and Stratford Engineering C o r p -

r i c h in isobutane,

is c o m p r e s s e d

propane and other light ends,

and,

This

50-70%.

after r e m o v a l of

i s r e t u r n e d to the r e a c t o r ; t h i s

If a n e x i s t i n g a l k y l a t i o n p l a n t ,

i s not effluent

refrigerated,

this means

the

much

either H F or H2SO4, deisobutanizer

t o w e r i s about t w i c e the s i z e r e q u i r e d w i t h effluent tion.

cool

flashed

step c a n r e d u c e the u s u a l C4 f r a c t i o n a t i o n t o w e r s i z e a s as

refrigera-

S u c h a p l a n t c a n be e x p a n d e d i n a l k y l a t e c a p a c i t y t w o

three times cally,

b y c o n v e r t i n g to e f f l u e n t

refrigeration.

patents

to date,

A l t h o u g h effluent

Information

p u b l i s h e d by the O i l I n s u r a n c e A s s o c i a t i o n ,

titled "Alkylation U n i t s " . " D u r i n g the p e r i o d f r o m

T h i s r e p o r t i n c l u d e s the 1961

t o 1972

O f t h i s t o t a l o f 18 l o s s e s ,

u n i t s a n d 13 i n H F u n i t s .

5 o c c u r r e d in H2SO4

T h i s indicates m o r e than a two

i n 1965

4

u n i t s s i n c e 1967,

to

Another

s i g n i f i c a n t f e a t u r e i s the fact that no l o s s e s have b e e n 2

17

o f at l e a s t o n e a d d i ­

one edge of l o s s e s i n H F units o v e r H 2 S O 4 u n i t s . in H S 0

en-

following:

the Ο Ι Α e x p e r i e n c e d

a l k y l a t i o n unit l o s s e s and has knowledge tional loss.

numerous

(29)

One disturbing factor is r e v e a l e d in a L o s s B u l l e t i n (30)

but

refrigera-

b e e n a p p l i e d to H F a l k y l a t i o n ,

have been i s s u e d for such use.

to

Metallurgi-

H F a l k y l a t i o n p l a n t s c a n be c o n v e r t e d to H 2 S O 4 ,

H 2 S O 4 c a n n o t be c o n v e r t e d t o H F . t i o n has not,

recorded

w h i l e H F unit l o s s e s f i r s t o c c u r r e d

and have i n c r e a s e d i n s u c c e s s i v e

y e a r s i n both m a g n i ­

tude and n u m b e r . These

18 o c c u r r a n c e s i n a g g r e g a t e

property damage

The

Tex-

the e v a p o r a t i o n of the r e a c t o r effluent to

a n d r e m o v e the r e a c t i o n heat f r o m the r e a c t o r . vapor,

potential.

jointly offered by

losses exceeding

represent

$6, 800, 0 0 0 .

total

T h i s d o e s not

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19.

Impact on Sulfuric Acid Industry

G R A H A M

321

include loss of earnings resulting f r o m these events. Interruption coverage was not p r o v i d e d f o r a l l these

Business instances,

b u t i n t h e t h r e e c a s e s w h e r e it w a s i n v o l v e d , t h e l o s t

earnings

r e p r e s e n t e d a n a d d i t i o n a l t o t a l o f a p p r o x i m a t e l y $1, 400, 000. Losses aggregate

i n H F u n i t s a c c o u n t f o r a b o u t $ 5 , 6 0 0 , 000 o f t h e

property damage total,

a n d of this a m o u n t

nearly

$4, 0 0 0 , 000 i s a c c o u n t a b l e t o t h e p a s t t w o a n d a h a l f y e a r s . " Thus,

82% of t h e l o s s e s i n the p e r i o d 1961-1972

r e d i n H F plants.

A f u r t h e r s e t o f l o s s r e p o r t s (31),

t h e p e r i o d f r o m 1973 t h r o u g h N o v e m b e r

1976 i n d i c a t e s t h i s h a s

continued and, i f anything, has i n c r e a s e d . p a s t 15 y e a r s ,

Therefore,

sulfuric a c i d alkylation has been

to be a m u c h s a f e r

f o r the

demonstrated

process.

So the c o m p e t i t i o n w i l l a p p a r e n t l y c o n t i n u e ,

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

occur-

covering

f i n e r y a l k y l a t i o n plant a n d c a t a l y s t s e l e c t i o n being

each r e evaluated

on a n individual basis. IV. tion

Developments

in sulfuric acid recovery and regenera-

methods. T h e r e g e n e r a t i o n of spent s u l f u r i c a c i d f r o m a l k y l a t i o n

h a s h i s t o r i c a l l y (32) b e e n t h a t o f d e c o m p o s i t i o n i n a c o m b u s t i o n c h a m b e r to r e d u c e the a c i d to e s s e n t i a l l y SO2 a n d H 2 O ,

oxidiz-

i n g the S O 2 to S O 3 c a t a l y t i c a l l y , a n d a b s o r b i n g the S O 3 i n w e a k a c i d to p r o d u c e f r e s h a c i d a n d e v e n o l e u m s . widely used.

This process

is

T h e t y p i c a l s u l f u r i c a c i d plant m u s t be d e s i g n e d

to i n c l u d e the c a p a b i l i t y f o r h a n d l i n g spent a l k y l a t i o n a c i d . plant m a k i n g a c i d f r o m m o l t e n s u l f u r i s the m o s t

A

economical

a n d e a s i e s t to o p e r a t e b e c a u s e o f t h e r e l a t i v e p u r i t y of the S O 2 produced.

If s p e n t a l k y l a t i o n a c i d i s b u r n e d ,

carbon oxides

and w a t e r vapor a r e also p r o d u c e d and this complicates the plant.

T h e w a t e r v a p o r m u s t be r e m o v e d p r i o r to the c a t a l y t i c

oxidation step.

T h e g a s b a l a n c e to c a t a l y t i c o x i d a t i o n m u s t be

c a r e f u l l y a d j u s t e d to a c c o m m o d a t e

the c a r b o n oxides

while

maintaining the surplus oxygen/ sulfur dioxide ratios r e q u i r e d f o r efficient o x i d a t i o n of the S O 2 to S O 3 .

(Although spent

lation a c i d has been used i n f e r t i l i z e r m a n u f a c t u r e , t i c e i s p h a s i n g out b e c a u s e of the o d o r s e m i t t e d f r o m

alky-

this p r a c such

plants a n d a l s o b e c a u s e of the g r a y i s h c o l o r i m p a r t e d to the final fertilizer product. ) Independent

chemical companies

of the s u l f u r i c a c i d p l a n t s .

own and operate

most

Plant capacities a r e generally in

the r a n g e of 500-1500 tons f r e s h s u l f u r i c a c i d / d a y .

However,

a n u m b e r of a c i d plants a r e installed within, o r i m m e d i a t e l y a d j a c e n t t o , the p e t r o l e u m r e f i n e r y a r e a ; m o s t of t h e s e a c i d

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

322

INDUSTRIAL

A N D L A B O R A T O R Y

p l a n t s a r e o w n e d o u t r i g h t b y the r e f i n i n g c o m p a n y . o f t h e s e p l a n t s r a n g e f r o m 50 t o a s m u c h a s 600

A L K Y L A T I O N S

Capacities

tons/day.

The economic importance of the refinery-owned a c i d plant i s i n c r e a s i n g . duced acid costs,

sulfuric

T h e i m m e d i a t e benefit i s that of r e -

both handling costs a n d p r o d u c t i o n

costs.

E c o n o m i c d a t a w e r e p u b l i s h e d i n 1972 i n a n a r t i c l e b y t h e a u t h o r (33) a n d s h o w e d t h a t n e t d i r e c t m a n u f a c t u r i n g c o s t s o f a r e f i n e r y - o w n e d a c i d p l a n t w e r e about acid market price.

1/4 t o 1/2 o f that of the

T h e industry p r a c t i c e i n the past has been

to allow a c r e d i t f o r t h e spent a l k y l a t i o n a c i d r e t u r n e d f o r r e g e n e r a t i o n ; t o d a y that p r a c t i c e i s c h a n g i n g i n s o m e a r e a s a n d a n additional charge is being made f o r handling the spent T h i s has happened because

acid.

of pollution control laws which r e -

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

q u i r e the a c i d plant o p e r a t o r s to t u r n down t h e i r p r o d u c t i o n r a t e a n d / o r to i n s t a l l expensive atmospheric Thus, today's

stack g a s cleanup s y s t e m s to a v o i d

pollution. a new a c i d plant w i t h i n the r e f i n e r y ,

built to m e e t

standards f o r conversion efficiency and non-polluting

emissions,

h a s a n e v e n g r e a t e r p o t e n t i a l e c o n o m i c benefit to

the r e f i n e r .

T h e fact that a m a j o r W e s t C o a s t ( U . S. A . ) r e f i n e r

b u i l t (in 1972-1973) a n d n o w o p e r a t e s stringent L o s Angeles

an a c i d plant w i t h i n the

pollution-control area,

that t h e plant

produces fresh acid from H2Sand also regenerates tion acid,

a t t e s t s to t h i s .

mately 275-300

spent a l k y l a -

T h e c a p a c i t y of this plant i s a p p r o x i -

tons/day.

Other a c i d plants a r e under serious f i n e r s at this t i m e .

consideration by r e -

P l a n t s a s s m a l l a s 15 t o n s / d a y

q u o t e d i n the f o u r t h q u a r t e r o f 1976.

have

been

Once the f i r s t s m a l l

has been built and operated successfully,

plant

it is the w r i t e r ' s

s i d e r e d o p i n i o n that m a n y of t h e s e plants w i l l be b u i l t .

con-

This

w i l l definitely influence the ratio of s u l f u r i c / h y d r o f l u o r i c a l k y lation plants; many s m a l l H F alkylation plants were built s i m p l y because

sulfuric acid was unavailable. A n a d d i t i o n a l e c o n o m i c benefit to the r e f i n e r i s b a s e d

upon the g o v e r n m e n t - i m p o s e d

r e q u i r e m e n t to d e s u l f u r i z e a l -

m o s t a l l the products leaving the r e f i n e r y .

T h i s has resulted in

the i n s t a l l a t i o n of s u l f u r - r e c o v e r y plants i n a high of the U . S. A . the w o r l d . sulfur.

percentage

r e f i n e r i e s a n d w i l l undoubtedly follow i n m o s t of

H y d r o t r e a t i n g i s the p r i m a r y p r o c e s s

H y d r o g e n sulfide i s the p r i m a r y p r o d u c t .

for removing P l a n t s to

convert hydrogen sulfide to sulfur i n quantities as s m a l l as 4 tons/day are i n operation within petroleum refineries; a s l a r g e a s 3 7 5 t o n s / d a y h a v e a l s o b e e n r e p o r t e d (34).

plants

(It i s

e s t i m a t e d that s u l f u r f r o m p e t r o l e u m w i l l a c c o u n t f o r 10% of the

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19.

323

Impact on Sulfuric Acid Industry

G R A H A M

f r e e w o r l d s u p p l y b y 1980.

) (35)

O n c e the f i r s t s u l f u r plant has b e e n r e q u i r e d , a s t a n d b y plant i s u s u a l l y r e q u i r e d to p r o v i d e a b s o l u t e for handling a l l sulfur-containing streams f i r s t plant shutdown. law,

second

capability

i n the event of the

If s u l f u r o x i d e e m i s s i o n s

are limited by

t h e n the r e f i n e r i s f a c e d w i t h shutting down the

refinery

if the f i r s t s u l f u r plant i s down a n d a s e c o n d plant i s not a v a i l able.

H y d r o g e n s u l f i d e c a n no l o n g e r be d i s p o s e d of b y b u r n i n g

w h e r e the s u l f u r o x i d e s a r e d i s c h a r g e d to the

atmosphere.

T h i s i s w h e r e the s u l f u r i c a c i d plant m e r i t s consideration.

additional

If t h e s u l f u r i c a c i d p l a n t i s e c o n o m i c a l l y

favor-

a b l e on the i n i t i a l b a s i s of s u p p l y i n g a n d r e g e n e r a t i n g a l k y l a t i o n c a t a l y s t , the e c o n o m i c s

become even m o r e favorable

if the a c i d

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

p l a n t i s d e s i g n e d w i t h e n o u g h c a p a c i t y to s e r v e a s the sulfur plant".

it c a n be c o n v e r t e d to f r e s h s u l f u r i c a c i d .

i n sufficient

c a n e l i m i n a t e the n e e d f o r s u p p l e m e n t a l f u e l i n the One t o n of H2S p r o d u c e s a l m o s t

t h a t s a m e t o n of H 2 S c a n p r o d u c e a l m o s t Thus,

sulfur,

H2S is i d e a l fuel i n

a n a l k y l a t i o n a c i d r e g e n e r a t i n g plant and, chamber.

"standby

I n s t e a d o f c o n v e r t i n g h y d r o g e n s u l f i d e to

quantities

combustion

one t o n of s u l f u r but

3 tons of s u l f u r i c a c i d .

the s u l f u r i c a c i d plant w i t h i n the r e f i n e r y c a n p r o v i d e

a l k y l a t i o n a c i d c a t a l y s t at l o w e s t p r i c e s a n d c a n p e r m i t r e f i n e r to m a r k e t h i s b y - p r o d u c t s u l f u r o p t i o n a l l y a s a c i d i f the m o n e t a r y r e t u r n is

the

sulfuric

greater.

A f u r t h e r p r o c e s s i n g a d v a n t a g e i s a v a i l a b l e to the

re-

f i n e r if a s u l f u r i c a c i d plant has been built for handling both a l k y l a t i o n a c i d a n d a l l the r e f i n e r y H 2 S .

W h e n the m a r k e t

con-

d i t i o n s d i c t a t e c o n v e r t i n g H2S to s u l f u r i n s t e a d of s u l f u r i c a c i d , the i d l e c a p a c i t y w i t h i n the a c i d plant c a n be u t i l i z e d by p u m p i n g t h e a c i d t h r o u g h a l k y l a t i o n at a f a s t e r r a t e ,

r a i s i n g the f i n a l

a c i d spending strength w h i c h produces a higher octane (especially w i t h butylènes alkylate).

alkylate

T h e extra utilities cost

r e g e n e r a t i n g m o r e a c i d m u s t be offset by the i n c r e a s e d of the h i g h e r octane a l k y l a t e . vantage w i l l be

In m o s t c a s e s ,

for

value

this economic

ad-

significant.

T h e newest improvement

i n f u r t h e r r e d u c i n g the

sulfur

d i o x i d e i n the s t a c k gas f r o m a contact s u l f u r i c a c i d plant d e s c r i b e d i n 1974

(36).

was

T o the best of o u r knowledge the plant

d e s c r i b e d i s the c l e a n e s t a c i d p l a n t ,

i . e. , n o n - p o l l u t i n g ,

in

the w o r l d today. A Soviet p r o c e s s acid-making costs".

r e p o r t e d i n 1971

was

c l a i m e d to

T h i s was based upon p r o c e s s

t i o n s a n d a new c a t a l y s t .

(The "technology

"slash

modifica-

is being offered

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

by

324

INDUSTRIAL

A N D

L A B O R A T O R Y A L K Y L A T I O N S

Newton C h a m b e r s E n g i n e e r i n g L i m i t e d , Sheffield,

England". .. )

(37). O t h e r patents have been i s s u e d c l a i m i n g i n c r e a s e d ciency in acid production.

One c l a i m s " a n important

effi-

advantage"

a c h i e v e d b y u s i n g r e a c t i o n h e a t to p r e h e a t r e c y c l e d t a i l g a s f i n a l c o n v e r s i o n to S O 3

A n a r t i c l e p u b l i s h e d i n E u r o p e i n 1972 sure process

for

(38).

for making H2SO4".

described a

T h e c o n v e r s i o n of S 0

S O 3 w a s c i t e d a s 99. 8 5 % a n d t h e i n v e s t m e n t

"presto

2

cost as about

10%

l e s s t h a n t h a t of a c o n v e n t i o n a l p l a n t . (39) One patented p r o c e s s

(40) w a s

i n t r o d u c e d i n the

mid-'60s

to r e d u c e t h e a m o u n t o f s u l f u r i c a c i d r e q u i r e d b y a l k y l a t i o n ; i t was

c a l l e d the S u l f u r i c A c i d R e c o v e r y P r o c e s s

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

jointly licensed by Texaco Development ford Engineering Corporation. c l a i m s m a d e f o r it.

(SARP) and was

Corporation and S t r a t -

Chemically,

S A R P proved all

U t i l i z e d only with propylene/butylène

a l k y l a t i o n the a c i d r e q u i r e m e n t w a s r e d u c e d as m u c h as a c t u a l a c i d d i l u t i o n r a t e s w e r e l o w e r t h a n 0. 2# alkylate.

However,

70%;

acid/gallon

the spent a c i d f r o m S A R P w a s

different

a n d c o u l d not b e r e g e n e r a t e d at t h e s a m e r a t e a s r e g u l a r alkylation acid.

spent

T h i s c a u s e d the c h e m i c a l c o m p a n i e s to i n -

c r e a s e the c h a r g e s f o r r e g e n e r a t i n g the S A R P spent a c i d to a p o i n t w h e r e t h e r e w a s no e c o n o m i c

i n c e n t i v e to o p e r a t e

SARP.

T h e two c o m m e r c i a l S A R P i n s t a l l a t i o n s a r e not i n u s e at the p r e s e n t t i m e a l t h o u g h new p o s s i b i l i t i e s f o r S A R P have j u s t i n the p a s t few V.

arisen

months.

T a k i n g i n t o a c c o u n t II.

Ill and IV,

l i k e l y future t r e n d i n

sulfuric a c i d consumption and regeneration. As

stated e a r l i e r ,

p r e d i c t i o n s of f u t u r e t r e n d s i n a l k y l a -

t i o n a n d a c i d u s e a r e too dependent u p o n p o l i t i c a l d e c i s i o n s to be even attempted on a p r a c t i c a l basis. are ignored,

then an estimate

If p o l i t i c a l

considerations

of a m a x i m u m a l k y l a t i o n capacity

a n d m a x i m u m a c i d r e q u i r e m e n t c a n be attempted,

although such

a p r e d i c t i o n m u s t b e v e r y g e n e r a l a n d s u b j e c t to c h a l l e n g e many

from

sources. A s s u m i n g the p r e d i c t e d w o r l d w i d e p e t r o l e u m

increases

4 5 % b y t h e y e a r 1990 (41),

that g a s o l i n e

refining

is 40% of the

r e f i n e r y o u t p u t a n d t h a t t e t r a e t h y l l e a d i s r e d u c e d to z e r o 60% of the g a s o l i n e , tion,

in

w h i c h r e s u l t s i n a 40% i n c r e a s e i n a l k y l a -

t h e p r e s e n t d a y a l k y l a t i o n c a p a c i t y of 1, 098, 000

w i l l i n c r e a s e b y a f a c t o r o f 1. 45 χ 1. 4 to 2, 229, 000 i n c r e a s e o f 1, 131, 000

BPSD.

BPSD

B P S D , or an

If t h e p r e s e n t r a t i o o f 5 5 %

i c / 4 5 % h y d r o f l u o r i c is maintained,

sulfur­

then 622,000 B P S D of this

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

19.

G R A H A M

Impact on Sulfuric Acid Industry

i n c r e a s e w i l l be s u l f u r i c a c i d c a t a l y z e d . m o s t of t h i s i s butylène a l k y l a t e , r a t e of 0 . 4 # / g a l l o n a l k y l a t e ,

325 If w e f u r t h e r

assume

with a typical acid dilution

the a c t u a l new a c i d

p l a n t c a p a c i t y r e q u i r e d w i l l b e 5225 t o n s / d a y .

regeneration

If n e w

develop-

m e n t s i n s u l f u r i c a c i d a l k y l a t i o n r e s u l t e d i n its u s e i n a l l the n e w a l k y l a t i o n , n e w a c i d p l a n t c a p a c i t y w o u l d b e a b o u t 10,

000

tons / day. O t h e r u s e s f o r s u l f u r i c a c i d i n the F r e e W o r l d have r e p o r t e d a s 82, 0 0 0 , 000

s h o r t t o n s i n 1970,

c r e a s e o f 2 5 % t h r o u g h 1975 1980.

a n d a f u r t h e r i n c r e a s e of 25%

by

T h i s w o u l d i n d i c a t e new a c i d p r o d u c t i o n r e q u i r e m e n t s

a b o u t 2 8 , 0 0 0 , 000 t o n s / y e a r 7 9 , 000 t o n s / d a y .

Thus,

1976-1980,

or

of

approximately

the new c a p a c i t y f o r a l k y l a t i o n a c i d

w o u l d be i n the r a n g e of 7 - 1 2 %

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch019

been

with a predicted i n -

of the t o t a l .

Literature Cited 1. 2. 3.

4. 5. 6. 7. 8. 9.

10. 11. 12.

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41.

G R A H A M

Impact on Sulfuric Acid Industry

327

Clonts, K.E., " L i q u i d - l i q u i d M a s s T r a n s f e r P r o c e s s and Apparatus", U.S. Patent No. 3, 758, 404, (Sept. 11, 1973). Clonts, Κ. Ε . , " A l k y l a t i o n U t i l i z i n g F i b e r s in a Conduit Reactor", U.S. Patent No, 3, 839, 487, (Oct. 1, 1974). U. S. Patent Nos. 2, 906, 796 (1959); 2, 949, 494 (1960); 2, 977, 397 (1961); and 3, 925, 501 (Dec. 9, 1975). O i l Insurance A s s o c i a t i o n r e p o r t (November, 1972). P r i v a t e Communication. Duecker, W. W. & West, J. R., "The Manufacture of S u l f u r i c A c i d " , (1959), Reinhold. Graham, W. A., " A l k y l a t i o n Integrates A c i d Plant", H y d r o c a r b o n P r o c e s s i n g , (August, 1972). Anon., "Why R e c o v e r Sulfur f r o m H S?", The Oil and Gas J o u r n a l , (Oct. 28, 1968), pp. 88-101. Buckingham, P. A. & Homan, H. R., "Sulfur and the E n e r g y Industry", H y d r o c a r b o n P r o c e s s i n g , (August, 1971), pp. 121-125. C o l l i n s , J . J . et a l , "The P u r a S i v S Process For Re­ moving A c i d Plant T a i l Gas", C h e m i c a l E n g i n e e r i n g P r o g r e s s , V o l . 70, (No. 6), (June, 1974), pp. 58-62. L a w r i e , Ν., "Soviet P r o c e s s Slashes S u l p h u r i c - A c i d M a k i n g Costs", C h e m i c a l E n g i n e e r i n g (Mar. 8, 1971). Jaeger, W., " P r o c e s s f o r the production of Sulfur Tri­ oxide by the C o l d Gas P r o c e s s " , U. S. Patent No. 3, 647, 360 (Mar. 7, 1972). Vidon, Β., C h e m i c a l & P r o c e s s Engineering, (July, 1972), pp. 34-35. U.S. Patents, Nos. 3, 234, 301; 3, 227, 774; 3, 227, 775; 3, 442, 972; 3, 534, 118; 3, 544, 653; and 3, 665, 050 (19661970). Anon., " O i l Still The K e y F u e l " , The Oil and Gas Journal, (Nov. 10, 1975), pp. 159-178. 2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

20 The IFP Dimersol Process for Dimerization of Propylene into Isohexenes An Attractive Alternate to Propylene Alkylation JOHN ANDREWS and PIERRE BONNIFAY

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

InstitutFrancaisdu Petrol, North American Office, 450 Park Avenue, New York, NY 10022 The 1974/75 slump i n g a s o l i n e demand is over, the 1976 demand is expected to top 6% while the 1977 demand will r e t u r n to a more normal 3 to 5%. The quest i o n o f lead phase-down appears r e l i e v e d with an EPA postponement, but as a r e s u l t o f the s t e a d i l y i n c r e a s ing number o f v e h i c l e s that use unleaded g a s o l i n e (about 10% increase annually on the t o t a l number o f automobiles i n the United States) by 1980 some 62% o f the t o t a l g a s o l i n e pool will have to meet no-lead g a s o l i n e s p e c i f i c a t i o n . (1) This i s what r e f i n e r s are faced with i n t h e i r planning s t u d i e s . An obvious answer to t h i s problem of supplying not only more g a s o l i n e but i n c r e a s i n g percentages o f no-lead grade, is expanded crude capacity. However t h i s leads to high investment costs f o r crude u n i t s and downstream processing u n i t s and j u s t now there seems to be some r e l u c t a n c e i n the r e f i n i n g i n d u s t r y to l a r g e s c a l e expansions. R e f i n e r s are l o o k i n g f o r other means to increase t h e i r g a s o l i n e producing c a p a c i t y while o p t i m i z i n g t h e i r ability to produce i n c r e a s i n g volumes o f no-lead g a s o l i n e . One s o l u t i o n to the problem i s couched i n r a i s i n g fluid c a t a l y t i c c r a c k i n g c a p a c i t y and conversion. F l u i d C a t a l y t i c Gasoline (FCC) full b o i l i n g range g a s o l i n e has a r e s p e c t i b l e RON o f about 92 and an R+M/2 o f around 87. Since current no-lead grade spec i f i c a t i o n s i n c l u d e 87 R+M/2, FCC g a s o l i n e can be utilized d i r e c t l y in the no-lead pool. The C3 a n d C4 s t r e a m s f r o m t h e F C C p r o d u c t distribution c a n be converted i n t o high octane b l e n d i n g components. One f a v o r i t e m e t h o d o f d o i n g t h i s i s b y means o f a l k y l a t i o n o f t h e C 3 / C 4 o l e f i n s w i t h i s o b u tane. A l k y l a t e i s p r o d u c e d from C 3 / C 4 FCC c u t s o r somet i m e s f r o m t h e C4 c u t a l o n e . These p r o d u c t s have good 328

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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329

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RON numbers which vary depending upon the o l e f i n composition.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

C3 A l k y l a t e C4 A l k y l a t e C3/C4 A l k y l a t e

RON 91 96 93.5

feed

R+M/2 90.5 95 92.5

A l k y l a t e s are very d e s i r a b l e no-lead i n g r e d i e n t s and obviously the C4 a l k y l a t e i s p r e f e r r e d because of i t s s u b s t a n t i a l l y higher octane q u a l i t y . Moreover, the manufacture of C4 a l k y l a t e r e q u i r e s about 157o l e s s isobutane than C3 a l k y l a t e . However, isobutane i s becoming more expensive as i t s supply decreases: - Both gas processing throughput and n a t u r a l gasl i q u i d s production f o r the past three years s i g n i f y that U.S. production of gas l i q u i d s i s i n a downward trend. S p e c i f i c a l l y , the production of isobutane from t h i s source has decreased almost 87o from 1974 to 1975. (2) - Isobutane from hydrocracking p l a n t s continues to be a v a i l a b l e , but c o n s t r u c t i o n of new hydrocrackers i s very expensive and t h e r e f o r e an increased supply from t h i s source i s , short term at l e a s t , d o u b t f u l . - Even when energy costs were a p p r e c i a b l y lower than now, i s o m e r i z a t i o n of butane to isobutane was no r e a l bargain because of the l a r g e energy requirement f o r f r a c t i o n a l separation of isobutane and butane. Today the s i t u a t i o n i s aggravated by high energy cost. - Therefore i n many cases economics w i l l not permit the r e f i n e r to make a v a i l a b l e s u f f i c i e n t isobutane to a l k y l a t e h i s e n t i r e C 3 / C 4 FCC stream and -there i s demand f o r a new or modified approach which w i l l r e t h i n k the e n t i r e problem of C 3 / C 4 u t i l i z a tion. Reviewing these thoughts and applying them to the r e f i n e r y s i t u a t i o n -- one scenario which has found favor i s the f o l l o w i n g : FCC Unit. U t i l i z i n g new c a t a l y s t s and r e c e n t l y developed technology i n c l u d i n g r e a c t o r m o d i f i c a t i o n s , r a i s e raw o i l charge r a t e and/or conversion. Gas Concentration. I f a good FCC revamp i s poss i b l e , i t follows that the gas concentration system w i l l need to be e x t e n s i v e l y revamped.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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A l k y l a t e and Dimate. The degree o f revamp necessary or the need to c o n s t r u c t a new alky u n i t w i l l depend not only upon the e x i s t i n g operation but by the isobutane the r e f i n e r w i l l be able to b r i n g to the alkylation unit. For example, i n the event a r e f i n e r has been a l k y l a t i n g a mixed C3/C4 stream and to expand the a l k y l a t i o n c a p a c i t y would s t r a i n h i s isobutane supply sources, the r e f i n e r can i n s t a l l a C3/C4 s p l i t t e r and a l k y l a t e only the C4's. The advantages are numerous : 1. Revamping of the a l k y l a t i o n may not be necessary 2. A l k y l a t e octane number w i l l improve 3. Isobutane e f f i c i e n c y w i l l increase ( l e s s iC4 r e q u i r e d f o r C4 a l k y l a t i o n than C3 a l k y l a t i o n ) . However, what w i l l the r e f i n e r do with the C3's, and how about h i s need f o r l a r g e r q u a n t i t i e s o f nol e a d gasoline? The IFP answer to t h i s question not only cuts new c o n s t r u c t i o n c o s t s , reduces o p e r a t i n g c o s t s , r e duces the r e f i n e r s dependence on isobutane, but a l s o increases the RON and the (R+M)/2 o f the g a s o l i n e produced from the C3/C4 o l e f i n s . The answer i s the IFP DIMERSOL PROCESS to produce isohexenes, which we w i l l r e f e r to as dimate, and the purpose o f t h i s paper i s to demonstrate how the Process accomplishes t h i s . Let us procède as f o l l o w s : Comparative Economics At A Glance F i g u r e I o f f e r s a means o f comparing the economics o f charging a FCC C3 stream to a new Dimersol Process Unit f o r dimate production or a new A l k y l a t i o n Process Unit f o r a l k y l a t e production. The s e r i e s o f s l a n t e d p a r a l l e l l i n e s represent v a r i a b l e isobutane p r i c e s which when r e l a t e d to the appropriate propylene p r i c e give the r e s u l t a n t cost of the a l k y l a t e product i d e n t i f i e d as g a s o l i n e i n ç/gal. The cents per g a l l o n values f o r propylene r e l a t e to the p r i c e f o r the FCC C3 stream with propane at the same p r i c e as propylene. Included i n the c o r r e l a t i o n are the a l k y l a t i o n operating costs shown i n Table IV a t 07o r e t u r n on investment. The s i n g l e broken l i n e r e l a t e s propylene p r i c e to dimate product cost i d e n t i f i e d as g a s o l i n e i n ç/gal. Included are the Dimersol operating costs shown i n Table I I I & IV a t 07<> r e t u r n on investment. This superimposed p l o t then makes i t p o s s i b l e to determine the most economic method o f d i s p a t c h i n g

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

20.

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ι 16

IFF Dimersol Process

BONNiFAY

T

I 17

I 18

I 19

I 20

I 21

I 22

I 23

I 24

I 25

I 26

331

I 27

I 28

I 29

ι 30

Propylene Price U/Gal.)

Figure 1.

Comparative economics for charging propylene to dimersol or alkylation

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

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r e f i n e r y propylene i n t o g a s o l i n e depending upon propylene and isobutane costs and i n c l u d i n g r e s p e c t i v e process o p e r a t i n g c o s t s . For example, i f a r e f i n e r ' s isobutane costs 25c/ gal, the case i s made f o r Dimersol o p e r a t i o n (over a l k y l a t i o n ) f o r any value of propylene up to 25.7c/ gal. Any set of c o n d i t i o n s l o c a t e d over the broken diagonal l i n e would favor Dimersol operations while the lower isobutane p r i c e s (below the l i n e ) would f a v o r the C3= a l k y l a t i o n route. S t i l l another method of u t i l i z i n g t h i s chart i s under the c o n d i t i o n s which say that a l k y l a t e o p e r a t i o n sets the value on the FCC C3 stream. For example: i f a r e f i n e r pays 25c/gal f o r isobutane and s e l l s C3 a l k y l a t e i n t o a 3 5 ç / g a l g a s o l i n e market, h i s propylene costs out at about 18.7ç/gal. This same 18.7c/ gal propylene would y i e l d g a s o l i n e at 3 0 ç / g a l i n the Dimersol Process thus r e a l i z i n g a 5 ç / g a l p r o f i t . F i g u r e 3 expresses the same data i n another way: i n terms of Dimersol p r o f i t over C3 A l k y l a t i o n i n ç/gal of product. Take A C l o s e r Look I f from t h i s r a t h e r quick economic s u r v e i l l a n c e dimate looks f a v o r a b l e , then one should examine: 1. the dimate product q u a l i t i e s comparing them with those of C3 a l k y l a t e 2. the comparison of the more d e t a i l e d economics i n c l u d i n g investment and o p e r a t i n g c o s t s . Table I compares p r o p e r t i e s of Dimersol Dimate and C3 a l k y l a t e . In studying t h i s t a b l e one sees a b a s i c d i f f e r e n c e between dimate and C3 a l k y l a t e v o l a t i l i t y manifested i n d i s t i l l a t i o n and RVP. In gasol i n e blending t h i s becomes important when one i s b l e n d i n g with reformate. To i l l u s t r a t e , we w i l l show a s e r i e s of bar c h a r t s g i v i n g the RON's of consecutive i n d i v i d u a l 10 volume 7> increments of f u l l b o i l i n g range g a s o l i n e s . S t a r t i n g with a t y p i c a l reformate i n F i g u r e 3, note the severe d r o p - o f f i n the f r o n t end octane. When t h i s same reformate i s blended with 157o C3 A l k y l a t e as shown i n F i g u r e 4, the change i n octane i s evenly d i s t r i b u t e d over p r a c t i c a l l y the e n t i r e g a s o l i n e b o i l ing range. (3) However, when 157> dimate i s blended with the i d e n t i c a l reformate, the octane e f f e c t i s concentrated i n the 10-30 v o l 7> range where the octane slump was most pronounced. The dimate s low b o i l i n g range coupled with a 97 RON, serve to f i l l t h i s gap 1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

A N D R E W S

A N D

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

20.

BONNiFAY

IFF Dimersol

Process

Figure 3. Research octane distribution over gasoline boiling range

Figure 4.

Research octane distribution over gasoline boiling range

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

333

334

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TABLE

A N D L A B O R A T O R Y

A L K Y L A T I O N S

I

PROPERTIES OF DIMERSOL DIMATE AND C3 ALKYLATE PRODUCT

DIMERSOL DIMATE

C3 ALKYLATION ALKYLATE

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

PRODUCT QUALITY SP. GR.

0.69

0.70

R.V.P.

6.5

2.0

RON CLEAR

97

91.0

RON + MON/2

89.5

90.5

ASTM BOILING RANGE IBP

133

150

10

136

195

50

140

210

90

160

250

EP

370

400

FOR DIMERSOL GASOLINE BLENDING VALUES - SEE NOTE 6.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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335

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

not only i n octane l e v e l but i n v o l a t i l i t y as w e l l . A balanced o c t a n e / v o l a t i l i t y g a s o l i n e makes any automob i l e perform b e t t e r i n any season.(4) Table I I shows the y i e l d s and product d i s t r i b u t i o n i n a Dimersol Unit charging 3803 BPSD of mixed C3's c o n t a i n i n g 2700 BPSD propylene. The conversion l e v e l on propylene i s 95%. Table I I I shows the d e t a i l e d d i r e c t o p e r a t i n g costs based upon the f o l l o w i n g base data: Steam per 1,000 l b High pressure Medium pressure Power, per KW Water c o o l i n g , per 1,000 g a l Operators, per s h i f t Operation Supervision

$3.50 $2.50 $0,012 $0.03 1.1 0. 2

In Table IV these same economics are compared against C3 a l k y l a t i o n costs f o r a given a v a i l a b i l i t y of propylene and r e f e r e n c e d against a b a r r e l o f product from each r e s p e c t i v e process. The base data i s the same as f o r Table I I I . Process D e s c r i p t i o n Figure 5 i l l u s t r a t e s the s i m p l i c i t y o f the Dimers o l Process. Dried feedstock, which may vary widely i n propylene composition, i s charged to the r e a c t o r where s o l u b l e c a t a l y s t i s added i n low c o n c e n t r a t i o n . Close r e a c t o r temperature c o n t r o l i s obtained by c i r c u l a t i o n of the r e a c t i o n mix through a c o o l e r which may be o f the a i r or water type. The r e a c t i o n occurs at e s s e n t i a l l y ambient temperature, a l l o w i n g f o r the exothermic heat o f r e a c t i o n , and at a pressure s u f f i c i e n t l y high to maintain a l i q u i d phase. Upon l e a v i n g the r e a c t o r , the e f f l u e n t enters a drum where ammonia i n j e c t i o n n e u t r a l i z e s the c a t a l y s t , forming s a l t s : subsequent water i n j e c t i o n d i s s o l v e s the s a l t s removing them from the system. The s c a l e o f t h i s washing o p e r a t i o n i s small because the c a t a l y s t c o n c e n t r a t i o n i s low-- with only about 15 gpm o f process water r e q u i r e d f o r 1000 BPSD of isohexenes product. I f r e q u i r e d , a subsequent small t r e a t i n g step can be s u p p l i e d with the u n i t to remove anions from the wash water. The depropanizer operates to separate the i s o hexenes from C3 LPG overhead.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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II

IFP DIMERSOL PROCESS CONVERSION

=

957. C3 VOL 7o

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

FEED

BPSD

LBS/HR

PROPYLENE

71

2700

20,550

PROPANE

29

1103

8,170

100

3803

28,720

4.2

135

1,030

PROPANE

34.6

1103

8,170

DIMATE

61.2

1952

19,520

3190

28,720

PRODUCTS LPG PROPYLENE

TOTAL

100

PROPERTIES OF DIMATE WT 7o ISOHEXENES

92.0 RON =97.0

NONENES

6.5

HEAVIER

1.5

(RON+MON)/2 =89.5

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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IFP

Dimersol Process

TABLE I I I IFP DIMERSOL PROCESS DIRECT OPERATING COSTS

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1952

BPSD DIMATE

$/BBL

LP STEAM

0.26

COOLING WATER

0.04

POWER

0.01

CATALYST

0.40

TOTAL UTILITIES & CATALYST

0.71

LABOR

0.11

SUPERVISION

0.03

MAINTENANCE

0.03 0.17

TOTAL DIRECT OPERATING COSTS

0.88/BBL

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IV

IFP DIMERSOL VS ALKYLATION ECONOMICS TOTAL OPERATING COSTS ($/BBL PRODUCT)

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DIMERSOL

ALKYLATION

BPSD PROPYLENE CHARGE

2700

2700

BPSD ISOBUTANE CHARGE

0

3645

BPSD PRODUCT

1952

4750

ESTIMATED BATTERY LIMITS ERECTED COST $MM

1.8

8.0

0.71

1.38

0.17

0.11

DIRECT OPERATING COSTS

0.88

1.49

OVERHEAD & CAPITAL COSTS

0.48

0.67

TOTAL OPERATING COSTS

1.36

2.16

UTILITIES & CHEMICALS OPERATING LABOR, SUPERVISION AND MAINTENANCE

ç/GAL @ 0% R.O.I.

3.2

5.1

ç/GAL @ 207o R.O.I.

4.5

7.5

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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feedA

Λ

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CATALYST

Figure 5.

IFP dimersol for dimate

Practical Application The process operates at p r a c t i c a l l y ambient tem­ perature and at s u f f i c i e n t pressure to maintain a l i ­ quid phase. M a t e r i a l of c o n s t r u c t i o n i s e s s e n t i a l l y a l l carbon s t e e l . Though the economics used i n t h i s paper are based upon a 1007o new p l a n t , the IFP Dimersol Process can be adapted to e x i s t i n g equipment because of i t s s i m p l i c i ­ ty and modest o p e r a t i n g requirements. For example, the r e a c t o r s e c t i o n f o r small to medium s i z e u n i t s may u t i l i z e an e x i s t i n g LPG b u l l e t - t y p e v e s s e l or an e x i s t i n g p o l y m e r i z a t i o n u n i t can be converted i n t o the Dimersol Process. Conclusions One has to be impressed with the economics of the Dimersol Process and the s i m p l i c i t y of the design which leads not only to ease of o p e r a t i o n but to f a s t c o n s t r u c t i o n as w e l l . The c o n s t r u c t i o n time schedule f o r one u n i t which i s now under design foresees opera­ t i o n by the end of 1977. The Dimersol Process o f f e r s r e f i n e r s a unique method of q u i c k l y s o l v i n g problems a s s o c i a t e d with the production of a g a s o l i n e pool r a d i c a l l y d i f f e r e n t i n composition from that produced j u s t 2 or 3 years ago.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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LITERATURE CITED 1. "Octane Crunch Threatens Petrochemicals," Chemical Week, (Sept. 15, 1976)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch020

2. Congram, Gary E. "U.S. Gas-Processing Throughput Dips While Ethane Recovery Rises 5.7%," The Oil & Gas J o u r n a l , (July 5, 1976) 3. A l b r i g h t , L y l e ; K.W. Li, Eckert, Roger Ε., " A l k y l a t i o n o f Isobutane with L i g h t O l e f i n s Using S u l f u r i c A c i d " I n d u s t r i a l & Engineering Chemistry, (1970) Vol. 9, A l k y l a t i o n . Data source used to c o n s t r u c t F i g u r e 4-1. 4. B a r b i e r , J.C.; D o u i l l e t , D.; Franch, J.C.; Raimb a u l t , C.; Bonnifay, P; Cha,B.; Andrews, J . "Gaso­ l i n e Pool: What it Needs," Hydrocarbon Processing, (May, 1975) 5. B a r b i e r , J.C.; D o u i l l e t , D.; Franch, J.C; Raimbault, C.; Bonnifay, P.; Cha, B.; Andrews, J . "Propylene Dimer; F u e l or Chemical" Hydrocarbon Processing, ( A p r i l , 1976) 6. Chauvin, J.A. " tion of Center,

Y.; G a i l l a r d , J.F.; Quang, D.V.; Andrews The IFP Dimersol Process f o r the DimerizaC3 & C4 O l e f i n i c Cuts: NPRA Convention San Antonio, Texas, (1973)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

21

Monsanto's E t h y l b e n z e n e Process

A. C. MACFARLANE

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

Monsanto Chemical Intermediates Company, Texas City, TX 77590

E t h y l b e n z e n e i s c o m m e r c i a l l y produced a l m o s t e n t i r e l y as an i n t e r m e d i a t e f o r t h e manufacture o f s t y r e n e . Since only a l i m i t e d amount can be made by t h e s u p e r f r a c t i o n a t i o n o f C p e t r o l e u m a r o m a t i c s , most e t h y l b e n z e n e i s produced by the a l k y l a t i o n o f benzene w i t h e t h y l e n e . The a l k y l a t i o n r e a c t i o n can o c c u r e i t h e r i n t h e vapor phase o r t h e l i q u i d p h a s e . A number o f proven p r o c e s s e s e x i s t . The l i q u i d phase p r o c e s s e s u s i n g aluminum c h l o r i d e c a t a l y s t s a r e c u r r e n t l y t h e most w i d e l y u s e d . The purpose o f t h i s paper i s t o d e s c r i b e a new and improved v e r s i o n o f t h i s l a t t e r p r o c e s s which has been c o m m e r c i a l i z e d . 8

Friedel-Crafts

Chemistry

The o l d e s t method o f a l k y l a t i o n w i t h e t h y l e n e i s t h e l i q u i d phase r e a c t i o n u s i n g anhydrous aluminum c h l o r i d e as the c a t a l y s t . T h i s r e a c t i o n i s a form o f t h e c l a s s i c F r i e d e l - C r a f t s r e a c t i o n and was d i s c o v e r e d i n 1879 by B a l s o h n . Most Lewis and B r o n s t e d a c i d s a r e known t o be a c t i v e f o r o l e f i n a l k y l a t i o n s . Alkylation by H S0it and H P0n was f i r s t shown by I p a t i e f f , e t a l , i n 1936 who extended t h e r e a c t i o n t o i s o p a r a f f i n s . F o r t h e l i q u i d phase a l k y l a t i o n o f benzene w i t h e t h y l e n e , however, aluminum c h l o r i d e i s p r e f e r r e d over the other a c i d s , although a c o - c a t a l y s t or promoter i s u s u a l l y needed t o o b t a i n e f f i c i e n t a l k y l a t i o n . A 1 C 1 when d i s s o l v e d i n benzene c o n t a i n i n g some HC1 forms a complex which can be s i m p l y d e s c r i b e d a s : 2

3

3

H

H

341

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

342

INDUSTRIAL

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

T h i s complex then r e a c t s

AND LABORATORY

with ethylene to give

ALKYLATIONS

ethylbenzene.

The a l k y l a t i o n r e a c t i o n i s c o m p l i c a t e d by the o c c u r r e n c e o f minor s i d e r e a c t i o n s such as c r a c k i n g , p o l y m e r i z a t i o n , hydrogen transfer, etc. However, o f major importance i s the f o r m a t i o n o f polyalkylated products. The f i r s t a l k y l group formed a c t i v a t e s t h e a r o m a t i c n u c l e u s so t h a t the second a l k y l a t i o n proceeds more r e a d i l y than the f i r s t and so on a t l e a s t u n t i l s t e r i c h i n d r a n c e i n t e r v e n e s , although hexaethylbenzene i s q u i t e r e a d i l y formed. T h i s r e s u l t s i n a r e a c t i o n p r o d u c t c o n t a i n i n g a m i x t u r e o f mono, d i , t r i , and h i g h e r e t h y l b e n z e n e s t o g e t h e r w i t h u n r e a c t e d benzene. The r a t i o o f e t h y l e n e t o benzene i n t h e r e a c t o r f e e d c a n , o f c o u r s e , be chosen to maximize the f o r m a t i o n o f monoe t h y l benzene; but the o t h e r p r o d u c t s cannot be e l i m i n a t e d . F o r t u n a t e l y , the r e a c t i o n i s r e v e r s i b l e , e . g . , d i e t h y l benzene w i l l r e a c t w i t h benzene under the i n f l u e n c e o f A 1 C 1 to form monoethylbenzene. 3

CôHsCCaHs^

+

ΟβΗε ^

2

CoHs'L^Hs

T h i s t r a n s a l k y l a t i o n r e a c t i o n p e r m i t s v i r t u a l l y a l l the e t h y l e n e and benzene f e d to the r e a c t i o n system t o appear e v e n t u a l l y as t h e monoethylbenzene p r o d u c t ; the r e a c t i o n was f i r s t demonstrated in 1 8 9 4 . ( 1 ) The e q u i l i b r i u m amounts o f t h e v a r i o u s p r o d u c t s a r e shown i n T a b l e I . The a l k y l a t i o n r e a c t i o n can be performed under two r a t h e r different conditions. I f , f o r example, i n a w e l l - s t i r r e d l a b o r a t o r y s e m i - b a t c h r e a c t o r a g i v e n amount o f e t h y l e n e i s added r a p i d l y to the benzene under g i v e n r e a c t i o n c o n d i t i o n s such t h a t t h e e t h y l e n e i s c o m p l e t e l y a b s o r b e d , i t w i l l be found t h a t the p r o d u c t formed i m m e d i a t e l y a f t e r a l l e t h y l e n e i s added i s r e l a t i v e l y r i c h i n h i g h e r p o l y e t h y l b e n z e n e s and r e l a t i v e l y poor i n t h e d e s i r e d monoethylbenzene. However, i f the same amount o f e t h y l e n e i s added r e l a t i v e l y s l o w l y to a n o t h e r batch o f benzene, t h e r e a c t i o n p r o d u c t w i l l be r e l a t i v e l y r i c h i n monoethylbenzene and poor i n the u n d e s i r e d p o l y e t h y l b e n z e n e s . The r a p i d i n i t i a l a b s o r p t i o n and r e a c t i o n o f e t h y l e n e forms p o l y e t h y l b e n z e n e s u n s e l e c t i v e l y , and t h e slow l i q u i d phase r e ­ a c t i o n o f the p o l y e t h y l b e n z e n e s w i t h u n r e a c t e d benzene r e s u l t s i n an approach towards thermodynamic e q u i l i b r i u m . That i s , although the amounts o f h i g h e r p o l y e t h y l b e n z e n e i s n e g l i g i b l e under thermo­ dynamic c o n t r o l , t h e y can be c o n s i d e r a b l y under k i n e t i c c o n t r o l .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

1. 2. 3. 4.

tr tr

tr tr

0.25

1.77 3.57

19.4 27.3

50.1 49.3

28.6 19.6

0.8

1.0

rings.

tr tr

0.02 0.09

0.72

11.9

46.8

40.6

0.6

M o l a r r a t i o o f e t h y l groups t o a r o m a t i c Ethylbenzene. T r a c e , l e s s than 0.01 wt %. C a l c u l a t e d from f r e e energy d a t a .

tr tr

tr

0.20

5.7

38.1

tr tr

56.0

Hexa-EB

Penta-EB

0.4

3

Tetra-EB tr

Tri-EB

Di-EB 0.02

2

1.5

EB 22.9

Benzene

Percentage

75.6

1

Weight

0.2

E/B

Molar Ratio

1

LIQUID PHASE *

THERMODYNAMIC EQUILIBRIA OF BENZENE AND ETHYLBENZENES

TABLE I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

344

INDUSTRIAL

Commercial

Alkylation

AND

LABORATORY

ALKYLATIONS

Process

Emmet R e i d and h i s c o - w o r k e r s a t Johns Hopkins demonstrated i n the 1920's the p r a c t i c a l i t y o f u s i n g e t h y l e n e f o r e t h y l b e n z e n e p r e p a r a t i o n w i t h the l i q u i d A1C1 c a t a l y s t . I t was, however, Dow Chemical i n t h e U n i t e d S t a t e s who d e v e l o p e d the F r i e d e l - C r a f t s r e a c t i o n w i t h A1C1 i n t o a c o n t i n u o u s e t h y l b e n z e n e m a n u f a c t u r i n g p r o c e s s i n 1937. BASF were a l s o s i m i l a r l y a c t i v e i n Germany i n the 1930"s. Dow showed t h e importance o f HC1 as a promoter and t h e n e c e s s i t y o f m a i n t a i n i n g s t r i c t l y anhydrous c o n d i t i o n s . The Dow p r o c e s s o p e r a t e d a t about 95°C and a t a s m a l l p o s i t i v e pressure. In 1942, w i t h the c u t o f f o f n a t u r a l r u b b e r s u p p l i e s from the P a c i f i c a r e a , a r a p i d i n c r e a s e i n s t y r e n e c a p a c i t y was required. Monsanto o p e r a t e d a p l a n t a t Texas C i t y f o r t h e government t h a t used t h e i r own v e r s i o n o f F r i e d e l - C r a f t s c h e m i s t r y f o r the ethylbenzene s t e p . C a r b i d e a l s o i n s t a l l e d t h e i r own A1C1 p r o c e s s a t I n s t i t u t e , West V i r g i n i a . Dow Chemical expanded t h e i r o r i g i n a l e t h y l b e n z e n e p r o d u c t i o n c a p a c i t y by b u i l d i n g i n Los A n g e l e s , C a l i f o r n i a , and F r e e p o r t , T e x a s . The v a r i o u s e t h y l b e n z e n e p r o c e s s e s , a l t h o u g h having i n d i v i d ual d i f f e r e n c e s , a l l seemed t o have been based on s i m i l a r principles. I n v a r i a b l y p r e s e n t were t h r e e p h a s e s — e t h y l e n e g a s , a r o m a t i c l i q u i d , and a l i q u i d c a t a l y s t complex. R e a c t i o n took p l a c e i n t h e c a t a l y s t complex, and e q u i l i b r i u m was e s t a b l i s h e d between t h e c a t a l y s t complex and the o r g a n i c p h a s e . The l i q u i d r e a c t i o n p r o d u c t was then c o o l e d and the two l i q u i d l a y e r s separated. The lower c a t a l y s t complex l a y e r was r e c y c l e d t o the r e a c t i o n system. A1C1 was l o s t from the system i n two ways, by s o l u b i l i t y i n the o r g a n i c l a y e r and by withdrawal o f a s l i p s t r e a m o f c a t a l y s t complex t o a l l o w a d d i t i o n o f f r e s h c a t a l y s t . The c a t a l y s t complex was then h y d r o l y z e d s e p a r a t e l y t o produce an aqueous A 1 C 1 waste s o l u t i o n and an o r g a n i c l a y e r which was added back t o t h e s y s t e m . The o r g a n i c r e a c t i o n p r o d u c t from t h e a l k y l a t i o n s t e p was washed t o remove d i s s o l v e d A1C1 and HC1. The washed a l k y l a t e was s e p a r a t e d i n t o i t s components i n a s e r i e s o f three d i s t i l l a t i o n columns. T h i s then i s the w e l l proven A 1 C 1 p r o c e s s t h a t i s p r e s e n t l y w i d e l y used i n v e r y l a r g e p l a n t s around the w o r l d . 3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

3

3

3

3

3

3

Disadvantages

o f Commercial

Process

S t y r e n e , and thus e t h y l b e n z e n e , a r e now commodity c h e m i c a l s . Economics have f o r c e d m a n u f a c t u r e r s t o c o n s t r u c t modern, h i g h l y e n g i n e e r e d p r o d u c t i o n u n i t s w i t h c a p a c i t i e s o f 1,000 m i l l i o n pounds/year and h i g h e r . T h u s , the b a s i c c h e m i s t r y and the manuf a c t u r i n g t e c h n i q u e s have t o be c l o s e l y s c r u t i n i z e d i n the l i g h t o f p r e s e n t day raw m a t e r i a l s h o r t a g e s , energy c o s t s , p r o d u c t p u r i t y demands, and e n v i r o n m e n t a l c o n s i d e r a t i o n s . In t h e s e b i l l i o n pound/year p l a n t s , r e l a t i v e l y small improvements can o f t e n l e a d t o i m p o r t a n t money s a v i n g s p r o v i d e d they a r e r e l i a b l e

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

21.

M A C F A R L A N E

Ethylbenzene

345

Process

and w e l l d e m o n s t r a t e d . In p l a n t s o f t h i s s i z e , not v e r y much u n c e r t a i n t y can be p e r m i t t e d . In some v e r s i o n s o f the e t h y l b e n z e n e m a n u f a c t u r i n g p r o c e s s , F i g u r e 1, a r e l a t i v e l y l a r g e volume o f c a t a l y s t complex, a f t e r c o o l i n g and s e p a r a t i o n from the a l k y l a t e , i s r e c y c l e d through t h e a l k y l a t o r to moderate the temperate r i s e o f t h e e x o t h e r m i c r e a c t i o n by a c t i n g as a heat s i n k . ( 2 ^ , 4 ) The c a t a l y s t c o m p l e x , however, tends to a b s o r b p r e f e r e n t i a l l y t h e h i g h e r p o l y e t h y l benzenes. These a r e then s u b j e c t e d t o a h i g h l y r e a c t i v e e n v i r o n ment a t an e l e v a t e d t e m p e r a t u r e f o r a f a i r l y l o n g a v e r a g e residence time. I t i s , t h u s , not s u r p r i s i n g t h a t such a system tends t o make c o n s i d e r a b l e p o l y m e r s , h i g h b o i l e r s , and t a r s . T h i s not o n l y l e a d s to a s i g n i f i c a n t l o s s i n y i e l d but a l s o to a h i g h e r than n e c e s s a r y usage o f aluminum c h l o r i d e c a t a l y s t , s i n c e the t a r s t i e up the c a t a l y s t i r r e v e r s i b l y and so r e n d e r i t inactive. T h u s , even more o f the c a t a l y s t complex has t o be withdrawn from t h e s y s t e m . The p r e s e n c e o f i n c r e a s e d amounts o f i m p u r i t i e s a l s o tends t o produce a r e l a t i v e l y impure e t h y l benzene p r o d u c t w i t h many o f t h e s e i m p u r i t i e s c a r r y i n g a l l the way through t o the p r o d u c t s t y r e n e . T h i s c a t a l y s t complex stream i s a l s o v e r y c o r r o s i v e and r e q u i r e s h i g h a l l o y m a t e r i a l s o f c o n s t r u c t i o n i n p i p i n g and equipment h a n d l i n g the complex. Improved A l k y l a t i o n

Process

A few y e a r s ago Monsanto a t Texas C i t y , T e x a s , d e c i d e d t o re-examine i t s p o s i t i o n i n e t h y l b e n z e n e m a n u f a c t u r e . Other proc e s s e s were a v a i l a b l e o r were becoming a v a i l a b l e a n d , as we have s e e n , t h e A l CI 3 c h e m i s t r y was q u i t e a n c i e n t . An e x a m i n a t i o n o f the o t h e r p r o c e s s e s r e v e a l e d t h a t they too p o s s e s s e d c e r t a i n serious shortcomings. One o f many p o t e n t i a l problems w i t h a new p r o c e s s i s the r i s k i n v o l v e d i n b e i n g t h e f i r s t t o b u i l d a 1.7 b i l l i o n l b / y e a r EB p l a n t u s i n g a not f u l l y proven t e c h n o l o g y . 1.7 b i l l i o n times a l m o s t a n y t h i n g i s a l o t o f money to be made o r l o s t so we had t o be s u r e t h a t any change was to the most economi c a l process a v a i l a b l e . We c o n c l u d e d t h a t r a t h e r than abandon the o l d A I C I 3 t e c h n o l o g y we ought f i r s t t o g i v e i t a f a i r chance and t r y t o d r a s t i c a l l y improve i t . T h u s , we d e c i d e d t o t a k e a new l o o k a t the b a s i c F r i e d e l - C r a f t s c h e m i s t r y . As a r e s u l t o f t h i s , we have d e v e l o p e d and c o m m e r c i a l i z e d a p r o c e s s u s i n g the b a s i c A1C1 c a t a l y s t but w i t h c h e m i s t r y i n an a r e a c o m p l e t e l y d i f f e r e n t from t h a t p r e v i o u s l y u s e d . T h i s new homogeneous process e l i m i n a t e s o r g r e a t l y reduces most o f t h e problems a s s o c i a t e d w i t h the two-phase s y s t e m . 3

The Monsanto Texas C i t y l a b o r a t o r y d i s c o v e r e d t h a t e t h y l e n e would r e a c t c o m p l e t e l y and v i r t u a l l y i n s t a n t a n e o u s l y w i t h benzene c o n t a i n i n g o n l y a small amount o f d i s s o l v e d A 1 C 1 . The A I C I 3 i s used o n l y once and t h e r e i s no r e c y c l e . In t h i s homogeneous a l k y l a t i o n s y s t e m , c a r e has to be taken t o m i n i m i z e the f o r m a t i o n o f the h i g h e r e t h y l benzenes. These compounds a r e more b a s i c than 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Dry Benzene

or HC1

Ethyl Chloride

Polyethyl benzenes

Figure 1.

cw

Ethylbenzene alkyhtion (two liquid phases)

Catalyst Complex

Alkylator

Ethylene

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

Separator

to Wash System

Alkylate

21.

Ethylbenzene

M A C F A R L A N E

Process

347

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benzene, i n a Lewis s e n s e . In f a c t , the t e t r a e t h y l b e n z e n e s a r e p r o b a b l y b a s i c enough to t i e up the small amount o f aluminum c h l o r i d e c a t a l y s t p r e s e n t as a r e l a t i v e l y s t a b l e s a l t , thus s t o p p i n g the a l k y l a t i o n . D o e r i n g , e t a l , ( 5 ) i n 1958 had shown t h a t c a t a l y s t s i n r e a c t i o n s o f t h e F r i e d e l - C r a f t s type r a p i d l y become i n a c t i v a t e d due t o the p r e s e n c e o f h i g h e r a l k y l a t e d b e n z e n e s . F o r example, when working w i t h methyl b e n z e n e s , they showed t h a t a h e p t a m e t h y l benzenium i o n even more b a s i c than penta and hexamethylbenzene c o u l d be formed. T h i s heptamethyl i o n was so b a s i c t h a t i t was even e x t r a c t a b l e by aqueous h y d r o c h l o r i c a c i d ! S i n c e o n l y a small amount o f aluminum c h l o r i d e i s used i n t h i s homogeneous a l k y l a t i o n p r o c e s s , more c a r e has t o be taken t o c o n t r o l the method and r a t e o f a d d i t i o n o f e t h y l e n e t o the benzene. The a l k y l a t i o n r e a c t i o n v e s s e l i s d e s i g n e d t o accommod a t e s i m u l t a n e o u s l y both the v e r y r a p i d e t h y l e n e - b e n z e n e r e a c t i o n and the r e l a t i v e l y slow p o l y e t h y l b e n z e n e t r a n s a l k y l a t i o n r e a c tions. By c a r e f u l d e s i g n o f the r e a c t o r and c o n t r o l o f o p e r a t i n g c o n d i t i o n s , the f o r m a t i o n o f h i g h e r p o l y e t h y l b e n z e n e s can be minimized. The absence o f a c a t a l y s t complex phase has c e r t a i n a d v a n t ages. The a l k y l a t i o n t e m p e r a t u r e i s no l o n g e r l i m i t e d t o the 100°C r a n g e . Much h i g h e r t e m p e r a t u r e s can now be used w i t h o u t e x c e s s i v e y i e l d l o s s e s , t a r f o r m a t i o n , e t c . , and w i t h o n l y a moderate A1C1 usage i n o r d e r t o m a i n t a i n h i g h c a t a l y t i c a c t i v i t y . The use o f h i g h e r t e m p e r a t u r e s i n a l k y l a t i o n a l s o p e r m i t s r e c o v e r y o f the heat o f r e a c t i o n i n a waste heat b o i l e r , g e n e r a t i n g steam a t a u s e f u l p r e s s u r e . T h i s steam has a s i g n i f i c a n t e f f e c t on the e c o n o m i c s . The h i g h e r t e m p e r a t u r e s a l s o p e r m i t d e c r e a s e d use o f aluminum c h l o r i d e . A d d i t i o n a l l y , i t a l s o leads to a l e s s c o r r o s i v e environment. The t r a n s a l k y l a t i o n and i s o m e r i z a t i o n r e a c t i o n s can be s a t i s f a c t o r i l y e x p l a i n e d by t h e S t r e i t w i e s e r mechanism((5). This mechanism proposes a 1 , 1 - d i p h e n y l e t h a n e - t y p e i n t e r m e d i a t e . For example, p a r a - d i e t h y l b e n z e n e . ( F i g u r e 3) Such an i n t e r m o l e c u l a r mechanism i s c o n s i s t e n t w i t h t h e e x p e r i m e n t a l d a t a and does not r e q u i r e the assumption o f a sequence o f i n t r a m o l e c u l a r 1,2 s h i f t s . The decay o f the p o l y e t h y l b e n z e n e s towards e q u i l i b r i u m i s c o n s e c u t i v e and not c o n c u r r e n t . The c a t a l y s t seems t o be a s s o c i a t e d w i t h the most b a s i c c e n t e r ; and when i t r e a c h e s s t e a d y - s t a t e , the c a t a l y s t t r a n s f e r s t o t h e next most b a s i c o n e . There i s a l s o a c o n c u r r e n t i n t r a m o l e c u l a r i s o m e r i z a t i o n such as 1 , 2 , 4 t r i e t h y l benzene g o i n g t o 1 , 3 , 5 t r i e t h y l benzene. T h e r e i s hence a movement towards isomer e q u i l i b r i u m as w e l l as p r o d u c t e q u i l i b r i u m . Monsanto's r e a c t o r l a y o u t , i n s i m p l i f i e d f o r m , i s shown i n F i g u r e 2. Dry benzene, e t h y l e n e , c a t a l y s t , and promoter a r e f e d c o n t i n u o u s l y to t h e r e a c t o r . The a l k y l a t o r e f f l u e n t i s mixed w i t h p o l y e t h y l b e n z e n e s , m a i n l y d i e t h y l benzene r e c y c l e d from the s u b s e quent r e c o v e r y s y s t e m . The t r a n s a l k y l a t o r a l l o w s enough r e s i d e n c e time f o r the p r o d u c t to approach e q u i l i b r i u m . The aluminum 3

American Chemical Society Library 1155 16th St., M-W. Washington, D.C. 20036 In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Polye thylben zene s Recycle

Ethylene Dry Benzene ' Alkylate

HC1

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AlClo

Alkylator Figure 2.

Transalkvlator

Alkyhtor reactor scheme (single liquid phase)

c

Figure 3.

Disproportionation of p-diethylbenzene

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c h l o r i d e c a t a l y s t i s f e d to t h e a l k y l a t o r i n v e r y small amounts together with the feed m a t e r i a l s . The a l k y l a t e d hydrocarbon p r o d u c t i s no l o n g e r s a t u r a t e d w i t h A 1 C 1 . The A1C1 f e d i s used once t h r o u g h o n l y . The m a t e r i a l l e a v i n g t h e t r a n s a l k y l a t o r i s a d i a b a t i c a l l y f l a s h e d by s i m p l e p r e s s u r e r e d u c t i o n ( F i g u r e 4 ) . The f l a s h e d o r g a n i c s and HC1 a r e r e c o v e r e d and r e c y c l e d t o t h e a l k y l a t o r while o f f - g a s i s f l a r e d o r burned. With h i g h p u r i t y e t h y l e n e , t h e o f f - g a s stream i s v e r y small s i n c e a l l the e t h y l e n e i s r e acted. However, w i t h low p u r i t y e t h y l e n e , t h e o f f - g a s becomes s i g n i f i c a n t and has a p p r e c i a b l e f u e l v a l u e . Recovery and r e c y c l e o f HC1 a l l o w s c o n t r o l o f t h i s o p e r a t i n g v a r i a b l e o v e r a wide range w h i l e s t i l l m a i n t a i n i n g v e r y low u s a g e . The major v e s s e l s i n t h e r e a c t i o n system a r e c o n s t r u c t e d o f b r i c k - l i n e d carbon steel. The use o f h i g h e r a l l o y s i s r e q u i r e d o n l y f o r r e l a t i v e l y s h o r t runs o f p i p e and f o r the a l k y l a t o r w a s t e - h e a t b o i l e r .

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Purification

o f Crude

3

Ethylbenzene

The p u r i f i c a t i o n o f t h e l i q u i d a l k y l a t e from t h e r e a c t i o n system i s done i n a c o n v e n t i o n a l f a s h i o n ( F i g u r e 5 ) . Before f e e d i n g the c r u d e e t h y l b e n z e n e t o d i s t i l l a t i o n , t h e aluminum c h l o r i d e and t h e r e s i d u a l HC1 must be c o m p l e t e l y removed. Water washing a c c o m p l i s h e s most o f t h i s t a s k ; f i n a l t r a c e s a r e removed by a c a u s t i c soda t r e a t m e n t . This process i s completely r e l i a b l e , i s f r e e from e m u l s i o n f o r m a t i o n , and t h e r e i s no downstream f o u l i n g o r c o r r o s i o n t o worry a b o u t . The washed a l k y l a t e i s f e d t o a s e r i e s o f t h r e e d i s t i l l a t i o n columns where benzene, e t h y l b e n z e n e , and d i e t h y l b e n z e n e - t r i e t h y l benzene m i x t u r e s a r e removed as overhead p r o d u c t s . The benzene i s r e c y c l e d t o the benzene d r y i n g column b e f o r e f e e d i n g a g a i n to the a l k y l a t o r . The d i e t h y l benzene m i x t u r e i s r e c y c l e d t o t h e transalkylator. The bottoms from the l a s t column i s what we c a l l "flux o i l . " This c o n s i s t s mainly of diphenyl ethanes. The amount o f t h i s m a t e r i a l i s good measure o f the o v e r a l l p r o c e s s y i e l d . The y i e l d l o s s i n t h i s p r o c e s s , depending on the a l k y l a t i o n system d e s i g n and c o n t r o l , i s between 0 . 6 and 0 . 9 l b f l u x o i l per 100 l b e t h y l b e n z e n e . Steam i s g e n e r a t e d by w a s t e - h e a t boilers. These t o g e t h e r w i t h t h e a l k y l a t i o n r e a c t o r w a s t e - h e a t b o i l e r a c c o u n t f o r 90 p e r c e n t o f the energy r e q u i r e d f o r t h e e n t i r e ethylbenzene u n i t . Catalyst

Manufacture

The aluminum c h l o r i d e c a t a l y s t f o r the a l k y l a t i o n p r o c e s s may be purchased m a t e r i a l o r t h e aluminum c h l o r i d e may be prepared i n s i t u . For l a r g e p l a n t s p r e p a r a t i o n i n s i t u from cheap powdered aluminum and anhydrous HC1 j s p r e f e r r e d ; however, e t h y l c h l o r i d e i s j u s t as e f f e c t i v e as HC1 a l t h o u g h more expensive. A small supplementary a g i t a t e d v e s s e l i s used t o

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

HC1

Benzene Ethylene Catalyst 1 Steam

Zone

Condenser

Flash-gas Absorber

Flash

Alkylationflowdiagram

Polyethylbenzene Recycle

TransAlky la tor

Figure 4.

Waste-heat Boiler

w

Alkylator

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Benzene

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Ethylene

Flux O i l

CZ=H Catalyst Preparation

Figure 5.

A1C1

3

Ethylbenzeneflowdiagram

• C2H5CI «• C H5'C H5 + Catalys t Complex • A l k y l a t e 6

2

(or HC1)

C

Figure 6.

2

H

5

Catalyst complex preparation

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p r e p a r e t h e c a t a l y s t i n t h e form o f t h e heavy l i q u i d c a t a l y s t complex o f f i x e d c o m p o s i t i o n [ 0 Η ^ Η ι , · Α ΐ 2 Π ~ ] ( F i g u r e 6 ) . T h i s i s a most c o n v e n i e n t way to h a n d l e , pump, and meter the a d d i t i o n o f the A 1 C 1 c a t a l y s t to t h e a l k y l a t o r , where i t promptly d i s s o l v e s i n the benzene m i x t u r e g i v i n g a c o m p l e t e l y homogeneous solution. 2

5

6

+

7

3

Spent C a t a l y s t

Disposal

The aluminum c h l o r i d e c a t a l y s t used i n the a l k y l a t i o n i s f i n a l l y r e j e c t e d from t h e system as an a c i d i c aqueous s o l u t i o n . T h i s b y - p r o d u c t A 1 C 1 i s u s u a l l y b e s t used f o r waste water t r e a t ­ ment. S a l e o r use o f t h i s m a t e r i a l i s o f t e n as an alum o r copperas s u b s t i t u t e i n water c l a r i f i c a t i o n . I t i s a l s o used i n U . S . m u n i c i p a l sewage t r e a t m e n t p l a n t s , where a v a l u a b l e s i d e e f f e c t i s phosphate r e m o v a l . In Japan i t i s c o n v e r t e d t o p o l y aluminum c h l o r i d e (PAC) and used f o r water t r e a t m e n t . O t h e r uses f o r t h i s aqueous aluminum c h l o r i d e stream e x i s t . The Monsanto Texas C i t y p l a n t chooses t o use an e v a p o r a t i v e t r e a t m e n t f o r aqueous A 1 C 1 e f f l u e n t from t h e wash s y s t e m . ( 7 } T h i s c o n c e n t r a t e s the A1C1 and r e c o v e r s the HC1 as m u r i a t i c acid. T h i s l a t t e r m a t e r i a l i s , o f c o u r s e , v e r y u s e f u l i n the r e g e n e r a t i o n o f z e o l i t e water t r e a t i n g b e d s . An a d d i t i o n a l advantage o f t h e e v a p o r a t i v e t r e a t m e n t i s t h e freedom o f t h e c o n c e n t r a t e d b y - p r o d u c t A1C1 from p o s s i b l e o r g a n i c c o n t a m i n a t i o n . The i n c r e a s e d markets f o r aqueous aluminum c h l o r i d e c o u p l e d w i t h t h e d e c r e a s e d A 1 C 1 r e q u i r e m e n t s i n t h e homogeneous a l k y l a t i o n p r o c e s s a r e such t h a t d i s p o s a l o f t h i s b y - p r o d u c t i s not f o r e s e e n as a p r o b l e m .

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3

3

3

3

3

Kinetic

Modeling

T h i s homogeneous v e r s i o n o f t h e c l a s s i c F r i e d e l - C r a f t s A 1 C 1 c h e m i s t r y has a n o t h e r i n t e r e s t i n g b y - p r o d u c t ; t h a t i s , t h e development o f an a c c u r a t e k i n e t i c model o f the r e a c t i o n . Earlier attempts t o model the r e a c t i o n w i t h t h e heavy c a t a l y s t complex phase p r e s e n t were u n s a t i s f a c t o r y . The i n f o r m a t i o n used i n b u i l d i n g t h e p r e s e n t m o d e l , and i t might be added f o r d e s i g n i n g the p l a n t , was g a i n e d from a o n e - l i t e r l a b o r a t o r y a u t o c l a v e opera­ t i n g under s e m i - b a t c h c o n d i t i o n s and a l s o from a f u l l y automated bench u n i t u s i n g r e a c t o r s w i t h d i a m e t e r s o f 1 1/2 i n c h e s . The m o d e l i n g work went hand i n hand w i t h t h e new i n s i g h t g a i n e d i n t o t h e chemical r e a c t i o n s t a k i n g p l a c e i n the s y s t e m . Two i m p o r t a n t p r e m i s e s made were f i r s t , t h a t t h e a l k y l a t i o n was an i r r e v e r s i b l e r e a c t i o n w i t h t r a n s a l k y l a t i o n a s e p a r a t e and independent r e a c t i o n , and s e c o n d , t h a t t h e r e a c t i o n r a t e o f molec­ u l a r e t h y l e n e i n the l i q u i d was not r a t e c o n t r o l l i n g as l o n g as the c o n c e n t r a t i o n s o f t h e h i g h e r p o l y e t h y l b e n z e n e s were low. This a l l o w e d t h e k i n e t i c c o n s t a n t s f o r the t r a n s a l k y l a t i o n model t o be e v a l u a t e d from t r a n s a l k y l a t i o n d a t a ; when t h e combined a l k y l a t i o n 3

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t r a n s a l k y l a t i o n model was f i t t e d to a l k y l a t i o n d a t a , o n l y the r e l a t i v e r e a c t i o n r a t e s o f the benzene, e t h y l b e n z e n e and p o l y e t h y l benzenes had to be e v a l u a t e d i n terms o f the p r o c e s s variables. The r e s u l t i n g k i n e t i c model e x t r a p o l a t e s c o r r e c t l y t o extreme v a l u e s o f r e a c t i o n c o n d i t i o n s and a l s o a c c u r a t e l y f i t s the a r e a o f p r a c t i c a l i n t e r e s t now used i n the o p e r a t i n g plant. Choice o f Operating

Conditions

The major v a r i a b l e s c o n t r o l l i n g the a l k y l a t i o n and t r a n s a l k y l a t i o n r e a c t i o n s a r e as f o l l o w s : TABLE

II

A 1 C 1 Catalyst Concentration HCl Promoter C o n c e n t r a t i o n Temperature R e s i d e n c e Time E/B M o l a r R a t i o ( E t h y l Groups/Benzene Pressure

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Rings)

The d e t a i l e d mathematical model o f the chemical r e a c t i o n s has r e v e a l e d t h e p r e s e n c e o f c e r t a i n r e l a t i v e l y sharp optima f o r these r e a c t i o n v a r i a b l e s . I f , f o r example, i t i s d e s i r e d t o reduce t h e A 1 C 1 usage t o a minimum v a l u e , then the k i n e t i c model can be used t o show the e f f e c t o f each o f the v a r i a b l e s on t h e A I C I 3 c a t a l y s t c o n c e n t r a t i o n . To make t h e comparison e f f e c t i v e , i t s h o u l d be made a t the same q u a l i t y o f a l k y l a t e . T h i s , f o r example, can be c o n v e n i e n t l y e x p r e s s e d as the c o n c e n t r a t i o n o f t e t r a e t h y l b e n z e n e i n the product. I t w i l l be r e c a l l e d t h a t i n t h e homogeneous system the amounts o f h i g h e r p o l y e t h y l b e n z e n e s must be s e v e r e l y r e s t r i c t e d because o f t h e i r r e l a t i v e l y basic nature. F i g u r e 7 shows a p l o t o f p e r c e n t t e t r a e t h y l b e n z e n e v e r s u s temperature a t v a r i o u s A 1 C 1 usages. The graph shows t h a t a t g i v e n p e r c e n t a g e the A 1 C 1 requirements can be reduced by i n c r e a s e s i n t e m p e r a t u r e . For s i m p l i c i t y o f p r e s e n t a t i o n , the o t h e r v a r i a b l e s have been h e l d c o n s t a n t . 3

3

3

S i m i l a r l y , F i g u r e 8 shows the e f f e c t o f l i q u i d r e s i d e n c e time on the A 1 C 1 requirements. The graphs showing t h e e f f e c t s o f the o t h e r v a r i a b l e s on A I C I 3 usage a l l show t h e same t y p e o f c u r v e s w i t h f a i r l y p r o nounced b r e a k p o i n t s . I t i s , o f c o u r s e , most advantageous t o operate at or c l o s e to the b r e a k p o i n t s . The homogeneous a l k y l a t i o n p r o c e s s a l l o w s a s u r p r i s i n g l y wide range o f o p e r a t i o n . Changes i n one o r more o f the v a r i a b l e s can be used t o m i n i m i z e a n o t h e r o f the v a r i a b l e s . T h u s , t h e r e a c t i o n c o n d i t i o n s can be t a i l o r e d t o o p t i m i z e the economics f o r a p a r t i c u l a r s e t o f l o c a l conditions. For example, a p l a n t can be d e s i g n e d to o p t i m i z e t o t a l c o s t c o n s i d e r i n g c a p i t a l , raw m a t e r i a l s , c a t a l y s t , and 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Tetra E B , wt. %

Temperature, ° C

Figure 7.

Alkylator—effect of temperature

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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Ethylbenzene

Process

Tetra E B , wt. %

Residence Time, minutes

Figure 8.

Alkyhtor—effect of residence time

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LABORATORY

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utilities. Once the p l a n t i s b u i l t i t can be o p e r a t e d f o r minimum c o s t w i t h o p e r a t i n g c o n d i t i o n s changed as r e q u i r e d by c h a n g i n g e n e r g y and raw m a t e r i a l c o s t s . The homogeneous a l k y l a t i o n p r o c e s s i s a l s o a d a p t a b l e t o t h e use o f d i l u t e e t h y l e n e s t r e a m s . Here t h e a l k y l a t i o n p r e s s u r e has t o be somewhat h i g h e r , but the p r o c e s s i n g i s q u i t e s i m i l a r . A modern s t y r e n e f a c i l i t y i s c u r r e n t l y under c o n s t r u c t i o n i n A u s t r a l i a u s i n g t h i s d i l u t e C Hi* homogeneous a l k y l a t i o n p r o c e s s . 2

Conclusions I t i s c o n c l u d e d t h a t e l i m i n a t i o n o f the s e p a r a t e c a t a l y s t complex phase i n the A1C1 a l k y l a t i o n p r o c e s s adds s i g n i f i c a n t l y to i t s a t t r a c t i v e n e s s . In a d d i t i o n t o the ease w i t h which a l i q u i d phase c a t a l y s t can overcome any p o i s o n i n g and g e t back on s t r e a m , t h e new homogeneous p r o c e s s can o p e r a t e a t h i g h e r t e m p e r a t u r e s and r e c o v e r the heat o f r e a c t i o n t o g e n e r a t e steam. I t can a l s o o p e r a t e i n a l e s s c o r r o s i v e environment w h i l e p r o d u c i n g an e t h y l b e n z e n e p r o d u c t o f e x c e p t i o n a l p u r i t y and can reduce t h e amount o f aluminum c h l o r i d e r e q u i r e d s e v e r a l f o l d . The p a y o f f i n any development such as t h i s i s i n u l t i m a t e plant operation. T h i s p r o c e s s was c o n c e i v e d i n the l a b o r a t o r y and s c a l e d up w i t h a good u n d e r s t a n d i n g o f t h e b a s i c c h e m i s t r y . The new a l k y l a t i o n p r o c e s s has been i n o p e r a t i o n a t M o n s a n t o ' s Texas C i t y p l a n t s i n c e F e b r u a r y 1974. T y p i c a l operating data a r e shown i n T a b l e I I I . I t i s b e l i e v e d t o be t h e w o r l d ' s largest s i n g l e - t r a i n a l k y l a t o r (Figure 9). I t has a demonstrated c a p a c i t y o f 30% to 115% o f d e s i g n and has o p e r a t e d e x t r e m e l y smoothly s i n c e s t a r t u p w i t h o u t p r o c e s s o r m e c h a n i c a l p r o b l e m s . O p e r a t i o n s have been c h a r a c t e r i z e d by low maintenance c o s t s and low c a t a l y s t u s a g e . We a r e w e l l p l e a s e d w i t h t h i s p r o c e s s and b e l i e v e i t t o be the b e s t proven a l k y l a t i o n a v a i l a b l e . Five companies have r e c e n t l y s e l e c t e d t h i s p a t e n t e d p r o c e s s (8) f o r i n s t a l l a t i o n around the w o r l d ; i n c l u d i n g Pemex a t t h e i r new complex a t La C a n g r e j e r a .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

3

Acknowledgement The a u t h o r wishes t o e x p r e s s h i s a p p r e c i a t i o n t o h i s c o workers on t h i s p r o j e c t , p a r t i c u l a r l y t o F. A p p l e g a t h and L. E. Dupree, f o r t h e i r s u g g e s t i o n s and a s s i s t a n c e w i t h t h i s paper.

Abstract The majority of the ethylbenzene manufactured in the world i s produced by the c l a s s i c a l Friedel-Crafts reaction involving the ethylation of benzene in the presence of aluminum chloride as a c a t a l y s t . It has been customary f o r the aluminum chloride to be present in f a i r l y large amounts as a separate heavy

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

M A C F A R L A N E

Ethylbenzene

Process

357

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

21.

Figure 9.

Single train alkylator used to produce 1.7 billion pounds of ethylbenzene per year

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

TABLE

AND

LABORATORY

ALKYLATIONS

III

TYPICAL OPERATING DATA ETHYLBENZENE FROM BENZENE AND ETHYLENE

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

Feed R e q u i r e m e n t s ,

l b / l b Ethylbenzene

(100% B a s i s )

Ethylene Benzene Co-Products,

lb/lb

0.267 0.742 Ethylbenzene

Steam Aluminum C h l o r i d e Catalysts

and C h e m i c a l s ,

Sol.,

25%

lb/lb

0.99 0.008

Ethylbenzene

Aluminum C h l o r i d e Anhydrous HC1 (a) C a u s t i c Soda (100% B a s i s )

0.0019 0.0006 0.00065

(a) May s u b s t i t u t e e t h y l c h l o r i d e on a mole f o r mole b a s i s . Utilities,

per lb

Ethylbenzene

Steam (200 p s i g ) Fuel ( L H V ) , Btu C o o l i n g Water (16°F R i s e ) , l b s P r o c e s s and B o i l e r Feed W a t e r , l b s E l e c t r i c i t y , kwh

0.037 832 23 1.11 0.013

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

21.

M A C F A R L A N E

Ethylbenzene

Process

359

catalyst complex phase which i s subsequently separated from the alkylated organics layer and continuously recycled to the alky­ l a t o r . This catalyst complex phase has been found to be not only unnecessary but actually harmful i n obtaining maximum y i e l d s , purity, and minimum catalyst usage. This paper describes the s i n g l e - t r a i n Monsanto ethylbenzene unit i n s t a l l e d at Texas City having a capacity of 1.7 b i l l i o n pounds a year. Literature Cited (1) (2) (3)

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch021

(4) (5) (6) (7) (8)

Radziewanoski, C., Ber., 27, 3235 (1894). Hornibrook, J . N., Chem. and Ind., May 19, 1962, p. 872. Donaldson, J . W., "ETHYLENE," Chapter 11 (edited by S. A. M i l l e r ) Benn London 1969. Albright, L. F., Process f o r Major Addition Type P l a s t i c s and Their Monomers, McGraw-Hill, 1974. Doering, W. Von E., et. al., Tetrahedron, 1958, Vol. 4, p. 178. Streitweisser, Α., and Reif, L. J . , Am. Chem. S o c , 1960, 82, 5003. Campbell, D. N. This Book, Next Chapter, 1977. U.S. Patent 3,848,012 (Nov. 12, 1974) to Monsanto Company. U.S. Patent 3,899,545 (Aug. 12, 1975) to Lummus Company.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

22 T h e Use of By-Product A1C1 from an Ethylbenzene 3

Plant to Treat Potable or Process Water DAN N. CAMPBELL

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

Monsanto Chemical Intermediates Co., Texas City, TX 77590

Most of the ethylbenzene used i n the manufacture of styrene i s produced by the classical Friedel-Crafts a l k y l a t i o n . The process i n v o l v e s the r e a c t i o n o f benzene and ethylene i n the presence of an anhydrous aluminum c h l o r i d e c a t a l y s t promoted by h y d r o c h l o r i c a c i d . An a l k y l a t i o n mixture c o n t a i n i n g mono-, di-, tri-, and higher ethylbenzenes together with unreacted benzene i s formed i n t h i s r e a c t i o n which i s separated by conventional distillation. P r i o r to feeding the a l k y l a t e to distillation, the aluminum c h l o r i d e and the h y d r o c h l o r i c a c i d are removed and recovered. The recovery of the spent a l k y l a t i o n c a t a l y s t i n v o l v e s two or three washing steps. The a l k y l a t e i s first washed (hydrolyzed) with water to remove the d i s s o l v e d A1C1 and then with d i l u t e c a u s t i c i n a second step to get rid of very small amounts o f r e s i d u a l a c i d . A t h i r d water wash may be used as a final clean-up if necessary. A by-product aqueous stream i s generated i n the first washing step that contains d i s s o l v e d HC1, a l k y l a t e and A1C1 . The uses f o r t h i s by-product depend upon its p u r i t y . I t has been used d i r e c t l y i n i n d u s t r i a l waste water t r e a t i n g and it has been shown to e f f e c t i v e l y remove phosphate from municipal sewage. In Japan it is converted to polyaluminum c h l o r i d e , a h i g h l y d e s i r a b l e coagulant f o r waste water. An a d d i t i o n a l use of t h i s m a t e r i a l i s a f f o r d e d through the use o f an evaporator system to p u r i f y the aqueous A1C1 . Such a system provides a means of recovering the HC1 as m u r i a t i c a c i d , concent r a t i n g the AICI3 and removing most of the s o l u b l e hydrocarbon contamination by water azeotroping. 3

3

1

3

360

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

22.

C A M P B E L L

Use of AlCl

to Treat Water

s

361

By-product A I C I 3 p u r i f i e d i n t h i s manner has been used as a s u b s t i t u t e f o r alum i n the paper i n d u s t r y . There i s s t i l l another economically a t t r a c t i v e use f o r t h i s m a t e r i a l . I t can be moved i n t o the more l u c r a t i v e and l a r g e r potable water t r e a t i n g markets as a replacement f o r e i t h e r alum or copperas (FeSCU). Heretofore, t h i s has not been p o s s i b l e because of hydrocarbon contaminants. This paper d e s c r i b e s a process that has been developed to upgrade the AICI3 s o l u t i o n i n t o a product that i s s u i t a b l e f o r t h i s use. The q u a l i t y of the p u r i f i e d A I C I 3 and the r e s u l t s obtained when i t was used as a coagulant in a commercial c l a r i f i e r are presented.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

PURIFICATION OF A1C1

3

CONCENTRATE

Even though the concentrated A I C I 3 by-product has been f l a s h - d i s t i l l e d , i t s t i l l contains some soluble organics (from the a l k y l a t e ) at the ppm level. These must be removed before i t can be used i n t r e a t i n g potable water because of p o s s i b l e harmful p h y s i o l o g i c a l e f f e c t s . Moreover, some p r e l i m i n a r y l a b o r a t o r y work has i n d i c a t e d that a 27% AICI3 s o l u t i o n c o n t a i n i n g as l i t t l e as 1 ppm benzene can impart odor to the t r e a t e d water. The data suggest that the nose can detect benzene i n water at a c o n c e n t r a t i o n of 10 p a r t s per t r i l l i o n . There are two obvious ways of removing the remaining hydrocarbon contamination. M u l t i - s t a g e s t r i p p i n g could be used but the most economical and simplest method i s to add a carbon bed adsorpt i o n step to the process as i n d i c a t e d i n Figure 1. Carbon bed removal can be j u s t i f i e d only i n conjunct i o n with the evaporator system where the hydrocarbon contamination i s very low. The c o n c e n t r a t i o n of s o l u b l e organic components i n a system where the evaporator i s not used i s simply too high and the bed i s exhausted too q u i c k l y . A f i b e r - p l a s t i c column, 1 foot i n diameter, f i l l e d with 12 f e e t of Calgon Corporation's CPG a c t i v a t e d carbon was used to prepare hydrocarbonfree A I C I 3 f o r a t e s t . This column was used simply because i t was a v a i l a b l e and a much l a r g e r diameter column with l e s s height would be designed f o r a commercial u n i t . A r e l a t i v e l y f a s t flowrate of 1 gal/min was used i n the adsorption column.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

362

INDUSTRIAL

AND LABORATORY

WASHED ALKYLATE

ALKYLATIONS

ORGANICS & AQUEOUS HCI

WATER

ALKYLATE WASH AQUEOUS AICI3

Commercial purification of AlCl solution s

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

Figure 1.

Figure 2.

Hydrocarbons in carbon bed feed

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

22.

C A M P B E L L

Use of AlCl

s

to Treat Water

363

A n a l y t i c a l r e s u l t s f o r the A1C1 s o l u t i o n before and a f t e r carbon treatment are shown i n Table I. 3

Table I ORGANICS IN BY-PRODUCT 27% A1C1

Contaminant

Feed, ppm

Ci-Ci* Non-Aromatics

0.19

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

Benzene

3

SOLUTION

Carbon Bed E f f l u e n t , ppm 0.0242

24.5

<0.0001*

Ethylbenzene

2.5

<0.0002*

Diethylbenzene

0.2

<0.0005*

Polynuclear Aromatics

-

<0.003*

Organic C h l o r i d e s

-

<0.003*

*None Detected Polynuclear aromatics i n the e f f l u e n t were determined by hexane e x t r a c t i o n and u l t r a v i o l e t absorption of the concentrated e x t r a c t . Benzene and the other low b o i l i n g organics were analyzed by vapor phase ( N 2 ) p a r t i t i o n i n g and gas chromatography. Suspended s o l i d s which are not shown i n t h i s data were i n the 100-200 mg/1 range. A c a r t r i d g e f i l t e r w i l l reduce the s o l i d s to the 50 mg/1 u s u a l l y s p e c i f i e d by producers o f a c t i v a t e d carbon very e a s i l y . As i n d i c a t e d i n Table I, only a very small amount of methane through butane (C1 -Ci» NonAromatics) remained i n the carbon bed e f f l u e n t . And as to be expected the carbon had a high a f f i n i t y f o r the aromatics. The gas chromatograph s t r i p chart i n Figure 2 i l l u s t r a t e s the s e n s i t i v i t y o f the gas chromatograph method f o r the hydrocarbons. Benzene and ethylbenzene were o f f s c a l e i n the feed whereas there was no evidence of even a t r a c e of benzene i n the carbon t r e a t e d A1C1 . 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

364

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

In some p l a n t s the aluminum c h l o r i d e c a t a l y s t i s made i n - s i t u from scrap aluminum and anhydrous HC1. Table II shows the l e v e l of m e t a l l i c components present i n the A1C1 used i n t h i s work. 3

Table II TRACE METALS IN AQUEOUS AICI3 SOLUTION Component Copper

ppm 469

Iron Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

Mercury

92 0.00007

Manganese

12

Magnesium

569

Zinc

725

Others

<5 ea.

Copper, magnesium and z i n c at the 1-2% l e v e l are normal components of scrap a i r c r a f t aluminum alloys. CLARIFIER OPERATING VARIABLES Coagulation e f f e c t i v e n e s s of the A1C1 was s t u d i e d i n a 164,000-gallon I n f i l c o A c c e l a t o r (clarifier). This commercial u n i t i s a combined c l a r i f i c a t i o n / s o f t e n i n g o p e r a t i o n u s i n g 30-35 ppm copperas, a by-product of the metal p i c k l i n g i n d u s t r y , as the coagulant. And i n a d d i t i o n , lime i s i n j e c t e d i n t o the c l a r i f i e r sludge blanket to adjust the pH to 10, r e s u l t i n g i n p r e c i p i t a t i o n of the Ca(HC0 )2 temporary hardness as CaC0 . Copperas has been the p r e f e r r e d coagulant f o r the t u r b i d and hard p l a n t raw water that i s obtained from the Brazos River. The e f f l u e n t from t h i s u n i t i s used f o r both process and potable water. 3

3

3

OPTIMUM A I C I 3

T u r b i d i t y and r e s i d u a l aluminum were the main p o i n t s of concern i n s u b s t i t u t i n g the A1C1 f o r copperas. Excess aluminum c a r r y o v e r could f o u l the i o n exchange r e s i n s i n the p l a n t d e m i n e r a l i z e r s 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

22.

C A M P B E L L

Use of AlCl

3

to Treat Water

365

and cause ΑΙΡΟι» or aluminum s i l i c a t e s c a l e i n downstream c o o l i n g equipment. Optimum coagulant treatment l e v e l was e s t a b l i s h e d f i r s t ; and as shown i n Figure 3, 10-15 ppm was most e f f e c t i v e . T u r b i d i t y and r e s i d u a l aluminum were at a minimum at these l e v e l s . Most of the t o t a l r e s i d u a l aluminum shown was f l o e carryover r a t h e r than d i s s o l v e d aluminum. This i s s i g n i f i c a n t because f l o e carryover i s r e ­ moved by an a n t h r a c i t e coal bed f i l t e r p r i o r to e n t e r i n g the potable water system. In Figure 3 the " d i s s o l v e d " aluminum was taken as that remaining i n the supernatant l i q u i d a f t e r the samples had been standing f o r 4-5 days. Aluminum analyses were done by atomic a d s o r p t i o n using a heated graphite atomizer to get r e l i a b l e low (<1 ppm! data. As i n d i c a t e d i n t h i s graph, the d i s s o l v e d aluminum was near that obtained with a copperas-treated potable water. C l a r i f i e r e f f l u e n t t u r b i d i t y l e v e l s were higher than normal [3.5 vs 3.0 nephelometric t u r b i d i t y u n i t s (NTU) f o r copperas] because the u n i t was operating with the sludge l e v e l i n the mixing chamber too low. Figure 4 i l l u s t r a t e s the e f f e c t of sludge l e v e l on t u r b i d i t y . The p o i n t s on t h i s curve were taken at 2-hour i n t e r v a l s and are s c a t t e r e d , but r e g r e s s i o n a n a l y s i s shows a good correlation. The curve i n d i c a t e s that the optimum percent sludge had not been reached. Sludge concentrations of 12-15 v o l % (measured a f t e r a 5-minute s e t t l i n g time) are normal i n t h i s u n i t with copperas. E f f e c t of pH Adjustment of the pH i n the c l a r i f i e r with lime produced s u r p r i s i n g r e s u l t s c o n s i d e r i n g the ampho­ t e r i c nature o f aluminum. At pH 8, as shown i n Figure 5, both t o t a l ( f l o e carryover + s o l u b l e ) and d i s s o l v e d aluminum were very low ( t u r b i d i t y also) but as the pH was i n c r e a s e d to 9, they i n c r e a s e d s h a r p l y . From pH 9-10, t o t a l and d i s s o l v e d aluminum decreased again. This was not expected because with NaOH aluminum i s more, not l e s s , s o l u b l e at pH 10. The data i n Figure 5 are i n r e p l i c a t e and the same phenomenon has been observed i n l a b o r a t o r y j a r t e s t a l s o . What causes t h i s has not been r e ­ solved at t h i s time. I t could be a r e s u l t of changes i n the charges at the c o l l o i d double l a y e r or

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

366

INDUSTRIAL

Figure 3. Optimum AlCl concentration (res. time = 82 min, pH = 10)

12

3

Figure 4. Effect of sludge volume (15 ppm AlCl , 82 min, pH 10)

AND

LABORATORY

16

ALKYLATIONS

20

AICI3, ppm

1

5

j

3

JÉ SLUDGE IN MIXING CHAMBER

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

28

C A M P B E L L

Use of AlCl

3

to Treat Water

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

22.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

367

368

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

C a ( A 1 0 ) 2 may have a lower s o l u b i l i t y at pH 10. Nevertheless, the lower aluminum at pH 10 i s a s i g n i f i c a n t advantage since as with copperas, c o l d lime s o f t e n i n g and c l a r i f i c a t i o n can be done i n one step. Figure 6 shows the reduction achieved i n the Brazos River water hardness as a f u n c t i o n of pH. Approximately 18 ppm l e s s hardness was obtained with the A1C1 than with copperas. S u l f u r i c a c i d , a n a t u r a l impurity of copperas, causes an increase i n permanent hardness i n lime s o f t e n i n g operations. 2

3

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

POTABILITY,

ETC.

Results of d r i n k i n g water analyses by an independent l a b o r a t o r y using standard methods of the Environmental P r o t e c t i o n Agency (EPA) are l i s t e d i n Table III f o r the A I C I 3 t r e a t e d and the raw Brazos River waters. In a l l cases, the aluminum c h l o r i d e water met EPA c r i t e r i a and i t i s potable. The EPA has been contacted about t h i s work, and i t was the opinion of one of t h e i r r e p r e s e n t a t i v e s that there i s no reason why A1C1 would not be an acceptable coagulant i n t r e a t i n g potable water. He expressed an i n t e r e s t i n g e t t i n g the work published so that the information would be a v a i l a b l e to a l l . A d d i t i o n a l analyses are given i n Table IV to i l l u s t r a t e f u r t h e r the t r e a t e d water q u a l i t y . Copper and z i n c analyses are i n c l u d e d to show that these ions are c a r r i e d down with the f l o e as would be expected. These two were the highest heavy metal contaminates of the by-product A1C1 (see Table I I ) . Zinc present i n the raw r i v e r water was a l s o removed. Brazos River water contains a r e l a t i v e l y high concentration of t o t a l organic carbon (TOC) i n the summer. Some of t h i s carbon i s removed i n the f l o e as i n d i c a t e d by both the CCE (Carbon Chloroform E x t r a c t ) and TOC. C h l o r i d e ion c o n c e n t r a t i o n i n a c l o s e d c o o l i n g water system may be concentrated as much as seven times and i t can c o n t r i b u t e to c o r r o s i o n of s t a i n l e s s s t e e l equipment. Brazos River water contains as much as 200 ppm during dry p e r i o d s . Thus, i t i s doubtful that the increased c h l o r i d e (7 ppm) would cause measurable a d d i t i o n a l c o r r o s i o n i n any case. 3

3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

22.

Use of Aid,

C A M P B E L L

to Treat Water

369

TABLE III DRINKING WATER STANDARDS-PLANT CLARIFIER TEST WITH A1C1 July 16, Ï975

EPA PROPOSED MAXIMUM, ppm

CONTAMINANT

3

RAW BRAZOS RIVER, ppm

0.05

<0.01

<0.01

Barium

1.0

<0.5

<1.0

Cadmium

1.01

<0.01

<0.01

Chromium

0.05

<0.01

<0.01

Arsenic

Fluoride Mercury Nitrate

0.2

0.05

<0.05

<0.05

0.002

<0.001

<0.001

6.65

7.3

0.01

<0.01

<0.01

0.05

<0.01

<0.05

10

Selenium Silver Turbidity,

0.4

1.4-2.4

Lead

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

A1C1 COAGULATION, ppm

3

(NTU)

1*

1

*Potable water i s

>10

filtered

Table IV ADDITIONAL WATER QUALITY ANALYSES PLANT CLARIFIER TEST WITH A I C I 3

AICI3

CONTAMINANT

MAXIMUM, ppm

COAGULATION, ppm < 0.1

Cyanide

0.5

Organics, CCE TOC

RAW BRAZOS RIVER, ppm < 0.1 2.43

81

87

TDS*

500

381

413

Chloride

250

79

72 0.15

Aluminum

1

0.3

Copper

1

< 0.01

< 0.01

Zinc

5

< 0.01

4.9

*Total dissolved s o l i d s .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

370

AND

LABORATORY

ALKYLATIONS

ECONOMICS The s i g n i f i c a n c e of the development i s that a low-value by-product from a styrene p l a n t has been upgraded to a very u s e f u l chemical. A o n e - b i l l i o n pound -per -year styrene p l a n t using the most modern technology w i l l produce approximately 2 m i l l i o n pounds of by-product aluminum c h l o r i d e . This i s enough to t r e a t the water r e q u i r e d annually by a C i t y of approximately 250,000 p o p u l a t i o n . T h i s estimate i s based upon the amount of coagulant needed to c l a r i f y the high hardness and t u r b i d i t y of waters i n Texas Brazos River. T o t a l costs of the evaporator system and the carbon bed to upgrade the by-product have been estimated to be about $0.05/lb of contained A I C I 3 . Recent potable grade copperas coagulant has been quoted at $0.10/lb d e l i v e r e d i n the Houston area and thus, the recovered A1C1 would be more than competitive. This use i n potable water t r e a t i n g a l s o w i l l provide an expanded and more s t a b l e market f o r the aqueous A I C I 3 .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch022

1

3

CONCLUSIONS In c o n c l u s i o n , the aqueous A I C I 3 from an ethylbenzene p l a n t can be upgraded to a by-product s u i t a b l e f o r use i n t r e a t i n g both process and potable water. The process i s economical, easy to operate, and a l l of the necessary e n g i n e e r i n g technology i s r e a d i l y a v a i l a b l e . REFERENCES CITED 1. C o n n e l l , C. Η., U n i v e r s i t y of Texas Medical Branch, Galveston, Texas f o r the Environmental P r o t e c t i o n Agency, "Phosphorus Removal and D i s p o s a l From Municipal Waste water," P r o j e c t No. 17010DYBO2171.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

23 A l k y l a t i o n of B e n z e n e w i t h P r o p y l e n e o v e r a Crystalline A l u m i n a Silicate E. F. HARPER

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

P. O. Box 836, Bristow, OK 74010 D. Y. KO Ε. I. du Pont de Nemours, Wilmington, DE 19899 H. Κ. LESE, Ε. T. SABOURIN, and R. C. WILLIAMSON Gulf Research & Development Co., P. O. Drawer 2038, Pittsburgh, PA 15230 There are many examples of the alkylation of aromatics with olefins to produce alkylbenzene in textbooks, the open literature, and in numerous patents. This reaction is catalyzed by both pro­ ton and Lewis acids in a homogeneous phase and in heterogeneous phases. The latter systems are characterized by both proton (H PO ) and Lewis acids (BF ) on supports and the amorphous and crystalline alumina silicates. And, the reaction has been studied extensively. However, up until the start of this investi­ gation (1969) there had not been a systematic investigation of the kinetic parameters nor an adequate catalyst aging study on the alkylation of benzene with propylene over a crystalline alumina silicate. The reaction is known to proceed through activation of the olefin by the catalyst (a rare earth exchanged Y Zeolite in this work) and this activated olefin then reacts with benzene and alkylbenzene. However, since the concentration of activated olefin is not known, the total concentration of olefin is used in obtaining kinetic parameters according to the following reactions. 3

4

3

k

l

Benzene + P r o p y l e n e

> Cumene k

(1)

2

Cumene + P r o p y l e n e

> Di-isopropylbenzene

Di-isopropylbenzenes + Benzene

k

3

k

4

>2 Cumene

<

(2) (3)

Other p o l y a l k y l b e n z e n e s a r e a l s o formed by t h e s e q u e n t i a l r e a c t i o n of d i - i s o p r o p y l b e n z e n e s w i t h p r o p y l e n e to form t r i - i s o p r o p y l benzenes w h i c h can f u r t h e r r e a c t . However, a t a molar r a t i o o f benzene t o p r o p y l e n e of 6 o r h i g h e r t h e s e compounds a r e not important.

371

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

372

INDUSTRIAL

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

Development of A K i n e t i c Model The above o v e r a l l r e a c t i o n scheme was used to r e p r e s e n t the process. The k i n e t i c models were developed to d e s c r i b e these r e a c t i o n s as shown. No attempt was made to s t u d y the b a s i c r e a c t i o n mechanisms. The f o l l o w i n g p o i n t r a t e models were f o r m u l a t e d and t e s t e d : r

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

r

=

l 2

k

=

C

C

( 4 a )

l B P k

2 C P C

C

( 4 b )

r

3

= k C C

r

4

- k c2

(4d)

k

4

= k /K

(4e)

3

D

(4c)

B

4

3

?

The s u b s c r i p t e d r s a r e the f o u r r e a c t i o n r a t e s r e p r e s e n t i n g the r e a c t i o n s shown above, and the u n i t s a r e moles per hour per u n i t w e i g h t of c a t a l y s t . The k s are the r a t e p a r a m e t e r s . The s u b s c r i p t e d C s a r e the c o n c e n t r a t i o n of benzene, B; p r o p y l e n e , P; cumene, C; and d i - i s o p r o p y l b e n z e n e s , D. E q u a t i o n (4e) d e f i n e s the e q u i l i b r i u m c o n s t a n t , K, f o r r e a c t i o n ( 3 ) . The c o n c e n t r a t i o n u n i t s used a r e moles of component per u n i t mass of t o t a l r e a c t o r fluid. Over the range of c o n d i t i o n s used i n t h i s work, the r e a c t o r f l u i d was a l i q u i d phase m a i n t a i n e d by s u f f i c i e n t p r e s s u r e a t a l l c o n d i t i o n s of temperature and composition. These b a s i c r a t e models were i n c o r p o r a t e d i n t o a d i f f e r e n t i a l mass b a l a n c e i n a t u b u l a r , p l u g - f l o w r e a c t i o n . T h i s g i v e s a s e t of c o u p l e d , n o n - l i n e a r d i f f e r e n t i a l e q u a t i o n s w h i c h , when i n t e ­ g r a t e d , w i l l p r o v i d e a s i m u l a t i o n model. T h i s model c o r r e s p o n d s t o the i n t e g r a l r e a c t o r d a t a p r o v i d e d by e x p e r i m e n t a t i o n . A m a t e r i a l b a l a n c e i s w r i t t e n f o r each of the f o u r components i n our system: f

f

Ί?dC

d c

r

r

(5

" i- 3 p

c

dT=

r

r

l " 2

+

2 r

3

( 7 )

dC

D dT=

r

" 3

+

r

2

+

r

4

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

( 8 )

>

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

23.

H A R P E R

E T

ΑΧ..

Crystalline Alumina

Silicate

373

The i n i t i a l c o n d i t i o n s ( c o n c e n t r a t i o n s ) a r e g i v e n f o r each component. The independent v a r i a b l e , τ, i s the t o t a l l i q u i d w e i g h t h o u r l y space t i m e , w e i g h t c a t a l y s t - h o u r per weight t o t a l l i q u i d f e e d . T h i s form of the d i f f e r e n t i a l e q u a t i o n s was used i n the s i m u l a t i o n and model b u i l d i n g . These were c o n v e n i e n t f o r r e p r e s e n t i n g the c o n c e n t r a t i o n p r o f i l e s i n the same form i n w h i c h the d a t a were t a k e n . An energy b a l a n c e was not r e q u i r e d at t h i s s t a g e , because the r e a c t o r s were o p e r a t e d i s o t h e r m a l l y f o r each s e t of r u n s . E q u a t i o n s ( 5 ) - ( 8 ) were mechanized and s o l v e d on an a n o l o g computer (EAI 680). The parameters were a d j u s t e d and determined f o r each s e t of c o m p o s i t i o n - s p a c e time d a t a . The parameters o b t a i n e d s h o u l d c h a r a c t e r i z e the r e a c t i o n r a t e s , the a c t i v a t i o n e n e r g i e s , the c h e m i c a l e q u i l i b r i u m , and i t s temperature dependence. Thus, i t was apparent what k i n d s of e x p e r i m e n t a l d a t a were r e q u i r e d . F o r a g i v e n r e a c t o r i n l e t c o m p o s i t i o n , and a g i v e n o p e r a t i n g temperature, r e a c t o r d a t a were c o l l e c t e d a t v a r i o u s space t i m e s . T h i s p r o v i d e d a c o m p o s i t i o n p r o f i l e f o r each component from w h i c h the parameters c o u l d be found by s i m u l a t i o n . S e q u e n t i a l l y , o t h e r temperatures and i n i t i a l c o m p o s i t i o n s were s e l e c t e d and a d d i t i o n a l d a t a were o b t a i n e d . The e x p e r i m e n t a l d a t a and s i m u l a t e d curves a r e shown i n F i g u r e s 1, 2, and 3. U s i n g d a t a of these t y p e s and a p o s t u l a t e d model, i t was p o s s i b l e t o s i m u l a t e the observed c o n d i t i o n s , determine the parameters, and p o o l the r e s u l t s . These p o o l e d parameter v a l u e s were combined and reduced t o one s i m p l e model r e p r e s e n t i n g a l l the d a t a , and thus the p r o c e s s under s t u d y . The k i n e t i c model forms were a l s o i n s p e c t e d f o r r e a s o n a b l e n e s s and c o n s i s t e n c y . A t the h i g h e r temperature l e v e l s , i t was n o t i c e d t h a t some u n r e a c t e d p r o p y l e n e was p r e s e n t a t a space time of 0.0125, o r 80 space v e l o c i t y . At h i g h e r space time, t h e r e was no u n r e a c t e d propylene. T h i s meant t h a t the p r i m a r y a l k y l a t i o n r e a c t i o n s were e x t r e m e l y f a s t — i m p l y i n g v e r y h i g h c a t a l y t i c a c t i v i t y f o r a l k y l a t i o n . The major p o r t i o n of the r e a c t o r space was used f o r t r a n s a l k y l a t i o n , g i v i n g an improvement i n s e l e c t i v i t y . T h i s was seen by n o t i n g the r a p i d decay of the d i - i s o p r o p y l b e n z e n e s c o n t e n t a f t e r they reached t h e i r maximum. I t was a l s o e v i d e n t t h a t e q u i l i b r i u m was c l o s e l y approached a t the h i g h e s t space times. The v a l u e s of the r a t e and e q u i l i b r i u m c o n s t a n t s a t two temperature l e v e l s , f r e q u e n c y f a c t o r s , the a c t i v a t i o n e n e r g i e s , and the heat of the t r a n s a l k y l a t i o n r e a c t i o n f o r the model f i n a l l y o b t a i n e d a r e l i s t e d i n T a b l e I . I t i s seen t h a t the e q u i l i b r i u m c o n s t a n t i n c r e a s e s w i t h d e c r e a s i n g temperature, i n d i c a t i n g the t r a n s a l k y l a t i o n i s an exothermic r e a c t i o n . The heat of r e a c t i o n f o r t r a n s a l k y l a t i o n i s about 6.5 k c a l per mole. T h i s means t h a t the cumene c o n t e n t a t e q u i l i b r i u m i s f a v o r e d by d e c r e a s i n g the temperature, a l t h o u g h the e f f e c t i s not p a r t i c u ­ l a r l y great.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

374

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

INDUSTRIAL

f*» o

o

*o o

· Λ


m ο

CN

ο

i-i ο

o ο

ϊ [ θ]

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

23.

H A R P E R

E T

A L .

Crystalline

Alumina Silicate

375

too

§

J Ο

"s

OS

a

U

><*·

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

il Si 1

il ο«-H oW q

»1

\Ω. ι « I. ~ csf „

§· £ ^ co Q S

Ο

•2 *»

•S

1 co Ο
too

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

376

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

's g

6

5

3 g

-ι! Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

^

I

LO

ο

η

H

So II

^

"Ι ο a. η a. Il > § « I

If I

I I

β


BQ

§ο

11 •S CO

S Ο

Ο cô

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

23.

H A R P E R

Crystalline

E T A L .

Alumina

Silicate

377

Table I REACTION BATE AND EQUILIBRIUM PARAMETERS Rate Constante: k. - k. · ~ Ε ι / β Τ , (g Total Fluid) /mole-g cat-hr 1 IO ΔΗ/ Equilibrium Constanta: Κ - Κ e RT, pimenalonleee ο Κ k χ 10~ k χ 10" k χ 10" 1^ χ 1 0 " Temp, • F 2

5

5

4

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

2

3

4

4

450

(232°C)

0.2485

0.8890

0.5805

0.1340

4.34

417

(214°C)

0.1578

0.5580

0.3250

0.0590

5.51

k

E

k io 4

i

(Kcal/* mole)

1

5.45

2

2.628 χ 1 0

3

3.80

χ

10

1 0

15.75

4

5.83

χ

10

1 2

22.27

K

χ

10

t

12.32

9

1 0

ΔΗ (Xcal/g mole)

Ko

1

6.52

Ko -

12.64

χ

10"

-6.52

3

, - ΔΗ - Ε -Ε, *40

*

'

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

378

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

W i t h t h e k i n e t i c s models a v a i l a b l e , one c a n now study t h e b e h a v i o r and t h e performance o f v a r i o u s types o f r e a c t o r systems, such as t h o s e used f o r commercial o p e r a t i o n . However, b e f o r e t h a t can be done, t h e t h e r m o p h y s i c a l p r o p e r t i e s o f t h e components a t t h e r e a c t i o n c o n d i t i o n have t o be determined.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

Thermophysical P r o p e r t i e s T h i s i s a l i q u i d - p h a s e c a t a l y t i c r e a c t i o n system and t h e r e a c t i o n c o n d i t i o n s a r e very c l o s e t o the c r i t i c a l c o n d i t i o n s of t h e r e a c t a n t s p r o p y l e n e and benzene. The v a l u e s o f t h e thermo­ p h y s i c a l p r o p e r t i e s ( e . g . , heat o f f o r m a t i o n and heat c a p a c i t y ) a r e g e n e r a l l y n o t a v a i l a b l e a t t h e r e a c t i o n c o n d i t i o n s and a r e d i f f i c u l t t o e v a l u a t e a c c u r a t e l y . We e v a l u a t e d how w e l l t h e t h e r m o p h y s i c a l p r o p e r t i e s were e s t i m a t e d by s i m u l a t i n g a commer­ c i a l cumene r e a c t o r , and comparing t h e a d i a b a t i c temperature r i s e o f t h e s i m u l a t i o n w i t h t h a t o f t h e observed d a t a a v a i l a b l e . Most p u b l i s h e d d a t a o f t h e heat o f f o r m a t i o n a r e f o r t h e components a t t h e i d e a l gas s t a t e . Heats o f f o r m a t i o n a t t h e l i q u i d s t a t e can be e v a l u a t e d by s u b t r a c t i n g h e a t s o f v a p o r i z a t i o n a t t h e temperature o f i n t e r e s t from h e a t s o f f o r m a t i o n a t t h e gas s t a t e (AH°f ). F o r t h e p r e s e n t system, a l l AH°f v a l u e s a r e a v a i l a b l e except that of the di-isopropylbenzenes. The v a l u e s of AH°fg o f d i - i s o p r o p y l b e n z e n e s were o b t a i n e d by group c o n t r i ­ b u t i o n methods and averaged t o p r e s e n t t h e average isomer d i s ­ t r i b u t i o n observed i n the r e a c t i o n . The h e a t c a p a c i t i e s used f o r a l l l i q u i d components were e s t i m a t e d from a v a i l a b l e e n g i n e e r i n g c o r r e l a t i o n s . These v a l u e s were reduced t o e q u a t i o n form. The models and c o e f f i c i e n t s and the heat o f f o r m a t i o n a t t h e l i q u i d s t a t e a r e l i s t e d i n T a b l e I I . g

g

Energy B a l a n c e . I t was d e c i d e d t h a t a s i m p l e , f i x e d - b e d , a d i a b a t i c r e a c t o r would be r e q u i r e d i n t h i s p r o c e s s . Since the r e a c t i o n s i n v o l v e d r e l e a s e considerable heat, t h i s i n f l u e n c e s the l o c a l t e m p e r a t u r e , w h i c h i n t u r n i n f l u e n c e s t h e r e a c t i o n r a t e s . An energy b a l a n c e , o r heat b a l a n c e , h a v i n g t h e f o l l o w i n g g e n e r a l form, was added a l o n g w i t h t h e mass b a l a n c e i n a l l subsequent s i m u l a t i o n s :

Ρ

i=l

M = a v e r a g e m o l e c u l a r w e i g h t o f the t o t a l

fluid

C = a v e r a g e h e a t c a p a c i t y , c a l / g mole, F R.= n e t r a t e o f p r o d u c t i o n o f t h e i - t h component, g-mole/hr-g c a t . AH

f i

= heat of formation

of i i n l i q u i d s t a t e , kcal/g-mole.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. e

fi

12.652 -10.503 -32.87*

Benzene

Cumene

Dlcumene

36.315

25.454

15.511

8.118

$T, C - cal/mole F, Τ - F Ρ

- Kcal/mole

*Eetlmated by group contribution methods.

-8.431

(330-480 F)

ΔΗ, "fi

Propylene

Compound

AH

Heat Capacity: C - α + Ρ

Heat of Formation:

THERMOPHYSICAL PROPERTIES AT LIQUID STATE

Table II

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

0.045

0.034

0.02194

0.01424

380

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

T h i s energy b a l a n c e when c o u p l e d w i t h m a t e r i a l b a l a n c e s , E q u a t i o n s (5) t h r o u g h ( 8 ) , g e n e r a t e d p o i n t temperatures over t h e range o f space t i m e s c o n s i d e r e d . D i g i t a l Computer S i m u l a t i o n Program. A d i g i t a l reactor s i m u l a t i o n program was used t o i n t e g r a t e t h e s t e a d y s t a t e d i f f e r e n t i a l mass b a l a n c e s and t h e energy b a l a n c e f o r a p l u g flow reactor. Numerical s o l u t i o n s f o r the r e s u l t i n g s e t of c o u p l e d , n o n - l i n e a r d i f f e r e n t i a l e q u a t i o n s were o b t a i n e d by u s i n g t h e f o u r t h - o r d e r Runge-Kutta method. The e n t i r e s e t o f d i f f e r e n t i a l e q u a t i o n s was i n t e g r a t e d s i m u l t a n e o u s l y a l o n g t h e r e a c t o r l e n g t h t o o b t a i n t h e c o m p o s i t i o n and temperature p r o f i l e s . The main program was g e n e r a l i n n a t u r e and t h e r e a c t i o n r a t e e q u a t i o n s and thermodynamic p r o p e r t i e s were i n t r o d u c e d i n a s u b r o u t i n e . T h i s program developed a p r i n t - o u t c o n t a i n i n g c o m p o s i t i o n and temperature i n f o r m a t i o n a l o n g t h e space-time i n t e g r a t i o n p a t h . I n a d d i t i o n , y i e l d s , s e l e c t i v i t i e s , and c o n v e r s i o n s were a l s o g e n e r a t e d . I n t h i s way, a l l d e t a i l s f o r t h e r e a c t o r s i m u l a t i o n were made a v a i l a b l e a t many s p e c i f i e d space-time c o n d i t i o n s . A d i a b a t i c Reactor Simulations. Using the chemical r e a c t i o n system model and t h i s d i g i t a l program, we conducted many s i m u l a ­ t i o n s . S i n c e a l l of o u r s i m u l a t i o n s were conducted t o approach an e q u i l i b r i u m c o n d i t i o n , a d i a b a t i c temperature r i s e i n f o r m a t i o n was g e n e r a t e d d i r e c t l y . A summary o f t h e s e r e s u l t s i s shown i n F i g u r e 4. T h i s temperature r i s e v a r i e d from about 30 t o 61°C o v e r t h e range o f v a r i a b l e s s t u d i e d . A major v a r i a b l e s t u d i e d was t h e cumene s e l e c t i v i t y based on p r o p y l e n e . F i g u r e s 5, 6, and 7 show g e n e r a t e d r e s u l t s r e l a t i n g s e l e c t i v i t y t o t h r e e process v a r i a b l e s . At a g i v e n i n l e t composition to the r e a c t o r , t h e s e l e c t i v i t y i s i n f l u e n c e d d i f f e r e n t l y by t e m p e r a t u r e . The magnitude and d i r e c t i o n depends on t h e space time employed. The optimum s e l e c t i v i t y a t h i g h space times was i n c r e a s e d w i t h reduced i n l e t temperature. Whereas, i n t e r m e d i a t e s e l e c t i v i t i e s a t low space times were i n c r e a s e d by an i n c r e a s e i n i n l e t t e m p e r a t u r e o v e r a space time range from about 0.04 t o 0.1. E f f e c t s of Operation Variables on t h e Performance o f t h e R e a c t o r Three o p e r a t i o n v a r i a b l e s , b e n z e n e - t o - p r o p y l e n e r a t i o (Rg)> temperature ( T ) , and space time (τ) a r e of prime concern t o a r e a c t o r d e s i g n e r . S i n c e a l k y l a t i o n r e a c t i o n s a r e so f a s t , t h e c o n t r o l l i n g performance o f t h e r e a c t o r i s determined by t h e r e a c t i o n s e l e c t i v i t y . A t a c o n s t a n t average t e m p e r a t u r e , examina­ t i o n o f t h e r e a c t i o n p a t h s and k i n e t i c s models i n d i c a t e d t h a t s e l e c t i v i t y increased w i t h i n c r e a s i n g benzene-to-propylene r a t i o r e g a r d l e s s o f t h e space time a p p l i e d . The temperature e f f e c t was s l i g h t l y more c o m p l i c a t e d . S i n c e most o f a p r o c e s s r e a c t o r

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

H A R P E R

E T

A L .

4

Crystalline

5

Alumina

6

Silicate

7

Benzene-to-Propylene Figure 4.

8

9

10

Ratio

Adiabatic temperature rise vs. benzene-to-propylene ratio. Parameter = reactor inlet temperature.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

AND

LABORATORY

ALKYLATION S

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

INDUSTRIAL

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

H A R P E R

E T

A L .

Crystalline

Alumina

Silicate

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

23.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

383

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

384

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

23.

H A R P E R

E T

A L .

Crystalline Alumina Silicate

385

w i l l be o p e r a t e d i n t h e t r a n s a l k y l a t i o n r e a c t i o n r e g i o n , and t h e l a t t e r r e a c t i o n i s a r e v e r s i b l e , exothermic r e a c t i o n , the s e l e c ­ t i v i t y i s f a v o r e d by l o w e r i n g t h e temperature when t h e r e a c t o r i s o p e r a t e d c l o s e t o t r a n s a l k y l a t i o n e q u i l i b r i u m . However, a t low space t i m e , t h e s e l e c t i v i t y i s determined by how q u i c k l y cumene c a n be formed. Thus, k i n e t i c s i n s t e a d of e q u i l i b r i u m would be t h e d o m i n a t i n g f a c t o r f o r s e l e c t i v i t y i n t h e low space time r e g i o n . I n o t h e r words, when t h e k i n e t i c temperature e f f e c t i s e v a l u a t e d , space time must be c o n s i d e r e d s i m u l t a n e o u s l y . The f o l l o w i n g a d i a b a t i c r e a c t o r a n a l y s i s w i l l e l a b o r a t e on and s u b s t a n t i a t e t h e above d i s c u s s i o n . In an a d i a b a t i c o p e r a t i o n , i n l e t temperature r a t h e r than r e a c t o r average temperature i s one o f t h e prime o p e r a t i n g v a r i a b l e s , because i t can be e a s i l y m a n i p u l a t e d . T a b l e I I I shows t h e e f f e c t o f t h e r e a c t o r i n l e t temperature on cumene s e l e c t i v i t y . A t a low space time (τ = 0.05), when r e a c t i o n r a t e i s s t i l l t h e d e t e r m i n i n g f a c t o r , h i g h e r i n l e t temperature g i v e s h i g h e r s e l e c t i v i t y , because o f t h e h i g h e r r e a c t i o n r a t e . However, at a h i g h e r space time (τ = 0.1) where e q u i l i b r i u m i s v i r t u a l l y r e a c h e d , a h i g h e r i n l e t temperature r e s u l t s i n a lower s e l e c t i v ­ i t y , because o f t h e temperature e f f e c t on t r a n s a l k y l a t i o n e q u i l i ­ brium. T a b l e I V shows t h e e f f e c t o f b e n z e n e - t o - p r o p y l e n e r a t i o i n the f e e d on s e l e c t i v i t y a t two space v e l o c i t i e s . I t i s very apparent t h a t when t h e r a t i o i s i n c r e a s e d , t h e s e l e c t i v i t y becomes h i g h e r . The r e a s o n s f o r t h i s a r e t h r e e - f o l d . Kinetics of t h e two a l k y l a t i o n r e a c t i o n s f a v o r p r o d u c t i o n o f cumene i f the b e n z e n e - t o - p r o p y l e n e i s h i g h e r . The e q u i l i b r i u m c o n c e n t r a t i o n of cumene i s h i g h e r , because o f h i g h e r benzene c o n c e n t r a t i o n . At t h e same i n l e t t e m p e r a t u r e , a h i g h e r benzene c o n c e n t r a t i o n r e s u l t s i n lower o u t l e t temperatures w h i c h i n t u r n i n c r e a s e t h e e q u i l i b r i u m constant of the t r a n s a l k y l a t i o n r e a c t i o n . It is i n t e r e s t i n g t o n o t e t h a t t h e i n c r e a s e i n s e l e c t i v i t y i s more s i g n i f i c a n t a t a h i g h e r space time because o f t h e more pronounced e f f e c t of the e q u i l i b r i u m . O p t i m a l A d i a b a t i c R e a c t o r D e s i g n . The s e l e c t i v i t y c u r v e s g e n e r a t e d i n F i g u r e s 5, 6, and 7 show a r e l a t i o n s h i p between t h e benzene/propylene molar r a t i o , i n l e t t e m p e r a t u r e , and space time f o r an a d i a b a t i c r e a c t o r . One would l i k e t o have a f o r m u l a , c h a r t , o r graph t h a t would e a s i l y p r e d i c t o p t i m a l y i e l d s as a f u n c t i o n o f t h e s e v a r i a b l e s . F i g u r e 8 does t h i s , and i s r e a l l y a n o t h e r way o f p r e s e n t i n g t h e envelopes d e f i n e d i n F i g u r e s 5-7. F i g u r e 8 a l s o a l l o w s one t o s e l e c t proper o p e r a t i n g c o n d i t i o n s as t h e c a t a l y s t ages. C a t a l y s t A g i n g C h a r a c t e r i s t i c s and P r o d u c t P u r i t y A l l o f t h e work done t o e s t a b l i s h t h e k i n e t i c parameters was conducted on t h e same c a t a l y s t bed used f o r a l o n g - t e r m

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

e

e

20.83 96.15 92.69

S e l e c t i v i t y Based on Benzene

S e l e c t i v i t y Based on Propylene

448 (231)

380 (193)

LWHSV, wt Liq/wt Cat-hr

Outlet Temperature, F (°C)

e

I n l e t Temperature, F ( C )

Run

93.16

96.38

20.83

457 (236)

390 (199)

Benzene/Propylene - 8.27 (Mole),

93.34

96.45

20.83

466 (241)

400 (204)

π » 514.7 p s i a

SELECTIVITY VERSUS INLET TEMPERATURE

Table I I I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

94.58

97.16

10.0

448 (231)

380 (193)

94.30

96.99

10.0

457 (236)

390 (199)

93.98

96.78

10.0

467 (241)

400 (204)

2

I I 1

> d

2

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

e

20.83 96.38 93.16

20.83 95.29 91.10

S e l e c t i v i t y Based on Benzene

S e l e c t i v i t y Based on Propylene

457 (236)

476 (247)

Outlet Temperature, *F (°C)

LWHSV wt Liq/wt Cat-hr

390 (199)

8.27

390 (199)

6

Bz/pp (Mole)

2

I n l e t Temperature, F (°C)

1

Run

93.85

96.75

20.83

446 (230)

390 (199)

10

3

SELECTIVITY VERSUS BENZENE-TO-PROPYLENE RATIO

Table IV

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

91.48

95.50

10.0

477 (247)

390(199)

6

4

10.0 97.55 95.56

96.99 94.30

447 (230)

458 (236) 10.0

390 (199)

10

6

390 (199)

8.27

5

ε-

s"

•8 g,

ο

8

INDUSTRIAL

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

388

4

5

6

7

AND LABORATORY

8

9

ALKYLATIONS

10

Benzene/Propylene (Mole) Figure 8.

Inlet temperature vs. benzene/propylene for maximum selectivity. Parameter = space time, t.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

23.

H A R P E R

E T A L .

Crystalline Alumina

Silicate

389

i s o t h e r m a l (232°C) a g i n g s t u d y . T h i s study l a s t e d f o r 9 months at an average LWHSV = 10 w i t h t h e c a t a l y s t h a v i n g produced 900 g cumeme/g-catalyst. The s t u d y was then t e r m i n a t e d w i t h no e v i d e n c e of t h e c a t a l y s t h a v i n g aged w i t h t h e e x c e p t i o n o f a s l i g h t d i m u n i t i o n i n s e l e c t i v i t y over t h i s time p e r i o d . A t y p i c a l w e i g h t p e r c e n t a n a l y s i s on t h e p r o d u c t was t h e f o l l o w i n g : cumene, 16.53%; d i - i s o p r o p y l b e n z e n e s , 0.69%; e t h y l b e n z e n e , 0.043%; a t r a c e o f n - p r o p y l b e n z e n e s ; and benzene, 82.53%. These d a t a g i v e an e f f i c i e n c y t o cumene o f 93.7% based on p r o p y l e n e and when c o u p l e d w i t h t h e a g i n g d a t a would a p p a r e n t l y j u s t i f y t h e c a t a l y s t b e i n g used i n a cumene u n i t . However, as we w i l l soon see, what happens i n an i s o t h e r m a l r e a c t o r does n o t nece s s a r i l y o c c u r i n an a d i a b a t i c r e a c t o r . A l a r g e r p i l o t p l a n t u n i t was b u i l t and p r o p e r l y i n s u l a t e d to a s s u r e e s s e n t i a l l y no heat l o s s . H i g h f e e d r a t e s were used to s i m u l a t e what happens i n a u n i t a r e a o f a commercial r e a c t o r and t o a c c e l e r a t e a v e r y s l o w r a t e o f c a t a l y s t a g i n g t o one we c o u l d measure over a p e r i o d o f 2-3 weeks. The f i r s t experiment was d e s i g n e d t o approximate t h e i s o t h e r m a l r e a c t o r . However, t h e c o n d i t i o n s a c t u a l l y were 180°C i n l e t temperature, 221°C o u t l e t t e m p e r a t u r e , and 8/1 molar r a t i o benzene/propylene a t a l i n e a r h o u r l y space v e l o c i t y o f 13. T h i s experiment s t a r t e d o u t as e x p e c t e d w i t h t h e a l k y l a t i o n r e a c t i o n o c c u r r i n g i n t h e f i r s t 2-3 i n c h e s o f t h e c a t a l y s t bed and t h e r e a c t o r was a d i a b a t i c . However, a f t e r about 3 h o u r s , i t was o b v i o u s t h e c a t a l y s t was a g i n g q u i t e r a p i d l y as e v i d e n c e d by t h e a l k y l a t i o n zone moving up t h e r e a c t o r . A f t e r 20 h o u r s , 12 i n c h e s (90 grams) o f t h e c a t a l y s t had been c o m p l e t e l y d e a c t i v a t e d and t h e experiment was t e r m i n a t e d . The r a t e o f a g i n g was 0.57 i n c h e s / h o u r . T h i s r a p i d a g i n g was q u i t e unexpected s i n c e t h e f e e d was pumped over t h e c a t a l y s t o n l y 1.3 t i m e s f a s t e r t h a n d u r i n g t h e i s o t h e r m a l r u n and t h e c a t a l y s t was c o o l e r i n t h e a l k y l a t i o n zone w h i c h s h o u l d have been b e n e f i c i a l a c c o r d i n g t o t h e t e a c h i n g s o f Wise.(1) A more c a r e f u l e x a m i n a t i o n o f t h e f e e d r a t e d a t a showed t h a t , w h i l e i t was t r u e t h e benzene/propylene f e e d was pumped over t h e e n t i r e c a t a l y s t bed 1.3 t i m e s f a s t e r than d u r i n g t h e i s o t h e r m a l r u n (LWHSV a d i a b a t i c = 1 . 3 LWHSV i s o t h e r m a l ) , t h e f e e d r a t e t h r o u g h t h e a l k y l a t i o n zone was much h i g h e r . A c o n v e n i e n t way of e x p r e s s i n g t h i s r a t e was t o determine how many grams o f t o t a l f e e d passed through a u n i t (cm^) o f c a t a l y s t s u r f a c e a r e a p e r hour. T h i s r a t e was termed as s u p e r f i c i a l v e l o c i t y and had g/cm^-hr d i m e n s i o n s . ^For t h e i s o t h e r m a l r e a c t o r t h e s u p e r f i c i a l v e l o c i t y was 180 g/cm - h r and i n t h e a d i a b a t i c r u n i t was 1400 g/cm^-hr o r s u p e r f i c i a l v e l o c i t y r a t i o o f about 8. T h i s c o u l d account f o r t h e a g i n g r a t e d i f f e r e n c e s ( l e s s than 10 g c a t a l y s t i n 9 months f o r t h e i s o t h e r m a l r e a c t o r v e r s u s 90 g c a t a l y s t i n 20 hours a d i a b a t i c ) i f t h e a g i n g r a t e d i f f e r e n c e was a tetramic function of t h i s r a t i o .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

390

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

23.

H A R P E R

E T

A L .

Crystalline Alumina

Silicate

391

T h i s h a r d l y seemed a r e a s o n a b l e r a t i o n a l of the f a s t a g i n g r a t e , b u t n e i t h e r d i d one i n v o l v i n g lower temperature. A s e r i e s of e x p e r i m e n t s were done t o a s c e r t a i n w h i c h of t h e s e i f e i t h e r was t h e dependent v a r i a b l e . F i g u r e 9 shows t h a t temperature was a v e r y unexpected and h e r e t o f o r e unknown i n v e r s e f u n c t i o n of the a g i n g r a t e . A l l o f t h e temperatures shown i n F i g u r e 9 a r e those o f t h e hot s p o t s l e a d i n g edge. Feeds e n t e r e d about 59°C l o w e r . The e f f e c t o f s u p e r f i c i a l v e l o c i t y was shown t o be d i r e c t l y p r o p o r t i o n a l t o t h e c o n c e n t r a t i o n o f p r o p y l e n e but was o n l y s l i g h t l y h i g h e r t h a n u n i m o l e c u l a r . The l i n e a r a g i n g r a t e then has t h e f o l l o w i n g form.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

L i n e a r A g i n g Rate =

A*f(propylene) i h s / h o u r n c

e

However, t h i s r a t e i s dependent on the c r o s s s e c t i o n a l a r e a of the r e a c t o r . A more a c c u r a t e r e l a t i o n s h i p would be one showing the volume o f c a t a l y s t aged per u n i t time. Volume A g i n g R u l e =

L i n e a r A g i n g Rate χ A r e a

The d a t a i n F i g u r e 9 s h o u l d t h e n be m u l t i p l i e d bg 0.8152 t o c o n v e r t t o i n /hr o r by 13.3586 t o c o n v e r t t o cm /hr i f these d a t a a r e t o be compared t o t h a t o b t a i n e d i n o t h e r r e a c t o r s . W h i l e the a g i n g c h a r a c t e r i s t i c s of t h e c a t a l y s t were b e i n g d e t e r m i n e d , GLC a n a l y s e s o f t h e p r o d u c t showed t h a t l a r g e r q u a n t i t i e s of e t h y l b e n z e n e and n-propylbenzene were produced a t the h i g h e r t e m p e r a t u r e s . These p r o d u c t s a r i s e from a c r a c k i n g and an i s o m e r i z a t i o n mechanism, r e s p e c t i v e l y . Both of t h e s e p r o d u c t s would then have temperature and c a t a l y s t r e s i d e n c e time as a dependent v a r i a b l e . A s t u d y of b o t h t h e s e p r o d u c t s as a f u n c t i o n o f temperature and LWHSV was then done by u s i n g a s m a l l a d i a b a t i c a l k y l a t i o n r e a c t o r o p e r a t e d a t h i g h space v e l o c i t y f o l l o w e d by a l a r g e r i s o t h e r m a l o r t r a n s a l k y l a t i o n r e a c t o r . T h i s i s e s s e n t i a l l y what an a d i a b a t i c r e a c t o r i s , b u t the tempera­ t u r e i n t h e i s o t h e r m a l zone i s dependent on the a d i a b a t i c heat g e n e r a t e d . The r e s u l t s o f t h i s s t u d y a r e shown i n T a b l e V. The d a t a show t h a t lower temperatures and h i g h e r f l o w r a t e s g i v e a c l e a n e r p r o d u c t w i t h h i g h e r e f f i c i e n c i e s . However, a t temperature lower t h a n 221°C and LWHSV's h i g h e r than 5, e f f i c i e n c i e s a r e lowered due t o t h e e q u i l i b r i u m r e a c t i o n 3. Experimental The c a t a l y s t used i n most o f t h e work r e p o r t e d h e r e was Union C a r b i d e ' s SK-500. T f r y c a t a l y s t i s a Y f a u j a s i t e w i t h the f o l l o w i n g c o m p o s i t i o n : (La ) g 3 ( ^ 4 )οχ j / '3 3 ^ ^ ^ 2 ^ 5 5 7 ( S i 0 ) £ ] * Z H 0 . The c a t a l y s t was a c t i v a t e d b y " H e a t i n g t o 550 C f o r 90 minutes w i t h a N stream t o d r i v e o f f NH and H 0. t

|

N

o

1O

o

a

o

0

0

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

o

392

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

Table V 1

ALKYLATION CONDITIONS : 8/1 B/P, LHSV - 23 h" , 4.2 MPa (600 PSIC). 252*C (485*F)

Transalkylation LHSV

2.3

4.5

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

Transalkylation Temperature e

221 C (430 F) e

227 *C (440 F) e

e

232 C (450 F) e

e

252 C (485 F) e

X NPB X BB

0.025 0.037 0.18 96.1

X NPB X EB

0.037 0.061 0.27 96.1

X NPB X EB

0.051 0.086 0.38 95.6

0.038 0.085 0.23 95.2

X NPB X EB

0.166 0.351 1.10 92.2

0.112 0.280 0.70 92.9

X NPB/Cumene Benzene Selectivity

X NPB/Cumene Benzene Selectivity

X NPB/Cumene Benzene Selectivity

X NPB/Cumene Benzene Selectivity

0.023 0.042 0.14 95.4

NPB - n-Propylbenzene EB

- Ethylbenzene

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

23.

H A R P E R

E T

A L .

Crystalline Alumina

Silicate

393

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

+

G u l f ' s commercial grade benzene ( 9 9 % benzene) and a l k y l a t i o n grade p r o p y l e n e (73-75% p r o p y l e n e and 27-25% propane) were used i n a l l the work. The k i n e t i c s t u d i e s were done i n a 1/2-inch p i p e j a c k e t e d r e a c t o r w i t h a 1/8-inch t h e r m o w e l l down the m i d d l e . The f i r s t 7 i n c h e s of the r e a c t o r was f i l l e d w i t h q u a r t z c h i p s and used as a p r e h e a t e r . Ten grams of 10-20 mesh SK-500 was then mixed w i t h t w i c e i t s volume o f q u a r t z and p l a c e d on top of the p r e h e a t s e c t i o n . The f e e d was pre-mixed i n a p r e s s u r i z e d tank and then pumped u p f l o w through the r e a c t o r . The temperature was c o n t r o l l e d by pumping Dow Therm t h r o u g h the j a c k e t w i t h heat b e i n g s u p p l i e d e x t e r n a l l y . T h i s r e s u l t e d i n the r e a c t o r b e i n g i s o t h e r m a l . The remainder of the e x p e r i m e n t a l r e s u l t s were o b t a i n e d i n a 1 - i n c h p i p e r e a c t o r w i t h a 1/4-inch t h e r m o w e l l which was w e l l l a g g e d w i t h 2.5 i n c h e s of a s b e s t o s and equipped w i t h heat compens a t i o n t o i n s u r e an a d i a b a t i c r e a c t o r . The lower 12 i n c h e s of the r e a c t o r was used as a p r e h e a t s e c t i o n and f i l l e d w i t h g l a s s beads. The c a t a l y s t s e c t i o n was f i l l e d to 72 i n c h e s w i t h a 1/16-inch e x t r u d a t e which weighed 565 grams. Benzene and propyl e n e were pumped i n t o a p r e s s u r i z e d a u t o c l a v e which s e r v e s as a p a r t i a l p r e h e a t e r and m i x e r and then u p f l o w through the r e a c t o r . The d e s i r e d temperature was o b t a i n e d by a d j u s t i n g the p r e h e a t s e c t i o n t o a temperature about 43°C below the d e s i r e d one and the exotherm then r a i s e d i t t o the d e s i r e d l e v e l . The p r e s s u r e ^ on t h e r e a c t o r was m a i n t a i n e d a t 3.47 MPa (500 p s i g , 35.4 kg/cm ) at 216-227°C and 4.32 MPa (700 p s i g , 49.4 kg/cm ) a t 252°C. O f f - g a s a n a l y s e s were done by mass s p e c t r o m e t r y and r e a c t o r e f f l u e n t samples were a n a l y z e d by g l c . Most of the g l c work was done w i t h an 8 - f o o t 1/4-inch OD column c o n t a i n i n g 10% SE-30 on a c i d washed Chromsorb W. However, the s e p a r a t i o n of n - p r o p y l benzene from cumene had t o be done w i t h a d u a l 3/16-inch copper column c o n s i s t i n g of a 1 2 - f o o t s e c t i o n h a v i n g 10% Bentone 34 and 10% Dow C o r n i n g s i l i c o n e gum 550 on 60-80 mesh a c i d washed Chromsorb W and a 6-foot s e c t i o n c o n t a i n i n g 20% A p i e z o n L on 60-80 mesh a c i d washed Chromsorb P. 2

D i s c u s s i o n of t h e R e s u l t s The k i n e t i c d a t a , w h i l e new, p r e s e n t e d n o t h i n g u n u s u a l . The d a t a were a c c u r a t e i n t h a t they d i d p r e d i c t p r o d u c t d i s t r i b u t i o n from an a d i a b a t i c r e a c t o r . The i n v e r s e temperature r e l a t i o n s h i p on the r a t e of a g i n g was unknown p r i o r t o t h i s i n v e s t i g a t i o n . Two e x p l a n a t i o n s of t h i s a r e o f f e r e d w i t h o u t s u b s t a n t i a t i n g d a t a . The f i r s t i s t h a t t h e r e a r e two d i s t i n c t l y d i f f e r e n t r e a c t i o n s o c c u r r i n g on the c a t a l y s t . One of w h i c h i s a r e a c t i o n l e a d i n g to l a r g e b u l k y m o l e c u l e s which a r e slow o r unable to escape the 13 A windows of the c a t a l y s t and i s a s s o c i a t e d w i t h a low energy of a c t i v a t i o n . These b u l k y m o l e c u l e s then dehydrogenate to form coke or p o l y n u c l e a r a r o m a t i c s . The o t h e r r e a c t i o n , a l k y l a t i o n , has a much

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

394

INDUSTRIAL

AND

LABORATORY

ALKYLATION S

h i g h e r energy o f a c t i v a t i o n . As t h e temperature i s i n c r e a s e d , t h i s becomes e s s e n t i a l l y t h e o n l y r e a c t i o n t o o c c u r . The second r a t i o n a l might r e a l l y be a n o t h e r way o f d e s c r i b i n g t h e f i r s t . T h i s says t h a t a t l o w t e m p e r a t u r e s t h e r e a c t i o n o f p r o p y l e n e w i t h benzene i s r e a c t i o n r a t e c o n t r o l l e d and i s a s s o c i a t e d w i t h h i g h c o n c e n t r a t i o n s o f p r o p y l e n e around t h e a c t i v e c a t a l y s t s i t e s . A t h i g h e r t e m p e r a t u r e s t h e r e a c t i o n s become mass t r a n s f e r c o n t r o l l e d ( r e a c t i o n r a t e v e r y f a s t ) and t h i s l e a d s t o v e r y low concentrations of propylene a t the a c t i v e s i t e s . The enormous d i f f e r e n c e s i n a g i n g r a t e s between t h e i s o t h e r m a l and a d i a b a t i c runs c a n be e a s i l y u n d e r s t o o d i f one a g a i n l o o k s a t F i g u r e 9. I n an a d i a b a t i c r e a c t o r t h e f e e d must e n t e r at a temperature c o n s i d e r a b l y lower than t h a t g e n e r a t e d by t h e heat o f r e a c t i o n . T h i s f e e d then i n i t i a l l y passes through t h e c a t a l y s t a t t e m p e r a t u r e s w h i c h produce v e r y f a s t a g i n g . I n t h e i s o t h e r m a l r e a c t o r , t h e e n t i r e c a t a l y s t must have been h o t enough t o produce e s s e n t i a l l y no d e a c t i v a t i o n . One might then t h i n k t h a t i f t h e f e e d was brought i n t o an a d i a b a t i c r e a c t o r a t around 232°C, l i t t l e o r no a g i n g would o c c u r . T h i s was o b s e r v e d t o be t r u e , b u t t h e h i g h temperature (271-277°C) g e n e r a t e d l e d t o e x c e s s i v e b y - p r o d u c t f o r m a t i o n . Process Design F i g u r e 10 shows t h e rough d e s i g n f o r t h i s p r o c e s s . The a l k y l a t i o n o r a d i a b a t i c r e a c t o r might be s p l i t i n t o two s m a l l e r p a r a l l e l r e a c t o r s . One o f w h i c h would be used f o r r e g e n e r a t i n g c a t a l y s t w h i l e t h e o t h e r was used f o r a l k y l a t i o n . The a l k y l a t i o n r e a c t o r would be o p e r a t e d a t r a t h e r h i g h space v e l o c i t i e s (1525 LWHSV), 7 o r 8 molar r a t i o benzene/propylene, and 210-215°C i n l e t t e m p e r a t u r e - 250-255°C o u t l e t t e m p e r a t u r e . The p r o d u c t would t h e n be heat exchanged t o reduce t h e temperature i n t h e t r a n s a l k y l a t i o n o r i s o t h e r m a l r e a c t o r t o 220°C. T h i s r e a c t o r would be o p e r a t e d a t an LWHSV = 5 and s h o u l d never age s i n c e i t would n e v e r see any p r o p y l e n e . By r e c y c l i n g t h e d i - i s o p r o p y l benzene back t o t h e r e a c t o r , t h e e f f i c i e n c y o f t h e p r o c e s s can be i n c r e a s e d from 93% (based on p r o p y l e n e ) t o 97-98%. Conclusions Of a l l t h e d a t a w h i c h c a n be o b t a i n e d from an i s o t h e r m a l a l k y l a t i o n r e a c t o r , o n l y t h e k i n e t i c and thermodynamic d a t a can be a p p l i e d t o an a d i a b a t i c r e a c t o r . I f the p r o c e s s o r r e a c t i o n i s d i v i d e d i n t o a l k y l a t i o n and t r a n s a l k y l a t i o n s e c t i o n s , t h e n one can s e l e c t c o n d i t i o n s f o r t h e p r o c e s s t o g i v e h i g h c a t a l y s t l i f e t i m e s and produce a p u r e p r o d u c t a t h i g h e f f i c i e n c i e s .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

R-l Alkylation Reactor

Benzene Figure 10.

Depropanizer

Transalkylation Reactor

Τ

PolylsopropylBenzones to Fuel Oil

Cumene to

Cumene Tower

Two-stage cumene process

Benzene Drag Stream to Fuel O i l Recycle Diisopropylbenzenes

t

Propane to LPG

T-2 Benzene Tower

T-l

R-2

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

INDUSTRIAL

396

AND LABORATORY

ALKYLATIONS

Acknowledgment The a u t h o r s w i s h t o thank a l l o f t h e t e c h n i c i a n s who were a s s o c i a t e d w i t h t h i s p r o j e c t . S p e c i a l thanks a r e due t o Mr. R o b e r t S. C l e r k who was w i t h t h e p r o j e c t t h e l o n g e s t and who p r e p a r e d a l l t h e f i g u r e s f o r t h i s paper. G l o s s a r y o f Terms LWHSV = L i q u i d w e i g h t h o u r l y space v e l o c i t y feed/g t o t a l c a t a l y s t - h o u r

= g total

τ = Space t i m e = 1/LWHSV

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch023

Superficial

V e l o c i t y = Weight r a t e of t o t a l s e c t i o n a l area

feed/cross-

= g t o t a l feed/cm^ h r . Literature Cited (1) Wise, John J . , U.S. Patent 3,251,897.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24

Some

Aspects

of

the

Direct

Alkylation

of

Pyridine

and

Methyl Pyridines

C. V. DIGIOVANNA, P. J. CISLAK, and G. N. CISLAK

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

Reilly Tar & Chemical Corp., Indianapolis, IN 46241

A s i g n i f i c a n t volume of l i t e r a t u r e exists regarding the a l k y l a t i o n of pyridine rings. For the purposes of t h i s report, only those processes w i l l be considered which involve intermolecular substitution d i r e c t l y on the pyridine r i n g with other r i n g substituents p a r t i c i p a t i n g i n merely a d i r e c t i v e or s t e r i c r o l e . This i s a substantial l i m i t a t i o n since there are many processes which,after a sequence of reactions, r e s u l t i n an a l k y l group becoming a substituent on a pyridine r i n g . Quaternization reactions have been disregarded, except when the quaternary s a l t represents an intermediate, since they are addition rather than substitution reactions. Further, reactions involving preliminary formation of the N-oxide of the pyridine ring have been eliminated from consideration since i n these materials the fundamental aromatic character of the ring i s altered. Within the l i m i t s imposed there exists a number of available procedures for introducing a l k y l substituents onto the pyridine ring. A l l of these involve either nucleophilic or homolytic substitution since a l k y l a t i o n v i a e l e c t r o p h i l i c s u b s t i t u t i o n , e.g. F r i e d e l Crafts a l k y l a t i o n , is not possible with the π-deficient pyridine nucleus. Nucleophilic Substitutions Rearrangement of Quaternary S a l t s . Ladenburg ( l - k ) reported rearrangement of methylpyridinium iodide to a mixture of 2-methylpyridine and similar rearrangements of other quaternary s a l t s have been reported by others (5-19). The product mix obtained from thermolysis of 1-methylpyridinium iodide i s given i n Table I.

397

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

398

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

TABLE I (12) THERMOLYSIS OF 1-METHYLPYRIDINIUM IODIDE

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

Product 2-Methyl 3-Methyl i+-Methyl 2-Ethyl U-Ethyl 2,U-Dimethyl 2,5-Dimethyl 2,6-Dimethyl

Yield( 30.1 5.8 3^.6 3.6 l.k

12.8 1.9 9.1

The formation of 3-methylpyridine and the ethylpyridines has been suggested as an indication of a free r a d i c a l mechanism f o r t h i s process ( l l , 1 2 ) . Use of Lithium Derivatives. There are only a few reports of a l k y l a t i o n procedures which provide a means for preparing predomi­ nately 3-substituted pyridines. Some ( l 6 - 1 9 ) involve reaction of the pyridine compound with a lithium derivative, e.g. phenyllithium or lithium aluminum hydride (LAH), followed by reaction with an a l k y l or arylhalide. The reaction steps are as follows:

The p h e n y l l i t h i o intermediate has been i s o l a t e d (2θΟ and treated with styrene and ethylene oxides, and N-benzylidene a n i l i n e to provide various 2-phenyl-5-substituted pyridines. Addition of perhalomethanes affords bis(6-phenyl-3-pyridyl)nethane and 6,6'-diphenyl-3,3 -dipyridyl ( l 8 ) . The y i e l d s of 3-substituted pyridines range, i n the LAH reaction, from 89% f o r 3-picoline to 63% f o r 3-benzylpyridine. Reaction of the LAH intermediate with bromine formed 3-bromopyridine i n kl% y i e l d ( I T ) . !

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24.

DiGiovANNA E T A L .

Pyridine and Methyl

Pyridines

399

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

Treatment of pyridine with excess a r y l and a l k y l l i t h i u m reagents i s reported to give good y i e l d s of 2-,2,6-, and, with t-butyllithium, 2,i+,6-substituted products (21-33). The l - l i t h i o - 2 - t - b u t y l - l , 2 - d i h y d r o p y r i d i n e intermediate (similar to the l-lithio-2-phenyl-l,2-dihydropyridine intermediate shown previously) has "been i s o l a t e d (21_), hut though t h i s material should lend i t s e l f to reaction with alkylhalides to form 2-t-butyl5- substituted pyridines, t h i s reaction has not been reported. An anomolous reaction i s reported to occur with benzyllithium which forms the U-benzylpyridine product exclusively ( 3 l ) . Use of A l k a l i and Alkaline Metal Compounds. The reaction of pyridines with Grignard reagents has been used to alkylate (and arylate) pyridines i n the 2- and U- p o s i t i o n (3^-^3). An anomalous a l k y l a t i o n of the pyridine system under the influence of sodium i n anhydrous ammonia has been reported(UU)as shown:

Homolytic Alkylations Free Radical Processes. Homolytic a l k y l a t i o n and a r y l a t i o n of pyridines has been studied extensively and reviewed (k5). The products are almost invariably mixtures of several isomers depending on the nature of the pyridine substrate, the free r a d i c a l (andits method of generation) and the type of medium i n which the reaction i s carried out. Though early reports suggested 2-, and U-substitution exclusively, more sensitive a n a l y t i c a l techniques have shown the e a r l i e r claims to be erroneous and studies into the various factors affecting product formation have been reported

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

400

INDUSTRIAL

TABLE II ISOMER RATIOS FOR

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

Ref 58 51 55 55 51 51 51 51

Radical Source t-Bu 0 2

2

Ac 0 PbiOAc)^ 2

2

II

tl

AND

LABORATORY

ALKYLATIONS

(51)

H0M0LYTIC ALKYLATION OF PYRIDINE ISOMER RATIO Medium 23' 23.0 19.0 Non-Acid 58.0 IT 62.0 22.9 1 5 . 1 62.Τ 20.3 17.0 62.1 20.5 17. h II 62.Τ 2 1 . Τ 15.6 HOAc 76.U 21.9 20.7 HOAc 77.9 2.7 19 Λ 6.8 HOAc+HCl 93.2 0

Yield

13.5

5.0 12.9 28.3 11.8

From a commercial point of view, the methods described above do not lend themselves to the production of a l k y l pyridines on a s u f f i c i e n t l y large scale or i n an economically a t t r a c t i v e fashion. This i s p r i n c i p a l l y because the reagents involved are expensive and the mixtures formed present an overwhelming problem of sepa­ ration. Catalytic Processes. Commercially, the most a t t r a c t i v e preparations involve c a t a l y t i c processes and there are three such processes reported. The f i r s t involves the reaction of a l k y l alcohols with pyridine i n the presence of "boron phosphate" catalyst at 200-250 atm. at 300-500°C. (63-6U). It should be noted that reaction with 2 - , or i+-methylpyridine l e d to side chain a l k y l a t i o n but that reaction with 3-picoline produced 3 , 5 - l u t i d i n e . The second c a t a l y t i c method involves reaction of pyridine with a l k y l alcohols at both atmospheric (65.) and elevated pressures (66-68) over alumina or alumino-silicate catalysts. The atmo­ spheric pressure reaction afforded a mixture of a l l three p i c o l i n e isomers i n approximately equal amounts with multi-substitution also reported. At elevated pressures, the substitution i s claimed to be primarily i n the 3- p o s i t i o n with low conversions. Considerable research has been reported on the t h i r d process which involves reaction of pyridine compounds with alcohols or p o t e n t i a l alcohols i n the presence of various n i c k e l c a t a l y s t s . The reaction was f i r s t reported i n 196U, ( 6 9 ) , as a reaction of 3-hydroxypropylpyridines i n the presence of Raney n i c k e l (RaNi). (Figure l )

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24.

Pyridine and Methyl Pyridines

DIGIOVANNA E TA L .

401

RaNi 150° C. 7

R" (1o conv.)

a 2-(CH ) 0H

R» (% conv.] 2-C H (27 Γ

6-C H

5

a 2-(CH ) 0H

2- C H (50)

6-C H

5

b 3-(CH )

3- C H (28) U-C H (35)

5-C H (12) 1+-C H (15)

2

3

2

2

3

2

2

3 0 H

c MCH ) 0H 2

a)

3

after 120 hrs. ;

2

5

5

2

5

2

5

2

2

a

(0) 5

2

5

b) 210° g 3000 PSIG hydrogen

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

Journal of the American Chemical Society

Figure 1.

Reaction of pyridyl ahohob with Raney nickel (69)

The mechanism proposed was as follows: R-CH CH_

RCH0 +

RCH0

RH + CO

CO

"CH

2

2H

M 3

I.

*

=

catalyst surface

The investigation of Reinke and Kray (13) was followed by that of Myerly and Weinberg (70) who revealed the scope of the reaction with regard to both methyl sources and pyridine substrates (Tables I I I and IV). The reactions were performed i n the vapor phase using supported n i c k e l .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

402

INDUSTRIAL

A N D L A B O R A T O R Y

A L K Y L A T I O N S

TABLE I I I (70) 8,

ALKYLATION OF PYRIDINE COMPOUNDS WITH METHANOL Pyridine Compound

Temp °C.

Mole Ratio MethanolPyridine Cmpd.

2- Picoline 3- Picoline U-Picoline Quinoline 2,U-Lutidine

260-5 265-9 260 260 260

3.6:1 3.7:1 3.6:1 U.0:1

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

a

k.0:l

Contact Time (sec.)

Product (Yield %

12.2 12.2 11.5 13. k 12.2

2,6-Lutidine ( l l ) 2,5-Lutidine (5*0 2,U-Lutidine (21) 2-Methylquinoline (65) s - C o l l i d i n e (5)

Harshaw catalyst N-OIOUT was used i n a l l experiments reported i n t h i s table TABLE IV (70) METHYLATION OF PYRIDINE Mole Ratio Contact Temp. Methylating Agent Time (Sec.) Pyridine

Methylating Agent

Methanol 295 Ethanol 263 1 - Propanol 300 2 - Propanol 295 1 - Butanol 298 2 - Methyl-l-Propanol 298 Acetone 325 Methylal 258 Ethyl Orthoformate 256 Ethyl Acetate 298 Methane 260 CO-Hydrogen 270 0

a c

15:1 3:1 2.5:1 2.5:1 2.1:1 2.1:1 2.5:1 2.3:1 1.3:1 1.6:1 3.8:1 2:l:l

11.5 11.6 11Λ 12.2 lh.0 lk.0

d

12.2 1U.0 20.6 16.2 9.8 11.0

2-Picoline #Yield 57^ 61 52 38 1+8 25 38 55 57 58 10 30

Harshaw catalyst Ni-OIOUT was used i n a l l experiments reported i n t h i s table, b 2,6-Lutidine formed i n 2k% y i e l d as coproduct. By-products from t h i s reaction were diethylether, carbon monoxide, carbon dioxide, and methane, d Mole r a t i o H -C0pyridine. 2

The methylation reaction has been reported to be catalyzed by n i c k e l - n i c k e l oxide ( 7 l ) and to be reversible (72). A further variety of suitable pyridine substrates has also been revealed (73)» Concurrently, work on the mechanism of the reaction was reported (7^75.) and a study of the effects of various c a t a l y t i c substrates has been reported ( 7 6 ) .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

24.

Pyridine and Methyl

DIGIOVANNA E T A L .

Figure 2.

Pyridines

403

Methylation of pyridines (Numbers on arrows denote conversion percents; others denote yield percents)

etc Figure 3.

etc

etc

etc

Methylation of pyridine—reaction pathways

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

404

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

In our laboratories a l l possible p i c o l i n e s and l u t i d i n e s plus pyridine, i t s e l f , have been investigated as precursors f o r the methylation reaction catalyzed by n i c k e l . The reactions are summarized i n Figure 2 . In addition, 2-ethylpyridine was methylated with a 39·8? conversion of s t a r t i n g material affording a 36? y i e l d of 2-methyl6-ethylpyridine, a 2.6% y i e l d of 2 , 6 - l u t i d i n e and a 3.lk% y i e l d of 2-picoline. The major reaction paths i n the methylation of pyridine may be depicted as i n Figure 3. With the a l k y l a t i o n steps, at l e a s t , r e v e r s i b l e , as shown i n the methylation of 2-ethylpyridine, the rate equation for the combination of p a r a l l e l and series reactions leading to production of 2-picoline i s very complicated. Further, the presence of piperidones i n the f i n a l product mix complicates the rate equation. Indeed, rigorous elucidation of the k i n e t i c s of the methylation reaction presents an overwhelming task. This task i s further complicated by the fact that preliminary studies i n our laborat o r i e s involving material r e s u l t i n g from large scale methylations have indicated the formation of 2,1+-, 2 , 3 - and, possibly, 2 , 5 l u t i d i n e as a result of the methylation of 2-picoline. This evidence suggests that another mechanism may be operating at the same time as the usually accepted reactions. It i s rather surprising, therefore, that the reaction proceeds to give good y i e l d s of, for example, 2-picoline from pyridine. Evidently k-^ i s larger than any of the other rate constants so that i t i s only when the concentration of the product, 2 - p i c o l i n e , becomes s i g n i f i c a n t that formation of by-products, other than hydrogénation products, begins to become a factor. Since methyl pyridines are r e a d i l y available from ring formation reactions, the methylation reaction i s u s e f u l , primarily, as a means of preparing polymethyl pyridines e s p e c i a l l y 2,1+-, 2 , 5 and 2 , 6 - l u t i d i n e and 2,1+,6-collidine. Acknowledgement The authors wish to express t h e i r appreciation to Drs. W. H. Rieger, F. A. Karnatz and Mr. R. A. Kattau. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8.

A. Ladenburg, Ber., 1 6 , 1408 (1883). Ibid., 2059 (1883). A. Ladenburg, Ann., 247, 1 (1888). Ibid., Ber., 1 8 , 2961 (1885). A. E. Chichibabin and P. F. Ryumshin, J . Russ. Phys. Chem. Soc., 47, 1297 ( 1 9 1 5 ) ; Chem. Abstr., 9 , 3057 (1915). J . von Braun and W. Pinkernelle, Ber., 64, 1871 (1931). J . Overhoff and J . P. Wibaut Rec. trav. Chim., 5 0 , 957 (1931). P. C. Teague, J . Am. Chem. Soc., 6 9 , 714 (1947).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24. DiGiovANNA E T A L .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

14.

24.

Pyridine and Methyl

Pyridines

405

9. Κ. E. Crook and S. M. McElvain, J. Am. Chem.Soc.,52, 4006 (1930). 10. Κ. E. Crook, J. Am. Chem.Soc.,70,416(1948). 11. J. Kuthan, et a l . , Coll. Czech. Chem. Commun., 35., 2787 (1970); Chem. Abstr., 73, 109091r (1970). 12. Yu. I. Chumakov and V. F. Novikova, Khim. Prom.Ukr.,2,47 (1968); Chem. Abstr., 69,43743m(1968). 13. N. S. Prostakov, et a l . , Khim. Geterotsikl. Soedin., 6, 779 (1970); Chem. Abstr., 73,109635u(1970). C. Mercier and J. P. Dubosc, Bull. Soc. Chim. Fr.,12,4425 (1969); Chem. Abstr., 72, 90221m (1970). 15. Yu. I. Chermakov and B. D. Kabulov, Ukr. Khim. Zh.,41(1), 99 (1975); Chem. Abstr., 83,58622j(1975). 16. C. S. Giam and J. L. Stout, Chem. Comm., 1970, 478. 17. C. S. Giam and S. D. Abbott, J. Am. Chem.Soc.,93 (5), 1294 (1971). 18. C. S. Giam, et a l . , Can. J. Chem., 51, 2305 (1975). 19. R. Grashey and R. Huisgen, Ber., 92,2641(1959). 20. C. S. Giam and J. L. Stout, Chem. Comm., 1969, 142. 21. R. F. Francis, et a l . , J. Org. Chem., 39 (1), 59 ( 1974). 22. R. F. Francis, et a l . , Chem. Comm., 1971, 1420. 23. F. V. Scalzi and N. F. Golob, J. Org. Chem., 36 (17), 2541 (1971). H. C. Brown and B. Kanner, J. Am. Chem.Soc.,88 (5), 986 (1966). 25. R. A. Abramovitch and C. S. Giam,Can.J. Chem.,42,(7), 1627 (1964); Chem. Abstr.,61,5477a(1964). 26. Ibid., 41 (12), 3127 (1963); Chem. Abstr., 60,3961f(1964). 27. Ibid., 40, 213(1960);Chem. Abstr., 57,12425d(1962). 28. K. Ziegler and H. Zeiser, Ann.,485,174(1931). 29. Ibid., Ber., 63B,1847(1930). 30. T. Kauffman, et a l . , Ber.,109(12),3864(1976). 31. H. Gilman and H. A. Mc Ninch, J. Org. Chem., 27, 1889 (1962). 32. H. Gilman and G. C. Gainer, J. Am. Chem.Soc.,71., 2327 (1949). 33. T. Taguchi, et a l . , Chem. Lett., 12, 1307 (1973); Chem. Abstr., 80,59904c(1974). 34. F. W. Bergstrom and S. H. Mc Allister, J. Am. Chem. Soc., 52,2845(1930). 35. W. von E. Doering and V. Z. Pasternak, J. Am. Chem. Soc., 72,143(1950). 36. E. Bergmann and W. Rosenthal, J. Prakt. Chem., 135 (2), 267 (1932); Chem. Abstr., 27, 982 (1933). 37. W. L. C. Veer and S. Goldschmidt, Rec. trav. Chim.,65,793 (1946); Chem. Abstr., 41, 3100g (1948). 38. R. A. Benkeser and D. S. Holton, J. Am. Chem.Soc.,73, 5861 (1951). 39. D. Bryce - Smith, et a l . , Chem.Ind.,495(1964). 40. Ibid., J. Chem.Soc.,Perkin I, 1976, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

406

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

41. R. A. Abramovitch and G. A. Poulton, J. Chem. Soc. (Β), 1969, 901. 42. N. Goetz-Luthy, J. Am. Chem. Soc., 71,2254(1949). 43. M. Gilman, et al., J. Am. Chem. Soc.,81,4000(1959). 44. F. J. Villani, et al., J. Org. Chem., 36 (12), 1709 (1971). 45. R. A. Abramovitch and J. G. Saha in "Advances in Heterocyclic Chemistry," A. R. Katritzky and A. J. Boulton, Eds., Vol. 6, Academic Press. New York, 1966, p.229. 46. A. Clerice, et al., Tetrahedron, 29, 2775 (1973). 47. F. Minisci, et al., Tetrahedron,28,2403(1972). 48. G. P. Gardini, et al., Chim. Ind. (Milan), 53, 263 (1971). 49. R. Galli, et al., Tetrahedron, 26,4083(1970). 50. Κ. C. Bass and P. Nababsing, J. Chem. Soc. (c), 1969, 388. 51. Ibid., 1970, 2169. 52. R. Noyovi et al., Tetrahedron, 25, 1125 (1969). 53. F. Minisci, et al., Tetrahedron Letters, 54, 5609 (1968). 54. H. Nozaki, et al., Tetrahedron Letters,43,4259(1967). 55. R. A. Abramovitch and K. Kenaschuk, Can. J. Chem.,45,509 (1967). 56. R. A. Abramovitch and M. Saha, J. Chem. Soc. (Β), 1966, 733. 57. R. A. Abramovitch and J. G. Saha, J. Chem.Soc.,1964,2175. 58. K. Schwetlick and R. Lungwitz, Z. Chem.,4(12),458(1964); Chem. Abstr., 62, 9101a (1965). 59. J. H. P. Utley and R. J. Holman, Electrochim. Acta. 21 (11), 987 (1976). 60. F. Minsci, et al., Ital. 906,418 (1972); Chem. Abstr., 83, 58667c (1975). 61. F. Minsci, et al., Gazz. Chim. Ital., 105 (9-10), 1083 (1975); Chem.Abstr.,84,168736j(1976). 62. T. Caronna, et al., Tetrahedron Letters, 1976 (20), 1731. 63. H. Moll and H. J. Uebel, German (East) Patent54,006(l967); Chem. Abstr., 68,59436d(1968). 64. Ibid., Chem. Tech. (Berlin), 18 (1O), 629 (1966); Chem. Abstr., 66,55348n(1967). 65. N. M. Cullenane, et al., J. Soc. Chem. Ind., 67,148(1948). 66. A. K. Dariev, et al., Tr. Buryat. Kompleks. Nauch Issled. Inst. Akad. Nauk. SSSR. Sib. Otd., 20, 3 (1966); Chem. Abstr., 68, 78091d (1968). 67. A. D. Dariev, et al., Izv. Sib. Otd. Akad. Nauk. SSSR. Ser. Khim. Nauk. SSSR. Ser. Khim. Nauk., 1966 (3), 105; Chem. Abstr., 67,64193f(1967). 68. V. N. Gudz, et al., Tr. Buryat. Kompleks Nauch. - Issled. Inst. Akad. Nauk. SSSR, Sib. Otd., 20, 3 (1966); Chem. Abstr., 68,104924z(1968). 69. M. G. Reinke and L. R. Kray, J. Am. Chem. Soc., 86, 5355, (1964). 70. R. C. Myerly and K. G. Weinberg, J. Org. Chem., 31, 2008 (1966). 71. Ibid., U.S. Patent3,354,165(1967). 72. Ibid., U.S. Patent3,334,101(1967).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

24.

DIGIOVANNA

ET

AL.

Pyridine and Methyl Pyridines

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch024

73. Ibid., U.S. Patent3,428,641(1969). 74. M. G. Reincke, et, al., Ann. N.Y. Acad. Sci., 145 (1), 116 (1967). 75. G. Grins"Catalytic-Methylationof Pyridines", Univ. Microfilms, Ann Arbor, Mich., (1970).

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

407

25

Friedel-Crafts Alkylation of Bituminous Coals

W. HODEK, F. MEYER, and G. KOLLING

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

Bergbau-Forschung GmbH, Frillendorfer Str. 351, 4300 Essen 13, West Germany

Coal and mineral oil are not only used as f u e l , but they are moreover important raw materials f o r the chemical industry, e s p e c i a l l y as carbonaceous materials f o r the production o f organic chemicals. For this use, mineral o i l s show two important advantages as compared with c o a l : (a) they are liquids and are therefor easier to handle and process; (b) t h e i r compositions are complicated but easier to analyze. Bituminous coals are r e l a t i v e l y insoluble s o l i d s , and t h e i r chemical compositions, which are based on aromatic structures, are still p a r t i a l l y unknown. I t is expected that a better knowledge of the chemical structure of coal may open new ways to develop new processes f o r an economic use o f coal. The e l u c i dation o f the chemical structure o f coal is hampered by the fact that only a small part of the coal is soluble in suitable solvents. Three reasons are thought to cause t h i s low extractability: a) b) c)

C o a l s c o n s i s t o f some c r o s s l l n k e d m a c r o m o l e c u l e s ; Hydrogen bonding - e s p e c i a l l y a t p h e n o l i c groups hold the coal molecules t o g e t h e r ; P h y s i c a l a t t r a c t i v e f o r c e s , caused by t h e h i g h a r o m a t l d t y o f t h e b i t u m i n o u s c o a l s , have an a d d i t i o n a l bonding e f f e c t .

In o r d e r t o o b t a i n I n s i g h t I n t o t h e chemical s t r u c t u r e o f c o a l , methods a r e needed t o c o n v e r t c o a l I n t o s u b s t a n c e s which a r e s o l u b l e 1n s u i t a b l e s o l v e n t s . T h i s c o n v e r s i o n s h o u l d be c o n d u c t e d a t m i l d c o n d i t i o n s so t h a t t h e c o a l m o l e c u l e s remain unchanged as much as p o s s i b l e . So f a r , t h e most u s u a l method a p p l i e d t o make b i t u m i n o u s c o a l s more s o l u b l e 1n s i m p l e l i q u i d s 1s h y d r o g é n a t i o n w h i c h , however, r e q u i r e s temperatures e x c e e d i n g 350° t o 400°C; c o n s e q u e n t l y c r a c k i n g r e a c t i o n s a l s o o c c u r . T h e r e a r e , however, c h e m i c a l r e a c t i o n s t h a t make 1 t p o s s i b l e t o Improve t h e e x t r a c t a b l H t y o f c o a l a t l o w e r t e m p e r a t u r e s , 1n p a r t i c u l a r those I n v o l v i n g F r i e d e l - C r a f t s c a t a l y s t s . Heredy and Neuworth (1) f o r e x a m p l e , used boron t r 1 f l u o r i d e and phenol f o r t h i s p u r p o s e ; and O u c h l , Imuta and Yamashlta ( 2 ) employed 408

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

25.

H O D E K

E T

A L .

Bituminous

Coals

409

p - t o l u e n e s u l p h o n l c a d d and p h e n o l . K r o g e r (3) s t u d i e d t h e r e a c t i o n s between b i t u m i n o u s c o a l s and p r o p y l c h l o r i d e 1n carbon d l s u l p h l d e a t 4 5 ° C , u s i n g aluminum c h l o r i d e as c a t a l y s t . Quite a d i f f e r e n t method o f a c h i e v i n g t h i s aim was used by S t e r n b e r g e t a l ( 4 ) , namely r e d u c t i v e a l k y l a t i o n o f b i t u m i n o u s c o a l w i t h sodium and a l k y l h a l l d e s . Heredy and h i s c o - w o r k e r s ( 1 , 5 ) have attempted t o I n t e r p r e t the r e a c t i o n w i t h phenol and boron t r l f l u o r l d e as a d e p o l y m e r l z a t l o n p r o c e s s f o l l o w e d by s a t u r a t i o n o f the f r a g m e n t s . In f a c t , they found t h a t c o n s i d e r a b l e q u a n t i t i e s o f phenol r e a c t e d w i t h the c o a l . In l o w - r a n k c o a l s , the tendency towards t h i s r e a c t i o n was g r e a t e r than w i t h c o k i n g c o a l s which d i d not show any n o t a b l e Improvement o f e x t r a c t a b l l l t y . There has a l s o been c o n s i d e r a b l e a d d i t i o n a l work by many I n v e s t i g a t o r s t o I n v e s t i g a t e d e p o l y m e r l z a t l o n and a l k y l a t i o n o f coal. In a r e c e n t l y p u b l i s h e d p a p e r by L a r s e n ( 6 ) , t h e most I n t e r e s t i n g r e s u l t s 1n t h i s s u b j e c t are assembled and d i s c u s s e d . The I n v e s t i g a t i o n s t o be d e s c r i b e d In o u r p a p e r a l s o s t a r t e d from the well-known f a c t t h a t Lewis a d d s , such as aluminum c h l o r i d e , can e x e r t n o t o n l y a c o n d e n s i n g but a l s o a c r a c k i n g e f f e c t on aliphatic-aromatic molecules. We hoped, however, t h a t 1 t would be p o s s i b l e to p r e v e n t most o f t h e s e s i d e r e a c t i o n s by u s i n g m i l d conditions. Our r e s u l t s f o r t h e F r i e d e l - C r a f t s a c y l a t l o n o f c o a l (7) i n d i c a t e t h a t bituminous c o a l becomes e x t r a c t a b l e not o n l y by d e p o l y m e r l z a t l o n but a l s o by the I n t r o d u c t i o n o f l o n g c h a i n s u b s t i t u e n t s Into the coal m o l e c u l e s . By the s u b s t i t u t i o n w i t h l o n g c h a i n a l i p h a t i c g r o u p s , the s e p a r a t i o n between t h e a r o m a t i c s t r u c t u r e s o f a d j a c e n t m o l e c u l e s can be i n c r e a s e d s o t h a t the p h y s i c a l a t t r a c t i v e f o r c e s are r e d u c e d . We t r i e d a l k y l a t i o n 1n o r d e r t o make b i t u m i n o u s c o a l more e x t r a c t a b l e . P o s s i b l y i n the f u t u r e e x t r a c t s can be o b t a i n e d e c o n o m i c a l l y by r e a c t i o n o f c o a l w i t h m i n e r a l o i l f r a c t i o n s under r e l a t i v e l y m i l d c o n d i t i o n s . A l k y l a t i o n with Alkyl

Chlorides

and A1C1

I n i t i a l l y we used a l k y l c h l o r i d e s 1n t h e p r e s e n c e o f aluminum c h l o r i d e as c a t a l y s t f o r a l k y l a t i o n . 10 grams o f a medium v o l a t i l e c o a l w i t h 24.6% v o l a t i l e m a t t e r were f i n e l y ground and s u s pended i n 50 c c o f carbon b i s u l f i d e . 10 grams o f powdered a l u m i num c h l o r i d e were then added. The m i x t u r e was then t r e a t e d a t 45°C w i t h 0.25 moles o f a l k y l c h l o r i d e . The r e a c t i o n time was 3 hours. A l k y l c h l o r i d e s o f d i f f e r e n t c h a i n l e n g t h - 3 up t o 18 carbon atoms i n t h e c h a i n - were u s e d . The c h l o r i d e s w i t h 16 and 18 carbon atoms r e q u i r e d a r e a c t i o n time o f 24 h o u r s . In a l l r e a c t i o n s , a l k y l groups were I n s e r t e d i n t o t h e c o a l which c o u l d be e a s i l y d e t e r m i n e d by t h e w e i g h t i n c r e a s e o f a l l s a m p l e s . From the i n c r e a s e i n w e i g h t , the number o f a l k y l groups p e r 100 carbon atoms which have r e a c t e d w i t h t h e c o a l were c a l c u l a t e d ( F i g u r e 1 ) .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

410

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

2f 1-1 3

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Figure 1.

1 6

1 8

1

1 12

1

1 16

1 — 18 C-atoms in alkyl groups

Alkylation of medium volatile coal with alkyl chlorides of different chain lengfih

Two t o t h r e e a l k y l groups r e a c t e d as a r u l e p e r 100 carbon atoms i n the c o a l . A remarkable e x c e p t i o n was p r o p y l c h l o r i d e . In t h i s c a s e , more t h a n 7 p r o p y l groups p e r 100 carbon atoms reacted. O b v i o u s l y , m u l t i p l e s u b s t i t u t i o n o f the aromatic coal c o n s t i t u e n t s was f a v o u r e d by the r e l a t i v e l y s m a l l p r o p y l g r o u p . With I n c r e a s i n g s i z e o f the a l k y l g r o u p s , the p o s s i b i l i t i e s o f s u b s t i t u t i o n were l i m i t e d w i t h t h e r e s u l t t h a t the degree o f a l k y l a t i o n d e c r e a s e d r a p i d l y u n t i l i t remained a t a c o n s t a n t val ue. A l k y l a t i o n c o n d u c t e d i n t h i s way had o n l y a s m a l l i n f l u e n c e on the e x t r a c t a b i l i t y o f t h e c o a l . 27.2% o f o u r u n t r e a t e d c o a l c o u l d be e x t r a c t e d w i t h p y r i d i n e . A f t e r a l k y l a t i o n , a maximum e x t r a c t a b i l i t y o f 35% was r e a c h e d . The e x t r a c t a b i l i t y 1n c h l o r o form i n c r e a s e d from 4 t o 16%. T h i s i n c r e a s e i n e x t r a c t a b i l i t y i s not only c a u s e d m a i n l y by the aluminum c h l o r i d e as we found i n a blank t e s t . The c o u r s e o f r e a c t i o n d u r i n g t h e a l k y l a t i o n o f c o a l can be p o s t u l a t e d as f o l l o w s : In t h e p r i m a r y s t e p , t h e c o a l i s d e p o l y m e r i z e d by the aluminum c h l o r i d e ; o t h e r i n v e s t i g a t o r s have a l s o shown t h i s phenomenon i n the p r e s e n c e o f Lewis a c i d s . Now, two r e a c t i o n s come i n t o c o m p e t i t i o n w i t h each o t h e r : 1) The r e c o m b i n a t i o n o f the fragments i n a t l e a s t o u r medium v o l a t i l e c o a l r e s u l t e d i n m a t e r i a l s w i t h low e x t r a c t a b i l i t y b e i n g formed a g a i n . 2) The c a p t u r e o f the fragments by r e a c t i o n w i t h the a l k y l c h l o r i d e s thus p r e v e n t i n g recombination r e a c t i o n s . When r e a c t i o n 2 p r e d o m i n a t e s , t h e coal has s p l i t t o form products with high e x t r a c t a b i l i t y . In our c a s e , r e a c t i o n 2 took p l a c e a t low r a t e s . T h u s , r e a c t i o n 1 predominated w i t h the r e s u l t t h a t the e x t r a c t a b i l i t y o f the medium v o l a t i l e c o a l was o n l y s l i g h t l y i n c r e a s e d by a l k y l a t i o n . The system a l k y l c h l o r i d e / aluminum c h l o r i d e was n o t r e a c t i v e enough 1n o r d e r to make t h e c o a l e x t r a c t a b l e by a l k y l a t i o n .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

25.

H O D E K

E T

A L .

Bituminous Coals

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

A l k y l a t i o n with O l e f i n s

411

and HF/BF.

We used f o r the f u r t h e r t e s t s the system hydrogen f l u o r i d e / boron t r l f l u o r i d e as c a t a l y s t and o l e f i n s as means o f a l k y l a t i o n . A 5% s o l u t i o n o f boron t r i f l u o r l d e i n hydrogen f l u o r i d e seemed t o b e , f o r s e v e r a l r e a s o n s , an advantageous c a t a l y s t f o r t h e alkylation of coal. L i q u i d hydrogen f l u o r i d e i s an e x c e l l e n t s o l v e n t f o r many o r g a n i c compounds such as a r o m a t i c s , a l c o h o l s , a c i d s , e t h e r s , e t c . ; t h e s e l a t t e r s u b s t a n c e s behave i n the p r e s e n c e o f hydrogen f l u o r i d e as weak bases and add one p r o t o n . T h u s , hydrogen f l u o r i d e can a c t as a r e a c t i o n medium and as a c a t a l y s t . Boron t r i f l u o r l d e combines w i t h hydrogen f l u o r i d e to produce F l u o b o r i c a c i d which i s a v e r y s t r o n g a c i d w i t h a c a t a l y t i c a c t i v i t y much h i g h e r than t h a t o f hydrogen f l u o r i d e . B e s i d e s t h a t , the low v i s c o s i t y and the low s u r f a c e t e n s i o n o f t h e hydrogen f l u o r i d e p e r m i t good m i x i n g i n heterogeneous r e a c t i o n s . A disadvantage i s the s t r o n g c o r r o s i v e e f f e c t o f H F - B F - m i x t u r e s . A "monel" a u t o c l a v e proved to be s u f f i c i e n t l y r e s i s t a n t even a t h i g h e r temperatures. Four d i f f e r e n t t y p e s o f c o a l were used f o r t h e a l k y l a t i o n tests (Figure 2): a h i g h v o l a t i l e c o a l w i t h 34.4% ( v o l a t i l e m a t t e r ) , a medium v o l a t i l e c o a l w i t h 24.2%, a low v o l a t i l e c o a l w i t h 19.4% and a s e m i - a n t h r a c i t e w i t h 14.4%. The t e s t s were made i n a 2 U t e r - s h a k l n g a u t o c l a v e . Initially the i n f l u e n c e o f hydrogen f l u o r i d e and H F - B F - was i n v e s t i g a t e d on the e x t r a c t a b i l i t y o f c o a l s w i t h p y r i d i n e . 20 grams o f f i n e l y ground c o a l were t r e a t e d w i t h about 1000 grams o f hydrogen f l u o r i d e o r a 5% s o l u t i o n o f BF~ 1n hydrogen f l u o r i d e f o r f o u r hours a t t e m p e r a t u r e s o f 20°C and 80°C. The e x t r a c t a b i l i t y o f c o a l s w i t h p y r i d i n e a f t e r t h i s t r e a t ment 1s shown i n F i g u r e 3. The l e f t column I n d i c a t e s the e x t r a c t a b i l i t y o f the u n t r e a t e d c o a l . The two columns on the r i g h t - h a n d s i d e show the I n f l u e n c e o f t h e hydrogen f l u o r i d e . As a c o m p a r i s o n , the i n f l u e n c e o f aluminum c h l o r i d e has been p l o t t e d , t o o . I t can be seen t h a t the e x t r a c t a b i l i t y o f h i g h v o l a t i l e c o a l d e c r e a s e d , p r o b a b l y due t o t h e c o n d e n s i n g e f f e c t s o f t h e c a t a l y s t s on t h e coal molecules. I t seems t h a t t h e medium v o l a t i l e c o a l remains unchanged. C l e a v i n g and c o n d e n s i n g e f f e c t s p r o b a b l y b a l a n c e each o t h e r . The e x t r a c t a b i l i t y o f t h e low v o l a t i l e c o a l i s however I n c r e a s e d , e s p e c i a l l y by hydrogen f l u o r i d e a t 80°C. The s e m i - a n t h r a c i t e i s e s s e n t i a l l y u n a f f e c t e d by such t r e a t e m e n t s because o f i t s h i g h l y condensed a r o m a t i c s t r u c t u r e . Aluminum c h l o r i d e and hydrogen f l u o r i d e have comparable e f f e c t s on the c o a l s . The a d d i t i o n o f boron t r i f l u o r l d e to the hydrogen f l u o r i d e has no s i g n i f i c a n t i n f l u e n c e on t h e e x t r a c t a b i l i t y o f the c o a l s . A f t e r we a s c e r t a i n e d t h e i n f l u e n c e o f the c a t a l y s t system on the e x t r a c t a b i l i t y o f the c o a l s , a l k y l a t i o n

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

volatile

coal

Semi-anthracite

Low

coal

coal

Medium v o l a t i l e

High v o l a t i l e

(dry

10,7

2,5

2,1

3,4

Figure 2.

basis)

Ash

87,6 89,7 91 ,0

24,2 19,4 14,4

H

3,88

4,54

4,94

5,04

(daf)

Analytical data of the coals

82,7

(daf)

C

34,4

(daf)

VM

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

1,74

1 ,59

1 ,82

1,59

(daf)

Ν

1 ,03

1 ,20

0,86

0,95

(daf)

S

0,07

0,23

0,12

0,25

CI (dry basis)

2,2

2,7

4,6

9,4

(daf

0

25.

HODEK E T A L .

Bituminous

Coals

413

I

20-1

•&15

I

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

Kl

high volatile coal

Figure 3.

1

medium volatile coal

I

untreated

•

AICI 3 (50 e )

0

HF

(20°)

1

HF

180°)

I low volatile coal

semianthracite

Extractability of bituminous coals after treatment with Lewis acids

•

high volatile coal

medium volatile coal

low volatile coal

untreated (in pyridine)

Π

Pyridine

0

Chloroform

semianthracite

Figure 4. Extractability of bituminous coals after alkyhtion with 1-hexadecene (HF/BF , 80°C) 3

t e s t s were begun u s i n g o l e f i n s . The r e a c t i o n c o n d i t i o n s were t h e same as d e s c r i b e d b e f o r e . 20 grams o f c o a l and 20 grams o f o l e f i n s were added to the a u t o c l a v e . Preliminary tests with short chain o l e f i n s such as e t h y l e n e , p r o p y l e n e and hexene I n d i c a t e d o n l y minor r e a c t i o n s with c o a l . Some o l i g o m e r s o f t h e o l e f i n s were p r o d u c e d , but t h e y d i d not r e a c t w i t h the c o a l . Under the c o n ­ d i t i o n s i n v e s t i g a t e d , however, l o n g c h a i n o l e f i n s r e a c t e d r e a d i l y

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

414

AND

LABORATORY

ALKYLATIONS

w i t h the c o a l . The a l k y l a t i o n was c o n d u c t e d w i t h o l e f i n s w i t n 12 up to 20 carbon atoms i n the c h a i n a t 80°C. We used a 5% s o l u t i o n o f boron t r i f l u o r l d e i n the hydrogen f l u o r i d e as c a t a l y s t w h i c h , as e x p e c t e d , y i e l d e d b e t t e r r e s u l t s than pure hydrogen fl uoride. The c o a l s were r e a c t e d w i t h hexadecene and the e x t r a c t a b i l i t i e s o f the r e a c t i o n p r o d u c t s were d e t e r m i n e d . The r e s u l t s are shown i n F i g u r e 4. The e x t r a c t a b i l i t i e s o f t h e low and medium v o l a t i l e c o a l were i n c r e a s e d s i g n i f i c a n t l y by t h i s r e a c t i o n . 68% o f the low v o l a t i l e c o a l and 65% o f the medium v o l a t i l e c o a l were extracted with p y r i d i n e . The e x t r a c t a b i l i t y 1n c h l o r o f o r m and b e n z e n e , t o o , I n c r e a s e d t o 50 and 30% r e s p e c t i v e l y . The h i g h v o l a t i l e c o a l and the s e m i - a n t h r a c i t e showed no e s s e n t i a l i n c r e a s e of extractability. As t h e n e x t s t e p , the e x t r a c t a b i l i t i e s o f t h e a l k y l a t e d c o a l s were d e t e r m i n e d as a f u n c t i o n o f the c h a i n l e n g t h o f t h e o l e f i n s used ( F i g u r e 5 ) . The e x t r a c t a b i l i t y i n c r e a s e d w i t h t h e l e n g t h o f c h a i n and r e a c h e d a maximum v a l u e o f about 70% f o r 18 carbon atoms i n the case o f both c o a l s . The number o f a l k y l groups i n s e r t e d i n t o the c o a l s d u r i n g a l k y l a t i o n was d e t e r m i n e d by the w e i g h t i n c r e a s e o f the samples and i s r e l a t e d , as d e s c r i b e d above, to 100 carbon atoms i n the coal (Figure 6). In case o f the low and medium v o l a t i l e c o a l s , two to t h r e e a l k y l groups p e r 100 carbon atoms were i n s e r t e d r e g a r d l e s s o f the l e n g t h o f c h a i n . For the high v o l a t i l e c o a l , t h i s v a l u e amounted o n l y t o 0.6 t o 0 . 8 , and w i t h the s e m i - a n t h r a c i t e , i t was below 0 . 5 . These r e s u l t s show t h a t low and medium v o l a t i l e c o a l s have a s i m i l a r c h e m i c a l s t r u c t u r e and t h a t t h e s e c o a l s have a maximum o f a r o m a t i c C-H g r o u p s , compared w i t h o t h e r types o f c o a l . The e x i s t e n c e o f t h e s e groups i s a c o n d i t i o n f o r the a p p l i c a t i o n o f a F r i e d e l - C r a f t s - a l k y l a t l o n as c o n d u c t e d 1n t h i s work.

12

Figure 5.

H

16

18

20

C-atoms of o l e f i n

Extractability with increasing chain length of olefin

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

25.

HODEK E T

AL.

Bituminous

Figure 6.

Coals

415

high

medium

low

semi-

volatile

volatile

volatile

anthracite

Alkylation of coals of different ranks

In case o f y o u n g e r c o a l s , t h e a r o m a t i c u n i t s a r e more s u b s t i t u t e d w i t h a l i p h a t i c and n a p h t h e n i c g r o u p s . Therefore, a l o w e r a r o m a t i d t y 1s g i v e n . With i n c r e a s i n g rank o f the c o a l s , the p e r c e n t a g e o f a r o m a t i c carbon n o t bound t o hydrogen I n c r e a s e s . T h e r e are s t i l l more h i g h l y condensed systems which cannot be alkylated sufficiently. The a f o r e m e n t i o n e d t e s t s showed t h a t b i t u m i n o u s c o a l s , e s p e c i a l l y low and medium v o l a t i l e c o a l s , can be a l k y l a t e d by the very r e a c t i v e system o f H F / B F / o l e f i n s and t h a t the e x t r a c t a b i l i t y o f such c o a l s can be g r e a t l y i n c r e a s e d . What 1s the reason f o r the h i g h e x t r a c t a b i l i t y o f the a l k y lated coals? We I n d i c a t e d above t h a t F r i e d e l - C r a f t s c a t a l y s t s caused c l e a v i n g and c o n d e n s i n g r e a c t i o n s i n the c o a l m o l e c u l e s . A c c o r d i n g t o what we p r e s e n t l y know, b i t u m i n o u s c o a l i s e s s e n t i a l l y a m i x t u r e o f h i g h m o l e c u l a r m a t e r i a l s , t h e m o l e c u l e s o f which c o n s i s t o f a r o m a t i c u n i t s l i n k e d by a l i p h a t i c o r by e t h e r b r i d g e s (Figure 7). A l i p h a t i c b r i d g e s i n p a r t i c u l a r are e a s i l y c l e f t by F r i e d e l - C r a f t s c a t a l y s t s as can be c o n f i r m e d by model t e s t s . Diphenyl-methane s t r u c t u r e s , which had been found 1n c o a l , are c l e f t by aluminum c h l o r i d e o r H F - B F - . In o r d e r t o demonstrate such c l e a v a g e s i n the c o a l , o u r t e s t c o a l s were f i r s t e x t r a c t e d w i t h p y r i d i n e i n o r d e r t o remove a l l l o w - m o l e c u l a r c o n s t i t u e n t s . T h e n , t h e y were a l k y l a t e d w i t h H F - B F - and hexadecene, and the p r o d u c t was e x t r a c t e d w i t h a c e t o n e . By l i q u i d - s o l i d c h r o m a t o g r a p h y , a f r a c t i o n was o b t a i n e d from t h e acetone e x t r a c t , the i n f r a - r e d spectrum o f which was v e r y s i m i l a r to t h a t o f the a l k y l a t e d c o a l and which c o n s i s t e d o b v i o u s l y o f a l k y l a t e d a r o matics. R e l a t e d t o the q u a n t i t y o f c o a l e x t r a c t e d t h e q u a n t i t y o f t h i s f r a c t i o n was 0.35% 1n t h e low and medium v o l a t i l e c o a l and 0.2% i n the h i g h v o l a t i l e c o a l . S e m i - a n t h r a c i t e s d i d not 3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

416

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

Ar=aromatic structural unit

X = CHo-.-CH-.-O-.-CH ,-0-,-CH ,-CH -

Ar-Ar. 2

3.

I*

Ar-X-Ar.

Ar

Ar.

Ar

Ar.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch025

Figure 7. Connections between aromatic units in coal

show t h i s f r a c t i o n . T h i s f r a c t i o n can be formed o n l y by s p l i t t i n g from t h e h i g h - p o l y m e r i c c o a l m o l e c u l e s . The q u a n t i t a t i v e p r o p o r t i o n s o b t a i n e d from t h e i n d i v i d u a l c o a l s c o r r e s p o n d t o t h e o b s e r v a t i o n s made b e f o r e ; both low and medium v o l a t i l e c o a l s are v e r y w e l l s u i t a b l e f o r the a l k y l a t l n g - c r a c k i n g s e q u e n c e . Summary: A l k y l a t i o n w i t h F r i e d e l - C r a f t s c a t a l y s t s can promote p r o d u c t i o n o f s o l u b l e p r o d u c t s from c o a l . T h i s method 1s c u r r e n t l y n o t e c o n o m i c a l but t h e I n f o r m a t i o n o b t a i n e d has c l a r i f i e d s e v e r a l points. The e x t r a c t s o b t a i n e d from the a l k y l a t i o n o f c o a l as d e s c r i b e d above, a r e b l a c k , s h i n y , s o l i d s u b s t a n c e s which a r e n o t d i s t H l a b l e and a p p a r e n t l y s t i l l have v e r y h i g h m o l e c u l a r weights. They a r e v e r y s i m i l a r i n t h e i r p r o p e r t i e s t o t h e e x t r a c t s which we have o b t a i n e d p r e v i o u s l y by a c y l a t i o n o f t h e same c o a l s w i t h c a r b o x y l l c a c i d c h l o r i d e s and aluminum c h l o r i d e . References: 1. 2. 3. 4.

L. A. Heredy and M. B. Neuworth, Fuel, Lond. 41, 221, (1962) K. Ouchi, K. Imuta and Y. Yamashita, Fuel, Lond. 44, 29, (1965) C. Kröger, Forschungsber. Nordrhein-Westfalen No. 1488 (1965) H. W. Sternberg, C. L. Delle Donne, P. Pantages, E. C. Moroni and R. E. Markby, Fuel, Lond. 50, 432 (1971) 5. L. A. Heredy, A. E. Kostyo and M. B. Neuworth, Adv. Chem. Ser. 55, 493 (1966); Fuel, Lond. 43, 414 (1964); Fuel, Lond. 44, 125 (1965) 6. J. W. Larsen and E. W. Kuemmerle, Fuel, Lond. 55, 162 (1976) 7. W. Hodek and G. Kölling, Fuel, Lond. 52, 220 (1973)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26 C o a l L i q u e f a c t i o n b y A r o m a t i c Interchange w i t h P h e n o l a n d Catalytic H y d r o g e n o l y s i s

R. H. MOORE, E. C. MARTIN, J. L. COX, and D. C. ELLIOTT

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

Pacific Northwest Laboratories, Division of Battelle Memorial Institute, Richland, WA 99352

Not only can coals be alkylated readily, they also can be used to alkylate aromatic compounds. L. A. Heredy, et al. (1-3) realized that coal could be depolymerized by using i t as an alkylating agent. The mechanism of the reaction was first demonstrated using model compounds to show that methylene groups joining two aromatic groups could be cleaved at the ring and the methylene group would then alkylate another aromatic substrate. The first step involves protonation of an aromatic ring adjacent to the methylene group. This is followed by nucleophilic b i molecular substitution of the aryl group by phenol and regeneration of the proton. (1)

(2)

(3) L. A . H e r e d y , e t a K employed BF3 as a c a t a l y s t . BF3 forms a s t a b l e a d d u c t w i t h phenol which y i e l d s t h e p r o t o n c a t a l y s t due to the d i s s o c i a t i o n e q u i l i b r i u m :

(4)

417

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

418

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

In a d d i t i o n t o d e p o l y m e r i z a t i o n H e r e d y , e t al_. showed t h a t a l k y l s i d e c h a i n s were removed from the c o a l ( d e a l k y l a t i o n ) and added to the phenol ( a l k y l a t i o n ) . They were a b l e t o demonstrate the e x i s t e n c e o f i s o p r o p y l groups i n c o a l by t h i s means. K. O u c h i , e t à\_. ( 4 - 8 ) l a t e r i n v e s t i g a t e d the r e a c t i o n u s i n g p - t o l u e n e s u l f o n i c a c i d as c a t a l y s t n e a r the r e f l u x t e m p e r a t u r e o f phenol ( 1 8 5 ° C ) . Based on subsequent p y r i d i n e e x t r a c t i o n , Ouchi r e p o r t e d d e p o l y m e r i z a t i o n s o f Y u b a r i c o a l as h i g h as 90 p e r c e n t w i t h a m o l e c u l a r w e i g h t o f 312 f o r the d e p o l y m e r i z e d c o a l monomer. For c o a l s o f i n c r e a s i n g rank (70-93 p e r c e n t maf C) the m o l e c u l a r w e i g h t o f the d e p o l y m e r i z e d p r o d u c t s i n c r e a s e d from about 300 t o >1000. The y i e l d o f m a t e r i a l s o l u b l e i n p y r i d i n e approached 100 p e r c e n t f o r c o a l s o f low t o i n t e r m e d i a t e rank and then f e l l o f f s h a r p l y f o r the h i g h r a n k i n g c o a l s . D a r l a g e , e t a K (9) employed a v a r i a t i o n on H e r e d y ' s t e c h niques. They o x i d i z e d c o a l w i t h 2M HNO3 a t 60-70°C f o r 24 h o u r s , d e p o l y m e r i z e d u s i n g BF3 as c a t a l y s t , and a c e t y l a t e d u s i n g a c e t i c a n h y d r i d e t o b l o c k the p h e n o l i c h y d r o x y l groups and p r e v e n t i n t e r m o l e c u l a r hydrogen b o n d i n g . F o l l o w i n g t h i s t r e a t m e n t , some c o a l s e x h i b i t e d 95-96 p e r c e n t s o l u b i l i t y i n c h l o r o f o r m w h i l e a n o t h e r was o n l y 7 p e r c e n t s o l u b l e ( a l l Hvab r a n k ) . A Lvb c o a l from West V i r g i n i a was o n l y 14 p e r c e n t s o l u b l e . None o f the c o a l s e x h i b i t e d more than a few p e r c e n t s o l u b i l i t y i n c h l o r o f o r m p r i o r t o t r e a t ment. Throughout the r e f e r e n c e d work, t h i s v a r i a b i l i t y i n the b e h a v i o r o f c o a l s from d i f f e r e n t s o u r c e s i s n o t i c e a b l e , though perhaps n o t so d r a m a t i c a l l y as i n t h i s c a s e . The s o l u t i o n s o f d e p o l y m e r i z e d c o a l s are complex m i x t u r e s . In a few c a s e s , pure compounds have been i s o l a t e d and i d e n t i f i e d though they c o m p r i s e <1 p e r c e n t o f d e p o l y m e r i z e d c o a l s u b s t a n c e . In a l l c a s e s c i t e d the d e p o l y m e r i z e d c o a l p r o d u c t c o n t a i n e d phenol. Ouchi showed t h a t as d e p o l y m e r i z a t i o n p r o g r e s s e d the i n t e n s i t y o f i n f r a r e d a b s o r p t i o n a t t r i b u t e d to phenolic hydroxyl increased r e g u l a r l y . Ouchi a l s o showed t h a t the a l i p h a t i c c o n t e n t o f benzenealcohol extracts increased during successive cycles of depolym e r i z a t i o n and the r e s i d u e s showed an i n c r e a s i n g l y dense network of aromatic s t r u c t u r e s . Increased a l i p h a t i c content i m p l i e s a l k y l a t i o n has o c c u r r e d . On-going work a t B a t t e l l e Northwest i s i n g e n e r a l agreement w i t h the r e s u l t s o f Ouchi ( 1 0 ) . A c i d c a t a l y z e d d e p o l y m e r i z a t i o n o f c o a l w i t h phenol a f f o r d s a means f o r d i s s o l u t i o n o f c o a l under r e l a t i v e l y m i l d c o n d i t i o n s (185°C, ambient p r e s s u r e ) . Once d i s s o l v e d , s e p a r a t i o n o f ash c o n s t i t u e n t s and u n r e a c t e d c h a r i s a c c o m p l i s h e d by f i l t r a t i o n o r c e n t r i f u g a t i o n ( a l s o under m i l d c o n d i t i o n s ) . Depolymerized coal r e c o v e r e d as a low ash p r o d u c t from e x c e s s phenol c o u l d be d i s s o l v e d i n a c o a l d e r i v e d s o l v e n t and hydrogenated t o s t a b l e liquids. I t m i g h t be a n t i c i p a t e d t h a t a c c e s s t o hydrogen and c o n t a c t w i t h the c a t a l y s t would be more e f f i c i e n t i n the c a s e o f the s o l u b i l i z e d c o a l s u b s t a n c e than f o r c o a l p a r t i c l e s l u r r i e s . H y d r o g é n a t i o n might p r o c e e d more e f f i c i e n t l y and w i t h l e s s

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26.

M O O R E

E T

A L .

Coal

Liquefaction

419

f o u l i n g o f c a t a l y s t s d u e , i n p a r t , t o the absence o f heavy m e t a l s . T h i s study was c o n d u c t e d t o a s s e s s the b e h a v i o r o f v a r i o u s c o a l s w i t h r e s p e c t t o s o l u b i l i z a t i o n by a c i d c a t a l y z e d depolymeri z a t i o n with phenol. Ash r e m o v a l , phenol u p t a k e , and r e a c t i o n s o f o t h e r s o l v e n t systems were c o n s i d e r e d and the h y d r o g e n o l y s i s o f a number o f c o a l s and o f t h e i r d e p o l y m e r i z e d p r o d u c t s were compared.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

Coal

Preparation

The c o a l s used i n t h i s work were f i r s t c r u s h e d t o -1/4 i n c h using a gyratory crusher. They were then p u l v e r i z e d and s i e v e d . A l l c o a l s were d r i e d under N2 a t 80°C f o r 24 hours p r i o r t o pulverizing. The p u l v e r i z e r produced f r a c t i o n s o f -7+20 and -60+115 mesh. Most samples employed i n t h i s work were o f -7+20 mesh. Only a few t e s t s were made w i t h c o a l o f f i n e r g r i n d . I t was found t h a t phenol n o t o n l y d e p o l y m e r i z e s c o a l t o c o l l o i d a l and m o l e c u l a r s i z e , b u t i t a l s o d i s i n t e g r a t e s c o a r s e c o a l p r o ducing a smaller screen s i z e d i s t r i b u t i o n . This l a s t e f f e c t i s b e l i e v e d t o be s i m i l a r t o t h a t r e p o r t e d by workers a t S y r a c u s e U n i v e r s i t y Research C o r p o r a t i o n . (11) As a r e s u l t , the e x t e n t and r a t e o f d e p o l y m e r i z a t i o n were n e a r l y independent o f i n i t i a l particle size. The c o a l s used i n t h e s e t e s t s were c h a r a c t e r i z e d by proximate and u l t i m a t e a n a l y s e s ( T a b l e I ) . Samples o f f o u r c o a l s were f u r n i s h e d us t h r o u g h the c o u r t e s y o f t h e C o l l e g e o f M i n e r a l S c i e n c e s , P e n n s y l v a n i a S t a t e U n i v e r s i t y and where r e c e i v e d too l a t e f o r a n a l y s i s ( e x c e p t f o r m o i s t u r e and a s h ) ; however, these c o a l s have been v e r y c o m p l e t e l y c h a r a c t e r i z e d by G i v e n , e t a l . (12,13) In a d d i t i o n , a few o t h e r c o a l s r e c e i v e d l a t e i n the program were n o t a n a l y z e d , b u t t y p i c a l a n a l y s e s p r o v i d e d by the mines a r e i n c l u d e d i n T a b l e I . P r o c e d u r e s were used i n t h i s work which c o u l d be c o n v e r t e d to i n d u s t r i a l p r o c e s s s t e p s . Coal was r e f l u x e d w i t h a p h e n o l c a t a l y s t mixture a t atmospheric p r e s s u r e . * The hot s o l u t i o n was f i l t e r e d through a t a r e d f i l t e r which had been p r e c o a t e d w i t h filter aid. C o n t e n t s o f the f i l t e r were washed, f i r s t w i t h hot phenol-methanol m i x t u r e ( 2 0 / 1 , v/v) t o remove a d h e r i n g depolymeri z e d c o a l , and f i n a l l y , w i t h methanol t o remove phenol and catalyst. The f i l t e r cake was d r i e d a t 10 mm Hg p r e s s u r e and 140-160°C and w e i g h e d . The r e s i d u e on the f i l t e r c o n t a i n s ash c o n s t i t u e n t s from the c o a l , u n r e a c t e d c o a l , and p o s s i b l y phenol combined w i t h p a r t i a l l y d e p o l y m e r i z e d c o a l o f m o l e c u l a r s i z e t o o l a r g e t o be s o l u b l e . From the w e i g h t o f the r e s i d u e the e x t e n t o f d e p o l y m e r i z a t i o n i s given by:

*

U n l e s s o t h e r w i s e s t a t e d the c a t a l y s t was p - t o l u e n e s u l f o n i c

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

acid.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

a

a

a

a

1.84 2.07 8.35

Montour #4 P i t t s b u r g h Seam Hvb

Kaiser Steel R a t o n , NM, Hvb

Midland, HVC

4.04

B i g Mine C r e s t e d B u t t e , CO hv Β to Cb 25.4

28.9

29.0

39.7

29.9

28.7

33.9

Volatiles

35.1

42.9

4.98

4.19

22.4

25.2

21.5

6.10

16.7

(12)03)

21.2 0.6 0.7

4.7

63.7

29.5

University.

20.23

0.67

1.21

3.72

9.67

59.42

45.2

4.50

60.14

15.7

46.0

10.0

2.62

1.36

0.22

0.68

0.10

6.54

0.37

1.2

4.55

69.27

19.1

50.1

1.05

8.6

1.90

1 .44

5.43

75.34

10.01

1.82

7.64

2.64

1.54

5.26

69.8

13.70

2.41

6.21

Pyritic Sulfur

Supplemental Analysis

4.21

1.17

4.82

69.50

14.48

50.5

Coals

Analysis

of

Ν

Ultimate

Characterization

Η

Ash

Fixed Carbon

Analysis

Samples f u r n i s h e d through c o u r t e s y o f P e n n s y l v a n i a S t a t e

Montana

34.5

9.34

N . Fork V i r g i n R. Iron Co. Utah hvCb

Savage L i g n i t e

3.50

B i g Seam S t r i p R o s l y n , WA hv Bb

22.1

B i g Horn S h e r i d a n , WY, S u b - B i t u m . 1.89

24.8

Dave J o h n s t o n G l e n r o c k , WY Sub-Bitum.

Q u e e n , WA hv Ab

5.47

Knife River B e u l a h , ND Lignite

IL

2.68

Georgetown #12 P i t t s b u r g h #8 Hvb

Trivoli,

1.10

Moisture

Consol. P i t t s burgh #8, Hvb

Coal Identification

Proximate

TABLE I.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

Ο

>

>

Ξ

26.

M O O R E

E T

A L .

Coal

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

% depolymerization

=

421

Liquefaction

(g maf c o a l ) (

g

m

a

f

(g maf l) c

o

residue) x

a

100

(5)

where (g maf c o a l ) i s t h e m a s s o f c o a l c h a r g e d c o r r e c t e d f o r i t s m o i s t u r e and ash c o n t e n t . The f i l t r a t e c o n t a i n s a d i s p e r s i o n o f p a r t i c l e s t o o small t o be t r a p p e d by the f i l t e r and s o l u b i l i z e d c o a l . Microscopic measurements i n d i c a t e the p a r t i c l e s a r e s l i g h t l y l e s s than 0 . 5 m i c r o n average d i a m e t e r . The d e t e r m i n a t i o n o f d e p o l y m e r i z e d c o a l i n t h i s f i l t r a t e was a c c o m p l i s h e d by d i l u t i n g a weighed a l i q u o t w i t h 20-30 t i m e s i t s weight o f water. Phenol and c a t a l y s t d i s s o l v e whereas the depolymerized coal product p r e c i p i t a t e s . * The p r e c i p i t a t e was f i l t e r e d , water washed, and d r i e d i n a vacuum a t 110°C. The w e i g h t o f t h i s p r e c i p i t a t e d p r o d u c t was d e s i g n a t e d as maf ( m o i s t u r e and ash f r e e ) d e p o l y m e r i z e d p r o d u c t . The amount o f phenol which has become c h e m i c a l l y combined with the coal i s given by: (maf r e s i d u e ) % phenol

+ (maf d e p o l y .

prod.)

- (maf

coal)

= (maf

coal)

χ 100.

(6)

E q u a t i o n (6) shows t h a t the combined phenol i s d e r i v e d from the t o t a l i n c r e a s e i n the w e i g h t o f c o a l . No d i s t i n c t i o n i s made between phenol t r a p p e d i n the r e s i d u e o r combined w i t h s o l u b l e depolymerized c o a l . The w e i g h t g a i n i s a measure o f the e x t e n t of r e a c t i o n . O u c h i , e t a K a l s o u t i l i z e d t h i s t o t a l weight i n c r e a s e as a measure o f the e x t e n t o f r e a c t i o n . Coal

Screening T e s t s .

Effect

o f Coal

Rank

S c r e e n i n g t e s t s were conducted o v e r a c o n s i d e r a b l e p e r i o d o f time as the v a r i o u s c o a l s became a v a i l a b l e f o r s t u d y so t e s t conditions exhibit s l i g h t variations. These v a r i a t i o n s a r e n o t r e g a r d e d as s u f f i c i e n t to m o d i f y c o n c l u s i o n s which may be drawn from t h e d a t a i n T a b l e I I . The e x t e n t o f d e p o l y m e r i z a t i o n o f t h e s e c o a l s ( T a b l e I I ) ranges from 2 5 . 3 t o 8 8 . 7 p e r c e n t . T h i s d e f i n e s the amount o f maf c o a l s o l u b i l i z e d . With t h i s p a r t i c u l a r a r r a y o f c o a l s , the c o a l s o l u b i l i z e d b e a r s a l m o s t an i n v e r s e r e l a t i o n s h i p t o the combined p h e n o l . T h i s appears t o be d i c t a t e d by c h a n c e ; n e v e r ­ t h e l e s s , the c o a l s t o the r i g h t s i d e o f T a b l e II t a k e up more phenol i n r e l a t i o n t o the amount s o l u b i l i z e d than t h o s e t o the *

With c e r t a i n c o a l s s l i g h t s o l u b i l i t y o f t h e d e p o l y m e r i z e d c o a l p r o d u c t i s e v i d e n c e d by c o l o r i m p a r t e d t o the aqueous p h a s e .

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

2

2

Coal Rank.

(11.09)

2

4

(3.85) i

.207

.201

77.3

30/.92/1

1.0

169

H S0

134

Conscri

(5.29)

.158

.137

72.5

24/1/1

1.0

168

PTSA*

108

Montour

(3.74)

.211

.179

67.0

48/2/1

1.0

164

PTSA*

89

George­ town

2

A

(2.44)

.290

.263

64.7

30/.92/1

1.0

164

H S0

178

Queen

2

4

1.0

164

S 0

lignite

(3.52)

.22

.16

61.7

48/2/1

H

211

Savage

lignite

(5.13)

.163

.113

58.0

48/2/1

1.33

163

PTSA*

64

Knife River

2

1.0

163

H S0,

180

Roslyn

(1.57)

.390

.298

46.7

Hv A to Β hv Β bituminous b i t u m i n -

(4.97)

.168

.100

49.7

30/.92/1 30/.92/1

1.0

162

PTSA*

78

Kaiser Steel

Comparison o f the R e a c t i v i t y o f Various Coals to the Depolymerlzatlon Reaction

sub eub hv hv A to Β bituminhv A bituminous bituminous bituminous bituminous ous bitumin-

/Coal De-.οΐχ. \ Cw.L-i.-.e3 Prenol \g/g Coal charged/

(4.79)

.173

Combined Phenol g/g coal depoly.

Figure of Merit

.08

.174

Combined Phenol g/g c o a l charged

.083

88.7

83.3

Coal Depoly. Ζ

30/.72/1

90/.92/1

1.0

A

l.n

H S0

164

4

209

155

H S0

193

Phenol: Cata­ lyst: Coal

Reaction Time, hr

Temperature, •c

Catalyst

Run Number

Big Horn

II.

Dave Johnston

TABLE

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

2

hv C biturain-

(2.58)

.278

.147

37.9

30/.92/1

1.0

161

H S0,

181

Virgin River

2

4

1.0

171

S 0

hv C bitumin-

(1.15)

.464

.319

36.8

30/.92/1

H

153

Midland

2

4

1.0

164

S 0

179

hv Β to C bituminous

(1.08)

.482

0.235

25.3

30/.92/1

H

Colorado

ο 2

κ!

>

ι

ο

>

> α

>

to ίο

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

26.

MOORE E T A L .

Coal

423

Liquefaction

l e f t s i d e o f the t a b l e . T h i s can be e x p r e s s e d n u m e r i c a l l y as a " F i g u r e o f M e r i t " by d i v i d i n g the p e r c e n t d e p o l y m e r i z e d by the p e r c e n t combined p h e n o l . The n u m e r i c a l v a l u e o f t h i s " F i g u r e o f M e r i t " ranges from 1.08 t o 1 1 . 0 9 . It i s obviously desirable to a c h i e v e maximum s o l u b i l i z a t i o n w i t h minimum phenol c o n s u m p t i o n . About h a l f o f the c o a l s t e s t e d a r e s u i t a b l e f o r a p r o c e s s which e n t a i l s s o l u b i l i z a t i o n o f c o a l as an i n i t i a l s t e p . These d i s s o l v e r e a d i l y t o y i e l d s o l u t i o n s which can be f i l t e r e d t o remove ash ( i n c l u d i n g i n o r g a n i c s u l f u r compounds). E i g h t y t o 90 p e r c e n t o f the maf c o a l goes i n t o s o l u t i o n t o become a v a i l a b l e f o r subsequent h y d r o g é n a t i o n to o i l s . Some c o a l s t a k e up l a r g e amounts o f phenol (>25 p e r c e n t ) but do not d i s s o l v e . Phenol has good s o l v a t i n g power f o r r e l a t i v e l y p o l a r s o l u t e s o f up t o about 1,000 i n m o l e c u l a r w e i g h t . Perhaps t h e s e c o a l s do not d e p o l y m e r i z e to c o a l fragments small enough t o e n t e r s o l u t i o n i n p h e n o l . A c o - s o l v e n t might h e l p d i s s o l v e these m o i e t i e s . I f s o , i t may be premature t o c o n c l u d e t h a t such c o a l s would be u n s u i t a b l e f o r p r o c e s s i n g . The d a t a o f T a b l e II were taken a t 1.0 hour r e a c t i o n t i m e . The r e a c t i o n c o n t i n u e s a t a r a p i d l y d i m i n i s h i n g r a t e as shown by d a t a i n F i g u r e 1. Here the r e l a t i v e r a t e s o f d e p o l y m e r i z a t i o n f o r a few c o a l s a r e compared o v e r a 6-hour p e r i o d . These t e s t s were c o n d u c t e d a t r e f l u x t e m p e r a t u r e (160-170°C) and a t comparable p h e n o l r c a t a l y s t : c o a l r a t i o s i n the range 5 0 : 1 : 1 . No l i n e i s drawn f o r the K n i f e R i v e r l i g n i t e c o a l . Its s o l u t i o n s f i l t e r with d i f f i c u l t y and a c c u r a t e d a t a a r e d i f f i c u l t t o a c q u i r e . Data f o r t h i s c o a l ( s o l i d s q u a r e s ) s c a t t e r about the l i n e f o r the K a i s e r Steel c o a l . Reaction

Kinetics

The r e a c t i o n o f phenol and the e n s u i n g d i s s o l u t i o n o f c o a l i n the phenol c a t a l y s t m i x t u r e appears to f o l l o w no s i m p l e r a t e mechanism. O u c h i , et_ a]_. were a b l e t o f i t t h e i r d a t a t o a s i m p l e f i r s t o r d e r r a t e e q u a t i o n which upon i n t e g r a t i o n i s o f the f o r m : In (1-a) = k t

(7)

where w

a

t

= —

.

(8)

w

oo w. i s the w e i g h t i n c r e a s e due t o r e a c t i o n w i t h phenol a t t i m e , t and w^ i s the maximum w e i g h t i n c r e a s e . When the d a t a taken on Montour°°coal a r e p l o t t e d i n a c c o r d a n c e w i t h t h i s s i m p l e r a t e mechanism, the r e s u l t shown i n F i g u r e 2 i s o b t a i n e d . The open c i r c l e s r e p r e s e n t the r a t e o f d i s s o l u t i o n , the shaded c i r c l e s

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

424

INDUSTRIAL

0

1

2

3

4

AND

LABORATORY

5

ALKYLATIONS

6

7

TIME, HRS

Figure 1.

Relative rates of depolymerization (160°-170°C) sulfonic acid catalyst

with p-toluene-

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

E T

A L .

Coal

Liquefaction

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

M O O R E

TIME, HRS

Figure 2.

Depolymerization of Montour coal in accordance with first-order rate mechanism

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL AND LABORATORY ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

426

r e p r e s e n t the r a t e o f phenol c o m b i n a t i o n . C l e a r l y , the r a t e p r o c e s s i s not f i r s t o r d e r and t h i s i s t r u e o f a l l the c o a l s t e s t e d . W i s e r (14) has compared the k i n e t i c s o f c o a l p y r o l y s i s and s o l v e n t e x t r a c t i o n . In s o l v e n t e x t r a c t i o n , the y i e l d c u r v e s o f f r a c t i o n e x t r a c t e d v e r s u s time c l o s e l y resemble the c u r v e s shown i n F i g u r e 1. Wiser showed such d a t a e x h i b i t c o m p l i a n c e w i t h second o r d e r k i n e t i c s i n the e a r l y p e r i o d o f r e a c t i o n and r e v e r t t o c o m p l i a n c e w i t h f i r s t o r d e r k i n e t i c s i n l a t e r stages. H i l l , e t a K (15) a l s o showed t h a t a c t i v a t e d e x t r a c t i o n o f c o a l w i t h hydrogen donor s o l v e n t s behaved i n t h i s manner. Data f o r d i s s o l u t i o n o f the Montour c o a l can be f i t t e d t o a second o r d e r e q u a t i o n o f t h e f o r m : £ = k

2

( a - x )

2

(9)

where ko = r e a c t i o n c o n s t a n t , a = maximum p e r c e n t d e p o l y m e r i z a t i o n a t t a i n a b l e w i t h t h i s c o a l ( a r b i t r a r i l y e s t i m a t e d t o be 87 p e r c e n t ) and χ = the p e r c e n t d e p o l y m e r i z a t i o n a t t i m e , t . The i n t e g r a t e d

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26.

MOORE

ET

AL.

Coal

e q u a t i o n w i t h a lower l i m i t χ a(a-x)

427

Liquefaction o f χ = ο when t = ο has t h e f o r m :

k t.

(10)

2

F i g u r e 3 shows how w e l l the d a t a f i t second o r d e r k i n e t i c s d u r i n g the f i r s t s i x h o u r s . Beyond s i x h o u r s , the d a t a do not l i e a l o n g t h i s l i n e , b u t i n s t e a d f o l l o w s i m p l e f i r s t o r d e r k i n e t i c s as shown i n F i g u r e 4. The e q u a t i o n which d e s c r i b e s t h i s p o r t i o n o f the r e a c t i o n i s :

dt

l

K

(a-x).

Integrating, with l i m i t s

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

In

(Π) χ = ο when t = ο ,

leads

to:

= k-,t.

(12)

T h u s , a p l o t o f In - — v e r s u s t y i e l d s t h e r e s u l t shown i n F i g u r e 4, where " a " fias the same d e f i n i t i o n as a b o v e . Similar r e s u l t s a r e o b t a i n e d upon p l o t t i n g the d a t a f o r C o n s o l i d a t i o n , Georgetown, M i d l a n d , K a i s e r S t e e l and K n i f e R i v e r c o a l s . In the c a s e o f the C o n s o l i d a t i o n c o a l , a few d a t a were o b ­ tained at d i f f e r e n t temperatures. F i g u r e 5 shows t h e r e s u l t o f p l o t t i n g the d a t a as a second o r d e r r a t e p r o c e s s a t t e m p e r a t u r e s

s

3

Figure 4. Compliance of Montour dissolution rate at long time intervals with a first-order rate mechanism

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

428

AND

LABORATORY

ALKYLATIONS

o f 95°C, 125°C, and 161°C. The s l o p e s o f t h e s e l i n e s g i v e the second o r d e r r e a c t i o n r a t e c o n s t a n t s . A p p l y i n g a b s o l u t e r e a c t i o n r a t e t h e o r y as demonstrated by H i l l , e t al_. the r a t e c o n s t a n t can be e x p r e s s e d a s :

where k = B o l t z m a n n ' s c o n s t a n t h = P l a n k ' s c o n s t a n t and R = U n i v e r s a l Gas c o n s t a n t . A p l o t o f In (ko/T) v e r s u s 1/T ( F i g u r e 6) a l l o w s e v a l u a t i o n o f the e n t h a l p y o f a c t i v a t i o n , ΔΗ, from the s l o p e , and the e n t r o p y o f a c t i v a t i o n , AS, from the i n t e r c e p t . The v a l u e o f ΔΗ, 1 5 . 2 K c a l / m o l e , i s about h a l f t h a t which W i s e r (14) o b t a i n e d ( 2 8 . 8 Kcal/mole) f o r d i s s o l u t i o n o f c o a l by hydrogen donor s o l v e n t s i n the 350-450°C temperature regime and by the second o r d e r r a t e p r o c e s s . On the o t h e r hand, i t i s about t w i c e the v a l u e o b t a i n e d by H i l l , e t a l k (15) f o r low temperature d i s s o l u t i o n o f c o a l i n a hydrogen donor s o l v e n t under the d r i v i n g f o r c e o f u l t r a s o n i c e n e r g y , i . e . , 8 . 7 K c a l / m o l e . E x t r a p o l a t i o n o f the l i n e drawn i n F i g u r e 6 t o 250°C (1/T = 1.912 χ 1 0 " ) l e a d s t o a v a l u e o f In k2/T = - 5 8 2 , from which k2 = 1.55 h r * . S i n c e the d a t a a r e i n good c o m p l i a n c e w i t h second 3

1

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26.

MOORE

Coal

ET AL.

Liquefaction

429

o r d e r r a t e t h e o r y a t s h o r t time p e r i o d s , e x t r a p o l a t i o n s h o u l d p r e d i c t t h e time r e q u i r e d f o r s o l u b i l i z a t i o n o f the c o a l a t 250°C. E q u a t i o n (10) shows t h a t complete d i s s o l u t i o n , where χ = a requires i n f i n i t e time. However, a t f i n i t e c o n v e r s i o n s to s o l u b l e p r o d u c t s ( e . g . , 80 p e r c e n t o f maximum and 90 p e r c e n t o f maximum [maximum = 87 p e r c e n t ] ) 1.8 and 4 . 0 m i n . , r e s p e c t i v e l y , a r e r e q u i r e d a t 250°C. E x p e r i m e n t s a t 250-300°C c o n f i r m t h a t n e a r l y complete s o l u b i l i z a t i o n o f c o a l i n such s h o r t time p e r i o d s can be a c h i e v e d .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

-8.0

2.2

2.3

2.4

2.5

2.6 1/T χ 10

Figure 6.

Ln K /T 2

2.7

2.8

2 9

3

vs. 1/T for evaluation of the activation enthalpy and entropy

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

430

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

The d a t a ( T a b l e I I I ) a l s o i n d i c a t e t h a t r e p o l y m e r i z a t i o n may o c c u r i f the system i s m a i n t a i n e d a t such h i g h t e m p e r a t u r e s f o r too l o n g a time i n t e r v a l . The e x p e r i m e n t s a t 250°-300°C were performed i n a 300 ml s t i r r e d autoclave. R e a c t i o n times r e f e r t o the " t i m e a t temperature." Some 30 m i n . was r e q u i r e d t o b r i n g the a u t o c l a v e and i t s c o n t e n t s to t e m p e r a t u r e and about 15 m i n . was r e q u i r e d t o c o o l i t a g a i n t o ambient t e m p e r a t u r e s .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

TABLE I I I .

D e p o l y m e r i z a t i o n o f C o n s o l i d a t i o n Coal a t Temperatures and P r e s s u r e s o f 100-200 p s i PTSA C a t a l y s t

Temp., °C

Time, Min

250 300 300 300 300

5 7 20 5 120

%

% Depolymerization 87.6 77.8 57.6 78.9 55.3

High Using

Phenol

Uptake

29.9 37.7 24.2 29.7 7.8

The e x t r a p o l a t i o n from d a t a a t l o w e r t e m p e r a t u r e s , t o g e t h e r w i t h d a t a i n T a b l e I I I , i n d i c a t e n e a r l y complete s o l u b i l i z a t i o n can be a c h i e v e d i n time p e r i o d s o f p r a c t i c a l i n t e r e s t f o r f l o w through r e a c t o r s . B e h a v i o r o f Other

Solvents

S o l v e n t s o t h e r than phenol have been t e s t e d f o r e f f e c t i v e n e s s in coal depolymerization. The r e s u l t s are summarized i n T a b l e IV. Both p e r c e n t d e p o l y m e r i z a t i o n ( s o l u b i l i z a t i o n ) and w e i g h t i n c r e a s e s (%) can be used as a measure o f the e x t e n t o f r e a c t i o n . Data u s i n g phenol s o l v e n t a r e i n c l u d e d f o r c o m p a r i s o n . Data f o r the w e i g h t i n c r e a s e a r e l a c k i n g i n c a s e s where the p r o d u c t was not i s o l a t e d . T h i s i s not easy t o a c c o m p l i s h when the s o l v e n t i s i n s o l u b l e i n w a t e r . This lack i s unfortunate in the c a s e o f c r e s o t e o i l and b e n z a l d e h y d e . Here the l a r g e n e g a t i v e v a l u e f o r p e r c e n t d e p o l y m e r i z a t i o n means the r e s i d u e weighed more than the maf c o a l c h a r g e d . This i s evidence of solvent-coal reaction. I t i s a p p a r e n t t h a t many o f the s o l v e n t s undergo r e a c t i o n w i t h c o a l , b u t the r e a c t i o n may n o t d e p o l y m e r i z e the c o a l t o soluble fragments. A l t e r n a t i v e l y , the s o l v e n t may be a poor one i n which t o d i s s o l v e the d e p o l y m e r i z e d c o a l p r o d u c t . The x y l e n e s , e . g . , y i e l d a l a r g e r p e r c e n t w e i g h t i n c r e a s e than does phenol and y e t no s i g n i f i c a n t s o l u b i l i z a t i o n o f the coal r e s u l t s . In o r d e r t o compare the p r o d u c t s from d e p o l y m e r i z a t i o n w i t h m-xylene t o t h o s e u s i n g p h e n o l , p r o d u c t s from t h e s e r e a c t i o n s were e x t r a c t e d w i t h p y r i d i n e f o r 24 hours u s i n g a soxhlet extractor. The phenol d e p o l y m e r i z a t i o n p r o d u c t proved

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

176

158 4

4

H S0

PTSA-H 0 (2.5) 5.0 PTSA-H 0 (5.0) 10.0

2..0 2..0

22..25 22,.75

211

190

212

200

108

127

127

41

46

47

48

105

189

190 2

2

4

4

4

m a

H S0

H S0

2

r o d u c t +

d e p o l y

m

a

Cresylic Acid (120)

-

(a)

Toluene (93)

c n a r

-

m

a

f

c o a l

χ 100

(a) f

(a)

Xylenes (135) m-Xylene (136)

1

150

134

128 (b)

— 10.5

Naphthalene (117.5) Phenol (2.5) Naphthalene (108) Phenol (13.4)

149

—

-

— —

--

—

41

56

18

-43

-28

-22

9

(a)

2-Naphthol (184)

3,5-Xylenol (78)

A n i l i n e (120)

Benzaldehyde (135)

Creosote 011 (120)

Creosote 011 (120)

Creosote Oil (100) Phenol (25)

61

125

—

77 65

Phenol (120) Naphthalene (30) Phenol (30)

% Wt. Incre<

% Coal Depoly.

Solvent, (q)

^Assuming 0.15g of 3.56% of the maf coal tracks with the f i l t r a t e during f i l t r a t i o n .

^ W e i g h t s of maf char exceeded maf coal charge indicating chemical reaction between coal and solvent.

- P maf coal

4.0

4.0

5.0

(3.68)

(3.68)

H S0 (2.6)

*% Wt. Increase ™ ^

2..0

2

PTSA-H 0 (5.0) 10.0

4.0

2,.0

2

2

2

2

(3.68)

PTSA-H 0 (5.0) 10.0

2

H S0

2..0

1.,0 4

PTSA-H 0 (5.0) 10.0

2.,0

165

4.0 4.0

160

(3.68)

37

2

164

1..0

170

170

(3.68)

4.0 4.0

159

2

(3.68)

(3.68)

160

4

H S0

4

3..0

2

H S0

2

H S0

1..0 2..0

4.0

161

2

(3.68)

162

4

PTSA-H 0 (1.0) 2.0

185

154

2

H S0

1.,0 2..0

169

134

Coal, g

Rx. Time, hr

Rx. Temp ., °C Catalyst, (g)

Comparison of Different Solvents 1n the Depolymerization of Consolidation Coal

Run No.

TABLE IV.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

6

-ο 05

ο

432

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

t o be 61 p e r c e n t s o l u b l e i n p y r i d i n e whereas the x y l e n e d e p o l y m e r i z a t i o n p r o d u c t was o n l y 30 p e r c e n t s o l u b l e . T h u s , t h e r e appears t o be something unique about the weakly a c i d i c phenolic materials. In a d d i t i o n t o phenol i t s e l f , 3 , 5 x y l e n o l , 2-naphthol, phenol-naphthalene ( 1 : 1 ) , and c r e s y l i c a c i d a l l show a b i l i t y t o s o l u b i l i z e the c o a l . Recently, Darlage and B a i l e y have s t u d i e d the phenol c a t a l y z e d d e p o l y m e r i z a t i o n o f a Kentucky c o a l (Pond Creek Seam, P i k e C o u n t y ) . (16) This coal does not d e p o l y m e r i z e e f f i c i e n t l y and would compare w i t h the p o o r e s t c o a l s t e s t e d w i t h d a t a shown i n T a b l e I I . These a u t h o r s a l s o show t h a t p h e n o l i c s o l v e n t s i n g e n e r a l cause s o l v a t i o n o f c o a l whereas n o n - p h e n o l i c a r o m a t i c s add t o c o a l b u t do not s o l u b i l i z e the c o a l . I f the d e p o l y m e r i z a t i o n r e a c t i o n proceeds by the mechanism o f e q u a t i o n s ( 1 ) , (2) and (3) i t s h o u l d be p o s s i b l e t o p r e d i c t a s o l v e n t r e a c t i v i t y sequence. The r e l a t i v e r e a c t i v i t y i s thus e x p e c t e d to be 3 , 5 - x y l e n o l > naphthol ^ phenol > x y l e n e > t o l u e n e > naphthalene > a n i l i n e ^ benzaldehyde. T h i s o r d e r , as measured by the i n d i c e s f o r r e a c t i o n used h e r e , i s n o t f o l l o w e d . Hydrogenolysis

Experiments

H y d r o g e n o l y s i s was done u s i n g a one l i t e r r o c k i n g a u t o c l a v e to which 30g c o a l , 15g c a t a l y s t , and 200 ml o f mixed d e c a l i n s were c h a r g e d . T h i s was p r e s s u r i z e d w i t h Hp heated t o t e m p e r a t u r e w i t h i n a 4-5 hour p e r i o d , r o c k e d -for a p r e d e t e r m i n e d r e a c t i o n p e r i o d ( u s u a l l y 4 hours) and c o o l e d t o ambient t e m p e r a t u r e ( w i t h i n 1.5 - 2.0 h o u r s ) . G a s e s , l i q u i d s and s o l i d s were r e c o v e r e d s e p a r a t e l y and a n a l y z e d . The y i e l d o f o i l was d e t e r m i n e d from the w e i g h t o f u n r e a c t e d c o a l a d j u s t e d f o r ash and m o i s t u r e , e . g .

%

y

i

e

l

d

=

( „ f

coal

( n i

Cha ed) - (coa1 S

c

a

residue)

x

1

Q

0

.

(

u

)

The d e c i s i o n to employ d e c a l i n as a s o l v e n t was made t o c i r c u m v e n t d i f f i c u l t i e s i n h a n d l i n g small q u a n t i t i e s o f c o a l and c a t a l y s t i n a l a r g e a u t o c l a v e and t o f a c i l i t a t e s e p a r a t i o n o f s o l v e n t and c o a l r e a c t i o n p r o d u c t s . In some r e s p e c t s t h i s was an u n f o r t u n a t e c h o i c e . Some r e a c t i o n w i t h d e c a l i n o c c u r r e d , so a c c u r a t e measurement o f Hp consumption by r e a c t i o n w i t h c o a l was not p o s s i b l e . F u r t h e r , both c o a l and d e p o l y m e r i z e d c o a l were v i r t u a l l y i n s o l u b l e i n t h i s s o l v e n t so the hoped f o r advantage o f s o l v e n t s o l u b i l i t y a n t i c i p a t e d f o r d e p o l y m e r i z e d c o a l may have been l o s t . C o m m e r c i a l l y a v a i l a b l e c a t a l y s t s were u s e d . With b u t few e x c e p t i o n s t h e s e were Harshaw-0402, Co-Mo, 1 / 8 - i n c h t a b l e t s and Harshaw-Ni-4301, Ni-W, 1/16 i n . e x t r u s i o n s . At constant c o a l ; c a t a l y s t i s o l v e n t r a t i o and w i t h H2 i n l a r g e e x c e s s the p r i n c i p a l v a r i a b l e s which e f f e c t h y d r o g e n o l y s i s y i e l d a r e t e m p e r a t u r e and catalyst type. As shown by d a t a i n F i g u r e 7 , the c o n v e r s i o n

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

26.

MOORE

ET

AL.

Coal

Liquefaction

433

y i e l d i s p r i m a r i l y a f u n c t i o n of temperature f o r a given c a t a l y s t i r r e s p e c t i v e o f c o a l type o r d e p o l y m e r i z e d c o a l . T h e r e appears t o be no s i g n i f i c a n t d i f f e r e n c e i n the c o n v e r s i o n y i e l d f o r d e p o l y m e r i z e d c o a l v e r s u s the c o a l from which i t was d e r i v e d w i t h the p o s s i b l e e x c e p t i o n o f the Georgetown c o a l where the d e p o l y m e r i z e d c o a l s performed b e t t e r . D e t a i l s o f the h y d r o g e n o l y s i s runs a r e c o l l e c t e d i n T a b l e V . In a l l c a s e s h y d r o g e n o l y s i s was c o n d u c t e d under m i l d c o n d i t i o n s . Attempts were made t o d e t e r m i n e t h e H2 consumed d u r i n g t h e c o u r s e o f r e a c t i o n , but i n t e r f e r e n c e by the s o l v e n t o b s c u r e s the r e s u l t s i n most c a s e s . T h i s i n t e r f e r e n c e i s most pronounced a t temperat u r e s e x c e e d i n g 400°C. The p r o c e s s o f h y d r o g e n o l y s i s i s d e s i g n e d t o fragment the coal s t r u c t u r e i n t o smaller molecular weight u n i t s : light o i l , heavy o i l , and a s p h a l t e n e s . A small amount o f gaseous p r o d u c t s also result.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

434

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

Table V Hydrogenolysis

o f Coal

and D e p o l y m e r i z e d

Coal Moles H / Moles H2/ g maf g maf Coal Coal Charged Convert. χ IP'

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

2

wt Sample maf Basis g

Run No./ Coal

Sample Description

20 Georgetown

As Received (no solvent)

22 Georgetown

Depoly. Ash Not 26.43 Sep. (no solvent)

420

15 Georgetown

As Received

25.06

Georgetown

Depolymerized Ash Free

Georgetown

Temp. °C

Time, hr

Initial P, psig (OPS)

Final P, p s i q (calc.)

Catalyst Type

Yield %

4

400

864

None

30.4

36.0

400

930

None

53.0

404

4.0

400

908

N1-W

130

220

30.0

292

4.2

1390

2170

N1-W

3

16

Depolymerized Ash Free

23.5

316

4.0

1310

2590

N1-W

36.5

94

26

11 Georgetown

As Received

25.06

281

4.2

1420

2640

Co-Mo

0.9

16

1700

10 Georgetown

As Received

25.06

316

4.3

1500

2965

Co-Mo

22.9

8 Georgetown

Depolymerized Ash Free

30.0

309

10.5

1700

3320

Co-Mo

35.8

Depolymerized Ash Free

24.2

322

4.0

1800

3595

Co-Mo

40.5

Georgetown 3 Georgetown

Depo1ymerize( Ash Free

30.0

338

4.0

1800

3690

Co-Mo

47.4

5B

As Received

26.45

404

1.0

1000

2272

Ni-W

84

26.45

426

4.2

1000

2346

Ni-W

Depolymerized + Ash

27.0

435

4.4

1000

2375

N1-W

As Received

25.44

397

7.6

1000

2248

N1-W

7B

371

6.2

300

410

460

Montour 6B Montour 2B As Received

25,44

422

Depolymerized + Ash

27.09

>388

8B 3B Knife River Knife River

Depolymerized + Ash

27.09

21 Consolidation

Depolymerized (No Solvent)

Knife River 4B Knife River

1000

2332

4.8

1000

-v-2225

414

3.0

1000

30

397

5.6

400

None

25.3

400

4.25

300

NI-W

Consolidation

4.5

( 4 )

14 Consolidation

Depolymerized

30

404

4.2

400

16 Consolidation

Depolymerized

30

412

4.0

300

25.3

370

4.8

30

410

4.0

Consolidation 17 Consolidation

Depolymerized

Depolymerized

30

421

4.0

2305

440

800

950

80

810

1010

72

440

610

79

410

530

33

156

192

72

180

249

73.8

110

150

76.3

110

150

380

420

90

240

85

N1-W

N1-W

NI-W

N1-W

Ni-W

Co-Mo

400

930

T-T1571^

2)

490

72

no

ConsolIdation 19 Consolidation

30 Depolymerized ( T e t r a H n Sol v . )

412

4.2

400

920

G-68

(3)

(1) G i r d l e r G-3A, Chromium promoted Iron o x i d e , 3/8 χ 3/16 1n. Tablets (2) G i r d l e r G-T1571, S i l i c a C a r r i e r , 3/16 1n. Spheres. (3) G i r d l e r G-68, Promoted Pd on Gamma Alumina, 3/16 χ 1/8 i n .

Tablets.

(4) Recorder Malfunctioned. **

Data Not Measured.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

150

26.

MOORE

ET

Coal

AL.

TABLE V I . Brief

Summary o f M a j o r

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

Heavy

Oil

3546 c m " 3012 2924 2857 1905 1754 1605 1449

1

1374 1252 1221 1032 877 698 675 Brief

Liquefaction

Principal

435

Features

IR A b s o r p t i o n

of

IR and NMR S p e c t r a

Bands

Asphaltenes

P r o b a b l e Band A s s i g n m e n t

3401 c m " 3012 2933 2865 1905 1776 1605 1451

OH Band ( s m a l l ) A r o m a t i c C-H S t r e t c h A l i p h a t i c C-H S t r e t c h A l i p h a t i c C-H S t r e t c h O v e r t o n e s and C o m b i n a t i o n f o r M u l t l Sub Benzenes Aromatic Ring U n s a t u r a t i o n Asym M e t h y l Band and A r o m a t i c Ring V i b r a t i o n Sym Methyl Band

1

1377 1250 — —

840

P e n t a - H e x a - S u b Benzene Di Sub Benzene Benzenoid (?)

Summary o f NMR Spectrum Heavy

Oil

0 . 9 ppm 1.23 1.50 1.71 2.22 2.39 2.60 3.76 6.92 7.05 7.20 7.39 7.42 7.75

Asphaltenes

Description

0.75, 0.84, 0 . 9 3 , 1.09 1.20 1.27 1.47

Methyl

Protons

Methylene

Protons

3.58 ( B r o a d Bands) Aromatic

Protons

7.21 (Broad Bands)

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDUSTRIAL

436

AND

LABORATORY

ALKYLATIONS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

The l i g h t o i l c o n s i s t i n g m a i n l y o f mononuclear a r o m a t i c compounds, was s e p a r a t e d d u r i n g steam d i s t i l l a t i o n t o remove decalin. The a c t u a l amount was q u i t e small and c o d i s t i l l e d w i t h d e c a l i n i n which i t a p p e a r s as an i m p u r i t y . An e f f o r t was made to d i s t i l l t h i s m a t e r i a l through a P o d b i e l n i a k d i s t i l l a t i o n a p p a r a t u s , b u t t h e amount o f each component was so s m a l l , ( i . e . , i n t h e range o f t e n t h s o f m i l l i l i t e r s ) , t h a t c l e a n s e p a r a t i o n s were not o b t a i n e d . P r o b a b l y a s p i n n i n g band column would have more a c c u r a t e l y i s o l a t e d t h e s e m a t e r i a l s . Gas c h r o m a t o g r a p h i c a n a l y s i s i n d i c a t e d t h e p r e s e n c e o f r o u g h l y 60 d i f f e r e n t compounds, more than h a l f o f which had s h o r t e r r e t e n t i o n t i m e s than d e c a l i n . Among t h o s e t e n t a t i v e l y i d e n t i f i e d a r e b e n z e n e , c y c l o h e x a n e , c r e s o l s , d i m e t h y l p h e n o l , phenol and d i p h e n y l e t h e r . The steam d i s t i l l a t i o n r e s i d u e c o n t a i n s heavy o i l s and asphaltenes. These were s e p a r a t e d by s o l u b i l i t y d i f f e r e n t i a t i o n . Both o f t h e s e m a t e r i a l s were s u f f i c i e n t l y s o l u b l e i n CCI* t o p e r m i t e x a m i n a t i o n by b o t h IR and NMR. Principal features of t h e IR and NMR s p e c t r a a r e shown i n T a b l e V I . The p o s s i b i l i t y o f c o l l o i d a l d i s p e r s i o n o f the asphaltenes i n s t e a d o f t r u e s o l u b i l i t y may have c a u s e d some l o s s o f f i n e s t r u c t u r e f o r the aromatic absorption r e g i o n s . The r a t i o o f a l i p h a t i c p r o t o n s t o a r o m a t i c p r o t o n s f o r the heavy o i l was 4.01/1 and o f methylene to methyl 1 / 1 . 7 5 . For the a s p h a l t e n e s , the r a t i o o f a l i p h a t i c p r o t o n s t o a r o m a t i c p r o t o n s was 3.49/1 and o f methylene t o methyl 1 / 1 . 1 . The a s p h a l t e n e s were o b s e r v e d t o m e l t a t 146°C. M o l e c u l a r w e i g h t s o b t a i n e d by vapor phase osmometry ( o - x y l e n e s o l v e n t ) were 407 f o r the heavy o i l and 638 f o r the a s p h a l t e n e s . T h e r e a p p e a r s t o be l i t t l e d i f f e r e n c e i n t h e r e l a t i v e y i e l d o f heavy o i l s and a s p h a l t e n e s from d e p o l y m e r i z e d c o a l as compared w i t h the "as r e c e i v e d " c o a l s . Acknowledgements The a u t h o r s w i s h t o e x p r e s s t h e i r a p p r e c i a t i o n t o D r . E r n e s t E. Donath f o r a d v i c e and encouragement t h r o u g h o u t t h i s work and t o the B a t t e l l e Energy Program f o r s u p p o r t and p e r m i s s i o n t o publish. The a u t h o r s a r e a l s o i n d e b t e d t o M e s s r s . W. A . W i l c o x and G. L. R o b e r t s who performed many o f the measurements i n v o l v e d i n t h i s work.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8.

Heredy, L. Heredy, L. Heredy, L. Ouchi, Κ., Ouchi, K., Ouchi, K., Ouchi, K., Ouchi, K.,

S., and M. B. Neuworth, Α., et a l . , Fuel (1964) Α., et al., Fuel (1965) et al., Fuel (1965) 44, et a l . , Fuel (1965) 44, Fuel (1967) 46, 319. et a l . , Fuel (1967) 46, et al., Fuel (1973) 52,

Fuel (1962) 41, 221. 43, 414. 44 125. 29. 205. 367. 156.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

26.

9.

E T

A L .

Coal

Liquefaction

437

Darlage, L. J., J. P. Wiedner, and S. S. Block, Fuel, (1974) 53, 54. Franz, J. Α., Private Communication. Annonymous, C. And E. News, (September 2, 1974) 16-17. Given, P. H., et al., Fuel (1975) 54, 34. Given, P. H., et a l . , Fuel (1975) 54, 40. Wiser, W. H., Fuel (1968) 47. H i l l , G. R., et al., Fuel (1974) 53. Darlage, L. J. and M. E. Bailey, Fuel (1976) 55. Donath, E. E., "Coal Hydrogenation Vapor Phase Catalysts," Advances in Catalysis, Volume III, Academic Press, 1956, p. 258.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch026

10. 11. 12. 13. 14. 15. 16. 17.

M O O R E

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

27 L i q u e f a c t i o n of W e s t e r n S u b b i t u m i n o u s Coals w i t h Synthesis G a s CHARANJIT RAI University of Wyoming, Laramie, WY 82071

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

HERBERT R. APPELL and E. G. ILLIG Pittsburgh Energy Research Center (ERDA), 4800 Forbes Ave., Pittsburgh, PA 15213 The r e c e n t energy c r i s i s on t h e e a s t c o a s t and c o n t i n u e d c o n c e r n r e g a r d i n g e n v i r o n m e n t a l e f f e c t s have once a g a i n emphas i z e d t h e importance o f p r o d u c i n g l o w - s u l f u r f u e l s by l i q u e f a c t i o n . Most l i q u e f a c t i o n p r o c e s s e s i n v o l v e some form o f hydrogen t r a n s f e r , where c o a l i s h e a t e d and l i q u e f i e d a t 400500°C i n a s o l v e n t . Falkum and G l e n (JL) suggested t h a t t h e i n i t i a l r e a c t i o n o f c o a l w i t h m o l e c u l a r hydrogen i n v o l v e d d e a l k y l a t i o n t o r e a c t i v e unsaturated m a t e r i a l s which a r e e i t h e r s t a b i l i z e d b y hydrogénation o r r e p o l y m e r i z e . Van K r e v e l e n (2.) r e p o r t e d t h a t c o a l p y r o l y s i s i n v o l v e d d e p o l y m e r i z a t i o n and d i s p r o p o r t i o n a t i o n i n w h i c h f r e e r a d i c a l s a r e formed. Hill e t a l . (3) d i s c u s s e d t h e l i q u e f a c t i o n o f a h i g h v o l a t i l e b i t u m i n o u s c o a l i n t e t r a l i n i n terms o f d i s s o l u t i o n and s t a t e d t h a t "the hydrogen t r a n s f e r r e a c t i o n a t 350-450°C i s a second o r d e r p r o c e s s , i n w h i c h t h e a c t i v a t i o n energy i n c r e a s e s as t h e r e a c t i o n p r o c e e d s . " C u r r a n e t a l . (4) d e s c r i b e d t h e t r a n s f e r of hydrogen from t e t r a l i n t o c o a l as a f r e e r a d i c a l r e a c t i o n i n v o l v i n g thermal cleavage of the c o a l molecules. Heredy and Neuworth (5) were a p p a r e n t l y t h e f i r s t i n v e s t i g a t o r s t o report the depolymerization of coal using F r i e d e l - C r a f t s c a t a l y s t s . They o b s e r v e d t h a t t h e s o l u b i l i t y o f c o a l c o u l d be c o n s i d e r a b l y i n c r e a s e d by t r e a t m e n t w i t h boron t r i f l u o r i d e i n p h e n o l a t 100°C. Subsequent s t u d i e s (6) i n d i c a t e d t h a t p a r a - t o l u e n e s u l f o n i c a c i d i n p h e n o l was t h e most e f f i c i e n t c a t a l y s t f o r t h e d e p o l y m e r i z a t i o n r e a c t i o n a t 185°C. Lower rank c o a l s were found t o be more r e a c t i v e r e s u l t i n g i n higher s o l u b i l i t y (T). More r e c e n t l y S t e r n b e r g (8) has s t u d i e d t h e d i s s o l u t i o n o f c o a l by r e d u c t i v e a l k y l a t i o n , w h i c h i n v o l v e s a v a r i e t y o f r e a c t i o n s , i n c l u d i n g f r e e r a d i c a l and e l i m i n a t i o n r e a c t i o n s . The r e d u c t i v e a l k y l a t i o n proceeds by t h e a d d i t i o n o f e l e c t r o n s t o t h e a r o m a t i c n u c l e i t o form t h e c o r r e s p o n d i n g a n i o n s f o l lowed by C - a l k y l a t i o n . Cleavage o f e t h e r bonds r e s u l t s i n p h e n o l a t e a n i o n s and subsequent O - a l k y l a t i o n o f t h e a n i o n s s o l u b i l i z e s c o a l . C o a l has a l s o been s o l u b l i z e d by a g r a f t i n g 438

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

27.

RAI

ET

AL.

Liquefaction

of Subbituminous

Coals

439

t e c h n i q u e w h i c h c a n be c a r r i e d o u t a t m i l d temperatures (140150°C) and a t m o s p h e r i c p r e s s u r e (£). P u l v e r i z e d b i t u m i n o u s o r a n t h r a c i t e c o a l i s mixed w i t h a c h e m i c a l g r a f t i n i t i a t o r and an a p p r o p r i a t e monomer, and t h e r e a c t i o n p r o d u c t i s l i q u e f i e d e i t h e r by h e a t i n g o r by a d d i t i o n o f s o l v e n t s d e r i v e d from c o a l o r p e t r o l e u m . N o n - p o l a r a l k y l monomer s u b s t i t u e n t s enhance the s o l u b i l i t y o f c o a l i n a l i p h a t i c h y d r o c a r b o n s ; whereas a r o m a t i c s u b s t i t u e n t s make c o a l s o l u b l e i n a r o m a t i c s o l v e n t s . The p o l a r groups make the g r a f t e d c o a l s more s o l u b l e i n p o l a r s o l v e n t s such as k e t o n e s and a l c o h o l s . V i g o r o u s e f f o r t s a r e b e i n g made t o d e v e l o p c a t a l y t i c hydrogénation p r o c e s s e s f o r p r o d u c i n g l i q u i d f u e l s from c o a l . The r o l e o f hydrogen i n l i q u e f a c t i o n o f c o a l i s t o s a t u r a t e t h e f r e e r a d i c a l s formed by bond c l e a v a g e o f c o a l a t r e a c t i o n temperature. T h i s can o c c u r d i r e c t l y o r through hydrogénation o f s m a l l e r s o l v e n t m o l e c u l e s w h i c h then donate t h e i r hydrogen t o r e a c t i v e c o a l s p e c i e s . D e s u l f u r i z a t i o n and s a t u r a t i o n o f d o u b l e bond and a r o m a t i c r i n g s t r u c t u r e s a l s o occurs i n t h e p r e s e n c e of hydrogen. Enormous amounts o f hydrogen a r e needed f o r h y d r o génation p r o c e s s e s and w i t h o u t a t e c h n o l o g i c a l b r e a k t h r o u g h f o r p r o d u c t i o n o f hydrogen a t low c o s t s , an e c o n o m i c a l p r o c e s s f o r l i q u e f a c t i o n w i l l n o t be a c h i e v e d . An a l t e r n a t i v e approach has been i n v e s t i g a t e d by A p p e l l e t a l . (10) c o n s i s t i n g o f l i q u e f y i n g l i g n i t e and b i t u m i n o u s c o a l w i t h low c o s t s y n t h e s i s g a s . Fu and I l l i g (11) have attempted l i q u e f a c t i o n and d e s u l f u r i z a t i o n o f h i g h s u l f u r b i t u m i n o u s c o a l s w i t h s y n t h e s i s gas a t temperat u r e s o f 400-450°C, and o p e r a t i n g p r e s s u r e s o f 3000-4000 p s i i n the presence o f c o b a l t molybdate and sodium c a r b o n a t e c a t a l y s t s , steam and a r e c y c l e o i l . The e f f e c t o f m i n e r a l m a t t e r p r e s e n t i n w e s t e r n c o a l s was i n v e s t i g a t e d i n an a t t e m p t t o d e v e l o p an e c o n o m i c a l n o n - c a t a l y t i c l i q u e f a c t i o n p r o c e s s u s i n g low c o s t s y n t h e s i s gas. The m i n e r a l s p r e s e n t i n the subbituminous c o a l s o f f e r an adequate, i n e x p e n s i v e and n a t u r a l l y o c c u r i n g source o f c a t a l y t i c m a t e r i a l s f o r l i q u e f a c t i o n and h y d r o d e s u l f u r i z a t i o n r e a c t i o n s i n v o l v e d i n c o a l conv e r s i o n . M i t c h e l l and G l u s k o t e r (12) have i d e n t i f i e d b a s s a n i t e , q u a r t z , k a o l i n i t e , c a l c i t e and p y r i t e i n the Rocky M o u n t a i n subb i t u m i n o u s c o a l s by low temperature a s h i n g t e c h n i q u e . Morooka and Hamrin (13) o b s e r v e d t h a t t h e m i n e r a l m a t t e r from two Kentucky c o a l s e x h i b i t e d c a t a l y t i c a c t i v i t y f o r t h e d e h y d r o s u l f u r i z a t i o n o f t h i o p h e n e and butene i s o m e r i z a t i o n . I n t h i s s t u d y subbituminous c o a l s were l i q u e f i e d and d e s u l f u r i z e d e f f e c t i v e l y by h y d r o t r e a t i n g w i t h s y n t h e s i s gas a t moderate o p e r a t i n g c o n d i t i o n s i n the p r e s e n c e o f steam and a n t h r a c e n e o i l used as a s o l v e n t . The d a t a were compared when the same c o a l s were l i q u e f i e d w i t h pure hydrogen under s i m i l a r e x p e r i m e n t a l c o n d i t i o n s . P y r i t i c and o r g a n i c s u l f u r p r e s e n t i n t h e s e c o a l s appear t o be r e s p o n s i b l e f o r t h e f o r m a t i o n o f c a t a l y t i c a c t i v e form o f i r o n s u l f i d e t h a t f u n c t i o n s as an e f f e c t i v e h y d r o t r e a t i n g c a t a l y s t ( 1 4 ) . The presence o f

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

440

INDUSTRIAL

AND

LABORATORY

ALKYLATIONS

a l u m i n o s i l i c a t e s and c a r b o n a t e s i n these c o a l s promote t h e con­ v e r s i o n o f complex o r g a n i c s t r u c t u r e s t o s o l u b l e l i q u i d p r o d u c t s . The water-gas s h i f t r e a c t i o n and the r e d u c t i o n o f c a r b o n y l groups i n the c o a l s t r u c t u r e s a r e c a t a l y z e d by a l k a l i m e t a l c a r b o n a t e s . The r e d u c t i o n o f c a r b o n y l groups proceeds v i a d o n a t i o n o f t h e a l d e h y d i c hydrogen i n the formate i o n t o the c a r b o n y l group. The formate i o n i s c o n t i n u a l l y r e g e n e r a t e d by the r e a c t i o n o f carbon monoxide w i t h a l k a l i n e m a t e r i a l s present i n coal ash. M >C = 0

+

+

+

OH"

+

CO

Η(φ>©

H-C-0 M —>· -C-0 M

+

C0

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

H 0 ® -Ç-0 Μ

+

Η 0

, H-C-OH

θ

+

OH

o

A

1

Φ

+

M

Experimental Equipment. The l i q u e f a c t i o n o f c o a l was s t u d i e d i n a 1 l i t e r m a g n e t i c a l l y s t i r r e d s t a i n l e s s s t e e l a u t o c l a v e . The a u t o ­ c l a v e was equipped w i t h a t h e r m o w e l l ; a gas i n l e t p o r t connected to a s y n t h e s i s gas (H :C0 r a t i o o f 1:1), o r t o a hydrogen c y ­ l i n d e r ; and t o a p r e s s u r e gauge; a p o r t f o r c o n n e c t i o n t o a r u p t u r e d i s k assembly; and a p o r t f o r gas d i s c h a r g e . The v e r ­ t i c a l magentic r o d w i t h dashers s t i r r e d the c o a l , s o l v e n t and a s h o r c a t a l y s t p a r t i c l e s . The a u t o c l a v e temperature was measured by a thermocouple p l a c e d i n t o the t h e r m o w e l l . 9

M a t e r i a l s . Twelve subbituminous c o a l s from f o u r major c o a l - b e a r i n g r e g i o n s o f Wyoming were s t u d i e d i n t h i s program. Chemical and p h y s i c a l a n a l y s e s o f these c o a l s a r e p r e s e n t e d i n T a b l e I . The c o a l samples were b a l l - m i l l e d t o minus 100 mesh under n i t r o g e n and s t o r e d i n a r e f r i g e r a t o r b e f o r e u s e . A C o - M o - A l 0 c a t a l y s t (Harshaw CoMo 0402T, 3% CoO - 15% Mo0 ) was used i n some experiments e i t h e r w i t h o r w i t h o u t p o t a s ­ sium c a r b o n a t e . P y r i t e i s o l a t e d from c o a l was a l s o used as a c a t a l y s t w i t h p o t a s s i u m c a r b o n a t e i n some e x p e r i m e n t s . An­ t h r a c e n e o i l o b t a i n e d from Crowley T a r P r o d u c t s Company was used as the s t a r t - u p s o l v e n t . I n the r e c y c l e runs w i t h S h e r i d a n F i e l d C o a l (W-74-45), 80% o f the a n t h r a c e n e o i l was g r a d u a l l y r e p l a c e d by c o a l - d e r i v e d o i l a f t e r n i n e r e c y c l e s . The benzene and pentane used f o r s e p a r a t i o n o f o i l , and a s p h a l t e n e were F i s h e r s o l v e n t grade. 3

3

3

P r o c e d u r e . I n a t y p i c a l e x p e r i m e n t , the a u t o c l a v e was charged w i t h subbituminous c o a l (80-110g), a n t h r a c e n e o i l ( 1 4 0 g ) , w a t e r as needed t o p r o v i d e 25 w t % o f t h e c o a l charge w i t h s y n ­ t h e s i s gas o r hydrogen as the r e d u c i n g a g e n t , and w i t h o r w i t h o u t

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

COAL NAME

ADAVILLE # 6

2

16.7

20.3

20.9

23.8

22.1

19.1

18.3

18.0

19.5

21.1

Ar 12.4 Maf

Ar 19.5 Maf

1

Ar Maf Ar Maf Ar Maf Ar Maf Ar Maf

POWDER RIVER COAL BASIN Ar WYO-74-40 WYODAK Maf (Anderson-Canyon) Ar WYO-74-45 UNNAMED DIETZ Maf (Sheridan F i e l d ) Ar WYO-74-50 MONARCH (Upper Bench) Ar WYO-74-52 MONARCH (Lower M i d d l e Bench) Maf Ar WYO-74-53 MONARCH Maf (Lower Bench)

HANNA COAL FIELD WYO-74-24 BED #80

WYO-74-19 ADAVILLE # 1 (Elkol) GREEN RIVER REGION WYO-74-20 DEADMAN

WYO-74-14 ADAVILLE # 3

WYO-74-12 ADAVILLE # 4

WYO-74-4

HAMS FORK COAL REGION WYO-74-3 ADAVILLE #10

SAMPLE NO.

35.0 47.7 32.9 50.0 36.8 49.6 37.5 51.0 28.3 48.0

38.4 52.3 32.8 50.0 37.4 50.4 36.1 49.0 30.7 52.0

39.6 50.3

42.0 56.2

32.6 43.8 39.2 49.7

37.9 54.9 37.8 53.3 41.2 54.9 37.8 50.5 42.8 54.0

31.1 45.1 33.1 46.7 34.0 45.1 37.1 49.5 36.5 46.0

21.9

8.1

7.8

14.8

5.5

8.8

5.9

4.0

4.8

3.9

5.3

8.9

PROXIMATE ANALYSIS (PERCENT) VOLATILE FIXED CARBON ASH MATTER MOISTURE

54.9 74.8 48.0 73.1 53.6 72.3 53.7 72.9 42.1 71.4

5.9 4.9 5.9 5.7 6.3 5.8 6.1 5.5 5.4 5.5

5.7 5.5

0.9 1.2 1.1 1.6 1.3 1.7 1.2 1.6 1.0 1.7

1.3 1.7

1.1 1.5

5.6 4.6 55.6 74.6 59.7 75.7

1.4 2.1 1.4 2.0 1.5 1.9 1.4 1.9 0.9 1.2 6.1 5.3 6.1 4.9 6.1 5.1 6.1 5.2 6.2 5.5

50.8 73.6 50.7 71.5 55.9 74.3 56.3 75.1 60.1 75.8

32.3 18.4 28.0 16.2 29.8 18.6 28.9 17.2 27.7 18.3

0.5 0.7 2.2 3.4 1.2 1.6 2.0 2.8 1.9 3.1

1.2 1.5

9480 12920 8560 13040 9450 12750 9600 13030 7380 12520

10450 13260

9270 12440 0.5 0.6 31.3 18.7 23.3 15.6

8980 13010 8560 12070 9750 12960 9780 13050 10530 13270 1.8 2.6 0.6 0.9 0.4 0.5 0.3 0.4 1.3 1.6

ΒTU/ LB

31.0 16.4 35.9 20.7 32.2 18.2 31.1 17.4 27.5 15.9

ULTIMATE ANALYSIS (PERCENT) s Ν 0 H c

TABLE I . ANALYSES OF SUBBITUMINOUS COALS FROM MAJOR WYOMING COAL FIELDS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

Η-'

Ο

ο

CO

1* ο

1"

S 5-

C/3

Ο

δ"

Ci

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

442

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

c a t a l y s t s . The a u t o c l a v e w i t h t h e r e a c t a n t s was f l u s h e d w i t h n i t r o g e n f o l l o w e d by s y n t h e s i s gas o r hydrogen and charged w i t h the a p p r o p r i a t e gas w i t h a n i n i t i a l p r e s s u r e o f 1600 t o 2000 p s i . The a u t o c l a v e temperature was t h e n i n c r e a s e d t o t h e d e s i r e d o p e r a t i n g temperature (400° t o 450°C) o v e r a p e r i o d o f 50 t o 60 m i n u t e s , m a i n t a i n e d a t t h e temperature from 15 t o 75 min. After the experiment was c o m p l e t e d , r a p i d i n t e r n a l c o o l i n g o f t h e a u t o c l a v e t o the ambient temperature was a c h i e v e d by c o l d w a t e r . The f i n a l p r e s s u r e i n t h e a u t o c l a v e was r e c o r d e d t h e n e x t d a y , the d i f f e r e n c e i n p r e s s u r e i n d i c a t i n g t h e volume o f gas consumed i n t h e e x p e r i m e n t . The p r o d u c t s were f i l t e r e d a t ambient or h i g h e r temperatures t o o b t a i n l i q u i d o i l s . F i l t e r cakes c o n t a i n i n g u n r e a c t e d c a r b o n , a s h and w a t e r were e x t r a c t e d w i t h benzene o r a c e t o n e . The w a t e r was removed by d i s t i l l a t i o n and the r e m a i n i n g o i l was r e c o v e r e d by removing t h e s o l v e n t i n a r o t a r y vacuum e v a p o r a t o r . Gaseous p r o d u c t s were a n a l y z e d by mass s p e c t r o m e t r y . Data on c o n v e r s i o n , o i l y i e l d and gas consumption a r e g i v e n as w e i g h t p e r c e n t based on m o i s t u r e - f r e e and a s h - f r e e (maf) c o a l . R e s u l t s and D i s c u s s i o n L i q u e f a c t i o n w i t h S y n t h e s i s Gas (1H :1C0) and Hydrogen. Subbituminous c o a l s from f o u r major c o a l - b e a r i n g r e g i o n s o f Wyoming: Hams F o r k , Green R i v e r , Hanna and Powder R i v e r C o a l B a s i n h a v i n g a s h from 4 t o 22 wt%, m o i s t u r e from 12 t o 25 w t % and s u l f u r from 0.6 t o 3.4 w t % (maf) were l i q u e f i e d and des u l f u r i z e d w i t h s y n t h e s i s gas i n a n t h r a c e n e o i l and i n absence of added c a t a l y s t s . The major elements p r e s e n t i n the m i n e r a l m a t t e r o f t h e s e c o a l s a r e shown i n T a b l e I I ( 1 5 ) . Some o f these m e t a l s a c t as c a t a l y s t s f o r d e p o l y m e r i z i n g and l i q u e f y i n g c o a l s . When Monarch (Lower Bench) c o a l (W-74-53) was h y d r o t r e a t e d w i t h s y n t h e s i s gas i n a n t h r a c e n e o i l and 25 w t % m o i s t u r e a t 425 + 5°C, an o p e r a t i n g p r e s s u r e o f 3900-4000 p s i , and a r e a c t i o n time o f one h o u r , a 99/o c o n v e r s i o n and 72% s e l e c t i v i t y t o o i l on a m o i s t u r e - and a s h - f r e e b a s i s was o b s e r v e d . The v i s c o s i t y o f the c o a l o i l i n a n t h r a c e n e s o l v e n t was r e m a r k a b l y low, 53 c e n t i p o i s e s a t 6 0 ° C A t l o w e r r e s i d e n c e time from 15 min. t o 30 min., t h e p r o d u c t o i l r e s u l t e d i n a h i g h v i s c o s i t y , eventhough t h e c o n v e r s i o n s were n o t g r e a t l y a f f e c t e d . These d a t a are shown i n T a b l e I I I and F i g u r e 1. E s s e n t i a l l y a l l the subbituminous c o a l s when h y d r o g r e a t e d w i t h s y n t h e s i s gas i n a n t h r a c e n e o i l and adequate amounts o f m o i s t u r e r e s u l t e d i n h i g h c o n v e r s i o n s v a r y i n g from 90 t o 99% on m o i s t u r e - and a s h - f r e e b a s i s a t a temperature o f 425 + 5°C, an o p e r a t i n g p r e s s u r e o f 3500 t o 4500 p s i g , and a r e s i d e n c e time o f a n h o u r . The p r o d u c t o i l i n v a r i a b l y had a low v i s c o s i t y . These a r e optimum c o n d i t i o n s f o r a u t o c l a v e e x p e r i m e n t s . H i g h e r temperatures r e s u l t e d i n i n c r e a s e d gas consumption, l o w e r conv e r s i o n s , and a p r o d u c t o i l o f low v i s c o s i t y . Likewise, Q

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

ADAVILLE #10 Kemmerer ADAVILLE # 6 Kemmerer ADAVILLE # 4 Kemmerer ADAVILLE # 3 Kemmerer ADAVILLE # 1 Kemmerer DEADMAN Rock S p r i n g s BED #80 Hanna WYODAK Powder R i v e r UNNAMED DIETZ Sheridan MONARCH (Upper Bench) Sheridan MONARCH (Lower M i d d l e Bench) Sheridan MONARCH (Lower Bench) Sheridan

WYO-74-3

WYO-74-53

WYO-74-52

WYO-74-50

WYO-74-45

WYO-74-40

WYO-74-24

WYO-74-20

WYO-74-19

WYO-74-14

WYO-74-12

WYO-74-4

COAL NAME COAL FIELD

SAMPLE NO.

0.012 0.019 0.017 0.032 <0.001 0.055 0.068 0.036 0.206 0.11

0.32 0.30 0.17 0.21 0.86 0.23 2.10 0.77 1.20 1.50

0.016

0.004 0.008 0.004 0.014 0.014 0.072 0.150 0.12 0.075 0.086

0.12 0.12 0.08 0.14 0.196 0.150 0.23 0.27 0.230 0.340

0.23 0.23 0.31 0.53 1.10

0.20 0.42 0.52 0.55 0.92 0.53 1.80 0.85 0.69 2.50

1.33 1.49 1.20 1.45 1.70 0.86 3.11 1.43 0.88 5.50

0.49

0.59

0.62

0.80

1.00

0.011 1.40

0.020

0.005

0.17

0.21

0.17

1.83

0.370

0.041

0.063

0.20

0.017

0.083

0.006

0.006

0.040

0.026

1.50

0.034

0.01

0.17

0.59

Ti

0.44

MAJOR ELEMENTS AS PERCENT OF WHOLE COAL Fe Na Κ Al Ca _Mg_

2.60

Si

TABLE I I . ELEMENTAL COMPOSITION OF WESTERN SUBBITUMINOUS COALS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

CO

<3"

C/3

ο

^3

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

*FeS , 2

C 0

3

w

a

s

u

s

e

d

a

s

a

60 30 15 30

5 26 27 28*

K

CONTACT TIME, MINUTES

RUN NO.

c a t a l y s t

«

420-25 425-26 424-25 424-26

TEMPERATURE, °C 3900 4100 3900 4150

PRESSURE, p s i g 99.4 95.9 91.1 97.8

CONVERSION, PERCENT

72.0 72.0 78.6 73.4

OIL YIELD, PERCENT

E f f e c t o f R e a c r i o n Time on C o n v e r s i o n and O i l Y i e l d w i t h S y n t h e s i s Gas

Monarch (Lower Bench, 74-53)

TABLE I I I . NON-CATALYTIC LIQUEFACTION OF WYOMING SUBBITUMINOUS COALS

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

136 355 595 97.83

VISCOSITY AT 60°C cp

r«

ο 2

>

w

Î

1

>

>

§

Liquefaction

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

RAI E T AL.

Ο

15

of Subbituminous

30

45

Coals

60

75

TIME, min. Figure 1.

Effect of reaction time on conversion and viscosity EFFECT OF PRESSURE ON COAL LIQUEFACTION SUBBITUMINOUS, I HR. H + CO, I HR, 4 2 5 ° C 2

INITIAL PRESSURE, PSIG Figure 2.

Effect of pressure on coal liquefaction

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

ADAVILLE #10 (W-74-3, No. 17) ADAVILLE #10 (W-74-3, No. 6) ADAVILLE # 6 (W-74-4, No. 19) ADAVILLE # 6 (W-74-4, No. 18) ADAVILLE # 4 (W-74-12, No. 25) ADAVILLE # 4 (W-74-12, No. 24) ADAVILLE # 3 (W-74-14, No. 23) ADAVILLE # 3 (W-74-14, No. 22) ADAVILLE # 1 (W-74-14, No. 14) ADAVILLE # 1 (W-74-19, No. 7) DEADMAN (W-74-20, No. 15) DEADMAN (W-74-20, No. 10)

COAL NAME RUN NO. 450 425 425-26 425-25 425-30 426-28 420-55 425 420-25 425-28 422-34 425-30

SYNGAS

HYDROGEN

SYNGAS

HYDROGEN

SYNGAS

HYDROGEN

SYNGAS

HYDROGEN

SYNGAS

HYDROGEN

SYNGAS

°c

HYDROGEN

GAS

3800

3650

3975

3510

4650

4350

4100

3900

4400

4130

4250

4200

420

210

205

200

150

300

375

325

250

220

125

350

PRESSURE, P.siR MAXIMUM ΔΡ

89.5

83.2

93.2

77.4

72.8

45.9

89.0

85.1

95.2

82.4

89.1

75.3

54.3

55.4

54.9

44.4

38.2

21.6

71.6

59.4

63.3

34.4

55.4

47.2

OIL YIELD, PERCENT

1 HOUR)

CONVERSION, PERCENT

ANTHRACENE OIL; CONTACT TIME:

TEMPERATURE

(SOLVENT:

208.7

726

128

379

392

185

191

215

242

517

372

124

VISCOSITY AT 60°C ci

TABLE I V . NON-CATALYTIC LIQUEFACTION OF WYOMING SUBBITUMINOUS COALS WITH SYNTHESIS GAS AND HYDROGEN

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

ο

s

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ι

in

c*

S

§ . S. S a s

s

Si-

? 3 3

Piîro P - cr

t I

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 260

250

300

4250

4175

4030

420-27

420-25

HYDROGEN

SYNGAS

3)

12)

380

426-28

3950

SYNGAS

425

32)

HYDROGEN

350

4450

425-26

SYNGAS

20)

36)

290

3820

425-30

HYDROGEN

21)

98.7

86.2

96.2

94.0

98.2

88.7

72.2

50.0

76.7

68.0

47.4

53.3

53

348

45

79

56.9

243

97.2

71.0

90.4

275

4160

425-27

SYNGAS

8)

155.6

34.4

290

4000

425-35

HYDROGEN

11)

80.6

93.6

240

4400

425-28

SYNGAS

1)

172

88.9

320 62.0

VISCOSITY AT 60°C cp 252

OIL YIELD, PERCENT 60.7

CONVERSION, PERCENT

4510

PRESSURE. p s i g ΔΡ MAXIMUM

420-30

TEMPERATURE °C

HYDROGEN

GAS

2)

CONTINUED

HANNA BED #80 (W-74-24, No. HANNA BED #80 (W-74-24, No. WYODAK (W-74-40, No. WYODAK (W-74-40, No. MONARCH (Upper Bench) (W-74-50, No. MONARCH (Upper Bench) (W-74-50, No. MONARCH (Lower M i d d l e Bench) (W-74-52, No. MONARCH (Lower M i d d l e Bench) (W-74-52, No. MONARCH (Lower Bench) (W-74-53, No. MONARCH (Lower Bench) (W-74-53, No.

COAL NAME RUN NO.

TABLE I V .

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

TABLE I V .

CONTINUED

UNNAMED DIETZ (W-74-45, No. 38) UNNAMED DIETZ (W-74-45, No. 39)

COAL NAME RUN NO. 425 425

HYDROGEN

TEMPERATURE °C

SYNGAS

GAS

3930

4140 570

270

PRESSURE, p s l g MAXIMUM ΔΡ

95.0

96.0

CONVERSION, PERCENT

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

71.0

70.0

OIL YIELD, PERCENT

49

46

VISCOSITY AT 60°C cp

27.

RAI E T

AL.

Liquefaction

of Subbituminous

Coals

449

h i g h e r p r e s s u r e s r e s u l t e d i n h i g h e r c o n v e r s i o n s and t h e b e s t r e s u l t s were o b t a i n e d a t a n i n i t i a l p r e s s u r e o f 1800-2000 p s i g , w i t h a c o r r e s p o n d i n g o p e r a t i n g p r e s s u r e o f about 3600-4200 p s i g . The e f f e c t o f p r e s s u r e i s shown i n F i g u r e 2 and compared w i t h the p u b l i s h e d d a t a ( 1 0 ) . L i q u e f a c t i o n o f these c o a l s w i t h pure hydrogen under s i m i l a r e x p e r i m e n t a l c o n d i t i o n s i n v a r i a b l y gave l o w e r c o n v e r s i o n s , lower s e l e c t i v i t y t o o i l and a p r o d u c t w i t h h i g h e r v i s c o s i t y i n the absence o f added c a t a l y s t s . The s u l f u r c o n t e n t and the v i s c o s i t y o f t h e p r o d u c t o i l b o t h decrease w i t h t h e amount o f hydrogen consumed i n each c a s e , however, l e s s t o t a l hydrogen i s r e q u i r e d f o r the same o i l q u a l i t y w i t h s y n t h e s i s gas than w i t h pure hydrogen. These d a t a a r e shown i n T a b l e IV and compared w i t h t h e r e s u l t s o b t a i n e d by u s i n g s y n t h e s i s g a s . C a t a l y t i c L i q u e f a c t i o n w i t h Co-Mo-Al 0a C a t a l y s t and C o n s t i t u e n t s o f C o a l M i n e r a l M a t t e r . Some l o w a s h c o a l s such as A d a v i l l e #3 (W-74-14), and A d a v i l l e #10 (W-74-3) from Kemmerer f i e l d e x h i b i t e d poor c o n v e r s i o n and s e l e c t i v i t y t o o i l under t y p i c a l h y d r o t r e a t i n g c o n d i t i o n s w i t h s y n t h e s i s gas. By cond u c t i n g t h e l i q u e f a c t i o n i n t h e presence o f p o t a s s i u m c a r b o n a t e , p y r i t e o r c o b a l t molybdate ( C o - M o - A l 0 ) , a remarkable i n c r e a s e i n o v e r a l l c o n v e r s i o n and s e l e c t i v i t y t o o i l was a c h i e v e d w h i l e the v i s c o s i t y o f p r o d u c t o i l i n a n t h r a c e n e s o l v e n t was a l s o c o n s i d e r a b l y l o w e r e d . With A d a v i l l e #3 (W-74-14), u s i n g s y n t h e s i s gas a t 425°C, and an o p e r a t i n g p r e s s u r e o f from 4150 t o 4225 p s i g , and a r e s i d e n c e time o f an h o u r , t h e c o n v e r s i o n i n c r e a s e d from 73% t o 947o w i t h K C 0 3 and o r p y r i t e , whereas the s e l e c t i v i t y t o p r o d u c t o i l i n c r e a s e d from 38% t o 68%. The v i s c o s i t y o f t h e p r o d u c t o i l was a l s o c o n s i d e r a b l y lowered from 392 t o 56-80 c e n t i p o i s e s a t 60°C. With C o - M o - A l 0 c a t a l y s t and K C 0 3 a s i m i l a r t r e n d was o b s e r v e d , t h e c o n v e r s i o n b e i n g 9 7 7 o , s e l e c t i v i t y t o o i l 55% and t h e p r o d u c t o i l v i s c o s i t y b e i n g 35 c e n t i p o i s e s a t 60°C. Monarch (Lower Bench) c o a l from the S h e r i d a n F i e l d a l s o e x h i b i t e d improved c o n v e r s i o n , h i g h e r p r o d u c t o i l y i e l d and l o w e r v i s c o s i t y o f the p r o d u c t o i l . These d a t a a r e shown i n T a b l e V.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

Q

2

3

2

8

s

2

E f f e c t o f R e c y c l e on L i q u e f a c t i o n and P r o d u c t D i s t r i b u t i o n . I t i s i m p o r t a n t t h a t t h e p r o d u c t o i l from a c o a l l i q u e f a c t i o n p r o c e s s s h o u l d have a low v i s c o s i t y so t h a t i t c o u l d be used for p r e p a r i n g c o a l - o i l s l u r r i e s f o r r e c y c l i n g i n a continuous l i q u e f a c t i o n p r o c e s s . The p r o d u c t o i l s h o u l d a l s o e x h i b i t r e a c t i v i t y o r s o l v e n c y f o r t h e c o a l s o t h a t the v i s c o s i t i e s do not d e t e r i o r a t e w i t h prolonged r e c y c l i n g o p e r a t i o n . The r e c y c l e c h a r a c t e r i s t i c s o f t h e l i q u e f i e d c o a l - o i l were determined by c o n d u c t i n g n i n e c o n s e c u t i v e r e c y c l e r u n s . I n t h i s set o f experiments a f r e s h l y p u l v e r i z e d subbituminous c o a l (W-74-45) w i t h 3.4 w t % s u l f u r (maf) from the S h e r i d a n f i e l d o f the Powder R i v e r C o a l B a s i n was used. I n each o f t h e experiments

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 56.7 56.1

92.3 94.4 96.9 95.9

97.8

175 220 380 220

220

4150 4150 4225 4100

4150

420-25 425-26 425-26 425-26

424-26

60 60 60 30

30

K C0 \

K C0 \

CoMo j None

K C0 \

3

3

3

2

2

J

FeS J

2

2

FeS J

2

2

K CO 3

68.14

91.9

275

4250

425

60

2

FeS

73.5

71.9

54.6

38.2

72.8

150

4650

425

136

355

35

83.5

80.5

56.2

392

OIL YIELD VISCOSITY PERCENT AT 60°C

60

CONVERSION PERCENT

None

PRESSURE, p s i g MAXIMUM

ADAVILLE NO. 3 (W-74-14, Run 22) ADAVILLE NO. 3 (W-74-14, Run 33) ADAVILLE NO. 3 (W-74-14, Run 31) ADAVILLE NO. 3 (W-74-14, Run 29) ADAVILLE NO. 3 (W-74-14, Run 30) MONARCH (Lower Bench) (74-53, Run 26) MONARCH (Lower Bench) (74-53, Run 28)

TEMPERATURE °C

CONTACT TIME, MIN.

Anthracene O i l )

CATALYST

(Solvent:

CATALYTIC LIQUEFACTION OF WYOMING SUBBITUMINOUS COALS WITH SYNTHESIS GAS

COAL MINE

TABLE V.

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

2!

ι

r

*<

>

»

I

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>

f

Ο

>

2

αχ ο

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 18.9 33.9 45.1 54.4 61.3 66.7 70.5 74.8 78.3 22 26 29 40 52 92 80 62 62 720 250 290 305 440* 550* 230 250 250

3840 3960 4010 3900 3710 3500 4020 4070 4020

55.3 53.7 47.3 48.3 41.3 38 33.3 40 37.3

94 94 92 87 90 88 85 88 87

1 2 3 4 5* 6* 7 8 9

* P r e s s u r e Loss

PERCENT COAL DERIVED

VISCOSITY CPA AT 60°C

ΔΡ

OPERATING PRESSURE, p s i g

PERCENT OIL YIELD

PERCENT CONVERSION

RECYCLE #

TABLE V I . RECYCLE RUNS USING SUBBITUMINOUS COAL (74-45) WITH SYNTHESIS GAS AT 425°C

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

ο

S ο

Ο

<3"

s

CO

a

3

INDUSTRIAL

452

AND LABORATORY

ALKYLATIONS

the p r o d u c t o i l d e r i v e d form c o a l was s e p a r a t e d by f i l t r a t i o n and then used i n the n e x t e x p e r i m e n t , thus g r a d u a l l y becoming r i c h e r i n the c o a l - d e r i v e d o i l u n t i l about 8 0 7 , o f the a n t h r a c e n e o i l used as a s t a r t - u p s o l v e n t , was r e p l a c e d by subbituminous coal-derived o i l . The r e c y c l e r u n d a t a a r e shown i n T a b l e V I . The v i s c o s i t y o f the p r o d u c t o i l a f t e r n i n e r e c y c l e runs was q u i t e l o w , 6 2 c e n t i p o i s e s a t 6 0 ° C , and t h e s u l f u r l e v e l was reduced t o 0 . 2 2 wtT, compared t o 3 . 4 wt7o (maf) i n the s t a r t i n g subbituminous c o a l as shown i n T a b l e V I I . High c o a l c o n v e r s i o n s from 8 5 t o 957o on maf b a s i s were a l s o observed when the p r o d u c t o i l was r e c y c l e d . TABLE V I I .

LIQUEFACTION OF SUBBITUMINOUS COAL USING RECYCLE OIL

( l h r , 4 2 5 ° C ; 1:1 s y n t h e s i s g a s ,

3500-4000

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

SHERIDAN FIELD. BIG HORN MINE - COAL CONVERSION, % OIL YIELD, 7o PRODUCT: C H 0 S Ν CENTIPOISES AT 60°C

1ST RUN 94 55.3

0.22 22

psig)

(74-45)

9TH RUN 87 37.3 88.24 7.04 3.03 0.22 1.63 62

The p r o d u c t o i l d e r i v e d by r e c y c l e has t h e f o l l o w i n g components: o i l , 61.37 ; a s p h a l t e n e s , 26.57.; and benzene i n s o l u b l e s , 12.27,. The o i l f r a c t i o n was a n a l y z e d by mass s p e c t r o s c o p y . The o r g a n i c compounds i d e n t i f i e d i n the o i l f r a c t i o n a r e shown i n T a b l e V I I I . 0

TABLE V I I I .

IDENTIFIED ORGANIC COMPOUNDS PRESENT IN COALDERIVED OIL FRACTION (74-45) BY MASS SPECTROSCOPY

COMPOUND INDANOL PHENYL NAPHTHALENES PHENOLS ANTHRACENE S/PHENANTHRENE S ACENAPHTHYLENE S/FLU0RENE S ACENAPHTHENES BENZOFURANE BENZOPYRENE NAPHTHALENES INDENES CHRYSENE INDANES AND TETRALINS PYRENES

PERCENT 1.0 6.7 9.1 25.4 5.1 8.5 0.1 0.5 21.4 0.1 2.0 2.1 18.0

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

27.

RAI E TA L .

Liquefaction

of Subbituminous

Coals

453

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

Conclusions Western subbituminous c o a l s can be r e a d i l y l i q u e f i e d and d e s u l f u r i z e d by n o n - c a t a l y t i c l i q u e f a c t i o n w i t h s y n t h e s i s gas and steam a t 400-450°C and an o p e r a t i n g p r e s s u r e o f 3800-4400 p s i . The m i n e r a l m a t t e r p r e s e n t i n these c o a l s f u n c t i o n s as e f f e c t i v e c a t a l y s t s f o r p r o m o t i n g the w a t e r gas s h i f t r e a c t i o n and the r e d u c t i o n o f c a r b o n y l groups t o o i l s o l u b l e p r o d u c t s . The s u l f u r c o n t e n t and the v i s c o s i t y o f the p r o d u c t o i l d e c r e a s e w i t h the amount o f hydrogen consumed w i t h b o t h s y n t h e s i s gas and hydrogen, however, much l e s s t o t a l hydrogen i s r e q u i r e d f o r the same q u a l i t y o i l p r o d u c t w i t h s y n t h e s i s gas t h a n w i t h pure hydrogen. The r e c y c l e c h a r a c t e r i s t i c s of c o a l - d e r i v e d o i l a r e v e r y i m p o r t a n t f o r the c o m m e r c i a l i z a t i o n o f a l i q u e f a c t i o n p r o c e s s . One subbituminous c o a l from the S h e r i d a n f i e l d o f the Powder R i v e r C o a l B a s i n was s t u d i e d f o r i t s r e c y c l e c h a r a c t e r i s t i c s and found t o be q u i t e a c c e p t a b l e . A f t e r n i n e r e c y c l e s the v i s c o s i t y o f the p r o d u c t o i l remained low and about 95% r e d u c t i o n i n s u l f u r l e v e l t o 0.22 wt% was a c h i e v e d . Such a l i q u e f a c t i o n p r o c e s s h o l d s promise f o r those Western c o a l s t h a t have h i g h s u l f u r and h i g h ash and cannot be e c o n o m i c a l l y t r a n s p o r t e d to d i s t a n t markets. Acknowledgement The a u t h o r s a r e g r a t e f u l t o Gary B. G l a s s o f the G e o l o g i c a l Survey o f Wyoming f o r p r o v i d i n g the c o a l samples. C. R a i g r a t e f u l l y acknowledges the f i n a n c i a l s u p p o r t from the Oak Ridge A s s o c i a t e d U n i v e r s i t i e s and the Amax F o u n d a t i o n under w h i c h t h i s s t u d y was c a r r i e d o u t . The a u t h o r s a r e a l s o i n d e b t e d t o the P i t t s b u r g h Energy Research C e n t e r (ERDA) f o r the use o f the f a c i l i t i e s d u r i n g the summer o f 1976. The a n a l y t i c a l s u p p o r t was p r o v i d e d by F o r r e s t E. Walker of the Bureau of Mines and Jane V. Thomas o f the U n i v e r s i t y o f Wyoming. Abstract The e f f e c t of mineral matter present i n subbituminous coals was investigated by carrying out non-catalytic liquefaction with hydrogen and synthesis gas. Most of the twelve coals studied could be readily l i q u e f i e d to a low v i s c o s i t y and low sulfur oil i n the absence of added catalysts with synthesis gas at temperatures of 400-450°C and operating pressures of 3800-4400 p s i . Comparison with coal l i q u e f a c t i o n using pure hydrogen at optimum l i q u e f a c t i o n temperature of 425°C and pressure of 3800-4000 p s i resulted i n lower conversions, lower s e l e c t i v i t y to oil and a product with higher v i s c o s i t y . Some low ash coals exhibited poor conversion and s e l e c t i v i t y to oil under t y p i c a l l i q u e f a c t i o n conditions with synthesis gas.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

454

INDUSTRIAL

AND LABORATORY

ALKYLATIONS

By conducting the l i q u e f a c t i o n i n the presence of potassium carbonate, p y r i t e or cobalt molybdate a remarkable increase i n the o v e r a l l conversion and s e l e c t i v i t y to oil was achieved while the v i s c o s i t y of product oil was considerably lowered. The r e ­ cycle c h a r a c t e r i s t i c s of l i q u e f i e d coal a f t e r nine recycles, when 80% of the start-up solvent was replaced with coal-derived oil, were quite acceptable. The v i s c o s i t y of the recycled product oil remained remarkably low, and the s u l f u r l e v e l was reduced from 3.4 maf% i n the s t a r t i n g coal to 0.22 wt%. Literature Cited

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch027

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15.

Falkum, F. and Glen, R. Α., Fuel 1952, 31, 133. Van Krevelen, D. W., Coal, E l s e v i e r , Amsterdam, 1961, 339. H i l l , G. R., Hairiri, H., Reed, R. I., and Anderson, L. L., Am. Chem. S o c , Advances i n Chem. Ser. 1966, 55, 427-447. Curran, G. P., Struck, R. T., and Gorin, E., Ind. Eng. Chem., Process Design Dev. 1967, 6 (2), 166. Heredy, L. A. and Neuworth, M. B., Fuel 1962, 41, 221. Ouchi, Imuta Κ., and Yamashita, Y., Fuel 1973, 52, 156. Heredy, L. Α., Kostyo, A. E., and Neuworth, M. B., Fuel 1965, 44, 125. Sternberg, H. W. and Delle Donne, C. L., Fuel 1974, 53, 172. Dichter, Μ., Mehta, Μ., and Nowacki,T., Chem. & Eng. News, Jan 24, 1977, 26-27. Appell, H. R., Moroni, E. C., and M i l l e r , R. D., Preprints, Div. Fuel Chem., Am. Chem. Soc. 1975, 20(1), 58-65. Fu, Y. C. and Illig, E. G., Ind. Eng. Chem. Process Design Dev., 1976, 15 (3), 392-96. M i t c h e l l , R. S., and Gluskoter, H. J . , Fuel (London), 1976, 55, 90. Morooka, S. and Hamrin, C. E., J r . , Chem. Eng. S c i . , 32, 125, 1977. Mukherjee, D. K. and Chowdbury, P. B., Fuel (London), 1976, 55, 4. Glass, G. B., Geological Survey of Wyoming, Report of Investigation No. 11, (1975), 32.

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

INDEX

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ix001

A

Absorption 294 Acid composition requirement 282 hydrofluoric 314 run-away 252, 305 sludge 129 -soluble hydrocarbons 129 decomposition of 139 production of 143 strong, reactions of alkyl chlorides with 198 sulfuric 271 alkylation technology 318 industry 314 make-up reduction 282 recovery of 284, 321 regeneration of 321 Adiabatic reactor simulations 380 Aging rate, linear 391 Aging rule, volume 391 Alcohols, pyridyl reaction with Raney nickel 401 Aldimines 218 Aliphatic amines 207 Alkane(s) alkylations, thermodynamics of 187 gaseous, reaction with ethylene 157 liquid 153 Alkenyl halides and Grignard reagents, iron catalysis in cross coupling of 174 Alkenylation of alkylbenzenes 213 Alkyl chlorides 158,409 reaction with ethylene 159 reactions with strong acids 198 halides and Grignard reagents, cross coupling with copper(I) catalysts 178 transfers from organometallic inter­ mediates in catalytic processes 169 Alkylaromatic hydrocarbons, reaction with olefins 212 Alkylate produced from pure olefin feeds 61 Alkylation(s) apparatus, hydrogen fluoride 58 commercial 344 homolytic 399 propylene—isobutane 27

Alkylbenzenes, alkenylation of 213 Alkylbenzenes, aralkylation of 214 Alkylcyclohexanes 147 Alkyllithium 167 Alkylmetal(s) complexes, decomposition of 168 complexes, formation of 167 cross coupling of aryl halides with 170 Alkylpyridines 215 reaction with olefins 215 Aluminum chloride 360, 409 catalysts 138,349 in water treatment, economics of .... 370 Amberlyst-15 resin 78 Amberlyst XN-100 resin 82 Amines, aliphatic 207 Ammonium ions, quaternary 17 Apparatus, HF alkylation 58 Aralkylation of alkylbenzenes 214 Arylalkylnickel(II) 170 Aryl halides, cross coupling with alkylmetals 170 Β

Bassanite Benzene Boron trifluoride 1- Butene 2- Butene Butene-1 alkylation Butene reactions, normal n-Butenes ί-Butyl cations ί-Butyl chloride, reaction with methycyclopentane Butyl fluorides /-Butyl ion Butyl sulfate(s) stability of Butylamine Butylène alkylate

439 343,371 408 130 19,130 69 36 98,109 131 2 126 1 100,136 100 89 325

C Calcite 439 Carbon-carbon additional reactions, homogeneous 216 Carbonium ion 304 isomerization 33, 37, 39 Carboxylic acid chlorides 416

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458

INDUSTRIAL

Cascade reactor 224 Catalysis, iron in the cross coupling of alkenyl halides and Grignard reagents 174 Catalysis, nickel 170 Catalyst(s) aging 250,385 aluminum chloride 138, 349 containing rare earth 90 containing transition metal cations 93 disposal 352 hydrogenfluoride/borontrifluoride 411 sulfuric acid 242 p-toluenesulfonic acid 418 zeolite 89 Cationic surfactants 16,19, 25 Cations, f-butyl 131 Cations, isoalkyl 143 Cetylamine 20 Chain initiation reaction 29 propagation reaction 30 termination 30 Charging of dialkyl sulfate extract .... 287 Chlorides alkyl 158,409 reaction with ethylene 159 hexyl 160 octyl 160 Chloroalkyl carbenium ions 200 Clarifier 364 effect of pH on 365 Coal(s) bituminous, Friedel—Crafts alkylation of 408 characterization of 420 depolymerized 418 hydrogenolysis of 434 liquefaction 417 preparation 419 screening tests 421 soluble products from 416 subbituminous 438 analysis of 441 liquefaction with synthesis gas .... 442 Codimerization 38 Commercial alkylation process 344 Computer simulation 260 digital 380 Conjunct polymers 2, 36, 96,129 Contacting 279 Copolymer, isobutene-butene 34 Copper(I) catalysts, cross coupling of Grignard reagents and alkyl halides with 178 Copperas 364 Cracking 41

AND LABORATORY

ALKYLATIONS

Cross coupling of alkenyl halides and Girgnard reagents, iron catalysis in 174 of aryl halides with alkylmetals 170 of Grignard reagents and alkyl halides with copper(I) catalysts 178 Crotonitrile 211 Crystallization 302 CTMAB 20 Cumene 371 Cyclization reactions, intramolecular .. 219 Cycloalkanes 153 reaction with ethylene 149 Cyclohexane 148,150

Decalin 432 Decomposition of acid-soluble hydrocarbon complexes 139 Deisobutanizer operation 266 Depolymerization reaction, reactivity of various coals to 422 Depolymerized coal, hydrogenolysis of 434 Dialkyl sulfates, extraction of 287 Dialkychloronium ions 197 Di-i-butyl peroxide 153 Diglyme 207 Diisopropyl sulfate 288 Diisopropylbenzene 371 Dimate 332 Dimersol, and C3 alkylate product 334 Dimer-esters 304 Dimerization 38 isobutene 33 olefin 32 Dimersol Dimate and C3 alkylate product 334 Dimethylhexanes 27,39,96,129,142 Diolefins 216 as impurities 273, 274 DIPS 288 Dispersion, liquid-liquid 235 Disposal of catalyst 352 Disproportionation 36, 41 DMH 96,129 Dying acid 256

Emulsification 277 Ester(s) 129,138,302 concentrator 307 reaction mechanism and alkylation 304 α,β-unsaturated 211 Ethane alkylation, ethylene192

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INDEX

Ethers reaction with ethylene Ethyl crotonate Ethylation of isobutyl chloride, peroxideinduced of tetrahydrofuran Ethylbenzene crude, purification of Ethylcyclohexane 2-Ethyldioxane Ethylene -ethane alkylation and hydrogen chloride, telomerization of as impurity -methane alkylation reaction with alkyl chlorides cycloalkanes ethers gaseous alkanes isopentyl chloride Extraction of dialkyl sulfates

163 164 211 212 160 163 341 349 152 165 147 192 160 273 190 159 149 164 157 161 296 287

H HE 96 Heavy ends 96 production of 143 Hexyl chlorides 160 High intensity turbine 244 HIT 244 Homo-coupling 179 Homolytic alkylation(s) 399 of pyridine 400 Hydride abstraction 33 Hydride transfer 4-6 Hydrocarbon complexes, acid-soluble, decomposition of 139 Hydrocarbon dispersion 47 Hydrofluoric acid 27, 314 Hydrogen chloride, telomerization of ethylene and 160 fluoride 186 alkylation technology 318 /boron trifluoride, catalyst 411 sulfide 322 transfer 34 Hydrogenolysis 432 of coal and depolymerized coal 434

F FBT FCC Feed impurity effects Flat blade turbine Flow from impeller, fluid mechanics of Flows generated by impellers Fluid catalytic gasoline mechanics of flow from impeller mixer design shear stress Free radical processes Friedel-Crafts alkylation of bituminous coals Friedel-Crafts chemistry

243 328 273 243 226 243 328 242 226 224 228 399 408 341

G Gas, synthesis liquefaction of subbituminous coals with Gasoline production Gasoline, unleaded Grignard reagents and alkyl halides, cross coupling with copper(I) catalysts iron catalysis in cross coupling of alkenyl halides and

438 442 95 328 167 178 174

I

Impeller(s) and theflowsthey generate 243 fluid mechanics offlowfrom 226 tip speed 246 Impurity effects, feed 273 Industry, sulfuric acid 314 Inhibition of telomerization 147 Ion(s) f-butyl 1 chloroalkyl carbenium 200 dialkylchloronium 197 quaternary ammonium 17 IPS 288 Iron catalysis in the cross coupling of alkenyl halides and Grignard reagents 174 Isoalkyl cations 143 Isobutane 1,44,51, 96,145,279 cost 329 -ethylene alkylation 188 -olefin alkylation 91 Isobutene-butene copolymer 34 Isobutene dimerization 33 Isobutyl chloride, peroxide-induced ethylation of 160 Isobutylene 103,109,123,137,139 Isohexanes 41 Isomerization, carbonium ion 33, 37,39 Isomerization, olefin 31

In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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INDUSTRIAL

Isoparaffin Isopentane Isopentyl chloride, reaction with ethylene Isoprene Isopropyl acid sulfate Isostripper

37 41 161 207 288 268

AND LABORATORY

ALKYLATIONS

Ν

Nickel catalysis Nickel, Raney, reaction with pyridyl alcohols Nitriles, α,/3-unsaturated Nonanes Nucleophilic substitutions

170 401 211 158 397

Κ Kaolinite Kinetics of butyl sulfate runs

439 110

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L

LAH 398 LE 96,129 Light ends 96,129,142 Linear aging rate 391 Liquefaction 438 coal 417 subbituminous, with synthesis gas 442 Liquid-liquid dispersion 235 Lithium aluminum hydride 398 derivatives 398 naphthalene 207 Lutidines 404 M Macroreticular acidic ion exchange resins 75 Macroreticular resins, physical properties of 77 MAPU 16 Mechanics, fluid, offlowfrom impeller 226 Methane alkylation, ethylene190 Methane condensation reaction 189 Methanol, alkylation of pyridine compounds with 402 Methyl pyridines 397 Methylation of pyridine 402 Methylcyclopentane, reaction with ί-butyl chloride 2 Methylcyclopentane, solubility in modified sulfuric acid 8 3-Methylpentane isomerization in tritiated sulfuric acid 13 1-Methylpyridinium iodide, thermolysis of 398 α-Methylstyrene 208, 209 /3-Methylstyrene 208, 210 Microalkylation pilot unit (MAPU) .. 16 MON 20 Mono-esters 304 Monoethylation 147

Ο

Octane 12 Octyl chlorides 160 Octylamine 18 Oil, red 2, 96,129, 304 Olefin(s) 1, 44, 51, 89,136, 411 dimerization 32 feed 48 isomerization 31 oligomerization of 206 polymerization 27 reaction with alkylaromatic hydrocarbons 212 alkylpyridines 215 miscellaneous compounds 218 refinery 20, 21 Oleum 252,311 Oligomerization of olefins 206 Organometallic intermediates in catalytic processes, alkyl transfers from 169 Organometallic reagents 167 Ρ PAC 352 PACER 260 Peroxide 150 Peroxide-induced ethylation of isobutyl chloride 160 Phenol 408,409 Picolines 404 Pilot plants 234 Plant evaluation 271 Polyaluminum chloride 352 Polyethylbenzenes 347 Polymerization 40 excess 35 olefin 28 Polymers, conjunct 2, 36, 96,129 Potable water 360 Process water 360 Production of heavy ends and acid-soluble hydrocarbons 143 Propene 206 Propyl chlorides 197,409,410 Propyl sulfates 138 Propylation 213

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INDEX

Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ix001

Propylene alkylation cost -isobutane alkylation with propane added reactions Purification of aluminum chloride concentrate Purification of crude ethylbenzene .... Pyridine(s) compounds, alkylation with methanol homolytic alkylation of methyl methylation of Pyridyl alcohols, reaction with Raney nickel Pyrite

371 68 330 27 45 39 361 349 397 402 400 397 402 401 439

Q

Quaternary ammonium ions 17 Quaternary salts, rearrangement of .... 397 Quartz 439 R Rare earths, catalyst containing 90 Rates, hydride transfer 5 RDC 289 Reaction of i-butyl chloride with methylcyclopentane 2 Reactor, cascade 224 Recovery of sulfuric acid 284, 321 Red oil 2, 96,129, 304 Refinery olefins 21 Regeneration of sulfuric acid 231 Research octane number 103 Resin(s) Amberlyst-15 78 Amberlyst XN-100 82 macroreticular acidic ion exchange 75 macroreticular, physical properties of 77 RMS 228 RON 103 Rotating disc contacter 289 S Salts, quaternary, rearrangement of .. 397 SARP, defined 324 Scale-up of alkylation 232 Scaling down alkylation 234 Sec-butyl sulfates 109 Shear rate 228 Simulation, digital computer 380 Simulations, adiabatic reactor 380 Sludge, acid 129

Sodium naphthalene 207 Solubility of methylcyclopentane in modified sulfuric acid 8 Space velocity 279 Speed, impeller tip 246 Styrene(s) 208,216,341,344 Subbituminous coals 438 analyses of 441 liquefaction with synthetic gas 442 Sulfates butyl 136 propyl 138 sec-butyl 109 Sulfur compounds, as impurities ...273,274 Sulfuric acid 1,271 alkylation technology 318 catalyst 242 industry 314 make-up, reduction in amount 282 recovery 284,321 regeneration 321 tritiated, 3-methylpentane isomerization in 13 tritiated, 2,3,4-trimethylpentane in.. 7 Surfactants, cationic 19, 20, 25 in alkylation 16 Synthesis gas 438 liquefaction of subbituminous coals with 442 Τ Tantalum pentafluoride 186 Technology of hydrogen fluoride 318 Technology of sulfuric acid alkylation 318 Telomerization, inhibition of 147 Telomerization of ethylene and hydrogen chloride 160 Temperature requirement 281 Tetrahydrofuran, ethylation of 163 Thermodynamics of alkane alkylations 187 Thermolysis of 1-methylpyridinium iodide 398 THF 207 TMP 96,129 p-Toluenesulfonic acid 409, 418 Transfer processes, turbulent 242 Transition metal cations, catalysts containing 93 Trialkyl esters 304 Trimer-esters 304 Trimethylpentane( s ) 2, 85, 96,129 2.2.3- Trimethylpentane 27 2.3.4- Trimethylpentane in tritiated sulfuric acid 7 2,2,4-Trimethylpentene-l 107 Triphenylmethyl cation 13 Turbine, flat blade 243

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INDUSTRIAL

Turbine, high intensity Turbulent transfer processes Turbulent velocity fluctuations

244 242 230

V Velocityfluctuations,turbulent Vinylpyridines Volume aging rule VTIP

230 216 391 246ι Zeolites

AND LABORATORY

ALKYLATIONS

w Water as impurity potable process

273, 275 360 360

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In Industrial and Laboratory Alkylations; Albright, L., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

75,89