Hydrocracking and Hydrotreating J o h n W. W a r d ,
EDITOR
Union Oil Co. of California Shai A. Q a d e r ,
EDITOR
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.fw001
Burns and Roe Industrial Service Corp.
A symposium sponsored by the Division of Petroleum Chemistry, Inc. at the 169th Meeting of the American Chemical Society, Philadelphia, Penn., April 9, 1975
ACS SYMPOSIUM SERIES 20
AMERICAN
CHEMICAL
SOCIETY
WASHINGTON, D. C. 1975
American Chemical Society 1155 16th St., N.W. Washington, D.C. 20036 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
TP 690.4 .H9 Copy 1
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.fw001
Hydrocracking and hydrotreating
Library of Congress Œ Data Hydrocracking and hydrotreating. (ACS symposium series; 20 ISSN 0097-6156) Includes bibliographical references and index. 1. Cracking process—Congresses. 2. Petroleum—Refining—Congresses. 3. Hydrogénation—Congresses. I. Ward, John William, 1937II. Qader, S. A. III. American Chemical Society. Division of Petroleum Chemistry. IV. Series: American Chemical Society. ACS symposium series; 20. TP 690.4.H9 665'.533 75-33727 ISBN 0-8412-0303-2
ACSMC8 20 1-168
Copyright © 1975 American Chemical Society All Rights Reserved PRINTED IN THE UNITED STATES OF AMERICA
American Chemical Society Library 1155 16th N.W. Ward, J., el al.; In Hydrocracking and St.. Hydrotreating; ACS Symposium Series; American Chemical Society: Washington, DC, 1975. Washington, D.C. 20036
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.fw001
ACS Symposium Series Robert F. Gould, Series Editor
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.fw001
FOREWORD The ACS S Y M P O S I U M S E R I E S was founded in 1974 to provide a medium for publishing symposia quickly in book form. The format of the S E R I E S parallels that of the continuing A D V A N C E S I N C H E M I S T R Y S E R I E S except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. As a further means of saving time, the papers are not edited or reviewed except by the symposium chairman, who becomes editor of the book. Papers published in the ACS S Y M P O S I U M S E R I E S are original contributions not published elsewhere in whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.pr001
PREFACE '"phe efficient upgrading of energy resources to desirable products is an important national goal. This volume contains a series of papers concerned with the hydroprocessing of petroleum stocks, shale oil, and coal. Subjects covered range from catalyst structure to product properties. The hydroprocessing routes discussed offer excellent means of selectively producing the desired fuels and the means of reducing potential polluting contaminants from fuels and their precursors.
Union Oil Co. of California Brea, Calif. Burns and Roe Industrial Services Corp. Paramus, N.J. September 4, 1975
JOHN
W.
WARD
SHAI
A.
QADER
vii In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1 T h e Influence o f C h a i n Length in H y d r o c r a c k i n g and Hydroisomerization o f n-Alkanes
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
JENS WEITKAMP Engler-Bunte-Institute, Division of Gas, Oil, and Coal, University of Karlsruhe, D-75 Karlsruhe, West Germany Since 1960 catalytic hydrocracking has received considerable importance in petroleum refining where it is used mainly for the production of gasoline, jet fuel, middle distillates and lubricants. Its outstanding advantages are flexibility as well as high quality of the products. In the course of its commercial growth the chemistry of hydrocracking over various types of bifunctional catalysts has been scrutinized with model hydrocarbons, most commonly with alkanes. Several reviews on this subject are now available (1-3) showing that the product distributions are markedly influenced by the relative strength of hydrogenation activity versus acidity of the catalyst. A unique type of hydrocracking associated with an utmost degree of product flexibility may be attained with bifunctional catalysts of both high acidity and especially high hydrogenation activity which have been counterbalanced carefully. The term "ideal" hydrocracking has been introduced (2) to characterize the reactions of n-alkanes with hydrogen on such catalysts. Typical features of ideal hydrocracking of long chain alkanes include: 1. low reaction temperatures 2. the possibility of high selectivities for isomerization 3. the possibility of pure primary cracking all being in contrast to catalytic cracking over monofunctional catalysts. Actually, both reactions may be looked upon as pure mechanisms of cracking with many intermediate mechanisms between them. Such a concept has been shown to be fruitful for classifying the numerous types of product distributions observable in hydrocracking of pure compounds over bifunctional catalysts with a hydrogénation activity ranging from very weak to very strong (2, 3). The validity of this concept for hydrocracking real feedstocks has also been confirmed, e. g., by Coonradt and Garwood (4) or by Sullivan and Meyer (5). 1 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
2
HYDROCRACKING AND HYDROTREATING
O t h e r p u r e m e c h a n i s m s of c r a c k i n g a r e t h e r m a l c r a c k i n g and hydrogenolysis over metals. V e r y detailed investigations on p l a t i n u m c a t a l y z e d h y d r o g e n o l y s i s of v a r i o u s a l k a n e s , e. g . , the i s o m e r i c h e x a n e s , have b e e n p u b l i s h e d r e c e n t l y (6-8). I d e a l h y d r o c r a c k i n g and h y d r o i s o m e r i z a t i o n of n - d o d e c a n e f u r n i s h e d m u c h i n s i g h t into the p r i m a r y r e a r r a n g e m e n t and c l e a v a g e r e a c t i o n s of a l k y l c a r b e n i u m i o n s (9). T h e s y s t e m s e e m s to be s t r o n g l y g o v e r n e d b y c o m p e t i t i v e c h e m i s o r p t i o n at the a c i d i c s i t e s and, to a l e s s e r d e g r e e , at the h y d r o g e n a t i v e s i t e s (10). It i s the i n t e n t i o n o f the p r e s e n t p a p e r to extend t h e s e data that s e e m to be of p r i n c i p l e s i g n i f i c a n c e f o r the c h e m i s t r y of c a t a l y t i c c o n v e r s i o n of h y d r o c a r b o n s , to the l o w e r m o l e c u l a r weight n - a l k a n e s . In l i t e r a t u r e o n h y d r o c r a c k i n g s o m e r e s u l t s have b e e n r e p o r t e d c o n c e r n i n g r e a c t i v i t i e s of and p r o d u c t d i s t r i b u t i o n s f r o m n - a l k a n e s of d i f f e r e n t c h a i n l e n g t h (11, 12). H o w e v e r , as a c o n s e q u e n c e of the c a t a l y s t s u s e d , h y d r o c r a c k i n g i n t h e s e cases was far f r o m being i d e a l . Experimental T h e e x p e r i m e n t s w e r e c a r r i e d out i n a s m a l l flow type f i x e d b e d r e a c t o r w h i c h has been d e s c r i b e d i n a r e c e n t p u b l i c a t i o n (9) a l o n g w i t h the m e t h o d s of a n a l y s i s by c a p i l l a r y g a s - l i q u i d c h r o m a t o g r a p h y . R e s u l t s a r e r e p o r t e d that w e r e g a i n e d w i t h a l l p u r e n - a l k a n e s r a n g i n g f r o m n - h e x a n e to n - d o d e c a n e . F e e d h y d r o c a r bons w e r e d e l i v e r e d f r o m F l u k a , B u c h s , S w i t z e r l a n d (purum). P u r i t y e x c e e d e d 99. 5 wt. - % i n any c a s e . T h e P t / C a - Y - z e o l i t e c a t a l y s t (0. 5 wt. - % P t , S K 200, U n i o n C a r b i d e , L i n d e D i v i s i o n ; v o l u m e of c a t a l y s t b e d : 2 c m ; p a r t i c l e s i z e : 0. 2 - 0 . 3 m m ) w a s c a l c i n e d i n a d r i e d s t r e a m of N and a c t i v a t e d i n a d r i e d s t r e a m of at a t m o s p h e r i c p r e s s u r e p r i o r to u s e . T h e m a s s of d r y c a t a l y s t was 1. 0 g. T h e t o t a l p r e s s u r e and m o l a r r a t i o h y d r o g e n : n - a l k a n e w e r e kept c o n s t a n t at 39 b a r and 1 7 : 1 , r e s p e c t i v e l y , w h e r e a s the r e a c t i o n t e m p e r a t u r e s and s p a c e v e l o cities were varied. 3
2
C o n v e r s i o n o f n - A l k a n e s , H y d r o i s o m e r i z a t i o n and H y d r o c r a c k i n g It was found that h y d r o i s o m e r i z a t i o n and h y d r o c r a c k i n g of n - d o d e c a n e o v e r the P t / C a - Y - z e o l i t e r e q u i r e l o w r e a c t i o n t e m p e r a t u r e s , a t y p i c a l v a l u e b e i n g 275 °C (9). T h i s t e m p e r a t u r e was c h o s e n i n the p r e s e n t w o r k to i n v e s t i g a t e the i n f l u e n c e of c h a i n l e n g t h o n the r e a c t i v i t y of the n - a l k a n e s . In F i g u r e 1 the d e g r e e of o v e r a l l c o n v e r s i o n has b e e n p l o t t e d v e r s u s the s u p e r f i c i a l
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
3
Influence of Chain Length
WEiTKAMP
h o l d i n g t i m e . A s e x p e c t e d r e a c t i v i t y of the h y d r o c a r b o n s i n c r e a s e s with i n c r e a s i n g chain length. F o r a quantitative c o m p a r i s o n appro x i m a t e v a l u e s of the i n i t i a l r e a c t i o n r a t e s m a y be d e r i v e d f r o m the i n i t i a l s l o p e s i n F i g u r e 1 u s i n g the equation
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
- ra
1 100
dX m , d(ysL) a
In T a b l e I t h e s e v a l u e s a r e r e p o r t e d , t h o s e f o r n-nonane and n - u n d e c a n e b e i n g l e s s a c c u r a t e on account of the r e l a t i v e l y h i g h d e g r e e s of c o n v e r s i o n even at l o w h o l d i n g t i m e s . F r o m n - h e x a n e to n - u n d e c a n e a t e n f o l d i n c r e a s e i n the i n i t i a l r e a c t i o n r a t e i s observed. T a b l e I.
Influence of c h a i n l e n g t h o n i n i t i a l r e a c t i o n r a t e s (T = 275 °C) ^2 Feed n
C
( "
H
" 6 14
n
-S
H
n
- 8 18
n
- 9 20
n
- ll
16
r
) ["raole n - a l k a n e l a Ig catalyst · h J 0.13 0. 38
C
H
0. 53
C
H
1.1
C
H
24
1. 3
H y d r o g e n a t i v e c o n v e r s i o n of n - a l k a n e s on the P t / C a - Y - z e p l i t e r e s u l t s i n two p r i n c i p l e r e a c t i o n s , h y d r o i s o m e r i z a t i o n o r h y d r o c r a c k i n g , the r e l a t i v e i m p o r t a n c e of e a c h d e p e n d i n g o n the r e a c t i o n c o n d i t i o n s . A t l o w s e v e r i t i e s and c o r r e s p o n d i n g l y l o w d e g r e e s of o v e r a l l c o n v e r s i o n h y d r o i s o m e r i z a t i o n p r e d o m i n a t e s . W i t h η - o c t a n e at 275 ° C , f o r e x a m p l e , the r a t e of h y d r o i s o m e r i z a t i o n i s h a r d l y affected b y h y d r o c r a c k i n g at l o w h o l d i n g t i m e s ( F i g u r e 2). A t h i g h h o l d i n g t i m e s , h o w e v e r , w h e r e the d e g r e e of h y d r o i s o m e r i z a t i o n c o n v e r s i o n goes t h r o u g h a m a x i m u m the r a t e of h y d r o c r a c k i n g i n c r e a s e s . It m i g h t be s u g g e s t e d f r o m the shape of the c u r v e s i n F i g u r e 2 that h y d r o i s o m e r i z a t i o n and h y d r o c r a c k i n g are reactions in series. A w i d e r i n s i g h t into the i n f l u e n c e of c h a i n l e n g t h o n r e a c t i v i t i e s o f n - a l k a n e s m a y be g a i n e d by p l o t t i n g the d e g r e e s of h y d r o -
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
4
20
40
60
80
SUPERFICIAL HOLDING TIME
100
[s]
Figure 1. Hydroisomerization and hydrocracking of n-alkanes with different chain length (T - 275°C)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
1.
W E I T K A M P
Influence of Chain Length
5
i s o m e r i z a t i o n c o n v e r s i o n and h y d r o c r a c k i n g c o n v e r s i o n v e r s u s r e a c t i o n t e m p e r a t u r e (cf. F i g u r e s 3 and 4, r e s p e c t i v e l y ) . S i m i l a r c u r v e s a r e o b s e r v e d f o r a l l n - a l k a n e s u s e d . It w i l l be noted that lower reaction temperatures are required for hydroisomerization than f o r h y d r o c r a c k i n g . T h e d e g r e e s of h y d r o i s o m e r i z a t i o n c o n v e r s i o n , h o w e v e r , a r e p a s s i n g t h r o u g h a m a x i m u m w h i c h i s due to the c o n s u m p t i o n of b r a n c h e d i s o m e r s b y h y d r o c r a c k i n g . W i t h d e c r e a s i n g c h a i n l e n g t h the p o s i t i o n of the m a x i m a s h i f t s t o w a r d s higher reaction temperatures reflecting decreasing reactivities. It s h o u l d be m e n t i o n e d that v e r y h i g h m a x i m u m v a l u e s e x c e e d i n g 60 % a r e a t t a i n a b l e e v e n f o r l o n g c h a i n n - a l k a n e s l i k e n - d e c a n e . T h i s r e s u l t has to be a t t r i b u t e d to the h i g h h y d r o g é n a t i o n a c t i v i t y of the P t / C a - Y - z e o l i t e and i s i n c o n t r a s t to h y d r o c r a c k i n g o v e r c a t a l y s t s of l o w h y d r o g é n a t i o n a c t i v i t y (9, 11,12) o r c a t a l y t i c c r a c k i n g (13), w h e r e l i t t l e o r no i s o m e r i z a t i o n of the feed t a k e s p l a c e . W i t h d e c r e a s i n g c h a i n l e n g t h the height of the m a x i m a i n c r e a s e s , indicating a d e c r e a s i n g tendency for cleavage. A n a c t i v a t i o n e n e r g y of 45 k c a l / m o l e i s c a l c u l a t e d f o r the h y d r o i s o m e r i z a t i o n of, e. g . , n - d e c a n e . A n e v e n m o r e m a r k e d i n f l u e n c e of c h a i n l e n g t h e x i s t s f o r the h y d r o c r a c k i n g r e a c t i o n ( F i g u r e 4). T h e d e g r e e s of h y d r o c r a c k i n g c o n v e r s i o n r a p i d l y i n c r e a s e w i t h t e m p e r a t u r e i n the c a s e of n - d e c a n e , n - n o n a n e and η - o c t a n e . W i t h t h e s e h y d r o c a r b o n s h y d r o c r a c k i n g i s c o m p l e t e at c a . 300 - 320 ° C . In s h a r p c o n t r a s t to t h i s the d e g r e e of h y d r o c r a c k i n g c o n v e r s i o n i n c r e a s e s v e r y s l o w l y w i t h r e a c t i o n t e m p e r a t u r e i n the c a s e of n - h e x a n e , whereas a somewhat intermediate behaviour is o b s e r v e d for η - h e p t a n e . It w i l l be s h o w n l a t e r i n c o n n e c t i o n w i t h p r o d u c t d i s t r i b u t i o n s that o n the P t / C a - Y - z e o l i t e h y d r o c r a c k i n g of h e x a n e p r o c e e d s v i a a d i f f e r e n t m e c h a n i s m as c o m p a r e d w i t h i d e a l h y d r o c r a c k i n g of the l o n g e r c h a i n h o m o l o g u e s . F r o m a p r a c t i c a l viewpoint catalysts with high h y d r o g é n a t i o n a c t i v i t y l i k e the P t / C a - Y - z e o l i t e p r o v i d e a h i g h d e g r e e of p r o d u c t f l e x i b i l i t y . L o n g c h a i n feed h y d r o c a r b o n s i n the b o i l i n g r a n g e o f k e r o s e n e m a y be i s o m e r i z e d w i t h e x c e l l e n t y i e l d s w h i c h i s of i n t e r e s t f o r p o u r p o i n t l o w e r i n g . If, o n the o t h e r h a n d , c o m p l e t e h y d r o c r a c k i n g i s d e s i r e d , t h i s m a y be a c h i e v e d s i m p l y b y a p p l i c a tion of somewhat higher r e a c t i o n t e m p e r a t u r e s . In P ' i g u r e 5 the g e n e r a l l y a c c e p t e d r e a c t i o n path (14) f o r h y d r o i s o m e r i z a t i o n of n - a l k a n e s has b e e n r e p r e s e n t e d a l o n g w i t h d i f f e r e n t p o s s i b i l i t i e s f o r the c r a c k i n g s t e p . T h e n - a l k a n e m o l e c u l e s a r e a d s o r b e d at a d e h y d r o g e n a t i o n / h y d r o g e n a t i o n s i t e w h e r e n - a l k e n e s a r e f o r m e d . A f t e r d e s o r p t i o n and d i f f u s i o n to an a c i d i c s i t e c h e m i s o r p t i o n y i e l d s s e c o n d a r y c a r b e n i u m i o n s that r e a r r a n g e
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
6
HYDROCRACKING
240
260
280
300
A N D
HYDROTREATING
320
340
TEMPERATURE
[ C] e
Figure 3. Influence of reaction temperature on hydroisomerization conversion of n-alkanes with different chain length (F = 12 · 10~ mole · h' ) 3
1
a
TEMPERATURE
[ Cj e
Figure 4. Influence of reaction temperature on hydrocracking conversion of n-alkanes with different chain length (F = 12 · 10~ mole · h' ) 3
a
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
1.
W E I T K A M P
Influence of Chain Length
7
into t e r t i a r y c a r b e n i u m i o n s w i t h a b r a n c h e d c a r b o n s k e l e t o n . D e s o r p t i o n of i - a l k e n e s and h y d r o g é n a t i o n at a m e t a l l i c s i t e f i n a l l y y i e l d s i - a l k a n e s . A l l s t e p s of the o v e r a l l h y d r o i s o m e r i z a t i o n r e a c tion are r e v e r s i b l e . F o u r p r i n c i p l e c r a c k i n g r e a c t i o n s , a l l of t h e m b e i n g i r r e v e r s i b l e , have to be t a k e n into account: h y d r o g e n o l y s i s of the n - a l k a n e feed; / 3 - s c i s s i o n of s t r a i g h t c h a i n c a r b e n i u m i o n s ; β - s c i s s i o n of b r a n c h e d c a r b e n i u m i o n s ; h y d r o g e n o l y s i s of i - a l k a n e s f o r m e d b y h y d r o i s o m e r i z a t i o n . It w i l l be s h o w n that the t h i r d step (full a r r o w i n F i g u r e 5) r e p r e s e n t s the m a i n r e a c t i o n path of i d e a l h y d r o c r a c k i n g . C a r b e n i u m i o n s w i t h a b r a n c h e d c a r b o n s k e l e t o n then p l a y the r o l e of k e y i n t e r m e d i a t e s i n that t h e y m a y e i t h e r d e s o r b o r c l e a v e thus d e t e r m i n i n g the d i r e c t i o n of the o v e r a l l r e a c t i o n . W h i l e the r a t e of c l e a v a g e i s g i v e n b y t e m p e r a t u r e , a c i d i t y of the c a t a l y s t and c o n c e n t r a t i o n of i - a l k y l c a t i o n s , the r a t e of d e s o r p t i o n i s a s s u m e d to be enhanced b y the s t e a d y s t a t e c o n c e n t r a t i o n s of n - a l k e n e s , i . e . , a h i g h d e h y d r o g e n a t i o n a c t i v i t y of the c a t a l y s t f a v o r s h y d r o i s o m e r i z a t i o n . T h i s i s the concept of competitive chemisorption which in ideal bifunctional catalysis k e e p s the r e s i d e n c e t i m e s of the a l k y l c a r b e n i u m i o n s l o w . H e n c e , p r i m a r y p r o d u c t s m a y be o b t a i n e d w h i c h i s not the c a s e in catalytic c r a c k i n g over monofunctional catalysts where f o r m a t i o n of c a r b e n i u m i o n s o c c u r s b y h y d r i d e a b s t r a c t i o n f r o m the n-alkane r a t h e r than v i a n - a l k e n e s . A c c o r d i n g to F i g u r e 5 a s e r i e s of e l e m e n t a r y r e a c t i o n s a r e i n v o l v e d i n h y d r o i s o m e r i z a t i o n and h y d r o c r a c k i n g o f n - a l k a n e s . A t the t i m e b e i n g , the r a t e c o n t r o l l i n g step of the o v e r a l l r e a c t i o n i s unknown b e c a u s e of the l a c k of a d e t a i l e d k i n e t i c a n a l y s i s of the s y s t e m . P o s s i b l e i n t e r p r e t a t i o n s of the i n f l u e n c e of c h a i n l e n g t h upon r e a c t i v i t y a r e s p e c u l a t i v e . M a x i m u m c o n c e n t r a t i o n s of n alkenes, l i m i t e d by thermodynamics, increase with i n c r e a s i n g c h a i n l e n g t h of the feed. T h e s a m e w i l l be t r u e f o r r a t e s of a d s o r p t i o n b o t h of the feed and the o l e f i n i c i n t e r m e d i a t e s . R a t e s of s u r face r e a c t i o n s too m a y depend on the c h a i n l e n g t h of the c h e m i s o r b e d s p e c i e s . T h e c h e m i s t r y of i d e a l h y d r o c r a c k i n g w i l l be d i s c u s s e d i n t e r m s of d e t a i l e d p r o d u c t d i s t r i b u t i o n s , p r o v i d i n g i n s i g h t into the p r i m a r y p r o d u c t s of b i f u n c t i o n a l c a t a l y s i s . Hydroisomerization L i t e r a t u r e o n h y d r o i s o m e r i z a t i o n of l o n g c h a i n a l k a n e s > C^ i s v e r y l i m i t e d (2, 9 , 1 5 , 1 6 ) due to both a n a l y t i c a l d i f f i c u l t i e s and the fact that h y d r o c r a c k i n g p r e d o m i n a t e s u n l e s s the b i f u n c t i o n a l
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
8
HYDROCRACKING
A N D
HYDROTREATING
c a t a l y s t has b e e n s u i t a b l y s e l e c t e d . In F i g u r e 6 the c o m p o s i t i o n of the o c t a n e and undecane f r a c t i o n have b e e n p l o t t e d v e r s u s h o l d i n g t i m e at a r e a c t i o n t e m p e r a t u r e of 275 ° C . T h e f o l l o w i n g g e n e r a l f e a t u r e s of h y d r o i s o m e r i z a t i o n m a y be r e c o g n i z e d : M o n o branched i s o m e r s are p r i m a r y products from which multiple branched i s o m e r s are formed in a consecutive reaction. The c h a i n l e n g t h o f the feed has a m a r k e d i n f l u e n c e both on r a t e of h y d r o i s o m e r i z a t i o n and the amount of m u l t i p l e b r a n c h e d i s o m e r s , which increases considerably with i n c r e a s i n g chain length. Q u a l i t a t i v e l y , t h i s i s i n a g r e e m e n t w i t h t h e r m o d y n a m i c s and m a y be a t t r i b u t e d to the n u m b e r of m u l t i p l e b r a n c h e d i s o m e r s w h i c h r a p i d l y grows with increasing chain length. A m o r e d e t a i l e d p i c t u r e of h y d r o i s o m e r i z a t i o n of n - o c t a n e and n - n o n a n e i s g i v e n i n T a b l e II i n w h i c h p r o d u c t d i s t r i b u t i o n s a r e l i s t e d f o r d i f f e r e n t d e g r e e s of c o n v e r s i o n a l o n g w i t h t h e r m o d y n a m i c e q u i l i b r i u m v a l u e s . T h e l a t t e r have b e e n c a l c u l a t e d f r o m G i b b s f r e e e n e r g y data a v a i l a b l e i n l i t e r a t u r e (17) the a c c u r a c y of w h i c h , h o w e v e r , i s not k n o w n . F r o m T a b l e II the f o l l o w i n g c o n c l u s i o n s m a y be d r a w n : H y d r o i s o m e r i z a t i o n proceeds towards thermodynamic equili b r i u m w h i c h i s a p p r o x i m a t e l y r e a c h e d b e t w e e n the n o r m a l , m o n o b r a n c h e d and d i - b r a n c h e d s t r u c t u r e s at h i g h d e g r e e s of o v e r a l l conversion. H y d r o c r a c k i n g , however, i s severe under these c o n d i t i o n s . It i s evident f r o m T a b l e II that m o n o m e t h y l i s o m e r s a r e p r i m a r y p r o d u c t s ; the s a m e i s a p p a r e n t l y t r u e f o r m o n o e t h y l i s o m e r s a l t h o u g h due to t h e r m o d y n a m i c r e a s o n s l o w e r c o n c e n t r a tions are obtained. D i m e t h y l i s o m e r s including those containing a q u a r t e r n a r y c a r b o n a t o m a r e f o r m e d as s e c o n d a r y p r o d u c t s . H o w e v e r , t r i m e t h y l i s o m e r s a r e f o r m e d v e r y s l o w l y so that t h e i r c o n c e n t r a t i o n s do not r e a c h e q u i l i b r i u m v a l u e s . It f o l l o w s f r o m t h i s that the n u m b e r of r a m i f i c a t i o n s i s d e c i d i n g as to w h e t h e r a branched i s o m e r is a p r i m a r y , secondary or t e r t i a r y product i n h y d r o i s o m e r i z a t i o n of η - o c t a n e and n - n o n a n e . T h o u g h m o n o m e t h y l i s o m e r s , as a w h o l e , a r e p r i m a r y p r o d u c t s , the r a t e s of f o r m a t i o n of i n d i v i d u a l m e m b e r s m a y d i f f e r s u b s t a n t i a l l y f r o m e a c h o t h e r . F u r t h e r m o r e t h e y depend o n the d e g r e e of c o n v e r s i o n . W i t h , e. g . , n - d e c a n e ( T a b l e III) at l o w d e g r e e s of c o n v e r s i o n r e l a t i v e r a t e s of f o r m a t i o n f o r 2 - m e t h y l nonane : 3 - m e t h y l n o n a n e : 4 - m e t h y l n o n a n e : 5 - m e t h y l n o n a n e a r e 1 : 2 : 2 : 1 and shift to 2 : 2 : 2 : 1 at h i g h d e g r e e s of c o n version. T h e l a t t e r r e p r e s e n t the t h e r m o d y n a m i c e q u i l i b r i u m d i s t r i b u t i o n w h i c h m a y e a s i l y be u n d e r s t o o d i n t e r m s of s t a t i s t i c s : L e t m r e p r e s e n t the c a r b o n n u m b e r of the n - a l k a n e feed. If i t i s e v e n
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
WEiTKAMP
Influence of Chain Length HYDROGENOLYSIS
n-ALKANE
— CRACKED PRODUCTS
-21
1
SEC. n-ALKYL CATIONS — f * C R A C K E D PRODUCTS
n-ALKENES
REARRANGEMENT
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
i-ALKENES
ι
•
2H1"Î"
/?-SCISSION
- H ®
1
/Î-SCISSION 7 / CRACKED PRODUCTS
TERT. i-ALKYL CATIONS HYDROGENOLYSIS
i-ALKANES
CRACKED PRODUCTS
Figure 5. Reaction scheme for hydroisomerization of n-alkanes on bifunctional catalysts and possible modes of cleavage
FEED: n-OCTANE
SUPERFICIAL HOLDING TIME [s]
F E E D : n-UNDECANE
SUPERFICIAL HOLDING TIME [s]
Figure 6. Course of hydroisomerization of η-octane and n-undecane (T — 275°C)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
10
HYDROCRACKING
Table II.
n- O C T A N E
[ c]
275
e
F -ΙΟ" a
3
[mole
h" ] 1
X ,so ['/·]
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
Xcr
HYDROTREATING
Mole-% of Isomers Formed in Hydroisomerization of «-Octane and w-Nonane
F E E D τ
A N D
W
n-Octane 2-Methylheptane 3-Methylheptane 4-Methylheptane 3-Ethylhexane 2,3-Dimethylhexane 2,4-Dimethylhexane 2,5-Dimethylhexane 3,4-Dimethylhexane 2-Methyl-3-ethylpentane 2,2- Dimethylhexane 3,3- Dimethylhexane Trimethylpentanes n-Nonane 2-Methyloctane 3-Methyloctane 4-Methyloctane 3-Ethylheptane 4-Ethylheptane (b) 2,3-Dimethylheptane 2,4-Dimethylheptane 2,5*3,5-Dimethylheptane 2,6 *4,4- Dimethylheptane 2,2- Dimethylheptane 3,3- Dimethylheptane Others (c)
1 7
n-NONANE
275
310
275
275
3
13
43
7
12
67.1
24.3
9.3
72.6
29.6
67.0
26.5
25.8
<1
15.6
69.0
<1
69.5 20.3 9.1 19.0 11 .4 22.3 4.5 8.5 1 .5 2.8 0.7 4.1 1 .3 8.0 0.7 5.6 0.3 1.2 0.1 0.5 0.5 4.3 0.4 3.2 0.2 -
300
14.0 19.7 23.3 8.7
327 Thermo dynamic Equili brium (a) 13.8 14.3 17.3 5.7 8.0 2.7
2.8 4.6 9.2 6.3 2.2 0.7 4.6 3.7 0.2
9.8
8.5
3.8
1.1 5.0 4.6 5.4 74.1 5.7
7.8
6.7 1.4 1.4 0.3 0.4 0.9 0.4 0.3 0.3 0.3
25.9 13.7 15.8 13.2
2.8 4.0 2.6 3.5 8.6 4.0 2.3 1.9 1.7
11.1 15.0 16.7 13.5 3.2 5.2
3.8
5.1 11.3 6.0 3.2 2.7 3.2
(a) Thermodynamic equilibrium calculated from ref. (Γ7) (b) Including 3,4-dimethylheptane (c) Mainly trimethylhexanes
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
6.5 9.4 9.9 9.9 2.6 5.0 3.2 7.9 10.9 6.4 5.5 5.3 17.5
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
1.
W E I T K A M P
11
Influence of Chain Length
(e. g . , m = 10) t h e n the m a i n c h a i n i n the m o n o m e t h y l i s o m e r s c o n t a i n s an odd c a r b o n n u m b e r ( m - 1 = 9). In t h i s c a s e a s i n g l e c a r b o n a t o m e x i s t s f o r c e n t e r b r a n c h i n g (5~ methylnonane) where as two c a r b o n a t o m s a r e a v a i l a b l e f o r b r a n c h i n g i n any o t h e r p o s i tion. T h e l o w i n i t i a l r a t e of f o r m a t i o n f o r 2 - m e t h y l n o n a n e amoun t i n g to one h a l f as c o m p a r e d to that of 3 - m e t h y l n o n a n e o r 4m e t h y l n o n a n e r e v e a l s a r e m a r k a b l e k i n e t i c f e a t u r e of h y d r o i s o m e r i z a t i o n of l o n g c h a i n n - a l k a n e s . It i s not o b s e r v e d i n h y d r o i s o m e r i z a t i o n of n o r m a l a l k a n e s c o n t a i n i n g a r e l a t i v e l y s h o r t c h a i n , e. g . , n - h e x a n e as r e p o r t e d b y B o l t o n and L a n e w a l a (18). M o r e d a t a a r e r e q u i r e d f o r a d e t a i l e d u n d e r s t a n d i n g of the i s o m e r i z a t i o n of l o n g c h a i n p a r a f f i n s . P o s s i b l y , h o w e v e r , the s e l e c t i v i t i e s found w i t h n - d e c a n e at l o w d e g r e e s of c o n v e r s i o n r e f l e c t the r e a r r a n g e m e n t c h e m i s t r y of l o n g c h a i n a l k y l c a r b e n i u m i o n s . T a b l e III.
H y d r o i s o m e r i z a t i o n of n - d e c a n e . C o m p o s i t i o n of m o n o m e t h y l i s o m e r s (mole-%) ( F = 12 · 1 0 " m o l e decane · h " ) 3
1
τ
°c
j
224
250
274
300
x
"[% ]
2. 3
19
76
99. 8
2 - Methylnonane
17. 2
21. 7
27. 8
28. 5
3 - Methylnonane
34. 3
32. 3
31. 8
31. 2
4 - Methylnonane
31. 2
30. 1
26. 7
26. 8
5 - Methylnonane
17. 3
15. 9
13. 7
13. 5
C a r b o n N u m b e r D i s t r i b u t i o n of C r a c k e d P r o d u c t s S e l e c t i v i t i e s of h y d r o c r a c k i n g n - a l k a n e s n - C ^ with even and odd c a r b o n n u m b e r s o n the P t / C a - Y - z e o ï i t e r e s h o w n i n F i g u r e s 7 and 8, r e s p e c t i v e l y . R u n s have b e e n s e l e c t e d w i t h a m e d i u m d e g r e e of c r a c k i n g c o n v e r s i o n r a n g i n g f r o m 40 to 73 %. In e a c h c a s e the c u r v e s a r e s y m m e t r i c a l i n d i c a t i n g p u r e p r i m a r y c r a c k i n g . M e t h a n e and ethane as w e l l as C - i and C _ 2 v i r t u a l l y absent. P r o d u c t d i s t r i b u t i o n s l i k e this a r e t y p i c a l for ideal hydrocracking. H i g h h y d r o g e n a t i o n / d e h y d r o g e n a t i o n a c t i v i t y of the b i f u n c t i o n a l catalyst i s a p r e r e q u i s i t e for p u r e p r i m a r y c r a c k i n g of long c h a i n n - a l k a n e s (4, 19). T h u s it i s the s a m e type of c a t a l y s t that +
m
a
m
m
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
r
e
12
HYDROCRACKING AND HYDROTREATING
XCR F -103 Τ Pc] [mole-h-1] [%] 13 69 • n-CeHje 310 12 40 • n-CioH22 285 12 56 • n-C H 6 285 FEED
e
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
12
3
4
5
6
7
2
8
9
10
11
CARBON NUMBER OF C R A C K E D PRODUCTS
Figure 7. Hydrocracking of n-alkanes with an even carbon number. Distribu tion of the cracked products.
Τ
XCR Fa-10 PC] [moleh" ] ['/·] n-CyHi6 330 13 53 12 73 n-CgH20 300 8 46 n-CnH24 275
FEED
3
1
ο • •
3
4
5
6
7
8
9
10
C A R B O N NUMBER OF C R A C K E D PRODUCTS
Figure 8. Hydrocracking of n-alkanes with an odd carbon number. Distribu tion of the cracked products.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
1.
WEiTKAMP
Influence of Chain Length
13
m a k e s p o s s i b l e both h i g h d e g r e e s of h y d r o i s o m e r i z a t i o n c o n v e r s i o n and p u r e p r i m a r y c r a c k i n g . T h e m e c h a n i s t i c p a t h w a y of i d e a l h y d r o c r a c k i n g v i a a l k e n e s and c a r b e n i u m i o n s i s r e p r e s e n ted i n F i g u r e 5 by a full a r r o w . The c r a c k e d products formed by β - s c i s s i o n of the l o n g c h a i n c a r b e n i u m i o n s m a y s u f f e r two d i f f e r e n t i a t e s : R a p i d d e s o r p t i o n of b o t h p r i m a r y f r a g m e n t s f r o m the a c i d i c s i t e s f o l l o w e d by h y d r o g é n a t i o n of the o l e f i n i c i n t e r m e d i a t e s at the m e t a l l i c s i t e s . S u c h a p u r e p r i m a r y c r a c k i n g w i l l r e s u l t i n s y m m e t r i c a l p r o d u c t d i s t r i b u t i o n s . If, o n the o t h e r h a n d , d e s o r p t i o n of one of the p r i m a r y f r a g m e n t s f r o m the a c i d i c s i t e ( u s u a l l y the one w i t h the h i g h e r m o l e c u l a r weight) i s s l o w , s e c o n d a r y c r a c k i n g m a y o c c u r . T h u s r e l a t i v e r a t e s of d e s o r p t i o n and β - s c i s s i o n a r e d e c i s i v e as to w h e t h e r o r not p u r e p r i m a r y c r a c k i n g m a y be a c h i e v e d . T h e s t e a d y s t a t e c o n c e n t r a t i o n of l o n g c h a i n a l k e n e s i n f l u e n c e s the r a t e of d e s o r p t i o n of the p r i m a r y f r a g m e n t s ( c o m p e t i t i v e c h e m i s o r p t i o n ) but not the r a t e of the s u r f a c e r e a c t i o n , i . e . , β - s c i s s i o n . T h e c o n c e n t r a t i o n of l o n g c h a i n a l k e n e s , i n t u r n , depends on the d e h y d r o g e n a t i o n a c t i v i t y of the bifunctional catalyst. T h i s p i c t u r e e x p l a i n s the g r e a t d i f f e r e n c e s i n p r o d u c t d i s t r i b u t i o n s of i d e a l h y d r o c r a c k i n g and c a t a l y t i c c r a c k i n g . F u r t h e r m o r e , i t i s i n a g r e e m e n t w i t h the o b s e r v a t i o n that c a r b o n n u m b e r d i s t r i b u t i o n s a r e s i m i l a r i n i d e a l h y d r o c r a c k i n g of n - a l k a n e s and i n c a t a l y t i c c r a c k i n g of n - a l k e n e s w i t h the s a m e c a r b o n n u m b e r (19). A c c o r d i n g to the r o l e of c o m p e t i t i v e c h e m i s o r p t i o n p u r e p r i m a r y c r a c k i n g of n - a l k a n e s as s h o w n i n F i g u r e s 7 and 8 f o r m e d i u m d e g r e e s of c r a c k i n g c o n v e r s i o n m a y no l o n g e r be e x p e c t e d u n d e r s e v e r e r e a c t i o n c o n d i t i o n s w h e n the feed h y d r o c a r b o n i s e n t i r e l y c o n s u m e d . A c t u a l l y , i t has b e e n s h o w n (9, 20) that o n the P t / C a - Y - z e o l i t e s e c o n d a r y c r a c k i n g of n - d o d e c a n e ( m = 12) o r n - d e c a n e (m = 10) s t a r t s i f s e v e r i t i e s e x c e e d t h o s e that a r e n e c e s s a r y f o r a 100 % d e g r e e of c r a c k i n g c o n v e r s i o n . T h e s a m e , h o w e v e r , i s not t r u e i f n - a l k a n e s w i t h l o w e r c h a i n l e n g t h ( m £ 9) a r e u s e d . T h i s m a y be a t t r i b u t e d to the l o w r a t e s of h y d r o c r a c k i n g of a l l f r a g m e n t s f r o m p r i m a r y i o n i c c r a c k i n g (< 6) r e g a r d l e s s of w h e t h e r c o m p e t i t i v e c h e m i s o r p t i o n i s e f f e c t i v e o r not (cf. F i g u r e 4 f o r h e x a n e ) . C h e c k s f o r i d e a l i t y of a g i v e n h y d r o c r a c k i n g s y s t e m , t h e r e f o r e , s h o u l d be c a r r i e d out w i t h an a l k a n e feed of at l e a s t 10 c a r b o n a t o m s . I d e a l h y d r o c r a c k i n g of a l k a n e s r e q u i r e s a m i n i m u m of s e v e n c a r b o n atoms. T h i s m a y be d e r i v e d f r o m F i g u r e 9 i n w h i c h d i s t r i b u t i o n s o f the c r a c k e d p r o d u c t s a r e c o m p a r e d that w e r e g a i n e d w i t h n - h e x a n e (left hand side) and t h r e e of i t s h i g h e r h o m o -
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
14
HYDROCRACKING AND HYDROTREATING
l o g u e s ( r i g h t hand side) at s i m i l a r d e g r e e s of c r a c k i n g c o n v e r s i o n . H y d r o c r a c k i n g of n - h e x a n e r e q u i r e s a m u c h h i g h e r r e a c t i o n t e m p e r a t u r e and y i e l d s m e t h a n e and ethane i n c o n s i d e r a b l e c o n c e n t r a t i o n s . A b s t r a c t i o n of m e t h a n e i s f a v o r e d o v e r that of ethane. T h e s e f i n d i n g s m a y not be u n d e r s t o o d i n t e r m s o f c a r b e n i u m i o n c l e a v a g e . R a t h e r , they a r e i n q u a l i t a t i v e a g r e e m e n t w i t h the r e s u l t s , that h a v e been r e p o r t e d f o r h y d r o g e n o l y s i s of the i s o m e r i c hexanes catalyzed by p l a t i n u m on v a r i o u s supports (6-8). F r o m a l l data of the p r e s e n t w o r k i n c l u d i n g r e l a t i v e r e a c t i v i t i e s and d i s t r i b u t i o n of i s o m e r s a m o n g the c r a c k e d p r o d u c t s the f o l l o w i n g c o n c l u s i o n s c o n c e r n i n g the m e c h a n i s m of h y d r o g e n a t i v e c o n v e r s i o n of n - h e x a n e o v e r the P t / C a - Y - z e o l i t e a r e d r a w n : H y d r o i s o m e r i z a t i o n p r o c e e d s v i a the g e n e r a l l y v a l i d m e c h a n i s m out l i n e d i n F i g u r e 5. T h e m e c h a n i s m o f c l e a v a g e , on the o t h e r hand, d i f f e r s s u b s t a n t i a l l y f r o m the one w h i c h i s v a l i d f o r the h i g h e r h o m o l o g u e s . It i s m a i n l y h y d r o g e n o l y t i c s t a r t i n g f r o m both the n - h e x a n e feed and i - h e x a n e s f o r m e d b y h y d r o i s o m e r i z a t i o n . B e s i d e s , a s m a l l c o n t r i b u t i o n of i o n i c c l e a v a g e of a s e c o n d a r y n - h e x y l c a t i o n , v i z . the m e t h y l - n - b u t y l c a r b e n i u m i o n , β - s c i s s i o n of w h i c h y i e l d s C + C ^ , m a y not be t o t a l l y r u l e d out. In F i g u r e 8 the f o r m a t i o n o f m e t h a n e and ethane was s h o w n to a c c o m p a n y i d e a l h y d r o c r a c k i n g of η - h e p t a n e to s o m e v e r y s m a l l extent. It i s s o m e w h a t enhanced at l o w d e g r e e s of c r a c k i n g c o n v e r s i o n , w h i c h m a y be s e e n f r o m the r i g h t hand s i d e of F i g u r e 9. U n d e r t h e s e c o n d i t i o n s s u p e r i m p o s i t i o n of the m e t h a n e and ethane a b s t r a c t i n g m e c h a n i s m , v i z . h y d r o g e n o l y s i s , m a y be d e t e c t e d e v e n f o r η - o c t a n e and n - n o n a n e . P r o b a b i l i t y of O v e r a l l C r a c k i n g R e a c t i o n s A c c o r d i n g to the r e a c t i o n s c h e m e s h o w n i n F i g u r e 5 both h y d r o i s o m e r i z a t i o n and h y d r o c r a c k i n g of the n - a l k a n e s (except n-hexane) p r o c e e d v i a b r a n c h e d a l k y l c a r b e n i u m i o n s . In the r a n g e of m e d i u m d e g r e e s of c o n v e r s i o n (40 % < , X <, 90 %) both r e a c t i o n s m a y be i n v e s t i g a t e d s i m u l t a n e o u s l y . A r e l a t i o n s h i p b e t w e e n the p r o d u c t s of both t y p e s of r e a c t i o n w i l l be d i s c u s s e d i n the p r e s e n t s e c t i o n . F o r t h i s p u r p o s e s e l e c t i v i t i e s of h y d r o c r a c k i n g of the n a l k a n e s a r e e x p r e s s e d i n t e r m s of p r o b a b i l i t i e s of o v e r a l l c r a c k i n g r e a c t i o n s . T h e l a t t e r a r e c a l c u l a t e d f r o m the c a r b o n n u m b e r d i s t r i b u t i o n s of the c r a c k e d p r o d u c t s ( n ç . = n u m b e r of m o l e s of cracked products with carbon number i , f r o m F i g u r e s 7, 8 o r 9). E x a m p l e s f o r the m o d e of c a l c u l a t i o n a r e r e p r e s e n t e d i n the following scheme which is v a l i d for pure p r i m a r y c r a c k i n g .
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
Influence of Chain Length
W E I T K A M P
Overall Cracking Reaction c
c
C
-* 3 C
i o "-> 4
c
i o --> 5
c
u - -^ 3 u - ->c
c
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
icT
c
+
C
(=
C
+
C
C
+
C
V
(=n 6
+
P r o b a b i l i t y (%)
7
C
4
n-
+
15
5
8 c
7
n
n
r
r
)
^6
S 12
(=n
n
)
" S
"°* " S
(=n„ ) S (=n
p
)
°6
T h e v a l u e s defined i n t h i s m a n n e r do not r e p r e s e n t any p r o b a b i l i t y f o r r u p t u r e of d e f i n i t e c a r b o n - c a r b o n bonds i n the feed m o l e c u l e . T h i s t e r m i s m e a n i n g l e s s i f r e a r r a n g e m e n t of the c a r b o n s k e l e t o n p r e c e d e s the c r a c k i n g s t e p . R a t h e r , the v a l u e s i n d i c a t e the p r o b a b i l i t y of an n - a l k a n e f o r b e i n g h y d r o c r a c k e d a c c o r d i n g to the o v e r a l l c r a c k i n g r e a c t i o n i n q u e s t i o n . T h e s e p r o b a b i l i t i e s a r e u s e f u l f o r a c o m p a r i s o n w i t h 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 p r o d u c t s f o r m e d b y h y d r o i s o m e r i z a t i o n (cf. T a b l e I V ) . The mechanistic background for such a c o m p a r i s o n i s i l l u s t r a t e d i n F i g u r e 10 w h i c h r e p r e s e n t s i n m o r e d e t a i l the pathway o f h y d r o i s o m e r i z a t i o n and h y d r o c r a c k i n g of two n - a l k a n e s . B r a n c h e d c a r b e n i u m i o n s a r e f o r m e d v i a n - a l k e n e s and l i n e a r c a r b e n i u m ions. Then, either desorption o r β - s c i s s i o n m a y occur i n p a r a l l e l r e a c t i o n s . D e s o r p t i o n ( f o l l o w e d b y h y d r o g é n a t i o n ) of a g i v e n c a r b e n i u m i o n y i e l d s an i s o - a l k a n e w i t h the s a m e c a r b o n s k e l e t o n , β - s c i s s i o n , o n the o t h e r h a n d , y i e l d s f r a g m e n t s of definite carbon numbers ( β - s c i s s i o n s which would y i e l d C^ o r are excluded). Thus a c o m p a r i s o n between r e l a t i v e concentrations of the i s o - a l k a n e s and r e l a t i v e p r o b a b i l i t i e s o f the c r a c k i n g r e a c t i o n s m a y be i n f o r m a t i v e s i n c e both s e t s of data a r e d e t e r m i n a b l e independently f r o m each other. Such a c o m p a r i s o n i s made i n T a b l e I V for a l l n-alkanes with a c h a i n l e n g t h r a n g i n g f r o m 8 to 12 c a r b o n a t o m s . S u m s h a v e b e e n f o r m e d w h e n e v e r n e c e s s a r y , i . e . , i f the s a m e set of c a r b o n n u m b e r s i s f o r m e d b y β - s c i s s i o n of different c a r b e n i u m i o n s , o r , i f d i f f e r e n t s e t s of c a r b o n n u m b e r s m a y be f o r m e d b y β - s c i s s i o n
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
16
HYDROCRACKING AND HYDROTREATING
Figure 9. Hydrocracking of n-hexane and different n-alkanes at low degrees of conversion. Distribution of the cracked products.
FEED
PRODUCTS
INTERMEDIATES
n-HEPTANE
-2 M «
n-HEPTENES
* H ® NORMAL HEPTYLCATIONS
2- METHYLHEXANE i=?
C *C 4
3
3- METHYLHEXANE
2- METHYLNONANE
c *c 4
n-DECANE
-2H
n-DECENES
NORMAL DECYLCATIONS
6
3- METHYLNONANE C *C A-METHYLNONANE 5
c *c 6
5
4
5-METHYLNONANE | C *C 3
7
Figure 10. Reaction scheme for hydroisomerization and hydrocracking of n-alkanes
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
WEiTKAMP
17
Influence of Chain Length
Table IV. Hydroisomerization and Hydrocracking of w-Alkanes. Comparison Between Relative Concentrations of Iso-alkanes and Probabilities of Overall Cracking Reactions (F = 12 · 10" mole • h" )3
1
a
Feed
Reaction
Reaction Temperature [ C] e
265
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
n-Octane
2-Methylheptane
45.2 45.8 55.0 56.5
c *c
31.2 21.4
6
2- Methyloctane 1
3- Methyloctane J C
5
68.8
70.1
73.3
75.9
77.5
77.9
14.3 14.5
2-Methylnonane1 4-Methylnonanej C
53.3
54.5 54.7 54.8
53.3
54.5 54.6 54.7
32.4 31.1
31.8 31.9 31.8 32.0 32.1 31.4
7
6
3-Methylnonane C * c 5
5
2-Methyldecane1 5-Methyldecane j C *C ι C^C j 3
13.7 13.5
13.4 13.4 13.0 13.4
48.2 51.3
8
7
3- Methyldecane1 4- Methyldecanej c *c 5
n-Dodecane
29.9 26.7 21.7 21.5
5-Methylnonane C * C 3
n-Undecane
300 310 54.8 54.2 44.0 43.0
3
n-Decane
285
3-Methylheptane
4-Methyloctane
n-Nonane
275
51.8 48.5
6
3-Methylundecanel 5-MethylundecaneJ 49.0 C *C Λ 48.7 C *C J 3
9
5
7
47.6 46.9 47.8 47.5
2-Methylundecanel 29.1 6-MethylundecaneJ 29.6
30.5 31.2
21.9 21.7
21.2 20.4 21.7 21.3
8
4-Methylundecane Cf>*C 6
31.2 32.7
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
18
HYDROCRACKING AND HYDROTREATING
of a p a r t i c u l a r c a r b e n i u m i o n (e. g . , β - s c i s s i o n o f both the 3 - m e t h y l d e c y l c a t i o n and the 4 - m e t h y l d e c y l c a t i o n y i e l d s C + C^; β - s c i s s i o n of the 5 - m e t h y l d e c y l c a t i o n m a y y i e l d e i t h e r C or C + C ) . A good a g r e e m e n t b e t w e e n b o t h s e t s of data i s found f o r the l o n g c h a i n n - a l k a n e s , e s p e c i a l l y f o r decane and dodecane. In p a r t i c u l a r , the g r e a t d i f f e r e n c e s i n p r o b a b i l i t i e s of o v e r a l l c r a c k i n g r e a c t i o n s f r o m t h e s e n - a l k a n e s a r e r e f l e c t e d b y 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 m o n o m e t h y l c o m p o u n d s f o r m e d by h y d r o i s o m e r i z a t i o n . A s a w h o l e , the r e s u l t s s h o w n i n T a b l e I V f o r n - d e c a n e , n - u n d e c a n e and n - d o d e c a n e a r e c o n s i s t e n t w i t h a b r a n c h i n g s t e p o c c u r i n g p r i o r to the c r a c k i n g step (cf. F i g u r e 10). F o r n - n o n a n e the a g r e e m e n t b e t w e e n both s e t s of d a t a i s only qualitative whereas p r i n c i p l e deviations are observed for η - o c t a n e . P o s s i b l e interpretations include differences i n rate c o n s t a n t s of i s o m e r i c c a r b e n i u m i o n s e i t h e r f o r β - s c i s s i o n o r d e s o r p t i o n , o r s u p e r i m p o s i t i o n of a d i f f e r e n t m o d e of c r a c k i n g , the extent and s e l e c t i v i t y of w h i c h a r e u n k n o w n . W h i l e t h e r e i s v e r y l i t t l e doubt that c l e a v a g e i n i d e a l h y d r o c r a c k i n g of n - a l k a n e s s t a r t s f r o m b r a n c h e d c a r b e n i u m i o n s the e x a c t m o d e of β - s c i s s i o n m a y not be d e r i v e d u n a m b i g u o u s l y . T h r e e a l t e r n a t i v e s a r e r e p r e s e n t e d i n F i g u r e 11 w h i c h a l l p r o v i d e β - s c i s s i o n of c a r b e n i u m i o n s w i t h a s i n g l e r a m i f i c a t i o n . A d d i t i o n a l m o d e s of c l e a v a g e s t a r t i n g f r o m m u l t i p l e b r a n c h e d c a r b e n i u m i o n s m i g h t be c o n s i d e r e d as e m p h a s i z e d b y P o u t s m a (22). β - S c i s s i o n a s s h o w n b y m o d e N o . 1 r e s u l t s i n the f o r m a t i o n of a p r i m a r y c a t i o n w h i c h w o u l d s t a b i l i z e i n a r a p i d h y d r i d e s h i f t . T h e o c c u r e n c e of the p r i m a r y c a t i o n m a y be a v o i d e d b y a s s u m i n g (mode N o . 2) the s t a b i l i z i n g h y d r i d e shift to be concerted r a t h e r t h a n i n s e r i e s w i t h β - s c i s s i o n . In p r i n c i p l e , then, m o d e N o . 1 and 2 a r e s i m i l a r . A t h i r d m o d e of c l e a v a g e w h i c h has b e e n t a k e n into c o n s i d e r a t i o n (2) s t a r t s f r o m s e c o n d a r y c a r b e n i u m i o n s b e a r i n g the c h a r g e at c a r b o n a t o m 3 w i t h r e s p e c t to the t e r t i a r y c a r b o n a t o m . A c o n c e r t e d h y d r i d e shift a g a i n a v o i d s the i n t e r m e d i a c y of a p r i m a r y c a r b e n i u m i o n . A l t h o u g h 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 o f the s e c o n d a r y c a t i o n s r e q u i r e d f o r r o u t e N o . 3 w i l l be v e r y l o w , this mode of β - s c i s s i o n i s e n e r g e t i c a l l y attractive since a secondary — > tertiary reaction is involved. S t a r t i n g f r o m the c a r b o n s k e l e t o n of 2 - m e t h y l n o n a n e the c a r b o n n u m b e r s of the f r a g m e n t s a r e + C g , i r r e s p e c t i v e of the e x a c t m o d e of β - s c i s s i o n . T h u s e a c h r e a c t i o n shown i n F i g u r e 11 f i t s the o v e r a l l c r a c k i n g r e a c t i o n C — > C + C and h e n c e , any of the above m o d e s of c l e a v a g e m i g h t s t a n d f o r the c r a c k i n g r e a c t i o n s i n d i c a t e d i n F i g u r e 10. H o w e v e r , m o d e s +
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
g
4
?
1 Q
4
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
g
1.
WEiTKAMP
Influence of Chain Length
19
N o . 2 and 3 s e e m to be m o r e a p p r o p r i a t e to e x p l a i n the f i n d i n g that n - h e x a n e i s e x c l u d e d f r o m i d e a l h y d r o c r a c k i n g .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
D e g r e e of B r a n c h i n g i n the C r a c k e d P r o d u c t s F u r t h e r i n s i g h t into the c h e m i s t r y of h y d r o c r a c k i n g m a y be g a i n e d b y e x a m i n a t i o n of the i s o m e r d i s t r i b u t i o n a m o n g the c r a c k e d p r o d u c t s . A n y m o d e of β - s c i s s i o n shown i n F i g u r e 11 p r e d i c t s b o t h b r a n c h e d and u n b r a n c h e d f r a g m e n t s to be p r i m a r y p r o d u c t s of c l e a v a g e , w i t h a content o f b r a n c h e d i s o m e r s a m o u n t i n g to c a . 50 %. A c t u a l l y , h i g h e r v a l u e s a r e found i n i d e a l h y d r o c r a c k i n g i n d i c a t i n g the c o n t r i b u t i o n of β - s c i s s i o n of m u l tiple branched c a r b e n i u m ions o r some secondary i s o m e r i z a t i o n , i . e . , r e a r r a n g e m e n t r e a c t i o n s f o l l o w i n g the c r a c k i n g s t e p . H o w e v e r , the d e g r e e s of b r a n c h i n g i n i d e a l h y d r o c r a c k i n g a r e l o w e r t h a n t h o s e e n c o u n t e r e d i n h y d r o c r a c k i n g o v e r c a t a l y s t s of l o w d e h y d r o g e n a t i o n a c t i v i t y (12) and t h e y a r e m u c h l o w e r as c o m p a r e d w i t h c a t a l y t i c c r a c k i n g o v e r m o n o f u n c t i o n a l c a t a l y s t s (13, 19). T h i s i s c o n s i s t e n t w i t h a m o s t effective r o l e of c o m p e t i t i v e c h e m i s o r p t i o n i n i d e a l h y d r o c r a c k i n g w h i c h m i n i m i z e s the amount of s e c o n d a r y i s o m e r i z a t i o n . T h e i n f l u e n c e of c h a i n l e n g t h of the feed o n the d e g r e e of b r a n c h i n g of the c r a c k e d p r o d u c t s w i l l be d i s c u s s e d f i r s t l y f o r a m e d i u m d e g r e e of c o n v e r s i o n . F o r t h i s p u r p o s e e x p e r i m e n t a l data h a v e b e e n i n t e r p o l a t e d to a 50 % d e g r e e of c r a c k i n g c o n v e r s i o n . In F i g u r e 12 the content of b r a n c h e d i s o m e r s i n the a l k a n e f r a c t i o n s f o r m e d b y i o n i c h y d r o c r a c k i n g has b e e n p l o t t e d v e r s u s c h a i n l e n g t h o f the f e e d . R o u g h l y , t h e content of b r a n c h e d i s o m e r s i n a g i v e n f r a c t i o n of the c r a c k e d p r o d u c t s (e. g . , i - b u t a n e i n the C ^ - f r a c t i o n ) i s independent of the c h a i n l e n g t h of the feed. T h i s i s no l o n g e r t r u e , h o w e v e r , i f the c a r b o n n u m b e r f r a c t i o n i n q u e s t i o n i s f o r m e d b y s p l i t t i n g of C g . R a t h e r , i t m a y be s e e n f r o m F i g u r e 12 that, i f n-C H2 + 2 r e p r e s e n t s the f e e d , the content of b r a n c h e d i s o m e r s i s e x t r a o r d i n a r i l y h i g h i n the f r a c t i o n C p H 2 p +2 (ρ na-3). T h i s r e s u l t i s i n a g r e e m e n t w i t h any m o d e of β-scission r e p r e s e n t e d i n F i g u r e 11, s i n c e a C g - f r a g m e n t f o r m e d m a y not c o n t a i n the o r i g i n a l r a m i f i c a t i o n . T h i s i s i l l u s t r a t e d i n m o r e d e t a i l i n F i g u r e 13 w h i c h r e p r e s e n t s the p r i m a r y p r o d u c t s e x p e c t e d f o r β - s c i s s i o n a c c o r d i n g to m o d e N o . 2 and 3. C r a c k i n g of C ^ Q h a s b e e n c h o s e n as an e x a m p l e and a g a i n , c l e a v a g e of m u l t i p l e branched c a r b e n i u m ions has been omitted. It m a y be r e c o g n i z e d by s u m m i n g up the p r o d u c t s that b o t h n o r m a l and b r a n c h e d s t r u c t u r e s a r e p r e d i c t e d i n the C - , C m
m
=
4
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
5
HYDROCRACKING AND HYDROTREATING
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
20
7
8
9
10
11
CARBON NUMBER OF F E E D
Figure 12. Hydrocracking of n-alkanes (Xcr = 50%). Influence of chain length of the feed on content of branched isomers in the cracked products.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
Influence of Chain Length
W E I T K A M P
21
and C - f r a c t i o n s . B o t h m o d e s of c l e a v a g e , h o w e v e r , p r e d i c t a b r a n c h e d s k e l e t o n o n l y f o r the C ^ - f r a c t i o n . T h u s , the content of b r a n c h e d i s o m e r s i n the f r a c t i o n r e s u l t i n g b y a b s t r a c t i o n of s h o u l d be 100 %. A c t u a l l y , t h i s v a l u e i s a p p r o x i m a t e d , the s m a l l d e v i a t i o n of c a . 10 % b e i n g due to e i t h e r s e c o n d a r y i s o m e r i z a t i o n of the b r a n c h e d f r a g m e n t s i n d i r e c t i o n to u n b r a n c h e d s t r u c t u r e s o r to s o m e s m a l l c o n t r i b u t i o n of a n o n - b r a n c h i n g m e c h a n i s m . G e n e r a l l y , the d e g r e e of b r a n c h i n g i n an a l k a n e f r a c t i o n CpH 2 f o r m e d b y h y d r o c r a c k i n g of an n - a l k a n e feed n-C Tï + 2 50 % d e g r e e of c r a c k i n g c o n v e r s i o n depends on the v a l u e of ρ as c o m p a r e d w i t h m . It f o l l o w s f r o m T a b l e V that the a l k a n e f r a c t i o n s C p H g p ^ d i v i d e d into t h r e e g r o u p s a c c o r d i n g to t h e i r d e g r e e of b r a n c h i n g . 2
+
a
m
t
a
2 m
m
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
+
3
a
v
e
2
T h e content of b r a n c h e d i s o m e r s depends m a i n l y o n p . It i n c r e a s e s w i t h i n c r e a s i n g p, h o w e v e r , as a good a p p r o x i m a t i o n , i t i s not dependent on m . D e g r e e s of b r a n c h i n g are e x t r a o r d i n a r i l y high. R e p r e s e n t s the f r a c t i o n s f o r m e d b y a b s t r a c t i o n of and C^. C o n t e n t s of b r a n c h e d i s o m e r s a r e l o w e r as c o m p a r e d w i t h o t h e r f r a c t i o n s . T h e y a r e h i g h e r f o r ρ = m - 1 than f o r ρ = m - 2 . It i s r e c a l l e d h o w e v e r , that both f r a c t i o n s o c c u r at v e r y l o w c o n c e n t r a t i o n s except w h e n n - h e x a n e i s the f e e d . T h u s the d e g r e e of b r a n c h i n g i n t h e s e f r a c t i o n s i s of i n t e r e s t o n l y f o r the m e c h a n i s m of a b s t r a c t i o n of m e t h a n e and ethane r a t h e r t h a n f o r product quality.
ρ = m-3 m-3
H y d r o g e n o l y s i s has b e e n c o n c l u d e d i n a p r e c e e d i n g s e c t i o n to be m a i n l y r e s p o n s i b l e f o r the f o r m a t i o n of C ^ + C _ i d Cg + C _ . B r a n c h i n g i n the f r a c t i o n s ρ = m - 1 and ρ = m - 2 , t h e n , m a y be due to h y d r o i s o m e r i z a t i o n of e i t h e r the feed o r the c r a c k e d p r o d u c t s a c c o r d i n g to the r e a c t i o n s e q u e n c e s : a
n
m
m
n
n
C
2
H
- m 2m
C
+
2
+
2
H
- m 2m
> ^ m ^ m
(
^
C
1
o
r
C
2
+
+
n
2^ >
C
H
" p 2p + 2 " >
+
2
+
C
l
Ο
^ p ^ P
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Γ
S
+
2
22
HYDROCRACKING
MODE
2
MODE
i-C,
i-C
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
i-C
n-C
5
i-C
c
7
n-C
4
i-C
5
n-C
6
HYDROTREATING
3
n-C6
i-C
Figure 13.
A N D
n-C
5
-C
4
7
cr
FEED " m C
MOLE-% OF BRANCHED ISOMERS C p H p * 2
H2m*2
C^ 10 H
C
5 12 H
C
6 U H
C
7 16 H
C
8 18 H
41.0
56.5
n-HEPTANE
87.5
56
71
n-OCTANE
63.5
91.5
62
76
n-NONANE
63.7
75.8
91.0
71
79
n-DECANE
65.7
73.0
78.0
91.0
73
n-UNDECANE
67.3
75.7
78.1
83.1
92.0
n-DODECANE
65.6
74.1
78.0
82.8 X85.5
n-HEXANE * (
^CR
C
4
3
Primary products in β-scission of mono-branched decyl cations
Table V. Hydrocracking of «-Alkanes ( X = 50%). Classification of Cracked Products According to the Degree of Branching.
n
5
n-C
6
i-C
3
6
}
C
2
9 20 H
9 2
^
= 7 7.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
W E I T K A M P
Influence of Chain Length
23
T h e h i g h e r c o n t e n t s of b r a n c h e d i s o m e r s found i n the f r a c t i o n ρ = m - 1 as c o m p a r e d to the f r a c t i o n ρ = m - 2 a r e b e s t e x p l a i n e d b y the s e c o n d r o u t e : S e c o n d a r y h y d r o i s o m e r i z a t i o n of n-CpHgp g i s e x p e c t e d to be f a s t e r f o r ρ = m - 1 due to both h i g h e r r e a c t i v i t y (cf. F i g u r e 3) and c o m p e t i t i v e c h e m i s o r p t i o n . T h e d e g r e e of b r a n c h i n g i n the c r a c k e d p r o d u c t s has b e e n d i s c u s s e d , so f a r , f o r a m e d i u m d e g r e e of c r a c k i n g c o n v e r s i o n . In F i g u r e 14 h y d r o c r a c k i n g of η - h e p t a n e and η - o c t a n e h a v e b e e n s e l e c t e d to d e m o n s t r a t e the i n f l u e n c e of the r e a c t i o n t e m p e r a t u r e and, h e n c e , of the d e g r e e of c r a c k i n g c o n v e r s i o n . A g a i n , a c l a s s i f i c a t i o n of the c a r b o n n u m b e r f r a c t i o n s i s u s e f u l : +
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
m-3
ρ = m-3
C
H
a n c
C
H
f
r
o
m
( 5 12 * 6 14 η-heptane or C g H and CryH^g f r o m η - o c t a n e ) T h e d e g r e e of c r a c k i n g c o n v e r s i o n has a p r o n o u n c e d i n f l u e n c e o n the content of b r a n c h e d i s o m e r s i n t h e s e f r a c t i o n s . T h e s h a p e of the c u r v e s i s s i m i l a r to the one that i s o b s e r v e d f o r h y d r o i s o m e r i z a t i o n of the feed (cf. d a s h e d l i n e f o r heptane). T h i s i n f l u e n c e of the d e g r e e of c o n v e r s i o n i s i n a g r e e m e n t w i t h the h y d r o g e n o l y t i c m e c h a n i s m o u t l i n e d above. (C H from η-heptane or C H from η-octane) T h e d e g r e e of b r a n c h i n g i n t h e s e f r a c t i o n s p a s s e s t h r o u g h a m a x i m u m at m e d i u m d e g r e e s of c o n v e r s i o n . T h e d e c r e a s e at h i g h s e v e r i t i e s i n d i c a t e s an i s o m e r i z a t i o n reaction i - C H > n-C H w h i c h , due to c o m p e t i t i v e c h e m i s o r p t i o n , i s i n h i b i t e d as l o n g as the s y s t e m c o n t a i n s h i g h c o n c e n t r a t i o n s of n o r m a l - o r i ~ C H . T h e l o w e r contents of b r a n c h e d i s o m e r s found at l o w d e g r e e s of c o n v e r s i o n i n d i c a t e the c o n t r i b u t i o n of a d i f f e r e n t type of c r a c k i n g m e c h a n i s m which yields unbranched frag m e n t s . I n p r i n c i p l e , t h i s m i g h t be a s p e c i a l m o d e of β - s c i s s i o n o r , m o r e l i k e l y , h y d r o g e n o l y s i s of the u n b r a n c h e d feed. T h e l a t t e r i s i n a g r e e m e n t w i t h the s h i f t s i n c a r b o n n u m b e r d i s t r i b u t i o n s e n c o u n t e r e d at l o w d e g r e e s of c r a c k i n g c o n v e r s i o n (cf. F i g u r e 9). ( C ^ H ^ Q from η-octane) T h e s e a r e the m o s t important fractions i n ideal hydrocracking. It f o l l o w s f r o m F i g u r e 14, that the content 1 4
4
1 Q
5
p
2
p
+
2
1
2
R
s
+
2
o
m
3
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2
m
+
2
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
24
HYDROCRACKING
A N D
HYDROTREATING
Figure 14. Hydrocracking of η-heptane and τι-octane. Influence of reaction temperature and degree of cracking conversion on content of branched isomers.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
1.
W E I T K A M P
Influence of Chain Length
25
of b r a n c h e d i s o m e r s depends o n l y s l i g h t l y on the d e g r e e of c r a c k i n g c o n v e r s i o n . T h i s has b e e n s h o w n i n r e c e n t p u b l i c a t i o n s (2, 9, 21) to be g e n e r a l l y v a l i d f o r the f r a c t i o n s i n question. A d d i t i o n a l informations concern i n g d i s t r i b u t i o n s of i n d i v i d u a l i s o m e r s , e. g . , a k i n e t i c p r e f e r e n c e of 2 - m e t h y l i s o m e r s a m o n g the c r a c k e d p r o d u c t s o r the o c c u r r e n c e of e q u i l i b r i u m c o n c e n t r a t i o n s of q u a r t e r n a r y s t r u c t u r e s at h i g h s e v e r i t i e s , have been d i s c u s s e d there.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
Conclusions L o w t e m p e r a t u r e h y d r o c r a c k i n g of n - a l k a n e s o v e r s u i t a b l y selected bifunctional catalysts with a high h y d r o g é n a t i o n / d e h y d r o g e n a t i o n a c t i v i t y m a y be c o n s i d e r e d to be a p u r e t y p e of c r a c k i n g r e a c t i o n the p r o d u c t s of w h i c h d i f f e r s u b s t a n t i a l l y f r o m t h o s e obtained i n catalytic c r a c k i n g , hydrogenolysis o r t h e r m a l c r a c k i n g . It i s a c c o m p a n i e d b y h y d r o i s o m e r i z a t i o n and the d i s t r i b u t i o n of the c r a c k e d p r o d u c t s i s that of a p u r e p r i m a r y c r a c k i n g . P r o b a b i l i t i e s of o v e r a l l c r a c k i n g r e a c t i o n s , as w e l l as b r a n c h i n g of the c r a c k e d p r o d u c t s , i n d i c a t e a r e a r r a n g e m e n t step p r i o r to the c r a c k i n g step. C o m p e t i t i v e c h e m i s o r p t i o n p l a y s a n i m p o r t a n t r o l e b y e n h a n c i n g the r a t e s of d e s o r p t i o n o f c a r b e n i u m i o n s . T h u s i n i d e a l h y d r o c r a c k i n g p r i m a r y p r o d u c t s of i o n i c r e a r r a n g e m e n t and c r a c k i n g r e a c t i o n s a r e o b t a i n a b l e . T h e c h a i n l e n g t h of n - a l k a n e s h a s a m a r k e d i n f l u e n c e on r e a c t i v i t i e s f o r h y d r o i s o m e r i z a t i o n , and e s p e c i a l l y f o r h y d r o c r a c k i n g . T o a v e r y s m a l l extent a m e t h a n e and ethane a b s t r a c t i n g m e c h a n i s m , p r o b a b l y h y d r o g e n o l y s i s as p r e d i c t e d i n a b a s i c w o r k o n b i f u n c t i o n a l c a t a l y s i s (14), i s found to be s u p e r i m p o s e d when l o w e r c a r b o n n u m b e r feeds ( C ^ , C g , Cg) a r e u s e d . n - H e x a n e i s e x c l u d e d f r o m i d e a l h y d r o c r a c k i n g . O n the P t / C a - Y - z e o l i t e c a t a l y s t it i s c r a c k e d v i a a m e c h a n i s m that i s m a i n l y h y d r o g e n o lytic. F r o m a p r a c t i c a l v i e w p o i n t i d e a l h y d r o c r a c k i n g o f f e r s an u t m o s t d e g r e e of p r o d u c t f l e x i b i l i t y . H o w e v e r , as a c o n s e q u e n c e of the c a t a l y s t s r e q u i r e d c o n t e n t s of p o i s o n s i n the feed m a t e r i a l s s u c h as s u l f u r and n i t r o g e n c o m p o u n d s a r e s t r o n g l y l i m i t e d . Acknowledgement T h e a u t h o r i s i n d e b t e d to P r o f . K . H e d d e n who g e n e r o u s l y s u p p o r t e d t h i s i n v e s t i g a t i o n . I w o u l d a l s o l i k e to thank
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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HYDROCRACKING AND HYDROTREATING
M r s . H . Schlifkowitz and M r . G . Walter for their excellent ex perimental work. Symbols Used
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch001
Feed rate of n-alkane
[mole
-1
m
Carbon number of n-alkane feed
m cat
Mass of catalyst
η.
Number of moles of cracked products with carbon number i £ moles per 100 moles n-alkane cracked J
[gj
Carbon number of alkanes formed by hydrocracking
Τ
Reaction rate of n-alkanes ί mole η alkane j [ g catalyst. h J Reaction temperature [ ° c ]
Χ
Degree of overall conversion
Χ
Degree of hydrocracking conversion
cr c Χ.ISO
\%~\
Degree of hydroisomerization conversion [%j
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Langlois, G . E., and Sullivan, R. F., Preprints, Div. Petr. C h e m . , A . C . S. (1969), 14 (1), D - 1 8 .
(2)
P i c h l e r , Η., Schulz, Η., Reitemeyer, Η. Ο., and Weit kamp, J., Erdöl, K o h l e - E r d g a s - P e t r o c h e m . (1972), 25, 494.
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Hedden, Κ., and Weitkamp, 47, 505.
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Sullivan, R. F., and Meyer, J Α., Preprints, Div. Petr. C h e m . , A . C . S. (1975), 20, 508.
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F l i n n , R. A., L a r s o n , D . A., and Beuther, Η., Ind. E n g . C h e m . , (1960), 52, 153.
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Archibald, R. C., Greensfelder, B . S., Holzman, G., and Rowe, D. H., Ind. Eng. Chem.(1960), 52, 745.
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Orkin, Β . A., Ind. Eng. Chem. P r o d . Res. Develop. 8, 155.
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Stull, D . R., Westrum, E. F., Jr., and Sinke, G . C., "The Chemical Thermodynamics of Organic Compounds", John Wiley and Sons, Inc., New York, 1969.
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Bolton, A . P., and Lanewala, Μ. A., J. Catal. (1970), 18,1.
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In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2
Catalyst Effects on Yields and Product Properties in Hydrocracking R. F. SULLIVAN and J. A. MEYER
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Chevron Research Co., Richmond, Calif. 94802
The flexibility o f h y d r o c r a c k i n g as a p r o c e s s f o r refining p e t r o l e u m has r e s u l t e d in its phenomenal growth d u r i n g the p a s t 15 y e a r s . F e e d s t o c k s t h a t can be c o n v e r t e d t o lower boiling o r more d e s i r a b l e p r o d u c t s range from r e s i d u a t o n a p h t h a s . Products i n c l u d e such w i d e l y d i v e r s e m a t e r i a l s as g a s o l i n e , kerosene, middle distillates, lubricating oils, fuel oils, and various chemicals ( 1 , 2 ) . Commercial h y d r o c r a c k i n g is c a r r i e d out in a single s t a g e o r in two o r more s t a g e s in s e r i e s . Numerous h y d r o c r a c k i n g c a t a l y s t s have been d e v e l o p e d ; and the more r e c e n t o f t h e s e have e x c e p t i o n a l l y long lives, even at s e v e r e o p e r a t i n g c o n d i t i o n s . The c h o i c e of the c a t a l y s t and o f the particular p r o c e s s i n g scheme will depend on many f a c t o r s such as feed p r o p e r t i e s , p r o p e r t i e s o f the d e s i r e d p r o d u c t s , s i z e o f the h y d r o cracking unit, availability of other processing facilities, and v a r i o u s o t h e r economic c o n s i d e r a t i o n s . In t h i s p a p e r , we will examine s e v e r a l h y d r o cracking catalysts of varying acidities and hydrogenation-dehydrogenation activities and show differences in p r o d u c t distributions and p r o d u c t p r o p e r ties o b t a i n e d from two r e p r e s e n t a t i v e domestic f e e d s t o c k s in the second s t a g e o f a t w o - s t a g e h y d r o cracking process. I n such a p r o c e s s , the f e e d t o the second s t a g e has been h y d r o f i n e d in the first stage i n o r d e r t o remove most o f the i m p u r i t i e s such as n i t r o g e n and s u l f u r . In particular, we will emphasize (1) total liquid yield, i n c l u d i n g pentanes and all o f the h i g h e r boiling p r o d u c t , and (2) octane number o f the l i g h t p r o d u c t c o n s i s t i n g m a i n l y o f m o l e c u l e s w i t h carbon numbers o f 5 and 6, r e f e r r e d t o as C - l 8 0 ° F p r o d u c t . H i g h C5+ 5
28
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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l i q u i d y i e l d s are d e s i r a b l e i n s i t u a t i o n s i n which butanes and propane are i n o v e r s u p p l y o r o f l o w e r v a l u e than the l i q u i d products. A h i g h o c t a n e number i n t h e C5-l80°F product i s p a r t i c u l a r l y d e s i r a b l e because i t i s more d i f f i c u l t t o u p g r a d e t h i s l o w b o i l i n g f r a c t i o n t h a n t h e h i g h e r b o i l i n g n a p h t h a s , w h i c h c a n be u p g r a d e d r e l a t i v e l y e a s i l y by c a t a l y t i c r e f o r m i n g .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Background Most h y d r o c r a c k i n g c a t a l y s t s o f c o m m e r c i a l i n t e r est are dual f u n c t i o n a l i n nature, c o n s i s t i n g o f both a h y d r o g e n a t i o n - d e h y d r o g e n a t i o n component and an a c i d i c support. The r e a c t i o n s c a t a l y z e d b y t h e i n d i v i d u a l components a r e q u i t e d i f f e r e n t . In specific catalysts, t h e r e l a t i v e s t r e n g t h s o f t h e two components can be varied. The r e a c t i o n s o c c u r r i n g and t h e p r o d u c t s formed depend c r i t i c a l l y upon t h e b a l a n c e between t h e s e two c o m p o n e n t s . The a c i d f u n c t i o n o f t h e c a t a l y s t i s s u p p l i e d b y the support. Among t h e s u p p o r t s m e n t i o n e d i n t h e l i t e r a t u r e are s i l i c a - a l u m i n a , s i l i c a - z i r c o n i a , s i l i c a magnesia, alumina-boria, s i l i c a - t i t a n i a , a c i d - t r e a t e d c l a y s , a c i d i c m e t a l p h o s p h a t e s , a l u m i n a , and o t h e r such s o l i d a c i d s . The a c i d i c p r o p e r t i e s o f t h e s e amorphous c a t a l y s t s c a n be f u r t h e r a c t i v a t e d by t h e a d d i t i o n o f s m a l l p r o p o r t i o n s o f a c i d i c h a l i d e s s u c h as HF, B F , S i F i t , and t h e l i k e (3.). Z e o l i t e s s u c h as t h e f a u j a s i t e s and m o r d e n i t e s a r e a l s o i m p o r t a n t s u p p o r t s for hydrocracking c a t a l y s t s (2). The h y d r o g e n a t i o n - d e h y d r o g e n a t i o n c o m p o n e n t i s a m e t a l s u c h as c o b a l t , n i c k e l , t u n g s t e n , v a n a d i u m , molybdenum, p l a t i n u m . o r p a l l a d i u m , o r a c o m b i n a t i o n o f metals. The n o n - n o b l e m e t a l s a r e u s u a l l y p r e s u l f i d e d a l t h o u g h i t has been s u g g e s t e d t h a t the a c t u a l h y d r o g é n a t i o n a c t i v i t y f o r the s u l f i d e d c a t a l y s t s e x i s t s i n t r a n s i t o r y m e t a l l i c r e g i o n s on t h e s e c a t a l y s t s (h). The s u l f i d e d m e t a l s a r e g e n e r a l l y r e p o r t e d t o b e l e s s a c t i v e f o r h y d r o g é n a t i o n than the noble metal c a t a l y s t s (5.). The r e l a t i o n s h i p b e t w e e n t h e t w o c a t a l y t i c c o m ponents i s q u i t e complex. I n t e r a c t i o n s between the s u p p o r t and t h e h y d r o g é n a t i o n component c a n a l t e r t h i s relationship. F o r e x a m p l e , L a r s o n et- a l . (6) s h o w e d t h a t , w i t h p l a t i n u m on s i l i c a - a l u m i n a , a s e l e c t i v e a d s o r p t i o n o f p l a t i n u m by a c i d s i t e s c a u s e s a r e d u c t i o n in catalyst acidity. S i m i l a r l y , n i c k e l reacts w i t h the a c i d s i t e s on s i l i c a - a l u m i n a f o r m i n g n i c k e l s a l t s o f the s i l i c a - a l u m i n a a c i d s i t e s . I t has been s u g g e s t e d (7) t h a t one o f t h e e f f e c t s o f s u l f i d i n g a n i c k e l o n 3
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
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s i l i c a - a l u m i n a c a t a l y s t i s that hydrogen s u l f i d e r e a c t s w i t h t h e s e s a l t s and r e g e n e r a t e s t h e o r i g i n a l s t r o n g a c i d s i t e s of the s i l i c a - a l u m i n a . I n t h e r e a c t i o n s o f t h e many c o m p o n e n t m i x t u r e s t h a t make up m o s t c o m m e r c i a l f e e d s t o c k s , t h e r e l a t i o n s h i p b e t w e e n t h e t w o c a t a l y t i c c o m p o n e n t s may be f u r t h e r a l t e r e d by p r e f e r e n t i a l a d s o r p t i o n o f c e r t a i n h y d r o c a r b o n r e a c t a n t s o n c a t a l y t i c s i t e s ( £0 . For example, p o l y c y c l i c a r o m a t i c s have a h i g h l y v a r i a b l e e f f e c t d e p e n d e n t o n t h e t y p e a n d amount a s w e l l a s c a t a l y s t and r e a c t i o n c o n d i t i o n s . Catalyst poisons s u c h a s s u l f u r , n i t r o g e n , a n d o x y g e n may a f f e c t either or b o t h c a t a l y s t components ( £ ) . The l i t e r a t u r e o n t h e h y d r o c r a c k i n g o f v a r i o u s hydrocarbons i s summarized i n s e v e r a l r e v i e w a r t i c l e s (5310*11) and mechanisms o f h y d r o c a r b o n r e a c t i o n s presented. B e u t h e r a n d L a r s o n (h) a n d C o o n r a d t a n d c o w o r k e r s (9312,1331*0 compare t h e r e a c t i o n s o f n o b l e m e t a l c a t a l y s t s and the n o n - n o b l e m e t a l s u l f i d e s . C a t a l y s t s w i t h h i g h h y d r o g é n a t i o n a c t i v i t y s u c h as t h e noble metal c a t a l y s t s are reported to favor the format i o n o f h i g h e r b o i l i n g p r o d u c t s and minimum l i g h t hydrocarbon production. C a t a l y s t s w i t h low h y d r o g é n a t i o n a c t i v i t y r e l a t i v e to a c i d i t y y i e l d product with a higher r a t i o of branched paraffins to normal p a r a f f i n s and l e s s s a t u r a t i o n o f a r o m a t i c s . With the latter c a t a l y s t s , t h e naphtha p r o d u c t has a h i g h e r octane number. S c h u t z a n d W e i t k a m p (15.) show p r o d u c t d i s t r i b u t i o n s f o r t h e h y d r o c r a c k i n g o f dodecane on s e v e r a l n o b l e m e t a l s on z e o l i t e c a t a l y s t s . Product d i s t r i b u t i o n s are i n general s i m i l a r to those d i s t r i b u t i o n s p r e v i o u s l y r e p o r t e d f o r n o b l e m e t a l s on amorphous supports. T h e s e r e s u l t s show n o m a j o r u n e x p e c t e d e f f e c t o f t h e z e o l i t i c s u p p o r t ; d i f f e r e n c e s among t h e c a t a l y s t s t e s t e d a r e r e l a t e d t o changes i n h y d r o g é n a t i o n a b i l i t y or a c i d i t y . 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 measurements o f h y d r o g é n a t i o n a c t i v i t y and a c i d i t y , v a r i o u s schemes are employed. F o r e x a m p l e , m e t a l s u r f a c e a r e a has been r e l a t e d t o h y d r o g é n a t i o n a c t i v i t y and the a d s o r p t i o n o f b a s e s s u c h a s p y r i d i n e a n d ammonia h a v e b e e n c o r r e l a t e d w i t h a c i d i t y (6). Some a u t h o r s h a v e u s e d c e r t a i n k e y r e a c t i o n s i n v o l v i n g p u r e compounds a s a n i n d i c a t i o n o f c a t a l y t i c p r o p e r t i e s (16). Each o f these methods i s u s e f u l ; h o w e v e r , b e c a u s e o f t h e complex interdependence of the c a t a l y t i c functions of the h y d r o c r a c k i n g c a t a l y s t s and changes i n t h e s e f u n c t i o n s w i t h c a t a l y s t a g i n g , r e s u l t s f r o m e a c h method must be interpreted with caution.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
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31
C o o n r a d t a n d c o w o r k e r s (13_) u s e a n e m p i r i c a l h y d r o g é n a t i o n a c t i v i t y i n d e x b a s e d on t h e a r o m a t i o naphthene r a t i o i n the hydrocracked p r o d u c t . This a p p r o a c h does n o t p r o v i d e an i n d e p e n d e n t measure o f catalytic properties. However, i t has t h e a d v a n t a g e t h a t a c t i v i t i e s are measured under a c t u a l h y d r o c r a c k i n g c o n d i t i o n s ; and changes i n c a t a l y t i c p r o p e r t i e s w i t h c a t a l y t i c a g i n g can be o b s e r v e d . Most d i r e c t comparisons a v a i l a b l e i n the l i t e r a t u r e among c a t a l y s t s o f v a r y i n g h y d r o g e n a t i o n - t o a c i d i t y r a t i o s are f o r s i n g l e pass p r o c e s s i n g . Because o f t h e d i f f e r e n t r e a c t i v i t i e s o f t h e components o f comm e r c i a l feed m i x t u r e s , the s p e c i f i c molecules that r e a c t i n a s i n g l e pass w i l l depend s t r o n g l y upon t h e t o t a l conversion. I n o t h e r w o r d s , t h e most s t r o n g l y adsorbed s p e c i e s w i l l r e a c t p r e f e r e n t i a l l y ; and the r e s u l t i n g product d i s t r i b u t i o n w i l l r e f l e c t the propert i e s of these reacting molecules. As t h e c o n v e r s i o n i n c r e a s e s , the p r o p e r t i e s of the r e a c t i n g molecules and t h e r e f o r e the p r o d u c t w i l l change. A l s o , i f two c a t a l y s t s w i t h d i f f e r e n t p r o p e r t i e s are compared at constant conversion, the p a r t i c u l a r species that react i n t h e p r e s e n c e o f one c a t a l y s t w i l l n o t n e c e s s a r i l y b e t h e same s p e c i e s t h a t r e a c t p r e f e r e n t i a l l y u s i n g t h e other. I n t h i s p a p e r we c o m p a r e b e h a v i o r o f c a t a l y s t s i n extinction recycle hydrocracking. In such a p r o c e s s i n g scheme, a l l o f the feed i s u l t i m a t e l y c o n v e r t e d t o product b o i l i n g below a c e r t a i n p r e d e f i n e d temperature. The r e a c t i o n p a t h s o f i n d i v i d u a l f e e d c o m p o n e n t s may d i f f e r from c a t a l y s t t o c a t a l y s t . Product d i s t r i b u t i o n s and p r o p e r t i e s a r e examined t o d e t e r m i n e the g e n e r a l e f f e c t s o f changes i n c a t a l y t i c p r o p e r t i e s . Experimental Equipment. A l l o f the c a t a l y s t s were t e s t e d i n continuous flow, fixed-bed p i l o t plants equipped for b o t h l i q u i d and gas r e c y c l e o p e r a t i o n and c o n t i n u o u s d i s t i l l a t i o n of products. Hydrocarbons b o i l i n g above t h e d e s i r e d p r o d u c t end p o i n t were r e c y c l e d t o e x t i n c t i o n , t h a t i s , t o 100$ c o n v e r s i o n o f f r e s h f e e d . The p r o d u c t was c o o l e d a n d p a s s e d i n t o a h i g h p r e s s u r e phase s e p a r a t o r . H e r e , h y d r o g e n - r i c h r e c y c l e g a s was f l a s h e d from the h y d r o c a r b o n p r o d u c t and r e c y c l e d back to the r e a c t o r i n l e t . E l e c t r o l y t i c h y d r o g e n make-up was a d d e d o n demand t o m a i n t a i n c o n s t a n t s y s t e m pressure. The l i q u i d f r o m t h e h i g h p r e s s u r e s e p a r a t o r was d e p r e s s u r e d and f l a s h e d at a t m o s p h e r i c p r e s s u r e . The
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
32
HYDROCRACKING
A N D
HYDROTREATING
l i q u i d h y d r o c a r b o n p h a s e was f e d t o t h e f i r s t o f t w o c o n t i n u o u s d i s t i l l a t i o n columns f o r the p r o d u c t f r a c tionation. In the f i r s t column, the m a t e r i a l b o i l i n g a b o v e t h e d e s i r e d r e c y c l e c u t p o i n t was s e p a r a t e d f r o m the lower b o i l i n g product. The o v e r h e a d f r o m t h i s c o l u m n was c o m b i n e d w i t h t h e g a s e o u s p r o d u c t f r o m t h e low p r e s s u r e f l a s h and f e d t o the second column i n w h i c h t h e p e n t a n e s and l i g h t e r gases were s e p a r a t e d from the l i q u i d p r o d u c t . The g a s e o u s p r o d u c t f r o m t h i s d e p e n t a n i z e r was m e t e r e d a n d a n a l y z e d b y g a s chromatography. L i q u i d p r o d u c t was d i s t i l l e d b a t c h w i s e f o r d e t e r m i n a t i o n o f l i q u i d y i e l d s and p r o d u c t p r o p e r t i e s . In the batch d i s t i l l a t i o n , the f i r s t l i q u i d product c u t was made a t l 8 0 ° F ( t r u e b o i l i n g p o i n t ) . Isopentane and n - p e n t a n e were added back t o t h i s d i s t i l l a t i o n c u t i n t h e amount m e a s u r e d i n t h e g a s e o u s p r o d u c t . The r e s u l t i n g b l e n d , m a i n l y c o n s i s t i n g o f components w i t h c a r b o n numbers o f 5 a n d 6, i s r e f e r r e d t o as C5-l80°F product." The b o i l i n g r a n g e s o f t h e d i s t i l l a t i o n c u t s (shown as " t r u e b o i l i n g p o i n t " t e m p e r a t u r e r a n g e s ) were c h o s e n a r b i t r a r i l y a n d do n o t r e p r e s e n t o p t i m u m o r maximum p o t e n t i a l y i e l d s o f s p e c i f i c p r o d u c t s . In the e x a m p l e s g i v e n , t h e amount o f j e t f u e l o r n a p h t h a c o u l d be a l t e r e d b y c h a n g i n g t h e b o i l i n g r a n g e s , d e p e n d i n g on t h e d e s i r e d p r o d u c t p r o p e r t i e s . Simil a r l y , t h e r e c y c l e c u t p o i n t c o u l d be v a r i e d t o m a x i mize i n d i v i d u a l products. A l l o f t h e p i l o t p l a n t t e s t s w e r e made a t 60 l i q u i d volume p e r c e n t p e r pass c o n v e r s i o n below the r e c y c l e cut p o i n t . T e m p e r a t u r e s were a d j u s t e d as necessary to maintain t h i s conversion. Total pressure and r e c y c l e gas r a t e were h e l d c o n s t a n t f o r a l l o f t h e runs w i t h a g i v e n feed. M
Feeds. P r o p e r t i e s o f two h y d r o f i n e d t e s t f e e d s are given i n Table I . The C a l i f o r n i a g a s o i l b l e n d was u s e d i n t e s t s s i m u l a t i n g a h y d r o c r a c k i n g u n i t p r o d u c i n g b o t h naphthas and j e t f u e l , the M i d - C o n t i n e n t blend i n t e s t s r e p r e s e n t i n g a u n i t producing naphtha as t h e major p r o d u c t . Catalysts. Seven e x p e r i m e n t a l c a t a l y s t s were p r e p a r e d w i t h v a r y i n g h y d r o g é n a t i o n a c t i v i t y and a c i d i t y t o t e s t t h e e f f e c t s o f t h e s e p r o p e r t i e s on product d i s t r i b u t i o n s . A l l o f the c a t a l y s t s were reasonably s t a b l e at t e s t c o n d i t i o n s . In the f o l l o w i n g t a b l e , the c a t a l y s t s are l i s t e d i n order of decreasing ratios of hydrogénation
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2.
SULLIVAN
33
Catalyst Effects
A N D M E Y E R
TABLE
I
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
FEED PROPERTIES
G r a v i t y , °API Aniline Point, °F S u l f u r , ppm T o t a l N i t r o g e n , ppm
Hydrotreated California Gas O i l B l e n d
Hydrotreated Mid-Continent Gas O i l B l e n d
33.9 192.7 1 0.1
33-3 177.6 9 0.2
31.3 56.3 12.4
19.4 63-9 16.6
553/589 595/617 646 684/732 763/859
325/441 515/616 666 705/762 802/826
Mass S p e c t r o m e t r i c Type A n a l y s i s , LV % Paraffins Naphthenes Aromatics ASTM D 1160 Distillation, St/5 10/30 50 70/90 95/EP
°P
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
34
HYDROCRACKING
A N D
HYDROTREATING
a c t i v i t y to acid a c t i v i t y . N o m i n a l l y , C a t a l y s t A has the highest h y d r o g é n a t i o n a c t i v i t y r e l a t i v e to i t s a c i d i t y ; C a t a l y s t G has t h e l o w e s t h y d r o g é n a t i o n a c t i v i t y r e l a t i v e to i t s a c i d i t y . The a s s i g n m e n t i s b a s e d on a v a r i e t y o f l a b o r a t o r y t e s t s . As i n d i c a t e d p r e v i o u s l y , a l l such t e s t s are not completely unambig u o u s ; t h e r e f o r e , t h e a s s i g n m e n t may be r e g a r d e d as somewhat a r b i t r a r y . Experimental
Catalysts
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Metals Catalyst IdentiHydrogénation Content, Wt % fication Component
Support M a t e r i a l
A
Pd
0.5
A c t i v a t e d Clay (Low A c i d i t y )
Β
Pd
1.0
Amorphous Alumina
Silica-
C
Pd
0.2
Amorphous Alumina
Silica-
D
Pd
0.5
Activated (Moderate
Clay Acidity)
Ε
Pd
0.5
Faujasite
Ρ
Pd
0.5
Amorphous S i l i c a Alumina (Activated)
G
Sulfided Ni
Results With C a l i f o r n i a
10.0
Amorphous Alumina
Silica-
Gas O i l
Product D i s t r i b u t i o n s . A l l o f the t e s t s w i t h C a l i f o r n i a g a s o i l w e r e made a t a r e c y c l e c u t p o i n t o f 550°F, a r b i t r a r i l y c h o s e n and n o t n e c e s s a r i l y an optimum c u t p o i n t f o r o p e r a t i o n w i t h any o f t h e catalysts. T a b l e I I compares p r o d u c t d i s t r i b u t i o n s f o r c a t a l y s t s near to the extremes o f h y d r o g e n a t i o n - t o acidity ratios studied. Catalyst Β gives a higher y i e l d o f l i q u i d p r o d u c t i n c l u d i n g the pentanes and a l l h i g h e r b o i l i n g m a t e r i a l ( r e f e r r e d t o as "C5-550°F
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
SULLIVAN
Catalyst Effects
A N D M E Y E R
TABLE I I YIELDS AND PRODUCT PROPERTIES FROM HYDROCRACKING OF CALIFORNIA GAS O I L 60% PER PASS CONVERSION BELOW 550°F
Catalyst T e m p e r a t u r e , °F LV %
Wt %
ΤΪ(Γ LV % Wt %
No L o s s P r o d u c t Y i e l d s ( B a s e d on F r e s h F e e d ) 0.01 0.02 1.0 3.8 1.1
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Methane Ethane Propane Isobutane n-Butane C -180°F 180-280°F 280-300°F 300-550°F
10.1 21.6 4.9 59.2 95.8
5
Total
C -550°F 5
Chemical Hydrogen C o n s u m p t i o n , SCF/B Product
5.8 1.6
0.01 0.04 1.5 6.3 1.8
13.2 25.0 5.5 63-9
15.5 25.6 6.4 44.8
107.6
92.3
950
9.6 2.6 20.2 29.5 7.2 48.2
I 105.1 1000
Properties
C -180°F 5
Product
O c t a n e Number F - l Clear l80-280°F
85.0
58.7
63.4
47.5 52.5 0.0
42.6 55.5 1.9
44.0 56.0
40.1 57.5 2.4
42.6 57.2 0.2
41.5 56.0 2.5
Product
O c t a n e Number F - l Clear Type A n a l y s i s ,
LV %
Paraffins Naphthenes Aromatics 280-300°F
81.5
Product
Type A n a l y s i s ,
LV %
Paraffins Naphthenes Aromatics 300-550°F
Product
Type A n a l y s i s , Paraffins Naphthenes Aromatics ASTM D 86 D i s t . St/5 10/30 50 70/90 95/EP
LV %
Op
334/350 358/381 408 444/486 500/531
333/349 355/375 398 436/488 503/528
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
36
HYDROCRACKING
A N D
HYDROTREATING
product"). A l s o , t h i s c a t a l y s t p r o d u c e s more m a t e r i a l b o i l i n g above 280°F, a r b i t r a r i l y r e f e r r e d t o as j e t fuel. The p r o d u c t i s m o r e c o m p l e t e l y h y d r o g e n a t e d t h a n t h a t f o r C a t a l y s t G . C a t a l y s t G , on t h e o t h e r h a n d , p r o d u c e s more n a p h t h a , more p r o p a n e a n d b u t a n e , a n d h i g h e r octane numbers. The g e n e r a l t r e n d s shown b y t h e s e p r o d u c t d i s t r i b u t i o n s are i n b a s i c agreement w i t h the l i t e r a t u r e results discussed e a r l i e r . C -l80°F Product. T a b l e I I I shows t h e c o m p l e t e d i s t r i b u t i o n o f hydrocarbons from r e p r e s e n t a t i v e s a m p l e s o f C s - l 8 0 F p r o d u c t as d e t e r m i n e d by gas c h r o m a t o g r a p h y f o r t h e same t w o c a t a l y s t s . Both p r o d u c t s a m p l e s c o n t a i n a b o u t 90% p a r a f f i n s a n d 10$ cycloparaffins. The C 5 - l 8 0 ° F p r o d u c t f r o m C a t a l y s t G c o n t a i n s a t r a c e o f b e n z e n e (0.2%); t h a t f r o m C a t a l y s t Β c o n t a i n s no d e t e c t a b l e a r o m a t i c c o m p o u n d . The s m a l l d i f f e r e n c e i n t h e t o t a l c y c l o p a r a f f i n s c o n t e n t shown i n Table I I I i s p r o b a b l y not s i g n i f i c a n t . The C - l 8 0 ° F p r o d u c t c o n s i s t s m a i n l y o f C5 a n d C6 p a r a f f i n s ; t h e r e f o r e , i t i s p r i m a r i l y t h e s e components t h a t d e t e r m i n e t h e o c t a n e number. With a l l o f the c a t a l y s t s i n t h i s study, the r a t i o o f i s o p e n t a n e t o n o r m a l p e n t a n e v a r i e s d i r e c t l y as t h e r a t i o o f isohexanes to n-hexane. (In t h i s paper, the b r a n c h e d Ce p a r a f f i n s a r e c o l l e c t i v e l y r e f e r r e d t o a s isohexanes.) T h e r e f o r e , the i s o / n o r m a l r a t i o o f the p a r a f f i n s o f e i t h e r c a r b o n number c a n b e c o r r e l a t e d w i t h o c t a n e number f o r C s - l 8 0 F p r o d u c t o f a g i v e n c y c l o p a r a f f i n c o n t e n t a n d s e r v e as a c o n v e n i e n t i n d i c a t i o n o f c a t a l y s t performance. I n t h e s p e c i f i c example shown i n T a b l e I I I , t h e difference i n r a t i o s of i s o p a r a f f i n s to normal paraf f i n s i n t h e C - l 8 0 ° F p r o d u c t from t h e two c a t a l y s t s r e s u l t s i n a f o u r o c t a n e number d i f f e r e n c e . F i g u r e 1 shows t h e e f f e c t o f t e m p e r a t u r e o n isohexane/n-hexane r a t i o for Catalysts A - G , i n c l u s i v e . M o s t o f t h e c a t a l y s t s show a s l i g h t d e c r e a s e i n i s o - t o normal r a t i o w i t h i n c r e a s i n g temperature. The r a t i o s f o r t h e g r o u p o f c a t a l y s t s t e s t e d r a n g e f r o m 20/1 t o 3/1. The l a t t e r r a t i o i s a p p r o x i m a t e l y t h e e q u i l i b r i u m r a t i o f o r s i n g l y b r a n c h e d C6 p a r a f f i n s t o n o r m a l hexane. F i g u r e 2 i s a comparison showing the e f f e c t o f t e m p e r a t u r e on i s o p e n t a n e / n - p e n t a n e r a t i o s . The r e l a t i o n s h i p i s q u i t e s i m i l a r t o t h a t shown f o r t h e hexanes. 5
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
o
5
o
5
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
SULLIVAN
A N D M E Y E R
Catalyst Effects
TABLE
III
D I S T R I B U T I O N OP C - l 8 0 ° F PRODUCT PROM HYDROCRACKING OP C A L I F O R N I A GAS O I L 5
1
Catalyst Average C a t a l y s t Temperature, °F
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Product,
LV % o f
Paraffins
Cycloparaffins
Benzene Total
598
610
5
Cyclopentane Methylcyclopentane Cyclohexane Dlmethylcyclopentanes, Ethylcyclopentane Methylcyclohexane Total
G
C -l80°F
Butanes Isopentane n-Pentane 2.2- Dimethylbutane 2.3- Dimethylbutane 2- M e t h y l p e n t a n e 3- M e t h y l p e n t a n e n-Hexane Isoheptanes n-Heptane Total
Β
Aromatics
0.4 41.0 9.5 0.2 2.5 17.3 9.3 6.3 3.7 0.1
0.3 44.1 2.8 0.04 3.2 19.3 11.4 2.2 4.5 0.02
90.3
87.8
0.5 7.1 0.6 1.3
0.4 9.4 0.4 1.5
0.1
0.3
9.6
12.0
-
0.2 0.2
81.1
85.0
Isopentane/n-Pentane
4.3
16.4
Isohexanes/n-Hexane
4.6
15.5
Octane
No., F - l Clear
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
20 Γ-
600
630
Average Catalyst Temperature,
°F
Figure 1. Effect of temperature on isohexanes/n-hexane hydrocracking of California gas oil
|Τ0 40
201
550
600
650
Average C a t a l y s t T e m p e r a t u r e ,
700 °F
Figure 2. Effect of temperature on isopentane/n-pentane hydrocrack ing of California gas oil
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2.
SULLIVAN AND MEYER
Catalyst Effects
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
W i t h b o t h pentanes and hexanes, the r a t i o s appear to vary i n v e r s e l y w i t h the to-acidity ratios.
39 iso-to-normal hydrogenation-
Butanes. The b u t a n e s a r e t h e p r i n c i p a l l o w b o i l i n g p r o d u c t s ; a n d , as i n d i c a t e d e a r l i e r , c a t a l y s t s w i t h a low r a t i o o f h y d r o g é n a t i o n a b i l i t y to a c i d i t y p r o d u c e more b u t a n e t h a n do t h o s e w i t h r e l a t i v e l y h i g h hydrogénation activity. However, the d i f f e r e n c e s i n i s o b u t a n e / n - b u t a n e r a t i o s among c a t a l y s t s o f w i d e l y d i f f e r e n t h y d r o g e n a t i o n - t o - a c i d i t y r a t i o s are small. F i g u r e 3 shows t h e e f f e c t o f t e m p e r a t u r e on i s o b u t a n e / η - b u t a n e r a t i o f o r C a t a l y s t s A , B , F , and G , r e p r e s e n t i n g extremes o f h y d r o g e n a t i o n / a c i d i t y r a t i o s . The isobutane/n-butane r a t i o with Catalyst G i s s l i g h t l y h i g h e r than t h a t f o r the other c a t a l y s t s at the lower temperatures. However, at h i g h e r temperatures, the r a t i o s from a l l o f the c a t a l y s t s are e s s e n t i a l l y the same. T h i s r e s u l t i n d i c a t e s t h a t t h e r e i s no d i r e c t r e l a t i o n s h i p between i s o / n o r m a l r a t i o s f o r the butanes w i t h those f o r the pentanes and hexanes. The f o l l o w i n g hypothesis i s suggested to e x p l a i n t h i s r e s u l t . An i m p o r t a n t r e a c t i o n o c c u r s i n h y d r o c r a c k i n g w h i c h p r o d u c e s i s o b u t a n e more s e l e c t i v e l y f r o m c y c l o p a r a f f i n s t h a n from a r o m a t i c compounds. This reaction has b e e n r e f e r r e d t o as t h e p a r i n g r e a c t i o n . I t was s h o w n b y E g a n e t a l . (17) t h a t c y c l o p a r a f f i n s w i t h c a r b o n n u m b e r s o f 10 o r m o r e r e a c t v e r y s e l e c t i v e l y t o give isobutane plus lower molecular weight c y c l o paraf fins. A l k y l aromatics with side chains of three o r more c a r b o n s c r a c k m a i n l y b y d é a l k y l a t i o n , w i t h much l e s s i s o m e r i z a t i o n o f t h e a l k y l g r o u p (18.)· Therefore, i f the aromatics i n the feed are hydrog e n a t e d p r i o r t o c r a c k i n g , as w o u l d be e x p e c t e d w i t h a catalyst of high hydrogénation a c t i v i t y , a high isobutane/n-butane r a t i o i s favored. With a catalyst o f l o w e r h y d r o g é n a t i o n a c t i v i t y , c r a c k i n g w o u l d be expected to occur to a greater extent before hydrogénation. Therefore, a lower isobutane/n-butane ratio w o u l d be e x p e c t e d . H o w e v e r , b u t a n e s a r e p r o d u c e d by c r a c k i n g r e a c t i o n s other than the p a r i n g r e a c t i o n . In reactions s u c h a s p a r a f f i n c r a c k i n g , t h e same f a c t o r s t h a t f a v o r a h i g h i s o p e n t a n e / n - p e n t a n e r a t i o and a h i g h i s o p e n t a n e / n - p e n t a n e r a t i o and a h i g h i s o h e x a n e s / n-hexanes r a t i o ( i . e . , h i g h a c i d i t y ) w i l l f a v o r a h i g h isobutane/n-butane ratio. T h e r e f o r e , we h a v e t w o e f f e c t s o n i s o b u t a n e / η - b u t a n e r a t i o t h a t tend to o f f s e t each o t h e r . The r e s u l t , w i t h t h e C a l i f o r n i a gas o i l , i s t h a t t h e r e i s
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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HYDROCRACKING A N D H Y D R O T R E A T I N G
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
l i t t l e e f f e c t o f c h a n g i n g a c i d i t y and h y d r o g é n a t i o n a c t i v i t y on t h e i s o b u t a n e / n - b u t a n e ratio. This r e l a t i o n s h i p w i l l vary w i t h the aromatic cont e n t of the feedstock. With a highly aromatic feed, t h e c a t a l y s t w i t h t h e h i g h e r h y d r o g é n a t i o n a c t i v i t y may give a higher isobutane/n-butane r a t i o , although with the pentanes and hexanes the e f f e c t i s r e v e r s e d . T o t a l L i q u i d (C5+) Y i e l d . Product molecules w i t h c a r b o n numbers o f f i v e a n d h i g h e r c a n be c o m b i n e d i n a f r a c t i o n r e f e r r e d t o as "C5+" l i q u i d p r o d u c t . This f r a c t i o n i n c l u d e s the pentanes and a l l o f the p r o d u c t b o i l i n g below the r e c y c l e cut p o i n t . The e x a m p l e s i n T a b l e I I show t h a t t h e m o r e a c i d i c c a t a l y s t p r o d u c e s l e s s p r o d u c t i n t h e C 5 + f r a c t i o n , more b u t a n e s a n d p r o p a n e , and l e s s p r o d u c t i n the j e t f u e l b o i l i n g range t h a n does t h e c a t a l y s t w i t h h i g h e r h y d r o g é n a t i o n activity. F i g u r e 4 shows t h a t t h e t o t a l C5+ y i e l d c a n be r e l a t e d to the r a t i o of the isohexanes/n-hexane. No r e s u l t s a r e i n c l u d e d f o r C a t a l y s t A a s no a n a l y s e s w e r e a v a i l a b l e i n t h i s temperature range. W i t h i n t h i s r e a s o n a b l y narrow temperature span and w i t h p r e s s u r e and gas r a t e c o n s t a n t , t h e r e s u l t s correlate quite well. The same g e n e r a l f a c t o r s w h i c h contribute to a high t o t a l l i q u i d y i e l d also result i n a l o w e r i s o - t o - n o r m a l r a t i o and v i c e v e r s a . I t s h o u l d be e m p h a s i z e d t h a t i n a c t u a l p r a c t i c e i t i s t h e maximum f i n i s h e d p r o d u c t r a t h e r t h a n t h e q u a n t i t y o f C5+ h y d r o c r a c k a t e t h a t i s t h e most c r i t i c a l y i e l d a f f e c t i n g economic e v a l u a t i o n s o f h y d r o c r a c k i n g catalysts. A p o r t i o n o f the hydrocracked naphtha i s u s u a l l y c a t a l y t i c a l l y reformed to produce h i g h octane gasoline. K i t t r e l l , S c o t t , and L a n g l o i s (19) p r e s e n t e d and i n t e r p r e t e d r e s u l t s showing t h e optimum r e l a t i o n s h i p between h y d r o c r a c k i n g and r e f o r m i n g . Such a r e l a t i o n s h i p c a n be u s e d i n c o n j u n c t i o n w i t h r e s u l t s of the type d e s c r i b e d here to evaluate s p e c i f i c hydrocracking catalysts. Jet Y i e l d . F i g u r e 5 shows t h e r e l a t i o n s h i p b e t w e e n t h e y i e l d o f j e t ( a r b i t r a r i l y d e f i n e d as t h e p r o d u c t b o i l i n g between 2 8 0 ° F and 5 5 0 ° F ) and the i s o to-normal r a t i o f o r the hexanes. Although there i s more v a r i a t i o n h e r e t h a n shown f o r t h e t o t a l l i q u i d y i e l d , t h i s e m p i r i c a l r e l a t i o n s h i p i s r e a s o n a b l y good f o r most o f t h e c a t a l y s t s .
order
Preferential Poisoning of Catalytic Sites. In t o show t h a t y i e l d s a n d C s - 1 8 0 ° F o c t a n e n u m b e r s
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2.
SULLIVAN
41
Catalyst Effects
A N D M E Y E R
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
• • • Ο
600 Average
Catalyst
Catalyst A Catalyst Β Catalyst F Catalyst G
650 Temperature,
700 °F
Figure 3. Effect of temperature on isobutane/n-butane hydrocracking of California gas oil
ο
T3 -a- LJa> OJ
%
—
95
—
94
—
93
Έ "
92
•σ »
91
cr
90
—
+
89
—
Ο
Rft
>- -c
I
• A • ^ • Ο
Catalyst Β Catalyst C Catalyst D Catalyst Ε Catalyst F Catalyst G
I 10
15
20
I sohexanes/n-Hexane
Figure 4. Relationship between liquid yield and isohexanes/n-hexane at 590^615°F hydrocracking of California gas oil
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
42
HYDROCRACKING
A N D HYDROTREATING
a r e d i r e c t l y r e l a t e d t o t h e hydrogénation t o a c i d i t y r a t i o , s e v e r a l experiments were made w i t h C a t a l y s t C i n which c a t a l y t i c s i t e s were p r e f e r e n t i a l l y p o i s o n e d . N i t r o g e n (as q u i n o l i n e ) was used as a p o i s o n f o r a c i d s i t e s ; s u l f u r (as d i m e t h y l d i s u l f i d e ) was used t o p o i s o n the m e t a l hydrogénation s i t e s . Admittedly, either p o i s o n may i n f l u e n c e b o t h s e t s o f c a t a l y t i c s i t e s somewhat; however, i t i s r e a s o n a b l e t o assume t h e s e s e c o n dary e f f e c t s would be r e l a t i v e l y minor. T a b l e IV shows t h e r e s u l t s . When t h e a c i d i t y i s p r e f e r e n t i a l l y p o i s o n e d by e q u i l i b r a t i n g t h e c a t a l y s t w i t h a f e e d c o n t a i n i n g 8 ppm o f n i t r o g e n , t h e f o l l o w i n g e f f e c t s are noted: (1) T o t a l l i q u i d y i e l d i n c r e a s e s by about 1 wt %\ (2) t h e j e t f u e l i n c r e a s e s by 6 LV %\ (3) t h e C5-l80°P octane number d e c r e a s e s by two numbers. When t h e hydrogénation a c t i v i t y i s p r e f e r e n t i a l l y p o i s o n e d by o p e r a t i n g w i t h 100 ppm o f s u l f u r i n t h e f e e d , (1) t h e t o t a l l i q u i d y i e l d d e c r e a s e s by about 2%; (2) t h e j e t f u e l d e c r e a s e s by 6-755; (3) t h e octane number o f t h e C s - l 8 0 F p r o d u c t i n c r e a s e s by more than t h r e e numbers. o
C a t a l y s t Aging E f f e c t s . The y i e l d s f o r most o f the c a t a l y s t s remain r e l a t i v e l y s t a b l e w i t h c a t a l y s t aging. I n c o n s t a n t c o n v e r s i o n runs such as t h e s e , t h e c a t a l y s t temperature i s i n c r e a s e d t o m a i n t a i n c o n v e r s i o n ; and y i e l d s t a b i l i t y can be shown by a p l o t o f y i e l d v e r s u s average c a t a l y s t t e m p e r a t u r e . Figure 6 shows r e s u l t s f o r two amorphous c a t a l y s t s . F i g u r e 7 shows t h e R e l a t i o n s h i p between C 5 + l i q u i d y i e l d and isohexanes/n-hexane r a t i o i n t h e temperature range 640-660°F. The r e l a t i o n s h i p i s s t i l l good f o r most o f t h e c a t a l y s t s ; t h e average C 5 + y i e l d a t a g i v e n isohexanes/n-hexane r a t i o i s perhaps 0.5% lower t h a n t h a t shown i n F i g u r e 4 f o r t h e temperature range 590-6l5°F. A n o t a b l e e x c e p t i o n t o t h e r e l a t i o n s h i p shown i n Figure 7 i s C a t a l y s t Ε with a f a u j a s i t e support. In t h e temperature span between 640°F and 660°F, t h e t o t a l l i q u i d y i e l d decreases r a p i d l y without s i g n i f i c a n t change i n t h e isohexanes/n-hexane ratio. F i g u r e 8 shows t h e r e l a t i o n s h i p s between tempera t u r e , C 5 + y i e l d , and j e t y i e l d f o r C a t a l y s t E. C 5 + y i e l d i s r e l a t i v e l y s t a b l e t o 640°F; however, a s h i f t i n p r o d u c t d i s t r i b u t i o n from j e t f u e l t o naphtha o c c u r s between 6l0°F and 640°F. Above 660°F ( o f f s c a l e i n t h e p l o t s i n F i g u r e s 7 and 8 ) , t h e C 5 + and j e t f u e l y i e l d c o n t i n u e t o d e c r e a s e rapidly. At 677°F t h e C + l i q u i d y i e l d i s 80.4 wt %; the 280-550°F j e t y i e l d i s 15.1 LV %. 5
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
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43
TABLE IV PRODUCT FROM CATALYST C WITH CALIFORNIA GAS OIL EFFECTS OF SULFUR AND NITROGEN
Isohexanes/ n-Hexane
c+ Yield, Wt %
280°F+ Yield, LV %
C -180°F Octane, F-l Clear 5
Catalyst Temperat u r e , °F
5
Before A d d i t i o n of S u l f u r or N i t r o g e n
609 640
4.9 4.7
94.3 95.2
65.3 64.7
81.0 80.0
8 ppm N i t r o g e n Added to Feed ( C a t a l y s t Equilibrated)
650
3.0
95.8
71.0
78.0
100 ppm S u l f u r Added to Feed ( A f t e r 170 Volumes of Feed Containing Sulfur)
620
12.7
92.7
58.3
84.2
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING A N D H Y D R O T R E A T I N G
100 rCatalyst Β
Λ
95 Catalyst G
ΤΤΟ 90
JL
85
600
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
550 Average
700
650
Catalyst
Temperature,
°F
+
Figure 6. Effect of temperature on C liquid yield hydrocracking of Cali fornia gas oil 5
ι *641°F
644°F^
*645°F / • Catalyst A • Catalyst Β A Catalyst C $L Catalyst C + 8 ppm Ν in Feed * Catalyst Ε • Catalyst F Ο Catalyst G
Î9°F
90h
I 652°F*
Numbers by points for Catalyst Ε indicate temperatures.
l_
5
I
I
10
15
I sohexanes/n-Hexane +
Figure 7. Relationship between C yield and isohexanes/n-hexane 640^-660°F 5
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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A N D
M E Y E R
Catalyst Effects
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
2.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
45
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
46
HYDROCRACKING AND HYDROTREATING
The y i e l d s h i f t s f o r t h e s e f a u j a s i t e - c o n t a i n i n g c a t a l y s t s a r e a c c o m p a n i e d by a b u i l d u p o f h i g h b o i l i n g m a t e r i a l (650°F+) i n the l i q u i d r e c y c l e stream. The s h a p e s e l e c t i v e p r o p e r t i e s o f t h e a g e d f a u j a s i t e c a t a l y s t appear to a f f e c t the product d i s t r i b u tion. Composition o f the r e c y c l e stream i n d i c a t e s the r a t e o f r e a c t i o n o f the higher b o i l i n g molecules i s very low. Because h i g h m o l e c u l a r weight molecules d i d c r a c k more r e a d i l y i n t h e e a r l y p a r t o f t h e r u n , t h i s r e s u l t suggests that deposits o f carbonaceous m a t e r i a l ("coke") cause p a r t i a l p l u g g i n g o f the c a t a l y s t p o r e s . T h e r e f o r e , the l a r g e r m o l e c u l e s have l i m i t e d access t o catalytic sites. The h i g h r a t e o f c o k i n g i n a n a r r o w t e m p e r a t u r e r a n g e may b e r e l a t e d t o t h e h y d r o g e n a t i o n d e h y d r o g e n a t i o n e q u i l i b r i a o f c e r t a i n p o l y c y c l i c compounds w h i c h , i f d e h y d r o g e n a t e d , a r e w e l l known c o k e precursors. The r a t e o f c a t a l y s t d e a c t i v a t i o n , a s m e a s u r e d b y the temperature increase r e q u i r e d to m a i n t a i n convers i o n , does n o t i n c r e a s e a p p r e c i a b l y d u r i n g t h e p e r i o d that the y i e l d s h i f t occurs. The c a t a l y s t r e m a i n s a c t i v e f o r the c r a c k i n g o f r e l a t i v e l y low b o i l i n g molecules. However, the low y i e l d o f p r o d u c t i n the j e t b o i l i n g range i n d i c a t e s t h a t , at the c o n v e r s i o n l e v e l s u s e d , much i n i t i a l p r o d u c t f r o m t h e j e t b o i l i n g range i s f u r t h e r c r a c k e d t o naphtha and l i g h t g a s e s . The s e c o n d a r y c r a c k i n g o f p r o d u c t i n t h e j e t r a n g e may be t h e r e s u l t o f s e v e r a l f a c t o r s : ( 1 ) The r a t e s o f d i f f u s i o n o f j e t p r o d u c t o u t o f t h e c a t a l y s t may b e s l o w due t o t h e p a r t i a l p o r e p l u g g i n g . The l o n g e r r e s i d e n c e t i m e o f t h e j e t p r o d u c t p e r m i t s much s e c o n dary c r a c k i n g . (2) P a r t i a l p o r e p l u g g i n g does n o t a l l o w a s many o f t h e h i g h e r b o i l i n g r e a c t a n t m o l e c u l e s to reach the c a t a l y t i c s i t e s . Therefore, there i s l e s s c o m p e t i t i o n f o r c a t a l y t i c s i t e s ; and the apparent r a t e o f r e a c t i o n o f m o l e c u l e s i n t h e j e t r a n g e may increase. The c a t a l y s t a g i n g e f f e c t s s h o w n b y t h i s f a u j a s i t e c o n t a i n i n g c a t a l y s t a p p e a r t o be a g e n e r a l phenomenon; s i m i l a r e f f e c t s have been o b s e r v e d i n o u r l a b o r a t o r i e s w i t h o t h e r f e e d s t o c k s and o t h e r z e o l i t e containing catalysts. Other examples have been reported i n the patent l i t e r a t u r e (20). T h i s c a t a l y s t a g i n g p r o p e r t y does n o t n e c e s s a r i l y make s u c h a c a t a l y s t u n a t t r a c t i v e . R a t h e r , i t may l i m i t the temperature span i n which a d e s i r e d product d i s t r i b u t i o n c a n be o b t a i n e d . W i t h most amorphous c a t a l y s t s , a run i s u s u a l l y terminated at the p o i n t at which c a t a l y s t a c t i v i t y and s t a b i l i t y are sufficiently l o w t h a t c o n t i n u a t i o n o f t h e r u n i s no l o n g e r
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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attractive. the product
With c e r t a i n z e o l i t e - c o n t a i n i n g d i s t r i b u t i o n may b e t h e l i m i t i n g
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Results With Mid-Continent
47
Catalyst Effects
catalysts, factor.
Gas O i l
C a t a l y s t C and C a t a l y s t G were compared f o r t h e h y d r o c r a c k i n g o f t h e M i d - C o n t i n e n t gas o i l a t 4 0 0 ° F r e c y c l e c u t p o i n t w i t h n a p h t h a as t h e m a j o r p r o d u c t . Table I l i s t s the p r o p e r t i e s o f the h y d r o f i n e d f e e d ; T a b l e V shows y i e l d s a n d p r o d u c t p r o p e r t i e s a t comparable c o n d i t i o n s , and T a b l e V I g i v e s d e t a i l e d chromatographic analyses of representative Cs-l80°F products. The t r e n d s a r e g e n e r a l l y t h e same a s t h o s e a t t h e h i g h e r c u t p o i n t w i t h C a l i f o r n i a g a s o i l . The c a t a l y s t w i t h the higher r a t i o of h y d r o g é n a t i o n a c t i v i t y to a c i d i t y , C a t a l y s t C , p r o d u c e s more C 5 + n a p h t h a ; t h e more h i g h l y a c i d i c c a t a l y s t , C a t a l y s t G , y i e l d s p r o d u c t w i t h a h i g h e r octane number. Conclusions Most d u a l f u n c t i o n a l h y d r o c r a c k i n g c a t a l y s t s e x h i b i t an i n v e r s e r e l a t i o n s h i p between C5+ l i q u i d and t h e P - l c l e a r o c t a n e number o f t h e C 5 - C 6 p r o d u c t . P r e f e r e n t i a l p o i s o n i n g o f e i t h e r the a c i d s i t e s or the hydrogenation-dehydrogenation c a t a l y t i c sites indicates t h a t b o t h the y i e l d s and octanes are r e l a t e d t o the r a t i o o f h y d r o g é n a t i o n t o a c i d i t y p r o v i d e d by t h e c a t a lyst. A h i g h r a t i o favors h i g h l i q u i d y i e l d s ; a low r a t i o favors h i g h octane product. Some m o d e s t c h a n g e s i n t h e r e l a t i o n s h i p b e t w e e n C5+ y i e l d a n d l i g h t n a p h t h a o c t a n e number o c c u r as c a t a l y s t temperature i s i n c r e a s e d . Also, with certain aged c a t a l y s t s s u c h as t h o s e c o n t a i n i n g f a u j a s i t e , changes i n c a t a l y s t geometry b r o u g h t about by p o r e p l u g g i n g due t o c a r b o n a c e o u s d e p o s i t s may c a u s e s u b s t a n t i a l d e v i a t i o n s from t h i s r e l a t i o n s h i p . Acknowledgment The a u t h o r s w i s h t o t h a n k M e s s r s . G . E . and C. J . Egan f o r t h e i r h e l p f u l s u g g e s t i o n s the course of t h i s work.
Langlois during
Abstract Yields and product properties in hydrocracking are influenced by the relationship between catalyst acidity and the hydrogenation-dehydrogenation activity of the
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
48
HYDROCRACKING A N D H Y D R O T R E A T I N G
TABLE V Y I E L D S AND PRODUCT PROPERTIES FROM HYDROCRACKING OF MID-CONTINENT GAS O I L 60% PER PASS CONVERSION BELOW 4 0 0 ° F Catalyst Average C a t a l y s t
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
No L o s s P r o d u c t ( B a s e d on F r e s h
Temp.,
°F
G 632 Wt % L V %
Yields Feed) 0.02 0 . 04 1.7 7.5 2.1 19.1 33-6 38.1
Methane Ethane Propane Isobutane n-Butane C -l80°F 180-280°F 280-400°F 5
90.8
Total C -400°F 5
Chemical Hydrogen Consumption, SCF/B Product
C 6:!4 Wt % L V %
0.03 0.09 2.4 11.4 9-5 2.9 3-1 2 4 . 8 21.3 39-0 3 3 . 2 4 1 . 9 32.9 105.7
1220
14.4 4.2 27.7 38.2 35.9 101.8
87.4 1245
Properties
C -180°F 5
Octane N o . , F - l C l e a r
81.1
85.7
45.3
55.2
40.5 59.0 0.5
37.8 56.1 6.1
220/236 242/264 288 318/356 368/408
214/228 235/255 279 309/350 365/407
l80-400°F Octane N o . , F - l C l e a r Type A n a l y s i s , LV % Paraffins Naphthenes Aromatics ASTM D 86 Distillation, St/5 10/30 50 70/90 95/EP
°F
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
SULLIVAN
A N D M E Y E R
Catalyst Effects
TABLE V I D I S T R I B U T I O N OF C - l 8 0 ° F PRODUCT FROM HYDROCRACKING OF MID-CONTINENT GAS O I L 5
Catalyst Average C a t a l y s t Temperature, °F
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
Product,
Paraffins
Cycloparaffins
642
0.8 36.6 8.7 0.3 2.9
Aromatics
0.2
44.6 3.5
16.9 10.1
0.1 3.8 19.5 11.2
87.4
88.3
0.5 1.7
0.5 8.4 0.7 1.5
0.4
0.2
12.6
11.3
6.6 4.5
9.1
0.9
-
Benzene Total
627 5
Cyclopentane MethyIcyclopentane Cyclohexane Dlmethylcyclopentanes, Ethylcyclopentane MethyIcy clohexane Total
G
LV % o f C - l 8 0 ° F
Butanes Isopentane n-Pentane 2 . 2 - DimethyIbutane 2.3- DlmethyIbutane 2- Methylpentane 3- M e t h y l p e n t a n e n-Hexane Isoheptanes Total
C
-
1.8 3.6
0.3 0.3
81.3
85-7
Isopentane/n-Pentane
4.2
12.7
Isohexanes/n-Hexane
4.6
19.2
Octane
No., F - l Clear
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
50
HYDROCRACKING AND HYDROTREATING
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
dual functional catalysts employed. Hydrocracking catalysts can be tailored to meet specific refining objectives. In this paper both amorphous and crys talline catalysts of varying acidity and hydrogenation activity are examined at constant process conditions for (1) producing both jet fuel and gasoline and (2) producing gasoline as the major product. In general, as the hydrogenation activity of the catalyst is increased relative to its acidity, total liquid product (C5+) yield increases; and the octane number of the light naphtha (C5-C6) decreases. The reverse is also true. If either the acidity or hydrogenation activity is preferentially poisoned, the change is reflected in the yields and the C5-C6 octane number. Literature Cited 1. 2. 3. 4. 5. Vol 6. 7. 8. 9. 10. 11. 12. 13.
Scott, J . W., and Kittrell, J. R., Ind. Eng. Chem. (1969), 61, 18. Baral, W. J., and Huffman, H. C., World Petroleum Congress, Preprint PD 12 (1), (1971). Hansford, R. C., U.S. Patent 3,499,835 (March 10, 1970). Beuther, Η., and Larson, O. Α., Ind. Eng. Chem. Proc. Design Dev. (1965), 4, 177. Voorhies, Α., and Smith, W. Μ., Chapter in "Advances in Petroleum Chemistry and Refining," 8, ρ 1693 Interscience Publishers, New York (1964). Larson, O. Α., MacIver, D. S., Tobin, H. H., and Plinn, R. Α., Ind. Eng. Chem. Proc. Design Dev. (1962), 1, 300. Langlois, G. E., Sullivan, R. F., and Egan, C. J., J. Phys. Chem. (1966), 70, 3666. Doane, E. P., Preprints, Div. Petroleum Chem., (1967), ACS 12, (4), B-139. Coonradt, H. L., and Garwood, W. E., Ind. Eng. Chem. Proc. Design Dev. (1964), 3, 38. Langlois, G. E., and Sullivan, R. F., Advances in Chemistry Series No. 97, "Refining Petroleum for Chemicals," Chapter 3, p 38, ACS (1970). Beuther, H., McKinley, J. Β., and Flinn, R. Α., Preprints, Div. Petroleum Chem., (1961), ACS 6, (3), A-75. Coonradt, H. L., Ciapetta, F. G., Garwood, W. Ε., Leaman, W. Κ., and Maile, J. N., Ind. Eng. Chem. (1961), 53, 727. Coonradt, H. L., Leaman, W. Κ., Maile, J. Ν., Preprints, Div. Petroleum Chem., (1964), ACS 9, (1), 59.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2. 14. 15. 16. 17. 18. 19.
AND
MEYER
Catalyst Effects
51
Coonradt, H. L., and Garwood, W. Ε . , Preprints, D i v . P e t r o l e u m Chem., ( 1 9 6 7 ) , ACS 12 (4), B - 4 7 . S c h u l z , H., and Weitkamp, J., I n d . Eng. Chem. Prod. Res. Develop., ( 1 9 7 2 ) , 11 ( 1 ) , 46. Myers, C. G., Garwood, W. Ε . , Rope, B. W., W a d l i n g e r , R. L., and Hawthorne, W. P., J. Chem. Eng. Data ( 1 9 6 2 ) , 7 , 257. Egan, C. J., L a n g l o i s , G. Ε . , and White, R. J., J . Am. Chem. Soc., ( 1 9 6 2 ) , 84, 1204. S u l l i v a n , R. F., Egan, C. J., and L a n g l o i s , G. E . , J . C a t a l y s i s ( 1 9 6 4 ) , 3 , 183. Kittrell, J . R., L a n g l o i s , G. E . , and S c o t t , J . W., Hydrocarbon P r o c e s s ( 1 9 6 9 ) , 48, (5), 116. Hanson, F. V., and Snyder, P. W., U.S. P a t e n t 3 , 5 2 3 , 8 8 7 (August 1 1 , 1 9 7 0 ) .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch002
20.
SULLIVAN
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3 Raflinate Hydrocracking with Palladium-NickelContaining Synthetic Mica-Montmorillonite Catalysts JOSEPH P. GIANNETTI and DONALD C. FISHER
a
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
Gulf Research and Development Co., P. O. Drawer 2038, Pittsburgh, Penn. 15230
The demand for liquefied petroleum gas (LPG; consisting of propanes and butanes) is projected to increase rapidly in future years.(1) World consumption is dominated by the United States and Japan. Processing of natural gas accounts for the bulk of domestic LPG; however, natural gas production has leveled off forcing the LPG industry to examine other feedstock sources. Japan must look to other countries for future LPG supplies due to environmental and space limitations. An allied problem, especially in the United States, is the continuing need for isobutane to produce valuable alkylates for the gasoline pool. A recent publication(2) disclosed the use of a palladium— impregnated, nickel-exchanged synthetic mica-montmorillonite catalyst (Pd-Ni-SMM), a 2:1 layer lattice aluminosilicate clay, for the hydrocracking and hydroisomerization of various hydrocarbons including a raffinate fraction to predominately propane and butanes. The results showed that these SMM based catalysts exhibited hydrocracking and hydroisomerization activities greater than could be obtained with Pd-rare earth-zeolite or Pd-H— mordenite. It had earlier been shown that SMM had greater cracking activity than silica-alumina but less than Y zeolite. (_3) The greater activity for cracking over the silica-alumina may be due to the increased lability of the hydrogen atoms in SMM.(4) Our study was undertaken specifically to investigate the processing of a typical raffinate to produce either high yields of LPG or isobutane as well as to determine the octane improvement in the fraction due to hydroisomerization. A 0.7 wt % Pd-15 wt % Ni-SMM catalyst was used for all the experimentation. Experimental A l l u n i t s are expressed i n both the customary u n i t s as w e l l as the "SI" I n t e r n a t i o n a l System of U n i t s . The "SI" designated i s shown f i r s t followed by the customary u n i t s i n p a r e n t h e s i s . (a) Present Address - Alcoa Research L a b o r a t o r i e s , New Kensington, PA 15068
52
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3.
GiANNETTi
A N D FISHER
53
Raffinate Hydrocracking
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
Materials. The r a f f i n a t e used i n t h i s study was obtained from a commercial Gulf O i l Corporation r e f i n i n g run and used as received. The composition of t h i s r a f f i n a t e i s shown i n Table I . The 15 wt % Ni-exchanged SMM c a t a l y s t s were obtained from the Baroid D i v i s i o n of NL I n d u s t r i e s . The carbon d i s u l f i d e was obtained from F i s h e r S c i e n t i f i c while the palladium tetramined i n i t r a t e reagent (36.5 wt % palladium) was purchased from Matthey Bishop C o r p o r a t i o n . Hydrogen s u l f i d e was obtained from the Matheson Gas Company. A l l the chemical reagents were used as r e c e i v e d . Hydrogen, supplied by the A i r Reduction Company, was deoxygenated and d r i e d over Linde 13X molecular s i e v e s . C a t a l y s t P r e p a r a t i o n and Processing Procedure. The 15 wt % Ni-SMM c a t a l y s t was impregnated with the palladium tetramined i n i t r a t e reagent by the i n c i p i e n t wetness technique to r e s u l t i n the i n c o r p o r a t i o n of 0.7 wt % p a l l a d i u m . Since the 15 wt % nickel-exchanged SMM c a t a l y s t was obtained from the Baroid D i v i s i o n of NL I n d u s t r i e s , no exact d e t a i l e d synthesis was ob t a i n e d ; however, a t y p i c a l synthesis from our l a b o r a t o r i e s has been d e t a i l e d . ( 2 ) A l l c a t a l y s t s were e i t h e r reduced or s u l f i d e d p r i o r to use. Approximately 50 cm of c a t a l y s t d i l u t e d w i t h 50 cm quartz was used for each r u n . The r e d u c t i o n c o n s i s t e d of 1) t r e a t i n g the c a t a l y s t with 3.5 χ 1 0 kmol H2/hr (2.9 SCF H2/hr) at atmospheric pressure while heating to 538°C (1000 F) at a r a t e of 6 5 . 6 ° C / h r ( 1 5 0 ° F / h r ) , 2) h o l d i n g at 5 3 8 ° C ( 1 0 0 0 ° F ) with the hydrogen flow f o r 1 hour, and 3) c o o l i n g to room temperature with a small n i t r o g e n flow. The s u l f i d i n g c o n s i s t e d of 1) heating the c a t a l y s t to 3 1 6 ° C ( 6 0 0 ° F ) i n n i t r o g e n , 2) s u l f i d i n g for 3 hours at 3 1 6 ° C ( 6 0 0 ° F ) with 3.6 χ 10" kmol/hr (3 SCF/hr) of a 92% H2-8% H2S gas mix, and 3) c o o l i n g i n n i t r o g e n to room temperature. The Ni-SMM c a t a l y s t s received contained e i t h e r about 1 wt % or 0.6 wt % f l u o r i d e . Some i n i t i a l processing com parisons d i d not show one to be s i g n i f i c a n t l y d i f f e r e n t from the other. Thus, no separation of the runs by f l u o r i d e l e v e l ap peared necessary. Processing runs were conducted i n a fixed-bed automated u n i t employing a 2.54 cm (1-inch) ID r e a c t o r i n r o u n d - t h e - c l o c k operations. Operating c o n d i t i o n s were 316" to 399 C (600" to 7 5 0 ° F ) , 7,000 k i l o p a s c a l s : kPa (1,000 l b / s q i n gauge: p s i g ) , 1.2 to 2 l i q u i d hourly space v e l o c i t y (LHSV) defined as cm of hydro carbon feed per cm of c a t a l y s t per hour, and 5 hydrogen-tohydrocarbon mole r a t i o (to c a l c u l a t e t h i s r a t i o , the feed was assumed to have a molecular weight of 92). Temperatures were measured by thermocouples extending through the c a t a l y s t bed. S u l f u r , i n the form of carbon d i s u l f i d e , was added to the r a f f i n a t e to give the d e s i r e d s u l f u r l e v e l . The l i q u i d feed was combined with hydrogen, preheated, and passed downflow through the c a t a l y s t . The e f f l u e n t from the reactor entered a high pressure separator where a hydrogen-rich gas sample was taken. The hydrocarbon product from the separator flowed i n t o a 3
3
- 3
3
U
3
3
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
Table I RAFFINATE ANALYSIS
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
Component
Wt %
Isopentane
0.2
n-Pentane
0.2
Hexane Isomers
19.8
n-Hexane
14.6
Methylcyclopentane
4.6
Cyclohexane
0.4
Benzene
1-0
Heptane Isomers
31.5
n-Heptane
9.7
Dimethylcyclopentane
0.5
Cg and Heavier
17.5
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3.
GiANNETTi
A N D FISHER
Raffinate Hydrocracking
55
s t a b i l i z e r where a C4 and l i g h t e r gaseous product and a C5 and heavier l i q u i d product were taken. The gaseous products were metered and sampled, while the l i q u i d product was c o l l e c t e d , weighed, and sampled.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
Analyses. Hydrocarbon analyses for the gaseous products were made using a 1200 Varian gas chromatograph with a 30.5 m (100 f t ) support coated open tubular squalene c a p i l l a r y and a 21-104 Consolidated Electrodynamics Corp. mass spectrometer. T h i s combination a n a l y s i s was necessary i n order to a c c u r a t e l y determine both the hydrogen and hydrocarbon content of the gas as w e l l as a d e n s i t y . The l i q u i d samples only r e q u i r e d analyses by the c a p i l l a r y column gas chromatograph. Micro Research octane numbers were obtained using the s t a n dard CFR (Cooperative F u e l Research) knock r a t i n g u n i t . Results and D i s c u s s i o n Previous r e s u l t s ( 2 ) had shown that a Pd-Ni-SMM c a t a l y s t was e f f e c t i v e f o r hydrocracking hexane as w e l l as a r a f f i n a t e feed. Conclusions showed that t h i s c a t a l y s t system when c o n t a i n i n g two n i c k e l atoms per u n i t c e l l (15 wt % n i c k e l ) was approximately 15 times more a c t i v e than a P d - r a r e earth-Y z e o l i t e c a t a l y s t and 1.2 times more a c t i v e than Pd-H-mordenite. T h i s same c a t a l y s t system (0.7 wt % Pd-15 wt % Ni-SMM) was chosen for our r a f f i n a t e processing s t u d i e s . Comparison of S u l f u r - C o n t a i n i n g and S u l f u r - F r e e Systems. Our i n i t i a l experimentation was designed to show the e f f e c t s of a scheme c o n t a i n i n g l a r g e amounts of s u l f u r as opposed to a completely s u l f u r - f r e e system. This experimentation was p e r formed with a s u l f i d e d 0.7 wt % Pd-15 wt % Ni-SMM c a t a l y s t (hereafter r e f e r r e d to Pd-Ni-SMM c a t a l y s t ) using a r a f f i n a t e feed c o n t a i n i n g 1500 ppm s u l f u r and a hydrogen reduced Pd-Ni-SMM c a t a l y s t with a s u l f u r - f r e e feed. The LPG y i e l d s are presented i n F i g u r e 1 with the average product component d i s t r i b u t i o n s at 3 7 1 ° C ( 7 0 0 ° F ) presented i n Table I I . These r e s u l t s showed that the s u l f u r - c o n t a i n i n g system was more a c t i v e f o r hydrocracking but experienced aging e s p e c i a l l y at the elevated temperatures. The isobutane y i e l d was constant i n both systems r e s u l t i n g i n s i g n i f i c a n t l y higher 1 0 4 / ^ 4 and ÎC4/LPG volume r a t i o s i n the s u l f u r - f r e e system. Although converting more of the feed, the s u l f u r - c o n t a i n i n g system produced s i g n i f i c a n t l y l e s s C^ + C2 than the s u l f u r - f r e e system. Various Methods of I n c o r p o r a t i n g S u l f u r . The g e n e r a l l y poorer r e s u l t s f o r LPG from the s u l f u r - f r e e system i n d i c a t e d that s u l f u r should be incorporated at l e a s t somewhere i n the p r o c e s s i n g system. To determine whether best r e s u l t s are obtained with s u l f i d i n g o n l y , s u l f u r feed a d d i t i o n o n l y , or b o t h , a s e r i e s
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING A N D H Y D R O T R E A T I N G
1
1
1
I
—ι
r - ••• 399 ° C
100
(750°F)
3* g
·-·
90
\
371 ° C ( 7 0 0 ° F)
Ο °
0
-
•
ΟΟ-ο °
343 ° C ( 6 5 0 ° F)
ι 0
ο
I
I
ι
I
100
200
ι 300
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
HOURS PROCESSING
Figure 1. Effect of sulfur in Pd-Ni-SMM raffinate hydrocracking. 7000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. Feed—O* ff^~ note; Φ, raffinate + 1500 ppm sulfur. Catalyst—O, reduced 0.7 wt % — 15 wt % Ni-SMM; · , sulfided 0.7 wt% -15wt% Nir-SMM. ra
Table I I EFFECT OF SULFUR IN Pd-Ni-SMM RAFFINATE HYDROCRACKING Average Product D i s t r i b u t i o n s at 371°C ( 7 0 0 ° F ) , 7,000 kPa (1,000 p s i g ) , 2 LHSV, 5 Hydrogen-toHydrocarbon Mole Ratio
Vol % Y i e l d Based on Feed
Component Methane + Ethane (Wt %)
Sulfur Containing
Sulfur Free
3.2
4.7
Propane
46.8
37.5
Isobutane
28.4
28.5
n-Butane
18.9
11.7
C5 and Heavier
27.0
37.2
C3/C4 Ratio
1.0
0.93
iC^/nC^ Ratio
1.5
2.4
i C / L P G Ratio
0.30
0.37
4
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3.
GIANNETTI
57
Raffinate Hydrocracking
A N D FISHER
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
of c a t a l y s t s was treated and t e s t e d . The r e s u l t s are presented i n Table I I I . The f i r s t two runs (A and B) have already been discussed (Figure 1, Table II) and show the e f f e c t of a s u l f u r f r e e system and a s u l f i d e d c a t a l y s t along w i t h s u l f u r doping of the feed. Run C shows that a reduced c a t a l y s t with s u l f u r i n the feed ( i n - s i t u s u l f i d i n g ) was g e n e r a l l y comparable to a s u l f i d e d c a t a l y s t with the feed s u l f u r (Run Β with compensation made f o r aging). F i n a l l y , a s u l f i d e d c a t a l y s t (Run D) with no feed s u l f u r , while a c t i v e , produced high C3 and C i + C2 y i e l d s . I t appears from t h i s that whether the c a t a l y s t was reduced or s u l f i d e d had l i t t l e e f f e c t on product d i s t r i b u t i o n i f s u l f u r was present i n the feed. E f f e c t of Feed S u l f u r L e v e l on S u l f i d e d C a t a l y s t s . The im portance of s u l f u r i n the feed l e d to examining v a r y i n g s u l f u r levels. P r i o r to t h i s i n v e s t i g a t i o n , a l l s u l f u r doping was at the 1500 ppm l e v e l . During t h i s i n v e s t i g a t i o n an extended run was made i n which the s u l f u r i n the feed was incorporated at 0 ppm, 75 ppm, 200 ppm, and f i n a l l y 500 ppm. The r e s u l t s are presented i n Figures 2, 3, and 4. Looking f i r s t at F i g u r e 2, i t can be seen that the e n t i r e product d i s t r i b u t i o n remained constant at a high 108 v o l % LPG l e v e l through the 200 ppm doping. When the s u l f u r l e v e l increased to 500 ppm, however, pronounced aging began. This aging was accompanied by a de crease i n C 3 , n C 4 , and C^ + C2 y i e l d s , and an increase i n 1C4 and C5+ y i e l d s . A c t u a l l y , i f one assumes that i C 4 i s the most v a l u a b l e hydrocracked product, the d i s t r i b u t i o n became more favorable as the c a t a l y s t aged. This i s more d r a m a t i c a l l y shown i n F i g u r e 3 where v a r i o u s product r a t i o s are presented. The increase i n 1C4 accompanied by decreases i n the nC4 and C3 y i e l d s brought about a more favorable C 3 / C 4 , i C 4 / n C 4 and 1C4/LPG r a t i o s . T h i s i n d i c a t e s that the LPG composition can probably be a l t e r e d with processing s e v e r i t y . Thus i f one wished to produce maximum per pass C 3 , high processing s e v e r i t y should be employed while i f 1C4 y i e l d i s to be maximized, a lower processing s e v e r i t y would be i n o r d e r . No mention has yet been made of the C 5 m a t e r i a l . Since the feed was e s s e n t i a l l y C 6 , the C 5 s were formed from h y d r o c r a c k i n g ; however, they have been included i n with the C 6 m a t e r i a l s i n c e they would not normally be separated out but would e i t h e r be r e c y c l e d with the C 6 for f u r t h e r h y d r o c r a c k i n g , o r , i n a oncethrough o p e r a t i o n , be perhaps added with the C 6 to the g a s o l i n e pool. One t h i n g that occurred to both the C 5 s formed and to the remaining C 6 s was that there was a high r a t i o of the branched isomers to t h e i r normal c o u n t e r p a r t s . These r e s u l t s are i n keeping with those of Swift and Black(_2) who showed that Pd-Ni-SMM c a t a l y s t s are very e f f e c t i v e f o r h y d r o i s o m e r i z a t i o n . F i g u r e 4 d e t a i l s the i C 5 / n C 5 and i C 5 / n C 6 r a t i o s . The i C 5 / n C 5 r a t i o was r e l a t i v e l y constant at about 2.4 i n the product while the iCfc/nCfc r a t i o increased from a feed l e v e l of 1.4 to between +
+
f
+
+
+
f
?
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
(1,000 F ) , No S u l f u r
(1,000 F ) , 1500 ppm S u l f u r 5.2
2.2
26.8
31.8
28.4 (33)
28.5
1C4
18.0
16.8
18.9 (20)
11.7
nC/,
107.8
99.8
94.1 (106)
77.7
T o t a l LPG
Volume % Y i e l d
p r i o r to aging.
63.0
51.2
(a) Numbers i n parenthesis estimated at i n i t i a l throughputs
(D) S u l f i d i n g (600 F ) , No S u l f u r
(C) Reduction
46.8 (53)
3.2 (2.6) U )
Ç3 37.5
2
4.7
Ci + C
Wt % Y i e l d
371°C (700°F), 7,000 kPa (1,000 p s i g ) , 2 LHSV 5 Hydrogen-to-Hydrocarbon Mole Ratio 0.7 Wt % Pd-15 Wt % Ni-SMM
(B) S u l f i d i n g (600 F ) , 1500 ppm S u l f u r
(A) Reduction
C a t a l y s t Treatment
Catalyst —
Conditions —
EFFECT OF VARIOUS MEANS OF INCORPORATING SULFUR ON HYDROCRACKING
Table I I I
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
5
+
14.1
22.9
27.0 (18)
37.2
c
ο >
§5
GiANNETTi
Raffinate Hydrocracking
A N D FISHER
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I
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i Ο-οΌθΌ-ΟΟ-Ο-Ο-αο-0-Ο-ΟΟ
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5
+
V O L
*
VOL%
n C VOL%_| 4
Cj + CgWT%
J
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ι
105 Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
0 PPM S
I
' 75 PPM S 200
'
* \
200 PPM SI 500 PPM S ^
I
300
700
400
HOURS PROCESSING
Figure 2. Effect of sulfur level in product yields from hydro cracking. 371°C (700°F), 7,000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. 0.7 wt % Pd — 15 wt % Ni-SMM, sulfided.
O 0.4 <
Œ
'
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1
75
PPM S
! 100
' |200
\
I
200
300
500 PPM S ^OO^o
PPM S Q ^
!
400
500
600
700
HOURS PROCESSING
Figure 3. Effect of sulfur level in product ratios from hydrocracking. 37ΓC (700°F), 7000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. 0.7 wt% Pd — 15 wt % Nir-SMM, sulfided.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
60
HYDROCRACKING A N D H Y D R O T R E A T I N G
3 and 5 i n the product. The maximum iC6/nC6 r a t i o occurred when the s u l f u r l e v e l was at 75 ppm and 200 ppm s u l f u r . An increase i n the C5"*" octane number most l i k e l y d i d occur. A d d i t i o n a l i n formation on t h i s C 5 upgrading i s presented l a t e r i n conjunction with the production of maximum isobutane y i e l d s .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
+
E f f e c t of Feed S u l f u r L e v e l on a Reduced C a t a l y s t . I t has been shown i n Table I I I that g e n e r a l l y comparable r e s u l t s were obtained with a sulfur-doped feed and e i t h e r a reduced or s u l fided catalyst. To see i f the reduced c a t a l y s t had the same response to s u l f u r l e v e l as the s u l f i d e d c a t a l y s t shown i n Figure 2, a run was performed with a 200 ppm and 500 ppm s u l f u r level. Results are presented i n F i g u r e 5 where comparisons are made to the s u l f i d e d c a t a l y s t . Since the reduced c a t a l y s t was not run at 0 and 75 ppm s u l f u r , the data are l i n e d up at the comparable s u l f u r l e v e l s but not throughputs. The reduced c a t a l y s t followed the same p a t t e r n as the s u l f i d e d c a t a l y s t , i.e., no n o t i c e a b l e aging at 200 ppm but aging at 500 ppm. Expectedly, the reduced c a t a l y s t became s u l f i d e d during the i n i t i a l p r o c e s s i n g stages. The i n d i c a t i o n that the s u l f i d e d c a t a l y s t was more a c t i v e should not be considered s i g n i f i c a n t since a 3 to 4 v o l % d i f f e r e n c e i n LPG y i e l d could e a s i l y be due to s l i g h t f l u c t u a t i o n s i n the processing c o n d i t i o n s . Isobutane P r o d u c t i o n . The importance of isobutane domes t i c a l l y prompted experimentation aimed at maximizing the i s o butane y i e l d . I n d i c a t i o n s had been obtained from Figures 2 and 3 and discussed p r e v i o u s l y that as the c a t a l y s t aged, isobutane y i e l d s increased (at the expense of propane). I t appeared l i k e l y that processing at l e s s severe c o n d i t i o n s would be b e n e f i c i a l towards i n c r e a s i n g isobutane y i e l d s . Several runs i n the 3 1 8 ° - 3 2 9 ° C ( 6 0 5 ° - 6 2 5 ° F ) , 1.2-2 LHSV range were performed. Results as presented i n Figures 6 and 7, show that high y i e l d s of isobutane, as high as 50 v o l %, can be obtained. In comparing the r e s u l t s from Figure 6 with F i g u r e 2 from the more severe c o n d i t i o n s f o r LPG maximization, the i n creased y i e l d of isobutane was p r i m a r i l y at the expense of propane with η - b u t a n e y i e l d s being v i r t u a l l y i d e n t i c a l at the two c o n d i t i o n s . I t i s p o s s i b l e that other sets of c o n d i t i o n s , for example, 307°C (585 F) and 1 LHSV would produce even higher LPG y i e l d s . In t h i s processing to maximize isobutane y i e l d s , a s i g n i f i cant amount of normally l i q u i d product remained ( e . g . 40 v o l % based on f e e d ) . The i s o - t o - n o r m a l r a t i o s from the C 5 s and C 6 s are presented i n F i g u r e 8. The same type r e l a t i o n s h i p as p r e v i o u s l y shown i n F i g u r e 4 for LPG maximization r e s u l t e d , e . g . , a high iC5/nC5 r a t i o and a iCfc/nCô r a t i o of 4-5 as compared to 1.4 f o r the feed. The r e s u l t s i n d i c a t e d that t h i s total f r a c t i o n should have a s i g n i f i c a n t l y higher octane number than the C 6 feed. This was indeed the case as the product C^ " RON, f
+
!
4
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Raffinate Hydrocracking
GiANNETTi A N D F I S H E R
1
1
1 75
0 PPM S
I
ι
Ρ RM S
I 200 PPM
I
I
S
500 PPM S
ι
' i C c / n C e , FEED= 1.4
1 5.0
l°
1
-°°o
o°
1
o 4.0
° ο ο I ϋ
ο
%
i :t -
ι
Ο
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
3.0
• · ι'· · · · · · A
2.0
-
·
·
r
1
·
'C MC 5
ι 0
I
100
200
300
I
ι
ι 500
400
1
·
S
600
1
1
700
HOURS PROCESSING
Figure 4. Effect of sulfur level on isomer distribu tions. 371°C (700°F), 7000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. 0.7 wt % Pd — 15wt% Nir-SMM, sulfided.
I·
0 PPM S
·
Ο
75 PPM S
j 200 PPM S 25
300
Ο
, 500 PPM S
100 400
200 500
300 600
HOURS PROCESSING
Figure 5. Effect of sulfur level and catalyst treatment on LPG yields from hydrocracking. 371°C (700°F), 7000 kPa (1000 psig), 2 LHSV, 5 hydrogen-to-hydrocarbon mole ratio. O, reduced 0.7 wt % Pd- 15wt% Ni-SMM; m, sulfided 0.7 wt % Pd - 15 wt % Ni-SMM.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING
AND
HYDROTREATING
o—O—v.
50h
•
•"
40
o—o-
O >
329 °C ( 6 2 5 ° F),
329 °C ( 6 2 5 ° F),
318 ° C ( 6 0 5 ° F),
1.2 LHSV
1.2 LHSV
2 LHSV
g
9
20
9 •
C
3
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
50
O
i C
4 3
n
C
100
4 •
C
5
C^C =
+
2
150
200 HOURS
~
·
0.8 to 1.2 WT % T H R O U G H O U T
250
300
350
400
PROCESSING
Figure 6. Product distribution in hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Ni-SMM, sulfided.
329 °C ( 6 2 5 ° F ) , 2 LHSV
318 °C (605 ° F ) . 1.2 LHSV
329 °C (625 ° F ) , 1.2 LHSV
150
200
250
300
350
400
HOURS PROCESSING
Figure 7. Product ratios in hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Nir-SMM, sulfided.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
GIANNETTT
Raffinate Hydrocracking
A N D FISHER
329 ° C (625 ° F ) ,
329 °C (625 ° F ) ,
318 ° C (605 ° F ) ,
1.2 L H S V
1.2 LHSV
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
2 LHSV τ
τ-
1
—ι
1
r—
iCg/nCg, F E E D = 1.4
5.0
Ο — Ο
Ο Ο
Ο
Ο
O
4.0
3.0
iC /nC 5
~°
•
5
• •
• é
2.0
0
•
50
·
100
150
200
1
I
1
1_
250
300
350
400
HOURS PROCESSING
Figure 8. Isomer distributions in products from hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Ni-SMM, sulfided.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
64
HYDROCRACKING AND HYDROTREATING +
clear, was about 80 while the C6 feed was only 54. Thus, a significant upgrading of the normally liquid portion of the product over the feed was obtained. This C5 fraction could have application as a blending component to the gasoline pool. By process manipulations, it would be possible to alter the isobutane-C5 yield octane to meet specified needs. +
+
Acknowledgement The authors would like to express their appreciation to Dr. Sun W. Chun of Gulf Research & Development Company for his interest and timely suggestions.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch003
Abstract High yields of LPG or isobutane and octane improvement of the C5+ fraction can be simultaneously obtained by hydrocracking raffinate over a palladium-impregnated, nickel-substituted synthetic mica-montmorillonite catalyst (0.7 wt % Pd-15 wt % Ni-SMM). A critical sulfur level of about 100 to 200 ppm in the feed is essential to combine the features of desired product yields and good aging characteristics. Processing conditions ranged from 316° to 339°C (600° to 750°F), 7,000 kilopascals (1,000 psig), 1.2 to 2.0 LHSV and 5 hydrogen-to-hydrocarbon mole ratio with the lower temperatures allowing the high isobutane yields and the higher temperatures maximizing the total LPG yields. No significant aging was observed over 20 days processing as the sulfur level in the feed was increased to 200 ppm. Literature Cited (1) Muse, T. P., Hydrocarbon Proc., (1974), 53, 5, 85. (2) Swift, H.E., and Black, E.R., Ind. Eng. Chem., Product Res. Develop., (1974), 13, 106. (3) NL Industries, Baroid Division Brochure Introducing Barasym SMM. (4) Hattori, H., Milliron, D. C., and Hightower, J. W., Division of Petroleum Chemists Inc., Preprints, 165th National Meeting of the American Chemical Society, Dallas, Texas, (April, 1973), Vol 18, pp 33-51.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
4 Hydrocracking Condensed-Ring Aromatics Over Nonacidic Catalysts WEN-LUNG W U and HENRY W. HAYNES, JR.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
Department of Chemical Engineering, University of Mississippi, University, Miss. 38677
In recent years as the shortage o f domestic petroleum has become e v i d e n t , the l i q u e f a c t i o n o f c o a l has r e c e i v e d serious a t t e n t i o n as an a l t e r n a t i v e source o f clean liquid f u e l s . Research e f f o r t s have g e n e r a l l y concentrated upon e i t h e r o f two objectives: E a r l i e r i n v e s t i g a t i o n s were d i r e c t e d toward the production o f a "synthetic crude" from c o a l . This m a t e r i a l could then be processed i n a (more or l e s s ) conventional petroleum r e f i n e r y to yield a wide range o f products from g a s o l i n e to heavy fuel oils. More recent e f f o r t s have concentrated upon c o a l l i q u e f a c t i o n as a means o f producing a "solvent r e f i n e d c o a l " , i.e. a product low i n s u l f u r content and s u i t a b l e f o r use as a f u e l to an electric power p l a n t . The p r i n c i p a l f a c t o r which d i s t i n g u i s h e s between the s y n t h e t i c crude and solvent r e f i n e d c o a l processes i s the amount of hydrogen added during the l i q u e f a c t i o n and subsequent processing s t e p s . A s y n t h e t i c crude must contain somewhere i n the neighborhood o f 11-14% hydrogen if it i s t o be processed by conventional petroleum r e f i n e r y techniques. On the other hand s u b s t a n t i a l d e s u l f u r i z a t i o n can be accomplished i f hydrogen i s added to the c o a l t o the extent of only one or two per cent t o produce a product c o n t a i n i n g 6-7% hydrogen. The hydrogen generating cost i s of course a major f a c t o r i n the economics of a s y n t h e t i c f u e l s p l a n t . In p r i n c i p l e it i s p o s s i b l e to produce g a s o l i n e and s i m i l a r products from c o a l without consuming huge q u a n t i t i e s o f hydrogen. To illustrate, we can compare the H/C atom r a t i o s f o r a h i g h v o l a t i v e bituminous c o a l (0.8) with those f o r benzene ( 1 . 0 0 ) , toluene ( 1 . 1 4 ) , and mostly p a r a f f i n i c , petroleum d e r i v e d g a s o l i n e s (2.0). O b v i o u s l y , the more aromatic the r e f i n e d p r o d u c t , the l e s s is the hydrogen consumption i n the o v e r a l l processing sequence. The problem i s that petroleum c a t a l y t i c c r a c k i n g and hydrocracking processes r e q u i r e that the feedstocks be h i g h l y saturated p r i o r to, or during c r a c k i n g . More specifically, if one attempts to hydrocrack a multicondensed r i n g aromatic s p e c i e s , the tendency is to s u c c e s s i v e l y hydrogenate and split o f f t e r m i n a l end r i n g s to produce u l t i m a t e l y a s i n g l e aromatic molecule and s u b s t a n t i a l
65 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
66
HYDROCRACKING AND HYDROTREATING
q u a n t i t i e s o f C and l i g h t e r gases ( 1 , 16, 17, 22). This i s t r u e even though h y d r o g é n a t i o n at i n n e r r i n g l o c a t i o n s i s favored kinetically (18). The commerical c r a c k i n g o f petroleum hydrocarbons i s almost u n i v e r s a l l y executed over c a t a l y s t s having an a c i d i c component. For many years amorphous s i l i c a - a l u m i n a based c a t a l y s t s were the mainstay of the i n d u s t r y . In more recent years c r a c k i n g activities have been enhanced by orders o f magnitude by i n c o r p o r a t i n g c r y s t a l l i n e s i l i c a - a l u m i n a s or molecular sieves ( m u l t i v a l e n t and hydrogen forms) i n t o the c a t a l y s t composition. While a c i d i c c a t a l y s t s are by f a r the most a c t i v e c r a c k i n g c a t a l y s t s a v a i l a b l e , they are not s e l e c t i v e towards c r a c k i n g at i n n e r r i n g s of p a r tially s a t u r a t e d condensed-ring aromatics of the type present i n c o a l l i q u i d s . As we discuss below, there are suggestions i n the l i t e r a t u r e that n o n a c i d i c c a t a l y s t s , or c a t a l y s t s o f low a c i d i t y might o f f e r advantages i n terms o f selectivity. The c r a c k i n g r e a c t i o n s that take place over such c a t a l y s t s would presumably take place by free r a d i c a l mechanisms — s i m i l a r to the s i t u a t i o n encountered i n thermal c r a c k i n g . A study o f the thermal hydrogenolysis of phenanthrene at 80 atm and temperatures o f 4 7 5 ° C and 4 9 5 ° C was r e c e n t l y r e p o r t e d by Penninger and Slotboom (11). The main hydrogénation products were 1,2,3,4-tetrahydrophenanthrene and 9,10-dihydrophenanthrene. At the higher temperature c r a c k i n g products appeared. The p r i n c i p a l products were, i n decreasing order o f abundance, 2ethylnaphthalene, e t h y l b i p h e n y l , 2-methylnaphthalene, naphthalene, b i p h e n y l and diphenylethane. S e v e r a l r e a c t i o n paths were sugguested by t h e i r d a t a . The presence o f s i z e a b l e q u a n t i t i e s o f e t h y l b i p h e n y l and b i p h e n y l was explained by a mechanism i n v o l v i n g the r i n g opening of dihydrophenanthrene between the 10 and 11 carbon atoms. Thus we see here f o r the first time evidence o f hydrocracking the phenanthrene molecule at the c e n t r a l r i n g . Still, the major r e a c t i o n path i n v o l v e d cleavage o f end r i n g s . It can be argued, somewhat n a i v e l y perhaps, that the main obstacle t o hydrocracking 9,10-dihydrophenanthrene and s i m i l a r molecules, i s the 12,13- or "biphenyl" like bond. I t i s noted that b i p h e n y l itself was observed t o be i n e r t to c a t a l y t i c c r a c k ing over an a c i d i c , s i l i c a - a l u m i n a c r a c k i n g c a t a l y s t ( 8_). On the other hand the hydrogenolysis o f b i p h e n y l takes place thermally at temperatures i n the neighborhood of 1 3 0 0 ° F (10). Gardner and Hutchinson found t h a t low surface a r e a , low acidity, metal oxide c a t a l y s t s were e f f e c t i v e i n hydrocracking polyphenyls i n c l u d i n g biphenyl (7). A c i d i c c r a c k i n g c a t a l y s t s produced much lower conversions and s u b s t a n t i a l y i e l d s of coke. These observations were a major f a c t o r i n our s e l e c t i o n o f a chromia-alumina c a t a l y s t f o r this investigation. Chromia-alumina has demonstrated an ability t o c a t a l y z e many free r a d i c a l r e a c t i o n s .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
4
Chromia-Alumina C a t a l y s t s . Chromia-alumina c a t a l y s t s are most notable f o r c a t a l y z i n g the dehydrogenation and dehydro-
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
4. wu
A N D
H A Y N E S
67
Condensed-Ring Aromatics
c y c l i z a t i o n r e a c t i o n s o f hydrocarbons and the p o l y m e r i z a t i o n o f o l e f i n i c hydrocarbons. R e l a t i v e t o metal dehydrogenation c a t a l y s t s such as F e , N i , and Co, chromium oxide and chromiaalumina c a t a l y s t s possess l i t t l e a c t i v i t y f o r a c t i v a t i n g the the carbon-carbon bond ( 1 4 ) . Chromia-alumina i s remarkably i n s e n s i t i v e t o poisons which might be present i n the s t a r t i n g m a t e r i a l , though water vapor does act as a temporary poison (19). Chromium oxide by i t s e l f i s a h i g h l y a c t i v e c a t a l y s t , but t h i s a c t i v i t y i s not r e t a i n e d on prolonged use or upon regener a t i o n by o x i d a t i o n . T h i s decay i s due to conversion t o c r y s t a l l i n e C r 0 g which has been shown to be i n a c t i v e (20). But i f the chromium oxide i s deposited on alumina, i t r e t a i n s i t s o r i g i n a l high a c t i v i t y through regeneration at quite high tem peratures ( 9 ) . The alumina has an a d d i t i o n a l e f f e c t i n that i t s t a b i l i z e s the chromium against r e d u c t i o n below the C r ^ s t a t e i n hydrogen atmospheres at temperatures as high as 500°C (21). F i n a l l y the alumina may or may n o t , depending upon the method o f p r e p a r a t i o n , introduce an a c i d i c f u n c t i o n i n t o the c h a r a c t e r i s t i c s of the c a t a l y s t . For example, Pines and C s i c s e r y (13) observed that chromia-alumina c a t a l y s t s composed o f alumina obtained by h y d r o l y s i s of aluminum isopropoxide and alumina prepared from potassium aluminate behaved quite d i f f e r e n t l y i n the dehydro genation and d e h y d r o c y c l i z a t i o n o f C 5 and Cg hydrocarbons. The former c a t a l y s t , designated c a t a l y s t A , produced extensive s k e l e t a l i s o m e r i z a t i o n ; whereas, the l a t t e r , designated c a t a l y s t B , produced o l e f i n s with e s s e n t i a l l y the same s k e l e t a l arrange ment as the s t a r t i n g p a r a f f i n s . Catalyst A yielded large q u a n t i t i e s of aromatics — benzene, toluene and xylene — from n-pentane. Formation o f these products could be e x p l a i n e d by an a c i d c a t a l y z e d p o l y m e r i z a t i o n followed by i s o m e r i z a t i o n and β s c i s s i o n t o form propylene and isobutylene fragments which could then undergo an aromatization r e a c t i o n . C a t a l y s t Β produced only n e g l i g i b l e q u a n t i t i e s o f aromatics. Pines and h i s co-workers are r e s p o n s i b l e f o r a great body o f l i t e r a t u r e e l u d i c a t i n g the mechanisms o f hydrocarbon r e a c t i o n s over chromia alumina. [For number t h i r t y - e i g h t i n the s e r i e s see reference ( 1 2 ) ] . In g e n e r a l i t i s observed that r e a c t i o n s over the "nonacidic" chromia-alumina Β can be explained by f r e e r a d i c a l mechanisms. In a study o f the dehydroeraeking o f Cg-Cg p a r a f f i n s C s i c s e r y and Pines made s e v e r a l i n t e r e s t i n g observations (3): Cracking occurred most predominantly between s u b s t i t u t e d carbons, with l i t t l e c r a c k i n g of normal p a r a f f i n s t a k i n g p l a c e . This suggests a homolytic s p l i t t i n g of the molecule i n t o free r a d i c a l s since the s t a b i l i t y o f free r a d i c a l s increases with s u b s t i t u t i o n . Cracking was very much i n h i b i t e d i f n e i t h e r o f the fragments could form an o l e f i n . A comparison was made between the cracking o f 3-ethylhexane and 3-ethylhexenes. With the p a r a f f i n , c r a c k i n g occurred almost e x c l u s i v e l y between primary and t e r t i a r y carbon atoms. With o l e f i n s , c r a c k i n g took place β t o the double bond suggesting a mechanism i n v o l v i n g the a l l y l free radical. 2
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
+
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
68
The major products obtained from the dehydrogenation o f n butylbenzene over chromia-alumina were 1-phenylbutenes (_2). This r e a c t i o n was accompanied by s u b s t a n t i a l hydrogenolysis o f the side chain t o produce ethylbenzene (or styrene) and ethylene (or ethane). D e a l k y l a t i o n was a r e l a t i v e l y minor r e a c t i o n . The product d i s t r i b u t i o n again suggests that free r a d i c a l i n t e r mediates were i n v o l v e d . A review o f the p h y s i c a l - c h e m i c a l p r o p e r t i e s o f chromia-alumina was presented by Poole and Mclver (15).
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
Experimental The experimental p o r t i o n o f t h i s i n v e s t i g a t i o n was conducted i n the steady-flow m i c r o r e a c t o r i l l u s t r a t e d i n F i g u r e 1. The r e a c t o r c o n s i s t e d of a tube o f 1/2 i n c h heavy w a l l (0.083 i n c h ) type 316 s t a i n l e s s steel heated by a M a r s h a l l t u b u l a r f u r n a c e , model 1016. L i q u i d phenanthrene was metered i n t o the r e a c t o r by a p r e c i s i o n Ruska p r o p o r t i o n i n g pump, model 2252-BI, with a heated b a r r e l . Various discharge r a t e s from 2 c c / h r t o 240 c c / h r could be obtained by s e l e c t i n g the proper choice o f gear r a t i o s . The hydrogen flowrate was monitored by a flow meter constructed of a 34 i n c h length o f 0.009 inch I . D . c a p i l l a r y tubing and a Barton model 200 d i f f e r e n t i a l pressure c e l l . The c a p i l l a r y pressure and r e a c t o r pressure were c o n t r o l l e d r e s p e c t i v e l y by a Tescom pressure r e g u l a t o r , model 26-1023-002 and a Tescom back pressure r e g u l a t o r model 26-1723-24. Flow r a t e s were c o n t r o l l e d with a Hoke m i l l i - m i t e needle v a l v e . The high pressure accumulator was constructed o f 3/4 i n c h schedule 80 s t a i n l e s s s t e e l pipe with a Grayloc c l o s u r e . High p u r i t y hydrogen (99.995% according to m a n u f a c t u r e r ^ s p e c i f i c a t i o n s ) was s u p p l i e d by the Matheson Gas Products Company i n 3500 p s i g c y l i n d e r s . Phenanthrene, 98+% p u r i t y , melting point 9 9 - 1 0 1 ° C , was purchased from the A l d r i c h Chemical Company. The chromia-alumina c a t a l y s t , designated CR-0103-T,was s u p p l i e d by the Harshaw Chemical Company i n the form of 1/8 inch t a b l e t s . According to the manufacturer, the c a t a l y s t contains 12% C r 0 on a c t i v a t e d alumina, the surface area i s 63 m^/gm, and the pore volume i s 0.35 cc/gm. Approximately f i v e grams of f u l l s i z e c a t a l y s t p a r t i c l e s were charged to the r e a c t o r . A preheat zone o f g l a s s beads was s i t u a t e d above the c a t a l y s t bed. Thermocouples were i n s t a l l e d t o a depth o f 1/2 inch i n t o both ends o f the c a t a l y s t bed. With a f r e s h c a t a l y s t i n s t a l l e d , the system was pressured with hydrogen and t e s t e d f o r l e a k s . Hydrogen flow was s t a r t e d and the temperature r a i s e d slowly ( 1 6 0 ° F / h r maximum) to a temperature o f 500°F. At t h i s p o i n t the l i q u i d feed pump was switched on. The furnace temperature was g r a d u a l l y brought up t o r e a c t i o n c o n d i t i o n s by r a i s i n g the temperature at a r a t e not to exceed 1 6 0 ° F / h r . P r i o r t o beginning a y i e l d p e r i o d , a p e r i o d o f time s u f f i c i e n t f o r three displacements o f the r e a c t o r was allowed t o insure 2
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
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A N D H A Y N E S
Condensed-Ring Aromatics
69
steady-state operation. The y i e l d p e r i o d was begun my moment a r i l y c u t t i n g o f f the feed pump, depressuring and d r a i n i n g the high pressure accumulator, and p r e s s u r i n g the accumulator with pure hydrogen (through a l i n e not i n d i c a t e d on the s i m p l i f i e d schematic). The e x i t i n g l i n e was d i r e c t e d through a low p r e s sure accumulator ( i n dry i c e - a c e t o n e ) , a wet t e s t meter and a polyethylene gas bag. At the t e r m i n a t i o n of the y i e l d p e r i o d the high pressure accumulator was depressured through the wet t e s t meter and l i q u i d d r a i n e d . The l i q u i d product was capped and stored i n a f r e e z e r . The contents o f the gas bag were analyzed immediately. When i t became necessary t o place the u n i t on over n i g h t hold the feed pump was switched o f f and the r e a c t o r temperature lowered to 5 0 0 ° F . Hydrogen flow was maintained f o r the d u r a t i o n o f the h o l d p e r i o d . Both the l i q u i d and gas products were analyzed by gas chromatography. The column f o r the l i q u i d a n a l y s i s was 20% Apiezon L on 60-80 mesh Chromosorb P. The column measured 1/4 i n c h by 7 feet. The gas a n a l y s i s u t i l i z e d a 1/4 i n c h by 10 foot column o f 60-80 mesh Chromosorb 102. Temperature programming was r e q u i r e d i n both analyses. I d e n t i f i c a t i o n o f the GC peaks was based on r e t e n t i o n time o f pure compounds when these were a v a i l a b l e . In a d d i t i o n , two o f the samples were analyzed by combined gas c h r o matography -mas s spectrometry. By comparing the observed mass spectrometer fragmentation patterns with t a b u l a t e d patterns i t was p o s s i b l e t o i d e n t i f y v i r t u a l l y every component i n the p r o duct. Further d e t a i l s are a v a i l a b l e i n the theses by Wu (23) and E a r l y ( 4 ) . Results Sixteen y i e l d periods were s u c c e s s f u l l y completed at the c o n d i t i o n s summarized i n Table I . Product y i e l d s are t a b u l a t e d i n Table I I . These y i e l d s have been adjusted t o force a 100% carbon m a t e r i a l balance. While i t was beyond the scope o f t h i s i n v e s t i g a t i o n t o evaluate c a t a l y s t d e a c t i v a t i o n k i n e t i c s , i t was deemed necessary to maintain a r e c o r d o f any d e c l i n e s i n c a t a l y s t a c t i v i t y . The s e l e c t e d "Base Conditions" o f operation — 8 0 0 ° F , 2000 p s i g , 1.0 gm/hr/gm — were repeated p e r i o d i c a l l y f o r t h i s purpose. Two measures o f c a t a l y s t a c t i v i t y , phenanthrene conversion and conv e r s i o n t o C ] ^ , are p l o t t e d versus hours on c a t a l y s t i n Figure 2. While both i n d i c a t o r s r e v e a l that c a t a l y s t d e a c t i v a t i o n i s s i g n i f i c a n t , the c a t a l y s t does remain a c t i v e a f t e r 90 hours on stream. No a n a l y s i s o f the spent c a t a l y s t was undertaken; howe v e r , i t was s u r p r i s i n g l y observed that the c a t a l y s t s t i l l r e t a i n e d i t s o r i g i n a l green c o l o r at the run t e r m i n a t i o n . Evidently carbon d e p o s i t i o n was not extensive despite the high temperatures employed. The hydrogen p a r t i a l pressures e x p e r i enced by the c a t a l y s t are much higher than those experienced i n the u s u a l a p p l i c a t i o n s o f chromia-alumina, and the extent to
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
83.1
Liq. mat'l balance, wt %
Carbon mat'l bal., wt %
Feed conversion, mole %
16.3
103.0
101.4
10.1
103.8
102.4
101.3
0.0
5.1
95.1
0.0
3.4
97.3
Cg-Cg yield, mole % C -C yield, m o i e %
^13
g
14
1 2
v î e , d
'
g
m
o
,
e
%
Liq. yield ( C ) , wt %
+
92.8
7.3
0.0
101.6
1.6
0.36
3.2
2.4 1 1
7.2
4.9
0.27
86.2
74.0
0.07 101.4
1.5
0.17
2.7
60.1
20.5
4.7
10.0
10.7
4.4
1.95
0.51
2.5
235
2000
805
1.73
Gas yield iC^-C^), wt %
wt%
L(STP)/gm
Hydrogen consumption.
Conversion to C14" mole %
3
6.00
1.29
6.7
0.96
1.04
C O R R E C T E D Y I E L D S B A S E D ON LIQUID F E E D
4.6
84.3
Cum. gms oil/gm catalyst
4.5
15.1
Cum. hrs. on catalyst
Exit gas rate, L(STP)/hr
6.7
1.29
L(STP)/gm
0.97
1.04
5.1
230
250
5.1
2000
805
756
2000
2
3.00
1
3.00
L(STP)/hr
2
Approx. Η t r e a t rate.
Space time (gm/hr/gm)"
gm/hr/gm
Liquid space velocity.
Liquid feed rate, cc/hr
temp., °F
Pressure, psig High press, accumulator
Yield period length, hrs. Temperature, °F
Yield period no.
5
3.8 96.8
96.8
101.3 0.0
101.1 0.0 3.9
1.5 0.17
0.16
3.2
57.5
103.2
104.5
28.6
16.9 27.8
1.02
8.9
0.57
1.74
8.6
295
2000
805
1.50
1.3 0.22
0.14
3.2
50.2
98.6
99.6
21.0
24.5
24.9
0.86
14.3
0.30
3.29
16.3
255
2000
810
1.00
4
7
1.05
97.8
101.4 0.0 3.3 96.4
101.5 3.4 96.2
2.9 97.2
0.0
0.0
1.3
6.0
0.6 101.5
84.5
13.2
0.0
3.8 2.6 1.2
2.8
0.43
15.5
87.6
0.31
0.29
3.6
78.8
2.1
3.8
81.1
97.5
105.2
84.1
97.5
2.1
101.0 0.0
2.0 0.94
103.3
79.9
74.4
49.3
73.7
25.6
69.9
0.46 19.3 37.8
30.4
24.3 30.4
7.0 22.9 8.9
42.3
85.7 52.9 69.7 84.0 102.3 4.1
95.9
4.9
0.0
1.7 0.30 101.4
17.7 56.5 37.9 1.1
21.3
5.3
3.4
0.59
0.38
0.38
0.18
4.1 1.04
30.1
9.4
69.6
7.7
0.85
88.2 50.7
62.2
113.4 87.6
107.8
49.1
97.2
46.3
82.4
100.8 99.4
95.8 85.3 75.2
78.3
83.7
99.1
3.4
26.3
2.5 0.22
86.1
63.5
83.1
85.0
106.4
70.8 83.2
65.7
104.1
106.7
59.6 84.9
53.3
47.2
99.0
40.2
86.8
25.4 81.9
37.7 9.6 76.4
11.7
6.7 1.33
0.99
0.67
0.16 21.0 20.7 69.8
11.9 64.7
9.2 58.2
16.9 51.8
12.8
5.0 1.01
30.7 6.21
260
462
1.40
0.30
3.42
16.9
2000
803
24.0 1.75
1.72
8.9 1.79
8.9
0.99
0.97 8.9
1.02
5.0
1.03
6.7
1.01
0.99
1.34
1.00
1.00
5.1
90
100
4.9
88
110
4.9
16 3.00 2600
1009
2800
2800
3000
1002 2800
999
949
898
15 1.00
14 1.00
13 4.00
12 2.75
11 3.00
210
2000
806
45.8
1.75
8.9
0.98
1.02
5.0
228
3000
854
10 3.00
38.8
10.6
8.9 1.70
9 3.00
0.24
2.8
69.5
89.3
90.6
33.8
32.5
6.0
6.7 1.30
6.7
0.95
0.97
285 5.2
803 3000
1.05
1.28
0.96
8 3.00
1.03
5.1
275
314 5.2
2500
806
3.00
2000
800
6 3.00
R U N WLW02. H Y D R O C R A C K I N G O F P H E N A N T H R E N E O V E R 5.017 G M S H A R S H A W CR-0103-T
PRODUCT YIELDS
TABLE I
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
ο
ο
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
TOTALS
Y I E L D PERIOD NO. Methane C 1H4 Ethane C2H6 Propane C3H8 Isobutane C4H10 Butane C4H10 C5H12 C5H12 C5H10 Cyclopentane C6H14 C6H14 Benzene C6H 6 C7H16 C7H16 C7H 8 Toluene C 7H16 Ε thy I benzene C8H10 Xylenes C8H10 C8H10 C8H18 Alky I benzenes C9H12 Alkylbenzenes C9H12 Alkyl benzenes C10H14 C10H14 N-Buty I benzene C10H18 Decalin (Trans) Methylbutylbenzenes C11H16 C10H12 Tetralin C10H 8 Naphthalene C10H12 6-Methyltetralin C11H14 2-Methylnaphthalene C11H10 6-Ethyltetralin C12H16 Biphenyl C12H10 C12H12 2-Ethylnaphthalene C12H20 C12H24 6-N-Butyltetralin C14H20 2-N-Butylnaphthalene C14H15 C14H12 C14H12 2-Ethylbiphenyl C14H14 Dihydrophenanthrene C14H12 Octahy drophenanth rene C14H18 Tetrahydrophenanthrene C14H14 Phenanthrene C14H10
101.11
1 0.00 0.43 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.87 0.60 0.00 0.00 0.62 0.00 0.70 0.59 0.00 0.00 2.21 1.50 2.30 2.30 0.00 18.59 12.79 17.73 39.86
104.70
2 0.04 2.26 0.61 0.00 1.61 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.33 0.75 0.00 0.00 1.00 0.00 1.08 0.95 0.00 0.00 9.91 4.57 4.05 4.31 0.53 9.28 17.96 18.45 26.02 105.93
3 0.03 1.27 0.98 0.00 3.54 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 2.05 0.62 0.00 0.42 0.86 0.00 1.41 0.72 0.64 0.57 20.16 5.76 4.20 5.21 0.43 7.10 20.53 15.65 13.78 101.70
4 0.00 0.69 0.02 0.00 0.30 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.11 0.80 0.00 0.00 0.57 0.00 0.66 0.77 0.00 0.00 3.23 2.53 1.96 2.07 0.00 12.98 7.78 16.40 49.81
C O R R E C T E D PRODUCT Y I E L D S BASED ON LIQUID F E E D , M O L E
101.47
5 0.04 0.53 0.04 0.00 0.21 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.92 0.58 0.00 0.00 0.54 0.00 0.91 0.87 0.00 0.00 3.70 2.70 2.31 2.67 0.69 14.11 9.56 18.60 42.49
PRODUCT YIELDS
102.90
6 0.36 0.91 0.34 0.00 1.15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.13 0.46 0.00 0.00 0.80 0.00 0.56 0.00 0.00 0.00 9.68 4.10 3.36 4.20 0.62 11.05 14.10 19.61 30.50 104.54
7 0.39 1.25 0.61 0.00 2.65 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1.03 0.25 0.00 0.00 0.73 0.00 0.65 0.31 0.25 0.21 12.89 3.71 4.47 5.64 0.26 9.42 23.29 17.61 18.91 104.21
8 0.04 1.51 0.52 0.00 2.44 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.93 0.47 0.00 0.00 0.72 0.00 0.66 0.27 0.27 0.00 10.34 3.83 4.39 5.19 0.23 11.75 22.85 16.63 21.17 122.31
9 3.12 5.46 5.72 0.00 10.35 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.58 0.00 0.00 3.48 1.02 0.62 0.90 1.08 0.34 2.05 1.28 0.96 0.89 22.94 6.52 3.63 4.38 0.61 6.66 15.04 12.30 12.39 103.50
10 0.06 1.65 0.57 0.00 1.59 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.49 0.33 0.00 0.00 0.38 0.00 0.00 0.00 0.48 0.42 5.67 3.83 2.65 2.87 0.23 12.36 14.19 19.25 36.48 112.75
11 0.08 1.69 0.65 0.00 2.07 0.00 0.00 0.00 0.00 0.00 2.58 0.36 0.24 0.69 0.00 0.25 0.00 0.00 0.00 0.00 0.00 0.00 2.42 1.17 0.91 10.08 2.93 0.39 1.47 1.04 0.50 3.93 2.49 1.56 1.52 22.45 10.38 1.94 2.05 0.65 5.47 6.35 10.57 13.89 180.70
12 8.10 17.72 21.14 0.00 37.86 0.00 0.88 0.33 0.28 0.42 1.68 0.45 0.36 2.33 0.37 1.55 0.23 0.00 0.00 0.00 0.36 0.27 4.83 2.56 1.54 11.88 6.23 1.19 1.39 2.20 0.74 1.54 1.46 0.82 0.75 8.38 7.43 1.42 1.42 1.00 4.00 2.55 6.74 16.32 299.58
13 64.83 70.05 48.25 1.28 24.30 0.17 0.54 0.56 0.30 0.65 7.06 0.49 0.93 7.05 0.29 3.77 0.55 0.29 0.27 0.40 0.58 0.59 5.38 3.66 1.10 10.02 12.25 0.95 1.15 2.65 0.50 0.99 1.44 0.48 0.20 2.56 3.23 1.01 0.78 0.52 2.08 0.99 2.62 11.85 364.86
14 88.85 99.98 71.56 2.18 40.53 0.00 0.10 0.15 0.08 0.00 2.45 0.32 0.25 2.18 0.00 1.37 0.12 0.00 0.00 0.10 0.30 0.32 2.03 1.52 0.68 4.77 8,03 0.55 0.86 2.37 0.31 0.52 1.47 0.42 0.07 1.61 3.64 0.93 0.54 0.65 2.61 0.35 2.45 17.63 178.61
15 19.92 29.47 25.18 0.50 13.87 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.46 0.00 0.00 0.00 0.00 0.00 0.89 0.95 0.00 3.08 6.22 0.00 0.63 2.89 0.26 0.64 3.16 0.60 0.00 1.39 4.28 1.89 1.02 1.02 5.08 0.21 4.12 50.87
102.06
16 0.00 0.66 0.00 0.00 0.57 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.97 1.20 0.00 0.00 1.03 0.00 0.91 0.82 0.00 0.00 3.96 3.68 2.66 2.99 0.31 13.97 12.11 18.42 37.82
RUN WLW02, H Y D R O C R A C K I N G OF P H E N A N T H R E N E O V E R 5.017 GMS HARSHAW CR-0103-T
T A B L E II
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
72
HYDROCRACKING A N D H Y D R O T R E A T I N G
DPC
Hydrogen Supply
PG
PR f~\ KJ~
t
I
Proportioning Pump
7
\
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
,4 ,< ,
Cutoff
MV
Metering
PR
Pressure
Vent, W T M , or " G a s Bag
Lines
Valve
BPR
Back
PG
Pressure
Valve Regulator
Pressure
Regulator
Gauge
C
Capillary
DPC
Differential
Pressure
Call
Low Pressure Accumulator
Figure 1. Simplified flow diagram of steady-state microreactor
Figure 2. Deactivation of chromia-alumina catalyst
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
4.
wu
A N D H A Y N E S
73
Condensed-Ring Aromatics
which t h i s may have damaged the c a t a l y s t , e . g . by r e d u c t i o n o f chromium o x i d e , i s not known. Y i e l d s o f the various h y d r o g é n a t i o n products o f phenanthrene are presented i n F i g u r e 3 and Table I I . No perhydrophenanthrene was detected i n any o f the p r o d u c t s . This i s c o n s i s t e n t with the observation that h y d r o g é n a t i o n o f the l a s t r i n g o f a p o l y c o n densed r i n g aromatic proceeds with considerable d i f f i c u l t y as compared with the i n i t i a l h y d r o g é n a t i o n steps (18). It i s f r e q u e n t l y supposed that the h y d r o g é n a t i o n o f p o l y n u c l e a r a r o matics takes place r i n g - b y - r i n g i n a s e r i e s f a s h i o n . While conf i r m a t i o n o f t h i s behavior would r e q u i r e more p r e c i s e data at lower conversions than are a v a i l a b l e h e r e , i t i s apparent that tetrahydrophenanthrene appears almost simultaneously with d i hydrophenanthrene suggesting that the i n i t i a l h y d r o g é n a t i o n s might take place i n a p a r a l l e l manner. I t i s o f i n t e r e s t to compare the observed h y d r o g é n a t i o n product r a t i o s with e q u i l i b r i u m v a l u e s . E q u i l i b r i u m constants were c a l c u l a t e d using equations a v a i l a b l e i n the l i t e r a t u r e (5,6). A hydrogen mole f r a c t i o n o f u n i t y was assumed f o r c a l c u l a t i o n o f the e q u i l i b r i u m product r a t i o s , a reasonable assumpt i o n when the hydrogen t r e a t r a t e g r e a t l y exceeds the r a t e o f hydrogen consumption. Otherwise the extent o f h y d r o g é n a t i o n at e q u i l i b r i u m w i l l be somewhat l e s s than these c a l c u l a t i o n s would indicate. The c a l c u l a t e d r e s u l t s are compared with the observed r a t i o s i n Tables I I I and I V . At 8 0 0 ° F and 2000 p s i g only the phenanthrene-dihydrophenanthrene e q u i l i b r i u m appears t o be e s t a b l i s h e d at the l a r g e s t space time i n v e s t i g a t e d , 1.9 (gm/hr/gm)" . At the more severe c o n d i t i o n s 1 0 0 0 ° F and 2800 p s i g , the r a t e s are more r a p i d and the degree o f h y d r o g é n a t i o n i s l e s s under e q u i l i brium c o n d i t i o n s . A l l the h y d r o g é n a t i o n products o f phenant h r e n e , with the exception o f perhydrophenanthrene, approach t h e i r e q u i l i b r i u m values at l a r g e space t i m e s . The same i s t r u e of the n a p h t h a l e n e - t e t r a l i n - ( t r a n s ) d e c a l i n e q u i l i b r i a . Inspection o f Figures 4- and 5 r e v e a l s that the c r a c k i n g r e a c t i o n s at 8 0 0 ° F are l i m i t e d t o α - r i n g opening o f a saturated terminal r i n g . At higher temperatures d e a l k y l a t i o n r e a c t i o n s become s i g n i f i c a n t . The predominant r e a c t i o n at the lower temperatures was h y d r o g é n a t i o n t o sym-octahydrophenanthrene followed by r i n g opening t o 6 - n - b u t y l t e t r a l i n and d e a l k y l a t i o n to tetralin. At the higher temperatures naphthalenes were present i n greater abundance, presumably because o f the s h i f t i n thermodynamic e q u i l i b r i u m towards the more unsaturated s p e c i e s . The y i e l d s of n-butylnaphthalene and naphthalene are comparable t o the y e i l d s of n - b u t y l t e t r a l i n and t e t r a l i n r e s p e c t i v e l y at 9501000°F. Considerable q u a n t i t i e s o f n-butylbenzene (Table I I ) were observed i n the products suggesting a mechanism i n v o l v i n g α - r i n g opening of t e t r a l i n . D e a l k y l a t i o n o f the side chain was not as clean as had been observed with the b u t y l s u b s t i t u t e d two ring species. Toluene and benzene were formed i n approximately equal amounts with smaller amounts o f ethylbenzene. Some xylenes 1
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
74
TABLE I I I COMPARISON OF EQUILIBRIUM AND OBSERVED HYDROGENATION PRODUCT RATIOS ( T = 8 0 0 ° F P=2000 p s i g )
YP4
YP5
YP6
YP2
YP3
Space Time Hr
0.30
0.57
0.96
0.96
1.95
C
14 12 14 10
C
14 14 14 10
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
9
C
l i +
C
1 4
C
Equilibrium
H
/C
H
0.26
0.33
0.36
0.36
0.52
0.55
H
/C
H
0.33
0.44
0.64
0.71
1.14
2.5
0.16
0.22
0.46
0.69
1.49
6.1
0
0
0
0
0
40
1.39
1.60
2.5
1.9
3.3
12.7
0
0
0
0
0
24
0
0
0
0
0
118
H (sym)/C 1 8
H
2 ] +
H
1 1 +
H
(L.B.P.)/C / C
1 0
1 4
H
H
10 12 10 8
C
1 0
H
1 8
C
1 0
H
1 8
(cis)/C
1 0
H
(trans)/C
8
1 0
H
8
8
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
wu
Condensed-Ring Aromatics
A N D H A Y N E S
TABLE IV
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
COMPARISON OF EQUILIBRIUM AND OBSERVED HYDROGENATION PRODUCT RATIOS ( T = 1 0 0 0 ° F P=2800 p s i g )
YP 15
YP 14
YP 13
Space Time, Hr
0.16
0.29
0.98
C
14 12 14 10
C
14 14 14 10
H
/C
H
0.10
0.15
0.18
0.25
H
/C
H
0.081
0.14
0.22
0.29
0.004
0.02
0.084
0.084
0
0
0
0.018
0.50
0.60
0.82
1.53
0
0
0
0.10
0.15
0.19
0.30
0.37
C H (sym)/C 1 4
l 8
1 1 +
H
1 0
C H (L.B.P.)/C H W
C
C
M
U
H
/C
H
10 12 10 8
C
1 0
Equilibrium
H H
l 8
(cis)/C
10 18
1 0
( t r a n s ) / C
H
8
H
10 8
1 0
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
HYDROCRACKING A N D
0
0.2
0.4
0.6 SPACE
0.8
1.0
TIME,
1.2
1.4
1.6
HYDROTREATING
1.8
2.0
(gm/hr/gm)"
Figure 3. Hydrogénation reactions (2000 psig, 800°F nominal)
( 3 0 0 0 p s i g , 1.0
gm/hr/gm
NOMINAL)
Figure 4. Effect of temperature on product distribution (3000 psig, 1.0 gm/hr/gm nominal)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
4.
wu
A N D H A Y N E S
Condensed-Ring Aromatics
77
were a l s o p r e s e n t . Cracking w i t h i n the side chain of a l k y l benzenes i s i n d i c a t i v e o f a free r a d i c a l c r a c k i n g mechanism and i n agreement with the chromia-alumina c a t a l y z e d n-butylbenzene d e h y d r ο c r a c k i n g r e s u l t s r e p o r t e d by C s i c s e r y ( 2 ) . As shown i n Figure 5 b i p h e n y l and 2 - e t h y l M p h e n y l were observed i n the r e a c t i o n products i n s i g n i f i c a n t q u a n t i t i e s . Thus a r i n g opening o f dihydrophenanthrene between the 10 and 11 carbons i s l i k e l y t a k i n g p l a c e . This same mechanism, i t i s r e c a l l e d , was p o s t u l a t e d by Penninger and Slotboom to e x p l a i n the thermal h y d r o p y r o l y s i s o f phenanthrene. As shown i n Figure 5, the y i e l d o f b i p h e n y l at 2800 p s i g , 1.0 gm/hr/gm goes through a maximum o f approximately 4% at about 9 0 0 ° F . At these same conditions the y i e l d s of t e t r a l i n and naphthalene were 10% and 3% (Figure 4) r e s p e c t i v e l y . The decrease i n b i p h e n y l y i e l d at temperatures above 9 0 0 ° F can be explained by c r a c k i n g to produce benzene, or by the lower e q u i l i b r i u m concentration o f d i h y d r o phenanthrene . The product y i e l d s by carbon number are p l o t t e d in Figure 6. At a l l except the most severe conditions s t u d i e d , t h e major com ponent i n the gas phase was η - b u t a n e . This observation i s con s i s t e n t with the α - r i n g opening and d e a l k y l a t i o n mechanism proposed f o r t e t r a - a n d octa-hydrophenanthrene c r a c k i n g . At the most severe conditions ethane was present i n the greatest quantities. This can be explained by side chain cracking o f n butylbenzene according t o the R i c e - K o s s i a k o f f mechanism or by secondary r e a c t i o n s o f the n-butane. Conclusions Three r e a c t i o n paths were i d e n t i f i e d during the hydrocrack ing o f phenanthrene over chromia-alumina. These are summarized i n Figure 7. The major r e a c t i o n paths proceeded through s a t u r a t i o n and cleavage of t e r m i n a l end r i n g s as evidence by the presence o f n - b u t y l t e t r a l i n and n-butylbenzene intermediates and the l a r g e q u a n t i t i e s o f η - b u t a n e i n the p r o d u c t s . However the presence o f b i p h e n y l and 2 - e t h y l b i p h e n y l i n s i g n i f i c a n t quan t i t i e s i n d i c a t e s that a r e l a t i v e l y minor r e a c t i o n path i n v o l v e d cracking at the saturated middle r i n g . Because o f the impor tance o f t h i s l a t t e r r e a c t i o n , i t appears that f u r t h e r s t u d i e s i n v o l v i n g n o n a c i d i c c a t a l y s t s are warranted. Acknowle dgment s The f i n a n c i a l support f o r t h i s i n v e s t i g a t i o n was provided by the N a t i o n a l Science Foundation under grant GI-36597X. The a s s i s t a n c e o f a number of i n d i v i d u a l s i s g r a t e f u l l y acknowledged: Dr. Stephen B i l l e t s f o r conducting the GC-Mass Spec a n a l y s e s , Mr. W. F . E a r l y f o r a i d i n g i n the i n t e r p r e t a t i o n o f the massspec d a t a , and Mr. K. Chandrasekhar f o r h i s a s s i s t a n c e i n the c o n s t r u c t i o n and operation of the equipment. The authors would
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
78
HYDROCRACKING A N D
HYDROTREATING
Figure 5. Effect of temperature on product distribution (3000 psig, 1.0 gm/hr/gm nominal)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
4.
wu
Condensed-Ring Aromatics
A N D H A Y N E S
0
1
2
3
4
5
6
CARBON
7
8
9
79
10 11
12
13 14
NUMBER
Figure 6. Product distribution by carbon number (3000 psig, 1.0 gm/hr/gm nominal)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
80
HYDROCRACKING AND HYDROTREATING
also like to express their appreciation to the Harshaw Chemical Company for providing the catalyst.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
ABSTRACT This paper reports the results of an investigation of the reactions of phenanthrene over a commerical chromia-alumina catalyst. Chromia-alumina was selected because of i t s demonstrated a b i l i t y to catalyze free radical reactions. Three major reactions paths were identified. The f i r s t involved hydrog e n a t i o n to sym-octahydrophenanthrene, α - r i n g opening of a terminal ring and dealkylation to produce t e t r a l i n . The t e t r a l i n reacted further by a similar pattern to produce alkyl benzenes. The second reaction path was identical to the f i r s t except that the initial α-ring opening occurred with tetrahydrophenanthrene. A t h i r d , relatively minor reaction path involved saturation of the center r i n g , α-ring opening to produce 2-ethylbiphenyl, dealkylation and cracking at the 1,1 -position to produce benzene. '
LITERATURE CITED (1)
(2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15)
Catalytic Hydrotreating of Coal Derived Liquids, Project Seacoke Phase II Final Report, Prepared for Office of Coal Research by Arco Chemical Co., Contract No. 14-01-0001-473, Dec., 1966. Csicsery, S. M . , J. Catalysis, (1968), 9, 416. Csicsery, S. Μ., and Pines, H., J. Catalysis, (1962), 1, 329. Early, W. F., M.S. Thesis, University of Mississippi, 1975. Frye, C. G., J. Chem. Eng. Data, (1962), 7, 592. Frye, C. G., and Weitkamp, A. W., J. Chem. Eng. Data, (1969), 14, 372. Gardner, L. E., and Hutchinson, W. Μ., Ind. Eng. Chem., Prod. Res. Dev., (1964), 3, 28. Greensfelder, B. S., et al., Ind. Eng. Chem., (1945), 37, 1168. G r i f f i t h , R. H., Adv. Catalysis, (1948), 1, 103. Haynes, H. W., Jr., unpublished data, 1970. Penninger, M. L., and Slotboom, H. W., Erdol und Kohle, Erdgas, Petrochemie, (1973), 26, 445. Pines, H., and Abramovici, M., J. Org. Chem., (1969), 34, 70. Pines H., and Csicsery, M . , J. Amer. Chem. Soc., (1962), 84, 292. Pines, H., and Goetschel, C. T., J. Org. Chem., (1965), 30, 3530. Poole, C. P., and MacIver, D. S., Adv. Catalysis, (1967), 17, 223.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
4. wu AND HAYNES (16) (17) (18)
(19) (20) (21) (22)
81
Qader, S. Α . , et al., ACS Div. Fuel Chem. Preprints,(1973), 18 (4), 127. Qader, S. Α . , et al., PREPRINTS, Div. Petrol. Chem., ACS, (1973), 18 (1), 60. Smith, Η. Α . , "The Catalytic Hydrogenation of Aromatic Compounds", Catalysis, V o l . V, (P. H. Emmett, e d . ) , 175 (1957). Thomas, C. L., "Catalytic Processes and Proven Catalysts", Academic Press, New York, 1970. Turkevich, J., et al., J . Amer. Chem. Soc., (1941), 63, 1129. Voltz, S. E., and Weller, S. W., J. Amer. Chem. Soc., (1954) 76, 4701. Wiser, W. H., et al., Ind. Eng. Chem., Proc. Res. Dev., (1970), 9, 350. Wu, Wen-lung, M.S. Thesis, University of Mississippi, 1974.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch004
(23)
Condensed-Ring Aromatics
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
5 Conversion of Complex Aromatic Structures to Alkylbenzenes SHAIK A. QADER Burns and Roe Industrial Services Corp., Paramus, N.J. 07652
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
DAVID B. McOMBER University of Utah, Salt Lake City, Utah 84112 A l k y l b e n z e n e s (BTX) a r e m a i n l y made from p e t roleum and c o a l i n the U n i t e d S t a t e s . Petroleum refineries produce about 95% o f BTX and the r e s t comes from coal. C o a l based BTX i s o b t a i n e d as a b y - p r o d u c t from h i g h temperature c a r b o n i z a t i o n o f c o a l employed f o r the p r o d u c t i o n o f metallurgical coke. Carbonization p r o c e s s yields o n l y 2-3 g a l l o n s o f BTX p e r t o n o f c o a l . BTX can be produced i n l a r g e r q u a n t i t i e s by h y d r o genation and h y d r o c r a c k i n g o f c o a l ( 1 , 2 ) . The o r g a n i c matter o f c o a l i s m a i n l y a r o m a t i c i n n a t u r e and it c o n s i s t s o f c l u s t e r s o f each 3 t o 4 benzene r i n g s on an a v e r a g e , i n t e r - c o n n e c t e d b y aliphatic linkages. The clusters c o n t a i n m a i n l y a r o m a t i c r i n g s w i t h some h y d r o a r o m a t i c and n a p h t h e n i c s t r u c t u r e s (3). Conv e r s i o n of c o a l to s i n g l e r i n g aromatics involves r e l e a s e o f c l u s t e r s from complex o r g a n i c m a t t e r w i t h subsequent c o n v e r s i o n o f the clusters to f i n i s h e d products. T h e r e f o r e , p r o d u c t i o n o f a l k y l b e n z e n e s from c o a l i s due t o the o c c u r r e n c e o f hydrogenation and h y d r o c r a c k i n g r e a c t i o n s o f c o a l and p o l y n u c l e a r a r o m a t i c s t r u c t u r e s r e l e a s e d from coal. An u n d e r s t a n d i n g o f the hydrogenation and h y d r o c r a c k i n g r e a c t i o n s o f coal, c o a l oil and p o l y n u c l e a r a r o m a t i c h y d r o c a r b o n s will, t h e r e f o r e , l e a d t o the u n d e r s t a n d i n g o f the p r o d u c t i o n o f a l k y l b e n z e n e s from coal. In this investigation, c o a l , c o a l oil, a n t h r a c e n e and phenanthrene were h y d r o c r a c k e d over different catalysts i n batch systems. Product distributions, reaction kinetics and catalyst e f f e c t s were s t u d i e d .
82 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
5.
QADER
A N D M C O M B E R
Complex Aromatic Structures
83
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
E x p e r imenta1 H y d r o c r a c k i n g o f c o a l , c o a l o i l , a n t h r a c e n e and phenanthrene was c a r r i e d out i n b a t c h s t i r r e d tank r e a c t o r s ( F i g u r e s 1 and 2) i n t h e temperature range 450 - 540 c under p r e s s u r e s up t o 3500 p s i . R e a c t o r c o m b i n a t i o n shown i n F i g u r e 2 was used f o r t h e h y d r o cracking of coal. H y d r o c r a c k i n g experiments o f a n t h r a c e n e , phenanthrene and c o a l o i l were conducted i n t h e same manner as d e s c r i b e d e a r l i e r ( 4 ) . In case of c o a l , hydrogen was p r e h e a t e d i n r e a c t o r (_1) and p a s s e d i n t o r e a c t o r (2) c o n t a i n i n g c o a l . No s t i r r i n g was done d u r i n g c o a l h y d r o c r a c k i n g e x p e r i m e n t s . A b i t u m i n o u s c o a l from Utah (Table I) was used i n t h i s work. The c o a l o i l (Table I I ) used was o b t a i n e d from a b i t u m i n o u s c o a l b y hydrogénation u s i n g z i n c c h l o r i d e as the c a t a l y s t i n a s e m i - c o n t i n u o u s r e a c t o r system. A n t h r a c e n e , phenanthrene, WS~ and NIS used were pure grade c h e m i c a l s o f o v e r 99% p u r i t y . H-zeolon was a s y n t h e t i c mordenite c r a c k i n g c a t a l y s t and was s u p p l i e d by Norton C h e m i c a l Company. NIS-Hz e o l o n was p r e p a r e d b y s p r a y i n g n i c k e l on H-zeolon w i t h a subsequent s u l f i d i n g o p e r a t i o n . NIS-WS -SiC> Al 0 c a t a l y s t used was a commercial h y d r o c r a c k i n g catalyst. A n a l y s e s o f r e a c t a n t s and p r o d u c t s were done by s t a n d a r d methods. 2
R e s u l t s and D i s c u s s i o n H y d r o c r a c k i n g o f a n t h r a c e n e and phenanthrene was done b y u s i n g two d i f f e r e n t t y p e s o f d u a l - f u n c t i o n a l c a t a l y s t s , impregnated and p h y s i c a l m i x t u r e s . Data g i v e n i n T a b l e s I I I and IV i n d i c a t e d t h a t t h e g r o s s h y d r o c r a c k i n g p a t t e r n o f b o t h hydrocarbons remained almost same i r r e s p e c t i v e o f t h e n a t u r e o f c a t a l y s t used. Both impregnated and p h y s i c a l l y mixed c a t a l y s t s y i e l d e d almost s i m i l a r l i q u i d and gaseous p r o d u c t s i n d i c a t i n g t h a t h y d r o c r a c k i n g r e a c t i o n mechanisms remained same i n b o t h c a s e s under t h e e x p e r i m e n t a l c o n d i t i o n s used i n t h i s work. However, t h e r e were s l i g h t differences i n actual conversions obtained with impregnated and p h y s i c a l l y mixed c a t a l y s t c o m b i n a t i o n s . Product d i s t r i b u t i o n d a t a i n d i c a t e d t h a t h y d r o c r a c k i n g o f a n t h r a c e n e and phenanthrene proceeded t h r o u g h t h e
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
84
HYDROCRACKING
A N D
HYDROTREATING
9
X 11
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
10. Slurry Pump
1.
Heating Jacket
2.
Thermowell
3.
Magnetic Drive Assembly
15
|||
8.
Gas Sampling Line
^
9.
Pressure Gage
10.
Sample Injector
II.
Temperature
4.
Cooling Coil
5.
Stirrer
^
6.
Liner
10
7.
Thermowell,
Temperature
Indicator
12.
Hydrogen
13.
Stirrer
14.
Motor
15.
Temperature
Recorder
Tank
Controller
Controller
Figure 1. Batch stirred tank reactor
H2
1
Coal 2
Figure 2. Hydrocracking of coal. 1 and 2: Batch stirred tank reactor.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
5.
QADER
A N D M C O M B E R
Complex Aromatic Structures
TABLE I PROPERTIES OF COAL Proximate
(dry)
Wt,
V o l a t i l e Matter Ash F i x e d Carbon
%
42.4 6.9 50.7
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
U l t i m a t e (dry) Carbon Hydrogen Oxygen Sulfur Nitrogen
76.42 5.45 8.65 0.96 1.62
TABLE I I PROPERTIES OF COAL OIL
G r a v i t y °API B o i l i n g Range, c S u l f u r , wt. % N i t r o g e n , wt. % Oxygen, wt. % H/c (atomic)
: : : : : :
12.0 200-350 0.82 0.94 3.82 0.83
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975. 28.3 19.1
13.0 22.7
17.3
21.5
Methane
18.5
24.7
9.6
Ethane
Propane
10.7
0.8
Butanes 10.5
8.9
10.5
11.5
8.2
1.7
9.8
5.6
1.9
8.6
5.1
2.3
1.2
16.8
4.7
52.8
2
?
N I S - W S - S i O · AI9O3 (Physical Mixture)
0.3
8.5
3.0
3
8.4
Alkyl-
Tetralin,
Isomer
2
8.9
Benzene and benzenes
Naphthalene, Indanes
Hydro A n t h r a c e n e (C13)
2.8
1.7
Hydro A n t h r a c e n e ( 14) 1.9
1.8
2.5
2.1
Octahydro Anthracene 1.4
16.9
15.3
15.1
Tetrahydro Anthracene
Isomer
4.4
5.2
4.8
c
2
NIS-WS2-Si0 -Al 0 (Impregnated)
Dihydro Anthracene
NIS-H-Zeolon (Physical Mixture) 51.2
and
NIS-H-Zeolon (Impregnated) 55.1
%
1.0
54.5
Anthracene Higher
Products,
Anthracene Hydrocracking Temperature, °c : 475 P r e s s u r e , p s i : 3000 R e a c t i o n Time, mts. : 20 R e a c t a n t / c a t a l y s t , wt. :
TABLE I I I
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
5.
QADER
87
Complex Aromatic Structures
A N D M C O M B E R
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eu β 0 ω
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CM
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en
rH
00
φ β φ Ν β Φ
10 Φ β rd •Ρ
φ β rd
m
PQ
• Ikylbenzes
ο rd φ β Ν rj> I Φ Κ U
nthrene
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
Ο
•
m
•
rH tH
00
•
en fH
Ό β rd
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
ft
Ο
U
CU
Φ β rd ,β •Ρ Η
Φ β rd ,β •Ρ Φ
88
HYDROCRACKING A N D
o c c u r r e n c e o f hydrogénation, i s o m e r i z a t i o n and h y d r o c r a c k i n g r e a c t i o n s as a l s o shown p r e v i o u s l y by Qader e t a l (4-6). However, t h e r e were some d i f f e r e n c e s i n t h e c o n v e r s i o n s and n a t u r e o f p r o d u c t s o b t a i n e d from NIS-H-zeolon and N I S - W S - S i 0 - A l C > combinations from b o t h anthracene and phenanthrene. Product d i s t r i b u t i o n d a t a (Table V) o b t a i n e d i n t h e h y d r o c r a c k i n g o f c o a l , c o a l o i l , a n t h r a c e n e and phenanthrene over a p h y s i c a l l y mixed NIS-H-zeolon c a t a l y s t i n d i c a t e d s i m i l a r i t i e s and d i f f e r e n c e s between the p r o d u c t s o f c o a l and c o a l o i l on the one hand and a n t h r a c e n e and phenanthrene on t h e o t h e r hand. There were d i f f e r e n c e s i n the c o n v e r s i o n s which v a r i e d i n the o r d e r c o a l > a n t h r a c e n e > p h e n a n t h r e n e >· c o a l o i l . The y i e l d o f a l k y l b e n z e n e s a l s o v a r i e d i n the o r d e r a n t h r a c e n e > p h e n a n t h r e n e > c o a l o i l > c o a l under t h e c o n d i t i o n s used. The a l k y l b e n z e n e s and C -C^ h y d r o carbon p r o d u c t s from a n t h r a c e n e were s i m i l a r t o t h e p r o d u c t s o f phenanthrene. The most predominant component o f a l k y l b e n z e n e s was t o l u e n e and x y l e n e s were produced i n v e r y s m a l l q u a n t i t i e s . Methane was t h e most and butanes the l e a s t predominant components o f t h e gaseous p r o d u c t . The p r o d u c t s o f c o a l and c o a l o i l were a l s o found t o be s i m i l a r . The most p r e d o m i nant components o f a l k y l b e n z e n e s and gaseous p r o d u c t were benzene and propane r e s p e c t i v e l y . The d a t a a l s o i n d i c a t e d d i s t i n c t d i f f e r e n c e s between p r o d u c t s o f c o a l o r i g i n and pure a r o m a t i c h y d r o c a r b o n s . The a l k y l benzene p r o d u c t s o f c o a l and c o a l o i l c o n t a i n e d more benzene and x y l e n e s and l e s s t o l u e n e , e t h y l b e n z e n e and h i g h e r benzenes when compared t o the p r o d u c t s from a n t h r a c e n e and phenanthrene. The gaseous p r o d u c t s o f c o a l and c o a l o i l c o n t a i n e d more propane and butanes and l e s s methane and ethane when compared t o t h e p r o d u c t s o f a n t h r a c e n e and phenanthrene. The d i f f e r ences i n the h y d r o c r a c k e d p r o d u c t s were o b v i o u s l y due t o t h e d i f f e r e n c e s i n the n a t u r e o f r e a c t a n t s . Coal and c o a l o i l c o n t a i n h y d r o a r o m a t i c , n a p h t h e n i c , h e t e r o c y c l i c and a l i p h a t i c s t r u c t u r e s , i n a d d i t i o n t o polynuclear aromatic s t r u c t u r e s . H y d r o c r a c k i n g under s e v e r e c o n d i t i o n s y i e l d e d more BTX as shown i n T a b l e VI. The y i e l d s o f BTX o b t a i n e d from c o a l , c o a l o i l , a n t h r a c e n e and phenanthrene were r e s p e c t i v e l y 18.5, 25.5, 36.0, and 32.5 p e r c e n t . Benzene was the most 2
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
HYDROTREATING
2
2
3
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Conversion, wt. % A l k y l b e n z e n e s , wt.% Composition o f Benzenes, vol. % Benzene Toluene Ethylbenzene Xylenes P r o p y l and Butylbenzenes Composition of Gas, V o l . % Methane Ethane Propane Butanes
Coal O i l 45.0 3.5 40.2 17.5 8.7 14.3 19.3 13.2 26.1 45.3 15.4
Coal 61.0 2.6 45.9 20.2 10.2 16.3 7.4 12.4 24.6 35.9 27.1
42.6 35.4 20.6 1.4
17. 46, 15. 1, 19.
58.0 8.4
Anthracene
2
C a t a l y s t : H - z e o l o n (10) + W S T e m p e r a t u r e , ° c : 500 P r e s s u r e , p s i : 3000 R e a c t i o n T i m e , m t s . : 0 + 20 Reactant/catalyst, (wt) : 1.0
TABLE V NATURE OF HYDROCRACKED PRODUCTS
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
46.4 28.4 21.9 3.3
20. 44. 13, 1, 20,
49.0 4.4
Phenanthrene
CD
95
a
3
3
S"
1
Ο ο
η
ο
fO
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
BTX A n a l y s i s , v o l . % Benzene Toluene Ethylbenzene Xylenes
Temperature, c Pressure, p s i R e a c t i o n Time, mts C o n v e r s i o n , wt. % BTX y i e l d , wt. %
49.5 22.4 9.5 18.6
540 3500 30 82 18.5
Coal
48.4 20.8 10.2 20.6
520 3000 30 71 25.5
Coal O i l
21.5 54.6 19.1 4.8
520 3000 30 79 36.0
Anthracene
TABLE VI BTX PRODUCTION FROM DIFFERENT FEEDSTOCKS
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
24.8 51.3 18.8 5.1
520 3000 30 73 32.5
Phenanthrene
5.
QADER
A N D M C O M B E R
91
Complex Aromatic Structures
predominant component o f c o a l and c o a l o i l p r o d u c t s , whereas anthracene and phenanthrene p r o d u c t s c o n t a i n e d more t o l u e n e . Kinetics H y d r o c r a c k i n g c o n v e r s i o n d a t a were e v a l u a t e d b y 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 ( i ) where "x" i s f r a c t i o n a l c o n v e r s i o n o f r e a c t a n t and Q i s a c o n s t a n t . The d a t a were found t o be c o m p a t i b l e w i t h e q u a t i o n ( i ) as shown i n F i g u r e s 3 - 6 .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
L n ( l - x ) = -KT + Q ( i ) F i r s t o r d e r r a t e c o n s t a n t s (Table V I I ) v a r i e d i n t h e order c o a l >anthracene> ghenanthrene>coal o i l i n the temperature range o f 450 - 500 c under a p r e s s u r e o f 3000 p s i . The a r r h e n i u s a c t i v a t i o n e n e r g i e s (Table V I I I and F i g u r e 7) based on f i r s t o r d e r r a t e c o n s t a n t s i n d i c a t e d t h a t t h e r a t e s o f h y d r o c r a c k i n g were con t r o l l e d b y c h e m i c a l r e a c t i o n s . The r a t e d a t a o f phenanthrene and c o a l o i l were t e s t e d f o r c o m p a t i b i l i t y w i t h t h e d u a l - s i t e mechanism o f Langmuir and H i n s h e l wood. The model shown i n e q u a t i o n ( i i ) was e a r l i e r used f o r t e s t i n g h y d r o c r a c k i n g d a t a o f naphthalene, anthracene and pyrene by Qader e t a l (5, 6 ) . 1^ =
κ
1
2
(κ*
\ \ c
Κ h a 2
+ )h
(κ*
\ c
. C (ii) h
) h
r
where Κ = e x p e r i m e n t a l r a t e c o n s t a n t = c o n c e n t r a t i o n o f hydrogen = c o n c e n t r a t i o n o f r e a c t a n t hydrocarbon Κ*,
K
a #
or o i l
= constants
A t c o n s t a n t hydrogen p r e s s u r e , e q u a t i o n ( i i ) becomes e q u a t i o n ( i i i ) s i n c e C_ becomes c o n s t a n t . h l i = M + NC (iii) K 2
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
92
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
0.0
I 0
I
I
0+10
I
0+20 0+30 TIME, MINUTES
I 0+40
1 0+60
Figure S. First order plot of anthracene
TIME, MINUTES
Figure 4. First order plot of phenanthrene
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
0
,
5
Ο
04-10
0+20 0+30 0+40 TIME, MINUTES
Figure 6. First order plot of coal
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING A N D
94
HYDROTREATING
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Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
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In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
QADER
A N D M C O M B E R
Complex Aromatic Structures
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
-1.5 μ
1.40 1/TxlC?
Figure 7. Arrhenius plots
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
96
HYDROCRACKING A N D H Y D R O T R E A T I N G
1
Where M =
h
Κ
Ν =,
a
= constant
= constant
At constant c o n c e n t r a t i o n of hydrocarbon or o i l , C becomes c o n s t a n t and e q u a t i o n ( i i ) becomes e q u a t i o n (iv)
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
Κ = Ζ ·
c,
h
Where Ζ = Κ* Κ (1 + Κ
Κ C )
= constant (iv)
The e x p e r i m e n t a l d a t a o b t a i n e d i n t h e h y d r o c r a c k i n g o f c o a l , c o a l o i l and phenanthrene were t e s t e d w i t h e q u a t i o n s ( i i i ) and ( i v ) as shown i n F i g u r e s 8 and 9 and t h e d a t a were found c o m p a t i b l e w i t h t h e model. This c o m p a t i b i l i t y confirmed that the r a t e s o f h y d r o c r a c k i n g were c o n t r o l l e d by s u r f a c e c h e m i c a l r e a c t i o n s as were a l s o i n d i c a t e d b y a r r h e n i u s a c t i v a t i o n e n e r g i e s (Table V I I I ) . Acknowledgement T h i s work was done under t h e s p o n s o r s h i p o f t h e O f f i c e o f C o a l Research and t h e U n i v e r s i t y o f Utah. Some o f t h e h y d r o c r a c k i n g experiments on c o a l and c o a l o i l were done b y B i l l B e r r e t t and t h e a n a l y t i c a l work was done by Jim L i g h t and E a r l E v e r e t t .
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
5.
QADER
A N D
M C O M B E R
Complex Aromatic Structures
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
REACTANT
(gm.)
Figure 8. Variation of rate constant with weight
Figure 9. Variation of rate constant with pressure
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
97
98
HYDROCRACKING A N D H Y D R O T R E A T I N G
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005
Literature Cited 1. S c h r o e d e r , W.C., U. S. P a t e n t 30,030,297 and 3,152,063 2. Qader, S . A . - The Oil and Gas J o u r n a l , 72, No. 29, 58 (1974) 3. G i v e n , P. H. - F u e l , 39, 147 (1960) 4. Qader, S. Α., D. B. McOmber and W. H. W i s e r , 166th N a t i o n a l M e e t i n g , ACS, F u e l C h e m i s t r y Division, p r e p r i n t s 18, No. 4, 127 (1973) 5. Qader, S. A. - J o u r n a l o f t h e Institute o f Petroleum 59, No. 568, 178 (1973) 6. Qader, S. Α., L. Chun Chen and D. B. McOmber, 165th N a t i o n a l M e e t i n g , ACS, F u e l C h e m i s t r y Division - p r e p r i n t s 18, No. 1, 60 (1973)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
6 Diesel and Burner Fuels from Hydrocracking in Situ Shale Oil PHILIP L. COTTINGHAM and L E O G. NICKERSON
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
Laramie Energy Research Center, Energy Research and Development Administration, Laramie, Wyo. 82070
For several years, the Laramie Energy Research Center has conducted research in recovering shale o i l through in situ retorting by the underground combustion method. Crude shale o i l s produced by this method normally have lower specific gravities, viscosities, and pour points than do crude shale o i l s produced in the gas combustion or N-T-U retorts. They also contain somewhat less nitrogen, but the sulfur content is not greatly different from that of the crude o i l s from these aboveground retorts. Percentages of both elements are higher than desirable in liquid fuels or in feedstocks that are to be processed to high-quality liquid fuels by most catalytic refining processes. Catalytic hydrogenation at cracking conditions, referred to here as "hydrocracking," has been found by previous experiments to be a suitable method for producing low-sulfur, low-nitrogen "synthetic crude" o i l s from in situ crude shale o i l s (1,2,1). One of the primary objectives of these previous experiments has been to increase the quantity of gasoline contained in the hydrocracked synthetic crudes. A limited investigation of the s u i t a b i l i t y of fractions of the hydrocracked o i l s as catalytic reforming and catalytic cracking feedstocks for the production of gasoline has been made however, little attention has been given to the types of diesel fuels and fuel oils that can be prepared from the fractions. The purpose of the present work was to investigate the quant i t y and quality of diesel fuels and fuel o i l s that could be prepared from the liquid product obtained by hydrocracking of in situ combustion shale oil. A sample of the in situ crude o i l was hydrocracked at operating conditions that had been found by previous experiments to be effective in eliminating most of the nitrogen and sulfur from the o i l and in greatly reducing the average b o i l ing point of the oil. The hydrocracked o i l was d i s t i l l e d into a 350° F end-point reforming stock and small-volume heavier fractions. Diesel fuels, suitable for use also as fuel o i l s , were prepared by blending small-volume fractions.
99 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
100
HYDROCRACKING A N D H Y D R O T R E A T I N G
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
Apparatus and Operating Procedure A simplified flow diagram of the hydrocracking equipment is shown in Figure 1. The reactor was a type 316 stainless steel tube 40 inches long, with 9/16-inch inside diameter and 1-inch outside diameter. A stainless steel screen 10^ inches from the bottom of the reactor supported 50 ml of catalyst that extended approximately 12% inches above the screen. A second screen on top of the catalyst supported 50 ml of quartz chips in the upper, preheating section of the reactor. The reactor was surrounded by a c y l i n d r i c a l , 3-inch-outside-diameter aluminum block, contained in a 36-inch-long electric furnace that covered essentially a l l but the exposed high-pressure fittings at the ends of the reactor. Temperatures were measured by five thermocouples placed at uniformly spaced intervals along the catalyst-containing section of the reactor in a groove in the inner wall of the aluminum block. Other thermocouples were used to control the temperature of the surrounding furnace. Before the hydrocracking experiment, the catalyst was pretreated in the reactor for 16 hours at 700° F with a mixture of 1.1 standard cubic feet of a i r and 0.41 pound of steam per pound of catalyst per hour. After the pretreatment, the reactor was cooled to 500° F; then the steam was cut off. When the reactor cooled to 350° F, the a i r flow was cut off. The reactor was next purged with helium and pressurized to 250 psig with hydrogen. A stream of hydrogen containing 5 volume-percent hydrogen sulfide at a total pressure of 250 psig was then passed through the reactor at a rate of 1 scf per hour for 4 hours. During this time the reactor was heated from 350° to 600° F. The reactor was then heated to the planned hydrocracking temperature, and brought to the planned total reaction pressure with hydrogen, and a stream of hydrogen at the proposed experimental rate was passed through the reactor for 30 minutes. The o i l feed pump was then started. During the experiment, o i l pumped by positive displacement was mixed with hydrogen at the top of the reactor and passed downward through the catalyst. The resulting products passed through a backpressure regulator into a separator maintained at 200 psig and 75° F. Gas from the separator passed through a second backpressure regulator and was metered and sampled for gas chromatographic analysis. The liquid product was drained from the separator at the end of each 24-hour period and was washed with water to remove hydrogen sulfide and ammonia before i t was analyzed. Hydrogen flow was metered with a mass flowmeter, but total hydrogen feed was measured by the volume removed from calibrated storage vessels. Hydrogen consumption was calculated from the analyses of feed and product gases. After the experiment, the used catalyst was purged with steam and then regenerated with a mixture of steam and a i r ; the regeneration gas was dried and any carbon dioxide formed was absorbed by Ascarite for determination of the percent carbon deposit.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
6.
coTTiNGHAM A N D NiCKERSON
101
ROTAMETER
PRESSURE -REGULATOR
BACK-PRESSURE REGULATOR METERING VALVE
oc L U α. CO.
ζ
LU ο Ο χ
œ.
g ecu
SOR
TO GAS HOLDER
YDR
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
Diesel and Burner Fuels
PRODUCT OIL TO DISTILLATION
<
OIL
BACK PRESSURE REGULATOR
Figure 1. Simplified flow diagram of hydrogénation unit
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
102
HYDROCRACKING A N D H Y D R O T R E A T I N G
TABLE I.
- Hydrocracking of in situ crude shale oil over nickel-molybdena catalyst
Operating conditions: Temperature, F Pressure, psig Space velocity, V /V /hr Throughput, V / V Hydrogen feed, scf/bbl Hydrogen consumed, scf/bbl 0
0
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
0
c
c
800 1500 0.48 125 5000 1760
Yield, volume-percent Yield, weight-percent Properties: Specific gravity, 60/60° F API Nitrogen, weight-percent Sulfur, weight-percent Carbon/hydrogen weight ratio Carbon residue, weight-percent Pour point, F Viscosity at 100° F: Kinematic, cs Saybolt Universal Seconds ASTM d i s t i l l a t i o n , F: IBP 5 volume-percent recovered 10 volume-percent recovered 20 volume-percent recovered 30 volume-percent recovered 40 volume-percent recovered 50 volume-percent recovered 60 volume-percent recovered 70 volume-percent recovered 80 volume-percent recovered 90 volume-percent recovered EP Recovery, volume-percent Residue, volume-percent Loss, volume-percent 0
0
In situ crude 100.0 100.0
Hydrocracked oil 97.6 89.7
0.8800 28.75 1.62 0.82 7.01 1.8 40
0.8086 43.56 0.02 0.02 ND ND ND
5.82 45
ND ND
0
293 346 373 424 461 491 536 584 621 658 704 92.0 6.0 2.0
138 258 305 362 403 437 471 507 546 599 672 717 94.5 2.5 3.0
ND, not determined
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
6.
C O T T I N G H A M A N D NICKERSON
Diesel and Burner Fuels
103
Preparation of Hydrocracked Oil The in situ crude shale o i l feedstock was obtained during the 28th through the 37th day of operation of a 42-day in situ combustion retorting experiment at a site near Rock Springs, Wyo. (4^5,6). The crude contained 0.01 weight-percent ash, which was removed by f i l t r a t i o n with diatomaceous s i l i c a f i l t e r aid before the o i l was hydrocracked. The f i l t e r e d o i l was hydrocracked in a once-through operation at 800° F, 1,500 psig, and 0.48 volume of o i l per volume of catalyst per hour (V /V /hr) over a catalyst that contained nickel oxide and molybdenum oxide on alumina in the form of 1/8-inch by 1/16-inch extrusions. Total throughput of crude o i l in the planned 10-day run was 125 volumes of o i l per volume of catalyst (V /V ). Operating conditions, properties of the feedstock, yields, and properties of the hydrocracked o i l (total liquid product) are shown in Table I. The yield of synthetic crude was 97.6 volume-percent, or 89.7 weight-percent. The decrease in quantity of liquid was accompani ed by considerable reduction in the average boiling point, and specific gravity of the liquid product compared with those of the in situ crude. At the same time, about 98 percent of the nitrogen and sulfur content was eliminated. Gas formed was 9.4 weight-per cent of the feed, and carbon deposited on the catalyst was 0.13 weight-percent of the feed. The analysis of the product gas, calculated to a hydrogenfree basis, is shown in Table II. The high percentage of methane and the predominance of η-butane and n-pentane over the branched compounds suggest that they were produced by a thermal cracking reaction with hydrogénation of the olefins. 0
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
0
TABLE II.
c
c
- Analysis of gas from hydrocracking in situ crude
Gas Methane Ethane Propane i-Butane n-Butane i-Pentane n-Pentane
Volume-percent of gas 45.8 33.6 14.0 1.2 4.2 0.5 0.7
Diesel Fuels and Fuel Oil As a means of preparing high percentages of diesel fuels with good quality from the hydrocracked o i l , a batch d i s t i l l a t i o n of the o i l was made in a packed laboratory d i s t i l l a t i o n column in which a f i r s t fraction was removed at a corrected column head
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
104
HYDROCRACKING A N D H Y D R O T R E A T I N G
temperature of 364° F (at 760 mm). This fraction, considered as a catalytic reforming feedstock, had an ASTM-disti"Nation [7) end point of 350° F. Its Research Method octane numbers were only 39, clear, and 69 with 3 ml of tetraethyllead, and i t would require reforming before use in gasoline. The remainder of the d i s t i l l a tion was conducted at 10 mm absolute pressure, and 54 small-volume d i s t i l l a t e fractions were collected at 5° F intervals between dist i l l a t i o n column head temperatures of 145° F and 428° F (at 10 mm), corresponding to temperatures of 364° and 725° F at 760 mm. The d i s t i l l a t i o n residuum contained a large amount of wax that separated when the residuum was cooled to room temperature. The wax was removed by mixing the residuum with three times its volume of acetone, c h i l l i n g the mixture to 32° F, and f i l t e r i n g out the precipitated wax. Acetone was removed from both the f i l trate and precipitate by d i s t i l l a t i o n . Total wax removed, including a small quantity washed from the d i s t i l l a t i o n column with boiling acetone, amounted to 48 weight-percent of the residuum. From a study of the d i s t i l l a t i o n data for the hydrocracked o i l , i t was estimated that quantities of city bus (C-B), trucktractor (T-T), and stationary-marine (S-M) diesel fuels in the volume ratios of 2:2:1 and f i t t i n g the average d i s t i l l a t i o n characteristics (8) of diesel fuels now being sold could be made from the hydrocracked small-volume d i s t i l l a t e fractions. Beginning with the type C-B diesel f u e l , appropriate amounts of the smallvolume fractions were calculated that would produce a fuel approximately f i t t i n g the 10, 50, and 90 percent ASTM d i s t i l l a t i o n points of typical diesel fuels now being sold. Similar calculations were made for the desired types T-T and S-M fuels. The c a l culated quantity of each fuel was then adjusted to use up as much as possible of the available small-volume fractions without greatly changing the desired d i s t i l l a t i o n characteristics of the proposed fuels. According to these calculations, portions of some of the small-volume fractions would be l e f t over, and these leftover portions were considered suitable for mixing with the dewaxed dist i l l a t i o n residuum to make fuel o i l . The small-volume fractions were blended according to the above procedure, producing the quantities of diesel fuels shown (as percentages) in Table III. The dewaxed residuum was mixed with approximately four times i t s volume of lower boiling oil not used in the diesel fuel blends, and is reported in Table III as fuel o i l . Properties of the blended diesel fuels and fuel o i l are shown in Table IV. The total yield of diesel fuels was 51.6 volume-percent of the in situ crude. The properties of these fuels f e l l within the limits (Table V) of those of corresponding petroleum diesel fuels currently marketed in the United States (8) except for the carbon residue of the S-M shale-oil diesel f u e l ; this residue was slightly higher than those of the petroleum diesel fuels but was probably acceptable. The value of 0.36 weight-percent for the carbon residue on the 10-percent bottoms of the S-M fuel was only a
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
6.
coTTiNGHAM
TABLE III.
A N D
NiCKERsoN
- Yields of products from d i s t i l l a t i o n and blending
Reforming stock C-B diesel fuel T-T diesel fuel S-M diesel fuel Fuel o i l Wax Light ends from d i s t i l l a t i o n D i s t i l l a t i o n loss Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
105
Diesel and Burner Fuels
Weight-percent of in situ crude
Volume-percent of in situ crude
16.0 19.7 18.5 10.1 20.4 3.8 0.6 0.6
18.5 21.3 19.6 10.7 21.5 ND ND ND
ND, not determined t r i f l e greater than the upper ASTM limit of 0.35 percent for the lighter grade 2-D diesel fuels (7J, and no limit is listed for the grade 4-D which corresponds to type S-M. With the exception of the carbon residue and high flash point, the properties of the S-M shale-oil diesel fuel also f e l l within the limits of the properties of the type R-R (railroad) diesel fuels now being marketed. Most of the properties of the fuel o i l blend containing the dewaxed residuum were within the range of properties of the petroleum S-M diesel fuels shown in Table V, Its high cetane index of 65 suggests that this fuel o i l be used as an S-M diesel fuel rather than as a burner f u e l . The sulfur percentages of 0.02 weight-percent or less in the shale oil diesel fuels would permit these fuels to be classed as low-sulfur diesel fuels. Nitrogen percentages were low, ranging from 141 to 202 parts per million (ppm). Cetane indexes, calculated by ASTM method D-976 (7), were excellent, ranging from 48 to 56. Table VI shows the range of properties of grades 1, 2, and 4 burner fuel o i l s marketed in the United States in 1974 (9). Most of these fuels were also marketed as diesel fuels (8,9). The shale-oil types C-B and T-T diesel fuels would, respectively, f i t with the grades 1 and 2 burner fuels. The shale-oil S-M diesel fuel would also f i t with the grade 2 burner fuels. The shale-oil fuel o i l fraction had a d i s t i l l a t i o n range resembling the grade 2 fuels, but i t s viscosity was intermediate between those of the grade 2 and grade 4 fuels. The C-B, T-T, and S-M shale oil diesel fuels respectively met the ASTM requirements []) for grades 1-D, 2-D, and 4-D diesel fuels and Nos. 1, 2, and 4 fuel o i l s , with some minor exceptions. Thus, the 90-percent d i s t i l l a t i o n temperature of the T-T diesel fuel was 3° F lower than the ASTM lower limit for grade 2-D diesel and No. 2 fuel o i l . Also, the viscosity of the S-M diesel fuel was slightly lower than the lower limit specified for grade 4-D
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
106
HYDROCRACKING AND HYDROTREATING
TABLE IV. - Properties of reforming stock, diesel fuels, and fuel o i l
Specific gravity, 60/60° F °
A
P
I
0
Flash point, F Pour point, F C residue on 10 pet bottoms, wt-pct Ash, wt-pct Viscosity at 100° F: Kinematic, cs SUS Sulfur, wt-pct Nitrogen, ppm Cetane index ASTM d i s t i l l a t i o n , F at 760 mm: IBP 10 vol-pet recovered 20 vol-pet recovered 30 vol-pet recovered 40 vol-pet recovered 50 vol-pet recovered 60 vol-pet recovered 70 vol-pet recovered 80 vol-pet recovered 90 vol-pet recovered EP Recovery, vol-pet Residue, vol-pet Loss, vol-pet
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
0
Reforming stock
C-B diesel
T-T diesel
S-M diesel
Fuel oil
0.7600 54.68 NAp NAp
0.8159 41.93 188 -50
0.8262 39.75 212 -30
0.8300 38.98 265 -20
0.8367 37.62 325 30
0.14 <0.001
0.16 <0.001
0.36 0.42 <0.001 <0.001
NAp NAp <0.001 20 NAp
1.66 32 0.01 141 48
2.40 34.0 0.02 166 54
2.96 35.8 0.02 202 56
5.07 42.6 0.02 396 65
158 223 246 263 277 290 302 313 323 335 350 97.0 2.0 1.0
379 400 409 414 418 422 429 437 447 469 517 95.0 2.0 3.0
404 442 454 465 474 484 494 505 518 537 554 98.0 1.0 1.0
410 450 468 483 495 507 524 546 573 605 628 97.5 2.0 0.5
394 528 562 572 580 588 599 610 624 666 667 92.0 7.0 1.0
NAp NAp
0
NAp, not applicable
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
0
0
0
0
Gravity, API Flash point, F Viscosity at 100° F: Kinematic, cs Pour point, F Sulfur, weight-percent C res. on 10 percent, weight-percent Ash, weight-percent Cetane no. or index D i s t i l l a t i o n temperature, F: IBP 10 percent recovered 50 percent recovered 90 percent recovered EP
Test
320 357 403 454 476
488 520 558 603 663
4.34 25 0.52 0.18 0.005 65.8
1.50 -70 0.004 0.000 0.000 39.8 301 329 382 444 476
1.30 <-60 0.001 0.001 0.000 38.1 488 520 596 656 700
4.55 25 1.07 0.26 0.010 65.8
47.4 230
47.4 194
33.3 124
27.3 112
Type T-T Min. Max.
Type C-B Max. Min.
TABLE V. - Range of diesel fuels produced in the United States during 1974
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
310 376 434 476 514
1.60 -40 0.01 0.014 0.000 34.1
27.2 136
488 520 558 639 688
4.34 25 0.85 0.26 0.005 65.8
43.4 198
Type R-R Min. Max.
327 384 454 535 582
1.94 -35 0.06 0.05 0.000 38.0
9.6 136
535 595 680 656 700
22.1 65 2.85 0.18 0.02 63.1
41.1 290
Type S-M Min. Max.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
0
0
0
0
Gravity, API Flash point, F Viscosity at 100° F: Kinematic, cs Pour point, F Sulfur, weight-percent C res. on 10 percent, weight-percent C res. on 100 percent, weight-percent Ash, weight-percent Water and sediment, volume-percent D i s t i l l a t i o n temperature, F: IBP 10 percent recovered 50 percent recovered 90 percent recovered EP
Test
380 413 480 560 614
2.60 0 0.38 0.18 NR NR 0.025
1.28 -70 0.002 0.00 NR NR 0.000 303 336 382 440 464
47.9 160
36.2 104
Grade 1 Min. Max.
293 333 432 528 575
1.70 -50 0.03 0.002 NR NR 0.00
29.5 114
416 469 544 644 698
3.70 25 0.64 0.27 NR NR 0.10
43.0 192
Grade 2 Min. Max.
TABLE VI. - Range of properties of d i s t i l l a t e burner fuels produced in the United States during 1974
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
NR
9.64 -50 0.46 NR 0.52 0.002 0.06
17.6 156
NR
30.1 75 1.44 NR 7.6 0.03 0.2
28.2 216
Grade 4 Min. Max.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
6.
coTTiNGHAM
A N D
NiCKERSON
Diesel and Burner Fuels
109
diesel fuel and No. 4 fuel o i l . The pour points met the ASTM requirements for burner fuel o i l s . The ASTM pour point requirements for diesel fuels depend on the ambient temperature at the place of use; for most purposes, the pour points of the shale-oil diesel fuels would be satisfactory. The properties of the fuel o i l blend met the requirements for ASTM No. 4 fuel o i l (usually considered a d i s t i l l a t e fuel) except that its viscosity was low, f a l l i n g between the specified requirements for No. 2 and No. 4 fuel oils (7), and i t s pour point of 30° F was higher than the ASTM-recommended maximum of 20° F. The fuel could be used as a low-sulfur, high-cetane-index grade 4-D diesel fuel in warm weather or where preheating f a c i l i t i e s were available. The yield of fuel oil prepared from the blended dewaxed residuum was 21.5 volume-percent of the in situ crude. The total of this, plus the 51.6 volume-percent of diesel fuels, amounted to 73.1 volume-percent of the in situ crude that could be used as low-sulfur diesel fuels or Nos. 1 through 4 burner fuels. Summary In situ crude shale o i l , produced by the underground combustion retorting method, was hydrocracked over a nickel-molybdena catalyst at 800° F and 1,500 psig. The liquid product was dist i l l e d into a low-octane reforming feedstock amounting to 18.5 volume-percent of the in situ crude plus a large number of smallvolume higher boiling fractions and a small quantity of waxy residuum. Most of the small-volume d i s t i l l a t e fractions were blended into types C-B, T-T, and S-M diesel fuels whose properties resembled those of diesel fuels and d i s t i l l a t e fuels now being marketed. The diesel fuels also met the ASTM requirements for diesel fuels and d i s t i l l a t e fuel o i l s with minor exceptions. All of the shale-oil diesel fuels had very low sulfur contents and very high cetane indexes. The dewaxed d i s t i l l a t i o n residuum was blended with a portion of the small-volume d i s t i l l a t e fractions to form a fuel oil f i t ting the requirements for No. 4 fuel o i l except that its viscosity was between the viscosity limits for No. 2 and No. 4 fuels and its pour point of 30° F was higher than ASTM recommendations, although in the range of No. 4 fuel o i l s now being marketed. This fuel oil could also be used as a low-sulfur, high-cetane-index S-M diesel fuel. The yield of diesel fuels was 51.6 volume-percent of the in situ crude, and the yield of No. 4 fuel oil was 21.5 volume-percent, for a total of 73.1 volume-percent of the in situ crude that could be used as low-sulfur, high-cetane-index diesel fuels or Nos. 1 through 4 burner fuels.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
110 Literature Cited 1. 2. 3. 4. 5. 6.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch006
7. 8. 9.
Frost, C. Μ., and P. L. Cottingham. BuMines RI 7844 (1974). Frost, C. M., R. E. Poulson, and H. B. Jensen, Preprints, Div. of Fuel Chem., Inc., ACS (1974) 19 (2) 156. Poulson, R. E., C. M. Frost, and H. B. Jensen, Preprints, Div. of Fuel Chem., Inc., ACS (1974) 19 (2) 175. Burwell, E. L., H. C. Carpenter, and H. W. Sohns. BuMines TPR 16 (1969). Burwell, E. L., T. E. Sterner, and H. C. Carpenter. J . Petrol. Technol. (1970) 1520. Carpenter, H. C., E. L. Burwell, and H. W. Sohns. J . Petrol. Technol. (1972) 21. American Society For Testing Materials. 1973 Book of ASTM Standards. Part 17: Petroleum Products. Shelton, Ella Mae. BuMines PPS 87 (1974). . BuMines PPS 86 (1974).
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
7 Synthoil Process and Product Analysis HEINZ W. STERNBERG, RAPHAEL RAYMOND, and SAYEED AKHTAR
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
Energy Research and Development Administration, Pittsburgh Energy Research Center, 4800 Forbes Ave., Pittsburgh, Penn. 15213
Many power generating stations i n the United States burn im ported fuel oils, instead of coal, to meet environmental protec tion regulations. Large quantities of fuel oils are imported annually at considerable strain to the nation's balance of pay ment, a strain that could be removed by burning environmentally acceptable coal-derived fuels prepared from internal resources. Towards this end, the Energy Research and Development Administra tion is developing a process known as the SYNTHOIL process to convert coal to a low-sulfur, low-ash utility fuel. In the process, coal is liquefied and hydrodesulfurized catalytically in a turbulent-flow, packed-bed reactor (1-3). The gross liquid product on centrifugation yields a nonpolluting fuel oil suitable for power generation. The results of a study of the chemical composition and viscosity of the product oils obtained at differ ent operating conditions are presented in this paper. The inter relationship of chemical composition and viscosity i s of special interest in view of the importance of the latter in centrifugation of the gross liquid products and in pipeline transportation of the product oil. Plant and Operating Conditions The flowsheet of a 1/2-ton (slurry) per day SYNTHOIL bench scale plant, currently i n operation at the Energy Research and Development Administration laboratory in Bruceton, Pennsylvania, is shown i n figure 1. The v e r t i c a l l y placed reactor is made of two interconnected stainless steel tubings of 1.1-inch ID χ 14.5-ft long each. The upper end of the f i r s t section i s connected to the lower end of the second section with a 5/16-inch ID empty tubing. Thus, the plant may be operated with one or both sections of the reactor packed with catalyst while the fluids flow upwards through each. Hydrogen and a slurry of 35 to 45 percent coal i n recycle o i l are introduced concurrently in a 3-inch ID χ 11-ft long preheater packed with 3/4-inch χ 3/4-inch ceramic pellets which 111 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
112
HYDROCRACKING AND HYDROTREATING
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
proirote heat t r a n s f e r . The heated feed stream enters the r e a c t o r at the lower end of the f i r s t s e c t i o n and the product stream e x i t s at the upper end of the second s e c t i o n . The l i q u i d s and unreacted s o l i d s are separated from the gases and c e n t r i f u g e d to o b t a i n the product o i l . The gases, a f t e r scrubbing out H2S and NH3, are r e c y c l e d without d e p r e s s u r i z a t i o n . The flow of E2 through both the preheater and the r e a c t o r i s i n t u r b u l e n t regime. The o p e r a t i n g c o n d i t i o n s f o r the three runs FB-38, FB-39, and FB-40, the r e s u l t s from which are discussed i n t h i s paper, are given i n t a b l e I . The l e n g t h of the 1 . 1 - i n c h ID r e a c t o r was 29 f t i n run FB-38 and 14.5 f t i n FB-39 and FB-40. Runs FB-38 and FB-39 were both conducted at 4,000 p s i but the r e a c t o r temperature was 4 1 5 ° C i n FB-38 and 4 5 0 ° C i n FB-39. Run FB-40 was conducted at 2,000 p s i and 4 5 0 ° C . TABLE I . -
Run numbers and operating
conditions FB-39
FB-40
29
14.5
14.5
11
5.5
5.5
4,000
4,000
2,000
415
450
450
Feed r a t e o f (35 c o a l + 65 r e c y c l e oil) slurry, lb/hr
25
25
25
Time on stream, h r
30
380
360
Run No.
FB-38
Length of the 1 . 1 - i n c h ID reactor, ft Charge weight of C o - M o / S i 0 2 - A l 0 catalyst, lb 2
3
Plant pressure, psig Reactor temperature,
0
C
The a n a l y s i s of the c o a l used i n these runs i s given i n table II. The c o a l contained 5.5 percent s u l f u r and 16.5 percent ash. The p y r i t i c s u l f u r i n c o a l was 3.08 percent and the organic s u l f u r 1.95 p e r c e n t . Product A n a l y s i s The l i q u i d products were c o l l e c t e d i n 4-hour batches, c e n t r i fuged, sampled, and analyzed f o r asphaltene, o i l , elementary composition (C, H , N , S ) , a s h , s p e c i f i c g r a v i t y , and v i s c o s i t y . In runs FB-38 and FB-40, the asphaltene content i n c r e a s e d w i t h time. In run FB-39, on the other hand, the asphaltene content decreased during the f i r s t 120 hours from 18 percent to 7 p e r c e n t , remained around 7 percent f o r about 60 h o u r s , and
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
STERNBERG
E T
TABLE I I . -
A L .
Synthoil Process
Analysis
o f feed c o a l ,
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
Proximate a n a l y s i s , wt Moisture Ash V o l a t i l e matter F i x e d carbon U l t i m a t e a n a l y s i s , wt Hydrogen Carbon Nitrogen Oxygen Sulfur Ash Forms o f s u l f u r , wt Sulfate Pyritic
as
received
pet 4.2 · 36.2 43.1
1
6
5
pet 6
4.8 · I · 11.3 · ·
0
7
2
1
5
5
6
5
pet
Organic C a l o r i f i c value, Btu/lb Rank:
1
7
°-^ 3.08 ·
·
1.95 11,020
hvBb
A b l e n d from Kentucky seams #9, 11, 12, and 13 which mined t o g e t h e r . Ohio County, Western Kentucky.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
are
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
114
HYDROCRACKING AND HYDROTREATING
during the l a s t 200 hours i n c r e a s e d from 7 percent to 25 p e r c e n t . The analyses o f some of the samples c o l l e c t e d from runs FB-38, FB-39, and FB-40 are l i s t e d i n t a b l e s I I I , IV, and V . I n s p e c t i o n of the data shows that the v i s c o s i t y o f the product o i l i n c r e a s e s w i t h asphaltene content. To l e a r n more about the nature o f asphaltenes and t h e i r e f f e c t on v i s c o s i t y , we f r a c t i o n ated samples of product o i l from runs FB-38 and FB-40 according to the scheme shown i n f i g u r e 2. U l t i m a t e analyses and molecular weights o f the v a r i o u s f r a c t i o n s a r e shown i n t a b l e s V I , V I I , and V I I I . In a d d i t i o n to heavy o i l and asphaltene, these t a b l e s a l s o l i s t p y r i d i n e s o l s and p y r i d i n e i n s o l s . These two f r a c t i o n s are always lumped together as "benzene i n s o l s " , but we separated the benzene i n s o l s (toluene i n s o l s i n our case) i n t o a p y r i d i n e s o l u b l e and a p y r i d i n e i n s o l u b l e f r a c t i o n . I t i s a common p r a c t i c e to measure the e f f i c i e n c y of a c o a l l i q u e f a c t i o n process by the percent coal-to-benzene s o l s conversion on a m o i s t u r e and a s h - f r e e b a s i s , the assumption being that the benzene i n s o l u b l e m a t e r i a l i s unreacted c o a l and, by i m p l i c a t i o n , that i t i s not s o l u b l e i n the product o i l and does not c o n t r i b u t e to i t s v i s c o s i t y . These assumptions are m i s l e a d i n g . Tables V I , V I I , and V I I I show that i n a l l cases more than 50 percent of the toluene i n s o l s are p y r i d i n e s o l u b l e and therefore cannot be considered unreacted c o a l . I t i s only the p y r i d i n e i n s o l s that may be unreacted c o a l , carbon, or ash. Moreover, removal of the toluene i n s o l s r e s u l t s i n a considerable decrease i n the v i s c o s i t y o f the product o i l . F o r example, the v i s c o s i t y of a product o i l (FB-40, batch 88) dropped from 1,433 to 907 a f t e r removal o f 8.1 percent toluene i n s o l s . I t i s reasonable to assume that o f the 8.1 percent toluene i n s o l s removed, o n l y the 4.8 percent p y r i d i n e s o l s are r e s p o n s i b l e f o r t h i s decrease i n viscosity. A f u r t h e r and much l a r g e r decrease i n v i s c o s i t y occurred when the asphaltenes, r e p r e s e n t i n g 40.2 percent o f the sample, were removed. The v i s c o s i t y then dropped from 907 to 16, as shown i n f i g u r e 3. TABLE I I I . -
Batch No.
Analyses o f c e n t r i f u g e d l i q u i d product samples taken d u r i n g run FB-38
Vis Sp g r , c o s i t y , SSF at 60°F/ 60°F 180° F
OBI
1
Analyses5, Wt pet As phal C O i l Ash tenes
H
Ν
S
9.2
0.8
0.36
1
1.061
39.4
2.6
21.2
75.3
0.9
87.4
4
1.064
44.3
2.2
22.8
73.8
1.2
86.6
9.1
0.8
0.42
7
1.079
85.6
2.8
24.3
70.9
2.0
85.9
8.9
0.8
0.56
Organic benzene
insolubles
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
7.
STERNBERG
TABLE IV.-
E T
A L .
Synthoil Process
115
Analyses o f c e n t r i f u g e d l i q u i d product samples taken from run FB-39 Analyses, wt pet
S
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
Batch No.
1
P gr, V i s 60°F/ c o s i t y 60°F SSF
OBI
Asphaltenes
1
O i l Ash
_C
_H_
_N_
_S
1
1.082
21.5 a t 180° F
2.4
18.0
79.1
0.50 88.8
8.5
0.8
0.30
31
1.023
29.1 a t 77° F
0.4
7.2
92.3
0.01 88.7
9.5
0.6
0.17
49
1.034
67.2 a t 77° F
0.9
11.4
87.6
0.10 88.1
9.3
0.8
0.14
91
1.094
32.5 a t 180° F
1.6
25.4
71.9
1.06 86.5
8.4
1.2
0.51
Organic benzene i n s o l u b l e s
TABLE V.-
Batch No.
Analyses o f c e n t r i f u g e d l i q u i d product samples taken d u r i n g run FB-40
VisSp g r , c o s i t y , 60°F/ SSF a t 60°F 180° F OBI
1
Analyses, wt pet Asphaltenes O i l Ash
_C
_H__
_N_
_S
1
1.060
13.5
1.1
17.3
81.4
0.2
88.5
8.6
1.0
0.22
43
1.130
56.2
4.6
29.4
64.3
1.7
86.5
7.5
1.5
0.55
90
1.146
75.7
5.7
28.9
62.5
2.9
85.3
7.3
1.6
0.71
Organic benzene i n s o l u b l e s
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
116
HYDROCRACKING AND HYDROTREATING Reactor Recycle oi
Flare stack
COAL-
»H S,NH 2
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
Scrubber Furnaces-^
Gas meter
Centrifuge
Oil
—
Whole product
H 0 9
Light oil Cake
-Or
Recycle gas N E T P R O D U C T OIL
compressor
Figure 1. Synthoil pilot plantflowsheet
Centrifugea liquid product
Toluene
Toluene insolubles
Toluene solubles
Pyridine
Pentane
Pyridine
Pyridine
Pentane
Pentane
insolubles
solubles
insolubles (asphaltenes)
solubles (oil)
Figure 2. Fractionation scheme for centrifugea liquid product (CLP)
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3 l
H 0 2
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975. 81.97
2.6
2.2
Pyridine solubles
Pyridine insolubles
In c e n t i s t o k e s
85.44
23.5
Asphaltenes
89.01
71.7
C
Oil
Fraction
2.03
0.91
0.77
1.12
6.78 5.69
0.18
0.43
9.69
Ultimate a n a l y s i s , Ν S H
71.9
2.68
0.36
0.01
wt pet Ash
0.95 0.83
6.72
1.30
H/C
5.53
0.68
0
671
289
Mol wt
A n a l y s i s of c e n t r i f u g e d l i q u i d product (CLP) from run FB-38, batch 7 ( 4 1 5 ° C, 4,000 p s i ) . V i s c o s i t y of CLP; 85.6 SSF at 1 8 0 ° F
Pet of Total product
TABLE V I . -
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
53 at 100° F
1
Viscosity
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975. C 88.52
89.03 86.80
75.2
22.3
1.8
0.7
Oil
Asphaltenes
Pyridine solubles
Pyridine Insolubles
1
In centistokes
Fraction
Pet of total product
4.75
6.13
8.89
2.63
2.10
0.83
0.46
0.27
0.23
28.5
2.29
0.0
0.0
U l t i m a t e a n a l y s i s , v t pet H Ν S Ash
459
0.82
2.47 3.07
227
Mol wt
1.20
H/C
1.53
0
A n a l y s i s of c e n t r i f u p e d l i q u i d product (CLP) from run FB-40, batch 7 (450° C, 2,000 p s i ) . V i s c o s i t y of CLP: 58.9 c e n t i s t o k e s at 140° F, 14.3 SSF at 180°
TABLE VII.-
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
F
e
11.8 140
1
at F
V i s cosity
ο
°
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
3.3
Pyridine insolubles
In c e n t i s t o k e s
4.39
73.06
4.8
Pyridine solubles
1
6.27
87.33
40.2
Asphaltenes
8.49
0.0
0.62 1.41 14.28
2.14 2.32
65.5
0.0
0.42
1.10
4.54
3.64
2.42
Ultimate a n a l y s i s , wt pet H Ν 0 S Ash
87.57
C
51.7
total product
Oil
Fraction
___
0.72
0.86
1.16
H/C
417
225
Mol wt
1
16.5 at 140° F
V i s cosity
A n a l y s i s o f c e n t r i f u g e d l i q u i d product (CLP) from run FB-40, batch 88 (450° C, 2,000 p s i T T V i s c o s i t y o f CLP; 1,433 c e n t i s t o k e s a t 140° F, 97.6 SSF a t 180° F
TABLE V I I I . -
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
3
2. *a
si
<s?
ρ
M
a ο
H M
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
120
HYDROCRACKING A N D H Y D R O T R E A T I N G
A comparison of data in tables VI and VII shows that for a given asphaltene content the viscosity of the product o i l depends on the molecular weight of the asphaltenes: FB-40, batch 7, containing 22.3 percent of asphaltenes with a molecular weight of 459 has a viscosity of 14.3; while FB-38, batch 7, containing approximately the same amount of asphaltenes but with a molecular weight of 671 has a viscosity of 85.6. The increase in viscosity of the product o i l during a run is due primarily to an increase in asphaltenes and possibly pyridine sols content and not to a change in the molecular weight of the asphaltenes or to an increase in the viscosity of the heavy o i l . This may be seen by comparing batches 7 and 88 of run FB-40 in tables VII and VIII. The viscosity of the centrifuged liquid product increases from 59 to 1,433 with an increase in asphaltene content from 22 to 40 and an increase in pyridine sols content from 2 to 5. In contrast, the viscosity of the heavy o i l increases only from 12 to 17. There is no increase but rather a slight decrease in the molecular weight of asphaltenes from 459 to 416. The increase in viscosity of centrifuged liquid product with asphaltene content is shown in figure 4, where viscosities for runs FB-39 and FB-40 are plotted against asphaltene content. Abstract In the Energy Research and Development Administration's SYNTHOIL process, slurries of coal in recycle o i l are hydrotreated on Co-Mo/SiO2-Al2O3 catalyst in turbulent flow, packed-bed reactors. The reaction is conducted at 2,000 to 4,000 psi and about 450° C under which conditions coal is converted to low-sulfur liquid hydrocarbons and sulfur is eliminated as H2S. Product oils from SYNTHOIL runs carried out at 415° and 450° C and 2,000 and 4,000 psi H2 pressures were analyzed with respect to asphaltene and o i l content, elementary compositions (C, H, S, N), ash and physical properties (specific gravity and viscosity). Asphaltenes exert a large effect on the viscosity of the product oil, the viscosity increasing exponentially with asphaltene content. Viscosity of product o i l is not only dependent on the amount but also on the molecular weight of asphaltenes present. At 415° C, asphaltenes with a molecular weight of 670 are formed and at 450° C asphaltenes with a molecular weight of 460. Product o i l containing 24 percent asphaltenes of 670 molecular weight has a viscosity of 86 (SSF at 180° F, ASTM D88), while product o i l containing almost the same amount of asphaltenes (22 percent) but with a molecular weight of 460 has a viscosity of only 14. Benzene insolubles, heretofore regarded as unreacted coal, were found to be soluble in pyridine and to exert a large effect on viscosity.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
STERNBERG
E T
Synthoil Process
A L .
• •
Pyridine solubles (toluene insolubles)
777Ά I
I
Asphaltenes Oil
58
42
16
907
1400
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
VISCOSITY IN C E N T I S T O K E S
AT
I40°F
Figure 3. Effect of pyridine solubles (toluene insolubles) and of asphaltenes on viscosity
'
I
•
SYNTHOIL product FB-39 (lower scale,right ordinate)
•
SYNTHOIL product FB-40 (upper scale .left ordinate )
1
I
1
I
•—ι 500
H
o CO 60
400
300
a u_ to CO 50
CO CO
>
>-
CO ο 40 CO
CO 200
>
H
3
to >
100
3
çP . 16
20
L_
_L_ 10
22
24
26 I 15
28
30
32
_JL_ - J 20
ASPHALTENES .percent
Figure 4. Viscosity of CLP vs. asphaltene content
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
122
HYDROCRACKING AND HYDROTREATTNG
Literature Cited 1.
2.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch007
3.
Akhtar, Sayeed, Lacey, James J., Weintraub, Murray, Reznik, Alan Α., and Yavorsky, Paul M. The SYNTHOIL Process--Material Balance and Thermal Efficiency. Presented at the 67th Annual AIChE Meeting, December 1-5, 1974, Washington, D.C. Akhtar, Sayeed, Mazzocco, Nestor J., Weintraub, Murray, and Yavorsky, Paul M. SYNTHOIL Process for Converting Coal to Nonpolluting Fuel Oil. Presented at the 4th Synthetic Fuels from Coal Conference of the Oklahoma State University, Stillwater, Oklahoma, May 6-7, 1974. Yavorsky, Paul Μ., Akhtar, Sayeed, and Friedman, Sam. Process Developments: Fixed-Bed Catalysis of Coal to Fuel O i l . AIChE Symposium Series, v. 70, No. 137, pp. 101-105, 1974.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
8 Coal Liquifaction by Rapid Gas Phase Hydrogenation MEYER STEINBERG and PETER FALLON
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
Department of Applied Science, Brookhaven National Laboratory, Upton, Ν. Y. 11973
The Increased awareness in this nation's dependence on foreign sources of crude oil has generated much interest in de veloping and u t i l i z i n g U.S. domestic energy resources. Since coal is in such great abundance, it is of particular interest to find an economical method of converting it to a low sulfur al ternate fuel capable of being transported through existing pipe lines and used in existing equipment. This would have the three fold effect of 1) revitalizing the coal industry, 2) providing a greater domestic supply of fuel to the power industry, and 3) i n creasing the availability of feedstock to the petrochemical indus try. A number of coal gasification processes have been developed to the point where large scale application has become feasible. The development of the liquifaction of coal has lagged and when taken together with the advantages of handling, transporting, and higher conversion efficiency, the incentive to perform additional work in converting coal to liquid products becomes apparent. The technology for liquid phase coal hydrogenation has been in existence for a number of years. (J.) For example, during World War II Germany produced much of its liquid fuel via the Bergius Process. This involves forming a slurry of coal, oil and catalyst and heating it under high pressure (10,000 psi) for up to an hour while purging the mixture with hydrogen. Being essen tially a batch process involving the s o l i d , l i q u i d , and gas phase, a more direct less stringent method of hydrogenation was desired. In 1962, Schroeder (2) described a process whereby dry particles of coal entrained in a stream of hydrogen at total pressures in the range of from 500 to 6000 psi are rapidly heated to tempera tures in the range of 600 to 1000°C; the resulting stream contain ing the organic products is then quickly cooled to below the re action temperature and the products separated. This system i s claimed to u t i l i z e less hydrogen than the liquid phase method be cause the liquids produced are primarily unsaturated aromatics rather than saturated paraffins and cycloparaffins. Conversion of almost 50% of the coal (on a moisture and ash free basis) to 123 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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124
HYDROCRACKING A N D H Y D R O T R E A T I N G
l i q u i d p r o d u c t s , was obtained a t pressures above 2000 p s i , and temperatures i n the order o f 5 0 0 ° C , and when a molybdenum c a t a l y s t was used. Outside t h i s patent l i t e r a t u r e there appears to be no f u r t h e r information on t h i s system. Moseley and Paterson (3) p e r formed experiments s i m i l a r to Schroeder but were p r i m a r i l y i n t e r ested i n the production of methane. The fact that they d i d not r e p o r t the p r o d u c t i o n o f any l i q u i d product i s probably due p r i m a r i l y to the higher temperatures u t i l i z e d , 9 0 0 - 9 2 5 ° C Qader, et a l . , (4) reported work on h y d r o g é n a t i o n i n a d i l u t e phase free f a l l r e a c t o r at temperatures i n the order o f 5 1 5 ° C , pressures of 2000 p s i and w i t h a heavy dose of c a t a l y s t , 15% stannous c h l o r i d e by weight o f c o a l . Up to 75% conversion was r e ported with a product d i s t r i b u t i o n of 43% o i l , 32% gas and 25% char. The residence time o f the c o a l feed p a r t i c l e s was estimated to be i n the order of seconds, however, no measurement was made and aromatics were reported a f t e r f u r t h e r h y d r o r e f i n i n g i n a second stage h y d r o g é n a t i o n . More r e c e n t l y , Yavorsky, et a l . , (5) have r e p o r t e d on the development o f a l i q u i d phase ( s o l v e n t ) h y d r o g é n a t i o n of c o a l i n a h i g h l y t u r b u l e n t tubular r e a c t o r i n the presence of a packed s o l i d catalyst. Residence times i n the order o f s e v e r a l minutes were r e p o r t e d and an o i l product i s formed. This system i s a c o n s i d e r a b l e improvement over the Bergius Process since reduced p r e s s u r e , i n the order o f 4000 p s i and lower temperature o f 4 5 0 ° C are employed. From t h i s l i t e r a t u r e i t thus appears that coal can be converted to l i q u i d and gaseous hydrocarbon products i n substant i a l y i e l d s by means of an elevated temperature ( 4 5 0 - 9 5 0 ° C ) high pressure (2000-6000 p s i ) contact of coal with hydrogen gas. L i quid hydrocarbons are favored i n the lower temperature range and shorter contact time ( i n the order o f seconds), while gaseous hydrocarbons increase i n y i e l d a t the higher temperatures and longer residence times. The b a s i c mechanism appears to i n v o l v e a thermally induced opening o f the polymeric aromatic hydrocarbon s t r u c t u r e i n c o a l , a l l o w i n g h y d r o g é n a t i o n to occur i n a hydrogen atmosphere, followed by a r a p i d removal o f the l i q u i d and gaseous hydrocarbon products formed so that e i t h e r f u r t h e r dehydrogenation, r e p o l y m e r i z a t i o n and c a r b o n i z a t i o n i s prevented or further excess i v e h y d r o g é n a t i o n i s minimized. The purpose o f the present experiments i s to s u b s t a n t i a t e previous work and to gather a d d i t i o n a l process and k i n e t i c i n f o r mation e s p e c i a l l y i n a n o n - l i q u i d non-catalyzed gas phase hydrog é n a t i o n system. S p e c i a l e f f o r t was made to o b t a i n o v e r a l l mat e r i a l balances i n determining y i e l d s . A f t e r a few p r e l i m i n a r y runs using a caking eastern bituminous coal and s e v e r a l r e a c t o r c o n f i g u r a t i o n s , i t was found that b e t t e r r e s u l t s could be obtained w i t h a non-caking coal i n an e n t r a i n e d down-flow tubular r e a c t o r . The coal was dropped down i n t o a tubul a r r e a c t o r through which hydrogen was passed down-flow and ent r a i n e d and c a r r i e d the coal down through the heated tube.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
8.
STEINBERG
A N D
F A L L O N
Coal Liquifaction
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
D e s c r i p t i o n of Equipment, and Experimental
125 and A n a l y t i c Procedures
The experimental equipment (Figure 1) was designed to r a p i d l y heat c o a l i n the presence o f hydrogen a t elevated temperature and pressure, to maintain these conditions long enough f o r hydrogénat i o n to take p l a c e , to cool the products preventing f u r t h e r react i o n and f i n a l l y to separate and c o l l e c t the products. Hydrogen i s s u p p l i e d from standard 200 cubic f o o t c y l i n d e r s and the operat i n g pressure i s c o n t r o l l e d by a 4000 p s i pressure r e g u l a t o r . Argon i s s u p p l i e d a t low pressure to f l u s h the system before and a f t e r each run and to a c t i v a t e the normally c l o s e d pneumatic v a l v e which shuts the hydrogen supply o f f i n case o f sudden l o s s o f pressure. The hydrogen can then pass through e i t h e r or both o f two 5000 p s i s e r v i c e rotameters. The gas from one meter goes to the top o f the r e a c t o r through an e l e c t r i c a l l y heated preheater cons t r u c t e d from a ten foot length of 1/4 inch tubing formed i n t o a 6 i n c h diameter c o i l . Since heating i s by d i r e c t connection to a v a r i a b l e v o l t a g e transformer, one s i d e o f the system i s e l e c t r i c a l l y i s o l a t e d from the other. Gas from the other meter i s used to c o o l the l i n e between the r e a c t o r and the c o a l feeder and enters j u s t below the feeder. Experience has shown that even w i t h a non-caking c o a l , t h i s s e c t i o n w i l l become plugged i f the temperature i s not c o n t r o l l e d . This i s probably caused by a combinat i o n o f reduced cross s e c t i o n , small p a r t i c l e s i z e and d e v o l a t i l i z a t i o n o f the c o a l . The r e a c t o r column i s f a b r i c a t e d from an e i g h t foot length of 1 i n . O.D. χ 0.120 i n . w a l l thickness type 304 s t a i n l e s s s t e e l tubing. The c o a l feeder i s a p r e s s u r i z e d 40 gram c a p a c i t y hopper having an o r i f i c e i n the base and a tapered plug operated by an electromagnet a c t i n g through a non-magnetic s t a i n l e s s s t e e l w a l l of the hopper. The feed r a t e i s c o n t r o l l e d by both a p u l s e gener a t o r operating an e l e c t r o n i c r e l a y which actuates the s o l e n o i d and by c o n t r o l l i n g the distance the tapered plug i s r a i s e d o f f the seat during i t s v e r t i c a l c y c l i n g . A North Dakota l i g n i t e and a New Mexico sub-bituminous c o a l were mainly used i n these experiments. Coal p r e p a r a t i o n c o n s i s t e d o f s i z e reduction and d r y i n g . I d e a l l y , the p a r t i c l e s i z e should f a l l somewhere between the l a r g e s t s i z e with which the maximum r a t e o f hydrogénation takes place and a s i z e l a r g e enough so that i n t e r - p a r t i c l e a t t r a c t i o n and agglomeration does not occur. With the b a l l m i l l used i n these experiments f o r s i z e r e d u c t i o n , a l a r g e q u a n t i t y of f i n e s were produced when g r i n d i n g to a maximum p a r t i c l e s i z e o f £ 50 or ^ 150 μ . The i n s i d e of the feeder had to be coated with a fluorοcarbon r e l e a s e agent which was baked i n p l a c e . The coal was magnetically a g i t a t e d by pieces of a finned rod attached to the tapered plug to prevent aggregation and c l o g ging o f the feeder. To prevent o x i d a t i o n a l l g r i n d i n g was conducted i n an i n e r t atmosphere. Drying i n a i r a t temperatures s l i g h t l y above 100°C was a l s o found to cause o x i d a t i o n and f o r t h i s reason drying and storage was performed i n a vacuum oven.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
126
HYDROCRACKING AND HYDROTREATING
A n a l y s i s o f the c o a l used i n these experiments and of a t y p i c a l char from the l i g n i t e c o a l produced during a s e r i e s of runs through the hydrogenator are shown i n Table 1. The analyses are on a m o i s t u r e - f r e e b a s i s and were obtained by the U . S . Bureau of Mines u s i n g standard ASTM a n a l y t i c a l procedures. A f t e r the c o a l passed through the r e a c t o r , the char and any unreacted c o a l were c o l l e c t e d i n an a i r cooled tubular trap cont a i n i n g a s t a i n l e s s s t e e l wool f i l t e r attached to the base o f the column. The q u a n t i t y c o l l e c t e d i s determined by weighing the trap before and a f t e r each r u n . The products pass through the trap along with the excess hydrogen which i s s t i l l a t elevated temperature and r e a c t o r p r e s sure. These gases then pass through a double U-tube water cooled trap ( 2 5 - 3 0 ° C ) , which removes any o i l s produced and most o f the moisture. The o i l deposits on the w a l l s o f the trap and due to the r e l a t i v e l y small q u a n t i t y produced and the l a r g e trap surface a r e a , c o l l e c t i o n becomes d i f f i c u l t . By c l e a n i n g w i t h a cotton swab, the o i l c o l l e c t e d appears to be l i g h t i n c o l o r and r e l a t i v e l y low i n v i s c o s i t y , s i m i l a r to a motor o i l . The q u a n t i t y p r o duced i s determined by weighing the trap before and a f t e r the r u n . The gases are then passed through a metering valve reducing the pressure to atmospheric. The remaining l i q u i d s contained i n the gases are c o l l e c t e d i n a l c o h o l - d r y i c e cooled glass trap ( - 7 2 ° C ) . Samples o f the hydrocarbons c o l l e c t e d i n t h i s trap have c o n s i s t e n t l y been analyzed to contain over 98% benzene, the remainder being toluene w i t h a t r a c e o f xylene. The q u a n t i t y produced i s determined by weighing the trap before and a f t e r the run and by volume i n a small graduate attached to the glass t r a p . Water from the r e a c t o r u s u a l l y c o l l e c t i n t h i s trap and appears as a separate l a y e r i n the graduate. This water and that c o l l e c t e d i n the U-tube trap have been analyzed on a Beckman Carbon A n a l y z e r and shows some i n s i g n i f i c a n t amount o f d i s s o l v e d hydrocarbons. The l i q u i d hydrocarbons c o l l e c t e d i n t h i s trap are analyzed by gas chromatography u s i n g a column o f 50-80 mesh Porapak Q and a flame i r o n i z a t i o n detector. The chromatograph i s c a l i b r a t e d to detect benzene, toluene, xylene C6 l i q u i d s ) and a l l the l i g h t hydrocarbon gases, methane, ethane, propane, hexane and pentane C5 gases). The remaining gas i s then vented to the atmosphere. At about two-thirds o f the time p e r i o d through the r u n , a 300 cc gas sample i s taken i n a g l a s s sampling v e s s e l i n s e r t e d i n the vent l i n e . Due to the l i m i t e d capacity of the c o a l feed hopper, the duration o f most runs was i n the order of 10 to 15 minutes. Steady s t a t e operation i s u s u a l l y obtained q u i c k l y s i n c e i n about one or two minutes a t the flow r a t e s used s e v e r a l r e a c t o r volume changes have o c c u r r e d . The gas sample i s analyzed i n the same manner as the l i q u i d sample mentioned above. A s i d e from excess hydrogen, the gas sample u s u a l l y contains mostly methane and ethane, the methane being present i n approximately twice the abundance as the ethane. The next g r e a t e s t c o n s t i t u e n t i s u s u a l l y benzene i n the vapor phase. There appears to be very l i t t l e C3, C4, and C5 hydrocarbons p r e s e n t . P e r i o d i c a l l y these same samples
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
8.
STEINBERG
A N D F A L L O N
127
Coal Liquifaction VENT
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
VENT
REACTOR
TUBE
H E A T E D IN F O U R TWO FOOT SECTIONS
Figure 1.
Coal hydrogénation tubular reaction experiment
TABLE 1 COAL AND CHAR FEED ANALYSIS % by wt - Moisture Free Basis North Dakota Lignite Hydrogen Carbon
4.29%
New Mexico Sub Bituminous 4.86%
Char from Lignite 2.74%
62.39
64.21
73.63
0.97
1.41
0.85
21.75
12.26
0.37
Sulphur
1.17
0.61
1.42
Ash
9.43
16.65
20.99
100.00
100.00
100.00
Nitrogen Oxygen
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATTNG
128
were a l s o analyzed by mass spectrometry as a check on the gas chromatography and a l s o to determine the concentration o f cons t i t u e n t s not detected by the gas chromatograph, such as oxides of carbon.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
Experimental and C a l c u l a t e d Results Table 2 contains a summary of some of the experimental r e sults. Except as otherwise noted, most o f the runs were made u s i n g ground North Dakota l i g n i t e with no a d d i t i o n of c a t a l y s t . The r e a c t o r operating temperature c o n d i t i o n o f 700°C was chosen on the basis that t h i s was s l i g h t l y above 650°C found i n previous experiments to be the temperature below which l i t t l e r e a c t i o n w i t h the l i g n i t e was noted. The 1500 p s i operating pressure i s the upper s a f e t y l i m i t o f the r e a c t o r at the 700°C temperature. Lower pressures tended to r e s u l t i n lower l i q u i d y i e l d s . A thorough i n v e s t i g a t i o n o f the e f f e c t of pressure i s yet to be made. The residence time o f the c o a l p a r t i c l e s i n the r e a c t i o n zone was estimated by combining the l i n e a r gas v e l o c i t y through the tube with the free f a l l v e l o c i t y of the p a r t i c l e s as c a l c u l a t e d from data c o r r e l a t e d by Zenz and Othmer (6). The p a r t i c l e s were assumed to be uniform spheres d i s t r i b u t e d i n a h i g h l y d i l u t e gas phase. A t a f i x e d r e a c t o r operating temperature and p r e s s u r e , the residence time becomes dependent upon the p a r t i c l e s i z e and the gas flow r a t e . Most o f the o r i g i n a l experiments were conducted u s i n g £ 50 micron coal p a r t i c l e s . In an attempt to improve the u n i f o r m i t y of the coal feed flow and decrease the residence time, t h i s was increased to £ 150 microns. As shown i n Table 3, i t was not p o s s i b l e with the frequent s i e v i n g and g r i n d i n g method used to reduce the presence o f s i g n i f i c a n t amounts o f ^ 50 micron p a r ticles. Using Figure 2, which i s a p l o t o f residence time as a funct i o n of coal p a r t i c l e s i z e based on the Zenz and Othmer c o r r e l a t i o n , i t can be shown that due to the r e l a t i v e l y l a r g e q u a n t i t y of fines p r e s e n t , i n c r e a s i n g the maximum s i z e by a f a c t o r of three only reduces the average residence time by about 30%. F i g u r e 2 a l s o shows the e f f e c t o f reducing residence time by i n c r e a s i n g the hydrogen flow r a t e from the minimum used i n these experiments (0.7 gm/min) to the maximum (4.5 gm/min). Brown and Essenhigh (7) have suggested that the free f a l l v e l o c i t y may be much greater than that c a l c u l a t e d here. In t h e i r experiments u s i n g cork p a r t i c l e s f a l l i n g through an a i r f i l l e d tube, the p a r t i c l e cloud acted as a porous p l u g , f a l l i n g a t a r a t e o f approximately 57 f t / m i n . Using the Zenz and Othmer c o r r e l a t i o n , t h i s v e l o c i t y i s c a l c u l a t e d to be only 17 f t / m i n . Thus, the coal residence time may be much shorter than determined from Figure 2. A d d i t i o n a l experimental e f f o r t i s r e q u i r e d to measure the a c t u a l residence i n the system. The hydrogen fed to the system i s much i n excess o f that u t i l i z e d i n the h y d r o g é n a t i o n r e a c t i o n . The net use o f hydrogen
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
(1) (2) (3) (4) (5)
44.5
45.7 59.9
35 .8 24.1 6.0 34.1
81.5 121.6
35.8 45.7 6.0 34.1
16 20
61.1
21.2 39.9 6.0 32.9
31.8 70.7
21.2 10.6 6.0 32.9
16 17.5
6/7 1500 700 350 1.66 4.14 0.33 <50
50.0
17.5 32.5 6.0 44.0
37.0 87.0
17 .5 19.5 6.0 44.0
22 10
6/14 1500 700 R.T. 2.93 2.5 0.20 <50
52.1
25 .0 27.1 6.0 41.9
30.3 78.2
25 .0 5.3 6.0 41.9
20 11.5
7/30 1500 700 300 1.63 1.6 0.128 <150
66.1
19.1 47.0 6.0 27.9
20.8 54.7
19.1 1.7 6.0 27.9
18 10
9/9 1500 700 600 2.53 1.75 0.14 <150
51.1
23.8 27.3 6.0 42.9
50.6 99.5
23.8 26.8 6.0 42.9
18 10
9/13 1500 700 600 1.4 1.75 0.14 <150
49.9
12.9 37.0 6.0 44.1
43.5 93.6
12.9 30.6 6.0 44.1
16 10
2
15.0
4.0 11.0 16.2 68.8
11.7 96.7
4.0 7.7 16.2 68.8
30 10
3)
(3)
9/16 11/21 1500 1500 700 700 600 R.T. 3.7<' 1.08 2.1 21.3< 0.168 0.086 <150 <150
1% Ammonium Molybdate Added New Mexico Sub-Bituminous Coal Argon Used in Place of Hydrogen Char Collected from Previous Lignite Coal Runs Used in Place of Coal as Feed Material to the Tubular Reactor For Hydrogen Runs, Analysis Indicates 1% COn and 5% CO For Argon Run, Analysis Indicates 11.5% CO_ and 4.7 % CO
v 1
% Total Conversion of C to Gas & Liquid
41.6 95 .9
28.0 83.5 7.3 38.4 6.0 48.3
7.3 34.3 6.0 48.3
8.4 19.6 6.0 49.5
8.4 36.1 6.0 49.5
36 15
(1
5/21 6/3 1400 1500 700 700 350 350 0.7β ' 1.47 0.74 4.14 0.059 0.33 <50 <50
38 10
5/3 1000 700 350 1.5 0.7 0.056 <50
% C as Liquid HC {zC^ Gaseous HC (C -C ) (5) C Oxides Unreacted
Modified C Balance - % C Converted
Est. Max. Coal Residence Time (Sec) Duration of Run (Min) Raw Carbon Balance - % C Converted % C as Liquid HC (^Cg) Gaseous HC (C.-C ) C Oxides * ' Unreacted % Total Conversion of C to Gas & Liquid % c Accounted for
2
2
2
2
Run No. H Pressure (psi) Reactor Temp (°C) H Preheat Temp (°C) Coal Rate (gm/min) H Rate (gm/min) H Linear Velocity Pt/Sec Max.Coal Particle Size (Microns)
HYDROGENATION OF COAL IN AN ENTRAINED TUBULAR REACTOR Coal - North Dakota Lignite Reactor - 0.75" I.D . χ 8ft Long Stainless Steel
TABLE 2
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
4.7
95.3
-
0 4.7
0 95.3
95.3
-
0 0
18 10
(
9/11 1500 700 600 0.94 (4) 1.75 0.14 <150
HYDROCRACKING AND HYDROTREATING
TABLE 3 COAL PARTICLE SIZE DISTRIBUTION P a r t i c l e Size
(Microns)
Weight Percent
150 - 125
4.8
90
21.4
90 -
50
21.0
£
50
52.8
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
125 -
H F L O W RATE - Ο q /min -0.7 q/min ς4.5 q/min 2
20
40
60 80 100 120 PARTICLE SIZE (μ)
140
Fluidization and Fluid-Particle Systems
Figure 2. Coal particle residence time vs. particle size. H at 1500 psi + 700 C. e
2
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
8.
STEINBERG
A N D
F A L L O N
Coal Liquifdction
131
for a high y i e l d run where, for example, 60% o f the a v a i l a b l e carbon from the l i g n i t e i s hydrogenated i n t o equal parts o f l i q u i d and gas, i s o n l y about 5 grams hydrogen per 100 grams o f c o a l . An a d d i t i o n a l 50% of t h i s amount of hydrogen, o r i g i n a t e s from the coal i t s e l f to make up the hydrogen balance i n the hydrocarbon products. Hydrogen for r e a c t i o n w i t h the s u l f u r , n i t r o g e n and oxygen contained i n the coal i s taken i n t o account for t h i s b a l ance. I t should be noted that the l i g n i t e has an e s p e c i a l l y high oxygen content. The l a r g e excess hydrogen feed serves the purpose o f t r a n s f e r r i n g heat to the c o a l , t r a n s p o r t i n g the products out o f the r e a c t o r and producing v a r i a t i o n s i n the coal residence time by changes i n hydrogen v e l o c i t y . The carbon balance given i n Table 2 was made by weighing the l i q u i d s and char c o l l e c t e d i n each t r a p , determining a n a l y t i c a l l y o r , as i n the case o f the l i g h t o i l , estimating the carbon content and a n a l y s i s o f a sample o f the e f f l u e n t gas. The o i l was assumed to contain some amount of aromatic w i t h approximately 90% carbon content. I f t h i s o i l was p r i m a r i l y a l i p h a t i c , the carbon content would be c l o s e r to 85%. This would only a f f e c t the o v e r a l l b a l ance by a small amount s i n c e the o i l s make up approximately 40% of the l i q u i d s c o l l e c t e d , the r e s t being chromatographically analyzed as benzene, toluene and xylene (BTX) with the major f r a c t i o n (^ 98%) being benzene. As mentioned p r e v i o u s l y , a sample o f the e f f l u e n t gas i s analyzed chromatographically for l i g h t hydrocarbons (C1-C5). Only a small f r a c t i o n of higher hydrocarbons (^ 05) i s found i n the gas sample and t h i s i s added to the t o t a l l i q u i d formed. The t o t a l carbon content o f the gas i s obtained from the r e s u l t s o f t h i s a n a l y s i s , the gas flow r a t e and the d u r a t i o n o f the r u n . T y p i c a l r e s u l t s o f mass spectrometric analyses a l s o i n d i c a t e that about 5% o f the a v a i l a b l e carbon appears as carbon monoxide and 1% as carbon dioxide i n the e f f l u e n t gas. As shown i n Table 2, most of the experiments i n d i c a t e over 70% o f the carbon can be accounted f o r by d i r e c t a n a l y s i s . Since the amounts o f c o a l used and condensed l i q u i d and char produced were measured g r a v i m e t r i c a l l y and there was no holdup i n the system, any i n a b i l i t y to account f o r a l l the carbon fed to the r e a c t o r must be a t t r i b u t e d to l o s s i n the e f f l u e n t gas. The carbon balance was therefore modified by assuming the missing carbon to be i n the form o f a l i g h t hydrocarbon i n the e f f l u e n t gas. This modified carbon balance i s given i n the lower h a l f o f Table 2. Figure 3 shows the e f f e c t o f coal p a r t i c l e residence time on the f r a c t i o n o f carbon converted to l i q u i d and gaseous p r o d u c t s . Based on t h i s c o r r e l a t i o n , the p r o d u c t i o n of gaseous products appears to be l e s s s e n s i t i v e to c o a l residence time than the p r o duction of l i q u i d s . I t a l s o appears that the p r o d u c t i o n of l i quids i s favored by shorter residence time. F i g u r e 4 gives a p l o t o f the conversion to l i q u i d s as a function o f coal feed r a t e for the shorter c o a l residence times (16-22 s e c ) . This f i g u r e i n d i c a t e s a trend towards lower l i q u i d
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
132
HYDROCRACKING A N D H Y D R O T R E A T I N G
70 60
50
Ο ο
GAS + LIQUID
40 — —" GAS ·
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
g 30 < ο
aS 2 0 LIQUID
22 26 30 34 38 42 COAL PARTICLE RES. TIME (sec)
Figure 3. Gas phase coal hydrogénation yield vs. coal residence time. North Dakota lignite—reactor, 0.75" i.d. X 8 ft; pressure, 1000-1500 psi; temperature, 700°C; particle size, < 150 μ.
COAL F E E D RATE
(q/min)
Figure 4. Gas phase coal hydrogénation liquid yield vs. coal feed rate. North Dakota lignite—reactor, 0.75" i.d. X 8 ft; pressure, 1500 psi; temperature, 700°C; particle size, < 150 μ; residence time, 16-22 sec.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
8.
STEINBERG AND FALLON
Coal LiquifaCtlOYl
133
conversion a t higher coal feed r a t e s Even a t the higher feed r a t e s , the c o a l i s i n a very d i l u t e phase i n the gas, so that there should be no tendency towards a c o a l s a t u r a t i o n e f f e c t i n the system. Since much of the heat needed to b r i n g the c o a l to r e a c t i o n temperature can be obtained as r a d i a n t heat from the r e a c t o r w a l l , t h i s e f f e c t o f coal feed r a t e could be a t t r i b u t e d to a shadowing e f f e c t , reducing the heating rate a t higher coal feed rates. This assumes that r a p i d heating of the c o a l p a r t i c l e s i s needed for optimum l i q u i d y i e l d . From experience i n running the equipment, i t was a l s o found that while preheating the hydrogen increased the o v e r a l l y i e l d , the d i f f e r e n c e i n preheating between 3 5 0 ° C and 600°C d i d not appear a p p r e c i a b l e . Several runs were made with the a d d i t i o n o f 1% ammonium molybdate to the l i g n i t e for purposes o f t e s t i n g c a t a l y t i c effects. Under s i m i l a r flow conditions there appears to be l i t t l e e f f e c t on the y i e l d s . In the run made with a New Mexico sub-bituminous c o a l , an a p p r e c i a b l e q u a n t i t y of gaseous hydrocarbons was produced. The main d i f f e r e n c e between the New Mexico c o a l and the North Dakota l i g n i t e i s that the sub-bituminous coal has a lower oxygen content and a higher ash content. Runs were a l s o made using an i n e r t gas, argon, i n place of hydrogen at the s i m i l a r pressure and l i n e a r v e l o c i t y through the reactor. The r e s u l t s o f a t y p i c a l one o f these runs i s given i n Table 2. Although almost 11 grams o f coal was f e d , no measurable q u a n t i t y of product was found i n the high pressure water cooled t r a p , and only a few drops o f what was predominantly benzene was c o l l e c t e d i n the a l c o h o l - d r y i c e cooled t r a p . A n a l y s i s o f the gas sample showed methane and about o n e - f i f t h as much ethane. The char contained a higher carbon content (77%) than when hydrogen was used (72%). Almost 70% of the a v a i l a b l e carbon remained unreacted. The production of oxides o f carbon was much higher with argon (16%) than for a t y p i c a l hydrogen run (6%). A l s o , the CO to CO2 r a t i o was much higher (5 times) with hydrogen than with argon (2 t i m e s ) . These r e s u l t s i n d i c a t e that v o l a t i l i z a t i o n of l i g n i t e i n an i n e r t gas stream produces much l e s s gaseous and l i q u i d hydrocarbon products (15% o f C) under s i m i l a r conditions of p r e s s u r e , temperature and residence time than when hydrogen i s present (45 to 66% o f C) and thus a p p r e c i a b l e h y d r o g é n a t i o n i s occurring. A t e s t was made to determine the r e a c t i v i t y of the char r e maining a f t e r a h y d r o g é n a t i o n r u n . For t h i s purpose, char c o l l e c t e d from a s e r i e s o f previous runs was r e c y c l e d through the system. A n a l y s i s of t h i s char appears i n Table 1. Over 95% o f the m a t e r i a l fed was recovered as a s o l i d i n the f i r s t t r a p . No l i q u i d was produced and only a trace of l i g h t hydrocarbons were found i n the gas. S i m i l a r r e s u l t s were obtained when feeding a coconut charcoal to the system. There thus appears to be l i t t l e r e a c t i v i t y towards hydrogen i n the char produced from an o r i g i n a l l i g n i t e h y d r o g é n a t i o n run.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
134
HYDROCRACKING AND HYDROTREATTNG
Conclusions
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
The o b j e c t i v e s o f t h è s e h y d r o g é n a t i o n experiments were mainl y d i r e c t e d toward producing the l a r g e s t q u a n t i t y o f l i q u i d p r o duct and reducing the unreacted carbon remaining. Although f r a g mented, t h i s experimental study i n d i c a t e s that s i g n i f i c a n t y i e l d s o f l i q u i d and gaseous hydrocarbon products can be obtained by an elevated temperature and pressure gas phase h y d r o g é n a t i o n of North Dakota l i g n i t e without the a d d i t i o n o f a c a t a l y s t . Based on a modified carbon balance, a range o f y i e l d s obtained i n a number o f experimental runs under the operating conditions i n d i cated can be l i s t e d as f o l l o w s : Pressure Temperature Coal p a r t i c l e s i z e Coal residence time
1500 p s i 700°C £ 150 μ 16 to 22
Y i e l d as % conversion o f carbon i n Liquids %) Gas C5) Oxides of C Unreacted C
sec.
lignite
18-25% (~60% C H ) 27-40 (mainly CH4 & C H ) 6 33- 44 6
6
2
6
Several general trends were noted. The y i e l d o f l i q u i d p r o ducts i s s t r o n g l y favored by s h o r t e r coal residence times, while the y i e l d of gaseous hydrocarbons increases only s l i g h t l y with increases i n coal residence times. A t shorter residence times, i n c r e a s i n g the coal feed r a t e decreases the y i e l d o f l i q u i d p r o ducts. V o l a t i l i z a t i o n of l i g n i t e i n an i n e r t gas stream under s i m i l a r flow conditions produced much smaller y i e l d s o f l i q u i d and gaseous hydrocarbon p r o d u c t s . A d d i t i o n o f a c a t a l y s t caused no a p p r e c i a b l e e f f e c t s on the y i e l d . The r e s u l t s o f t h i s study should be considered as work i n progress. Much a d d i t i o n a l work needs to be performed to r e f i n e the experimental procedure and to o b t a i n a d d i t i o n a l information and a f u l l e r understanding o f the r e s u l t s . Acknowledgement The a u t h o r s w o u l d l i k e t o t h a n k M r . G e r a l d F a r b e r f o r t h e c o n s t r u c t i o n and o p e r a t i o n o f t h e equipment, the U . S . Bureau of Mines for the c o a l a n a l y s i s and R o b e r t S m o l , J o e F o r r e s t , and R o b e r t D o e r i n g o f B r o o k h a v e n N a t i o n a l L a b o r a t o r y f o r t h e g a s e o u s and liquid product a n a l y s i s . A c k n o w l e d g e m e n t i s a l s o made t o t h e g r o u p a t C i t y U n i v e r s i t y o f New Y o r k , A r t h u r S q u i r e s , R o b e r t G r a a f f , a n d Sam D o b n e r f o r t h e i r h e l p f u l dis c u s s i o n s on r a p i d r e a c t i o n s o f c o a l w i t h h y d r o g e n .
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
8.
STEINBERG AND F A L L O N
Coal
Liquifaction
135
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch008
Abstract The short contact time, high temperature, non-catalyzed gas phase reaction of hydrogen with coal in a tubular reactor has been investigated. A North Dakota lignite coal was hydrogenated by entraining fine coal particles (≤ 150 μ) in a hydrogen stream through a 0.75" I.D. by 8 ft long tubular reactor at 700°C and 1000 to 1500 p s i . The coal flow rate varied between 0.8 and 3.7 gm/min. and the hydrogen flow rate varied between 0.7 and 4.1 gm/min. Residence times were calculated to vary between 16 and 38 seconds. The unreacted carbon was collected in an a i r cooled trap, the light o i l s in a water cooled trap on the high pressure side of the system and the lighter liquids consisting predomin antly of benzene with smaller amounts of xylene and toluene (BTX) were collected in an alcohol-dry ice cooled trap after reducing the pressure to one atmosphere for venting. The exit gas was analyzed. Based on a modified carbon balance, the y i e l d , or con version of carbon in the feed coal, to liquid products (≥ C6) usually varied between 18 and 25%, approximately 60% of which is benzene. The gases ( ≤ C5) varied between 27 and 40% consisting mainly of methane and ethane, and the oxides of carbon were 6% of the available carbon feed in the l i g n i t e . A trend indicating higher liquid yields at shorter coal residence times was noted. A decrease in liquid yield at increased coal feed rate when the residence time remained approximately constant was also noted. Volatilization of lignite in an inert gas stream under simi lar flow conditions produced much smaller yields of l i q u i d and gaseous hydrocarbon products. Addition of a catalyst caused no appreciable effects on the y i e l d . Much additional work is re quired to obtain a fuller understanding of the results obtained. Literature Cited 1. M i l l s , G. Alex, Ind & Eng. Chem. (1969), 61, 6-17. 2. Schroeder, W. C. (assigned to Fossil Fuels, Inc.), U.S. Pat. 3,030,298 (April 17, 1962) and U.S. Pat. 3,152,063 (October 6, 1964). 3. Moseley, F. and Paterson, D . , J. Inst. Fuel (November 1967), 523-530. 4. Qader, S. Α . , Haddadin, R. Α . , Anderson, L . L., and Hill, G. R . , Hydrocarbon Processing (September 1969) 48, 147-152. 5. Yavorsky, P . , Akktar, S., and Friedman, S., Chem. Eng. Progress (1973) 69, 51-2. 6. Zenz, F. A. and Othmer, D. F., Fluidization and FluidParticle Systems, ρ 236, Reinhold Publishing, New York, 1960. 7. Brown, K. C. and Essenhigh, R. Η . , Dust Explosions in Factories : A New Vertical Tube Test Apparatus, Safety in Mines Research Establishment Research Report, No 165, Ministry of Power, Sheffield, England (April 1959).
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
9 Consideration of Catalyst Pore Structure and Asphaltenic Sulfur in the Desulfurization of Resids RYDEN L. RICHARDSON and STARLING K. ALLEY
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
Union Oil Co. of California, Union Research Center, Brea, Calif. 92621
The residuum f r a c t i o n of a full range crude is that f r a c t i o n remaining a f t e r all of the distillate i s taken overhead. As noted in Figure 1, t h i s residuum f r a c t i o n or r e s i d may be obtained with e i t h e r atmospheric or vacuum f r a c t i o n a t i o n , y i e l d i n g e i t h e r long or short r e s i d . Table I shows t h a t , upon distillation of a Kuwait crude i n t o s e v e r a l f r a c t i o n s , s u l f u r components concentrate mostly i n the r e s i d f r a c t i o n . Upon h y d r o t r e a t i n g each f r a c t i o n at f i x e d r e a c t o r c o n d i t i o n s , the r e s i d s u l f u r i s more difficult to remove than the gasoline s u l f u r or the gas oil s u l f u r . CHARACTERIZATION OF RESIDS The d i s t i n g u i s h i n g features of r e s i d feedstocks are (1) the presence of asphaltenes or p e n t a n e - i n s o l u b l e s , (2) high carbon r e s i d u e s , (3) the presence of metals, mainly n i c k e l and vanadium, and (4) unknown endpoints i n s o f a r as b o i l i n g range is concerned. Table II compares two atmospheric r e s i d s , West Coast and K u w a i t , i n a t r a d i t i o n a l manner. The obvious d i f f e r e n c e s i n c l u d e s u l f u r , n i t r o g e n , asphaltenes, t o t a l metals and m i d - b o i l i n g p o i n t . Apart from s u l f u r content, one might surmise a greater c a t a l y s t demand by the West Coast feedstock i n that the boxed values suggest heavy coke laydown and metals d e p o s i t i o n . Neither of the s u l f u r values i s boxed because there i s no i n d i c a t i o n as to (1) what f r a c t i o n of the s u l f u r i s r e f r a c t o r y or "hard" s u l f u r , nor (2) the degree of d e s u l f u r i z a t i o n to be achieved. Table I I I extends the comparison of these r e s i d s with an emphasis on r e a c t i v i t y , asphaltene c h a r a c t e r i s t i c s , compound types and the r e f r a c t o r y forms of s u l f u r , such as benzothiophenes and asphaltenic s u l f u r . The lower r a t e constant of the Kuwait feed i n d i c a t e s i t s greater r e f r a c t o r i n e s s or r e s i s t a n c e toward d e s u l f u r i z a t i o n . These second order r a t e constants were measured at 6 7 5 ° F w i t h a p r e s u l f i d e d c o b a l t moly c a t a l y s t having a c a t a l y s t age of 10 days. Conversion l e v e l s d i d not exceed 75% and hence d i d not go deeply
136 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
9.
RICHARDSON
Desulfurization of Resids
A N D A L L E Y
137
TABLE I
FRACTIONATION
AND
HYDROTREATING
HYDROTREATED SULFUR
PRODUCT
SULFUR
VOL. %
WT. %
S,%
REMOVAL, %
25
0.5
0.02*
96
400-650
25
1.8
0.5 *
72
650 +
50
3.7
1.6·
57
1050 +
(20)
(5)
BOILING FRACTION
RANGE, °F
GASOLINE
GAS
OIL
LONG
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
X-400
SHORT
RESID
RESID
e
• 780 F ,
1000 psig, 1 LHSV,
COMPARISON
OF
4000
TABLE
II
WEST
COAST AND
ATMOSPHERIC
FEED
DESIGNATION
SCF/B
KUWAIT
RESIDS
WEST
COAST
KUWAIT
11.5
17.4
IBP/10
536/725
447 / 6 3 4
50/60
996/1051
937/1020
GRAVITY, *API
DISTILLATION, °F
SULFUR, %
1.73
3.66
NITROGEN, %
0.90
0.203
ASPHALTENES,%
1 1.2
6.3
CONRADSON
10.7
8.1
CARBON,% e
POUR POINT, F
75
30
METALS, ppm COPPER
1
IRON
53
2
NICKEL
75
11
VANADIUM
63
38
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING AND HYDROTREATING
TABLE
III
EXTENDED COMPARISON OF WEST COAST AND KUWAIT RESIDS KUWAIT
DESIGNATION
RATE
CONSTANT
52
38
SULFUR,%
1.73
3.66
ASPHALTENIC SULFUR, %
0.22
0.38
60
70
0.72
0.78
TOTAL
GEL.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
WEST COAST
FEED
PERM. CHROMO. ASPHALTENE RELATIVE
MODE
AMOUNT
DlAM., A OF
ASPHALTENES AT D - 150 LIQUID
λ
CHROMO
C O M P O U N D TYPE
FEED
SATURATES, Jo
20.6
26.7
AROMATICS, %
41.2
50.4
POLAR AROMATICS, %
22.9
10.4
ASPHALTENES, %
10.7
6.3
WEST COAST
KUWAIT
DESIGNATION SULFUR
CONT ENT
SATURATES, ppm
22
34
AROMATICS, %
0.94
2.36
POLAR
0.4 1
0.59
0.22
0.38
AROMATICS, %
ASPHALTENES, % HIGH MASS O N X-1100 °F Q.H. THIOPHENES
2.9
2.3
BENZOTHIOPHENES
7.4
15.0
TRI BENZOTHIOPHENES
0.0
0.0
0.43
0.33
0.38
0.42
LOW
HIGH
IR ABSORBANCE AROMATIC ALKYL RATIO
GROUPS
OF NMR
CH /CH 2
RINGS
3
PEAK HEIGHTS
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
9.
RICHARDSON
A N D A L L E Y
Desulfurization of Resids
139
into asphaltenic s u l f u r . F i g u r e 2 shows the GPC curves of the c i t e d r e s i d s and t h e i r asphaltene f r a c t i o n s . Note the s l i g h t p r e dominance of very l a r g e asphaltenes i n the Kuwait r e s i d . A l s o note that very l a r g e molecules e x i s t i n the non-asphaltenic f r a c t i o n of both r e s i d s . For the conversion l e v e l s under c o n s i d e r a t i o n , we regard the l a r g e p r o p o r t i o n of s t e r i c a l l y hindered aromat i c s u l f u r i n the Kuwait r e s i d l a r g e l y r e s p o n s i b l e f o r i t s greater refractoriness. Returning to Table I I I , one notes the h i g h values for aromatic s u l f u r (2.36 v s . 0.94%) and benzothiophenes (15.0 v s . 7.4%) i n the Kuwait feed. A l s o , the IR and NMR s p e c t r a i n d i c a t e d that the Kuwait aromatics are more h i g h l y s u b s t i t u t e d , the R groups being naphthenes and/or long p a r a f f i n s . A p e r t i n e n t example of s t e r i c hindrance on the d e s u l f u r i z a t i o n of thiophenes has been reported by a Gulf i n v e s t i g a t o r (1). A l k y l or r i n g a d d i t i o n at the 2 p o s i t i o n can reduce the r e a c t i o n r a t e by a f a c t o r of 100. REFRACTORINESS OF ASPHALTENES When s u l f u r conversion l e v e l s are pushed above 90%, the unique r e f r a c t o r i n e s s of asphaltenes becomes dominant. The tendency of a f i n e pore c a t a l y s t to p a r t i a l l y exclude asphaltenes and the complete s t e r i c hindrance or "burying" of s u l f u r i n a s p h a l tenes c o n t r i b u t e to t h i s r e f r a c t o r i n e s s . However, before c o n s i d e r i n g the f a t e of a s p h a l t e n i c s u l f u r at high r e a c t o r s e v e r i t i e s , some patent aspects of c a t a l y s t pore s t r u c t u r e would be of i n t e r e s t . Table IV shows a divergence of o p i n i o n as to the d e s i r a b i l i t y of asphaltene e x c l u s i o n . I t i s noted that patent (2) favors the e x c l u s i o n of a s p h a l tenes by maximizing surface area contained by pore diameters of 30-70 Â. Patent (3) d i s c l o s e s an upper l i m i t on the amount of macropore volume represented by pore diameters greater than 100 A . Patents (4) and (5) suggest that c a t a l y s t s c o n t a i n i n g mostly m i c r o pores w i l l be poisoned soon; asphaltenes p e n e t r a t i n g the l a r g e r pores subsequently w i l l block entrance to the smaller p o r e s . Patent (6) claims the d e s i r a b i l i t y of intermediate pores (100-1000 Â) p l u s channels (>1000 Â) "to take up p r e f e r e n t i a l l y adsorbed l a r g e molecules without causing blockage, so that the smaller s i z e pores can d e s u l f u r i z e ' s m a l l e r molecules." Patent (7) a l s o p r e f e r s the open s t r u c t u r e for c o l l e c t i o n of coke and metals. It s p e c i f i e s 0.3 c c / g of pore volume i n diameters l a r g e r than 150 Â and "many pores from 1,000-50,000 A . " With t h i s b r i e f c o n s i d e r a t i o n of v a r i a t i o n s i n c a t a l y s t pore s t r u c t u r e , l e t us examine the pore s t r u c t u r e of two c a t a l y s t s used i n t h i s r e f r a c t o r i n e s s study. One observes i n Table V only s l i g h t d i f f e r e n c e s between the two c o b a l t moly c a t a l y s t s , Τ and R. They are t y p i f i e d by h i g h surface a r e a , small micropore mode diameters and low macropore volumes. Upon processing Kuwait r e s i d over these c a t a l y s t s , a s i m i l a r trend i n product d i s t r i b u t i o n i s shown i n Table V I . Saturates i n 1
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
HYDROCRACKING A N D
140 ATMOS
HYDROTRLATING
FRACTIONATION GASOLINE
TURBINE FUEL DIESEL
Λ
FUEL
20 mm Hg VAC COLUMN
CRUDE OIL LGO HEATER HG Ο
Λ
LVGO
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
HVGO HEATER
A T M O S . RESID OR L O N G RESID 650 F + e
V A C RESID OR SHORT RESID. 1050 F + e
Figure 1. Distillation of crude oil
DIAMETER, Â
Figure 2. GPC molecular size distribution
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
RICHARDSON
141
Desulfurization of Resids
A N D A L L E Y
TABLE IV
SOME OF
PATENT CODE
NUMBER
(2)
PATENTS
RESID
O N PORE
HYDROTREATING
CoMo,
CATALYSTS
SPECIAL
CATALYST COMPOSITION
STRUCTURE
PORE VOLUME
FEATURES PORE
DIAMETER
SURFACE
NiMo
AREA (SA)
OF 3 0 - 7 0 Â PORES
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2
> 100 m / g .
(3)
CoMo,
NiMo,WMo.
ALUMINA WITH 1-6%
<0.25 c c / g IN
TOTAL SA > 150 m V g .
PORES > 1 0 0 Â
SA OF 3 0 - 7 0 Â PORES 2
> 100 m / g .
SILICA.
APPROX. 85 7. OF PORE
(4)
VOLUME
IN 5 0 - 2 0 0 A
RANGE.
PATENT CODE
NUMBER
(5)
SPECIAL
CATALYST COMPOSITION
N i C o M o . NO SILICA
PORE VOLUME
0.46 c c / g
CoMo
(+ Ni)
PORE
DIAMETER
REGULAR DISTRIBUTION 0 - 2 4 0 A. A V E R A G E =
WITH
1 4 0 - 1 8 0 A.
ALUMINA.
(6)
FEATURES
0.45-0.50 cc/g
6 0 - 7 0 A PLUS 100-1000 Â PLUS CHANNELS > 1000 A. S A * 260-355 m /g. 2
(7)
CoMo, NiW. NO
0.3 c c / g
SILICA WITH
PORES >150 A
IN
MANY
PORES
1,000-50,000 Â
ALUMINA
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
142
HYDROCRACKING A N D H Y D R O T R E A T I N G
TABLE V PORE
STRUCTURE USED
CATALYST SURFACE MODE
IN
OF
COBALT
MOLY
REFRACTORINESS
STUDY
DESIGNATION
Τ 2
AREA (SORPT.), m / g
TOTAL PORE VOL., m l / g
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
100 A)
PORE VOL., ml/g
R
284
307
67
65
0.44
0.52
0.012
0.035
DIAMETER, Â
MACRO ( D >
CATALYSTS
T A B L E VI
CHANGE
IN
PRODUCT
ASPHALTENIC
C O M P O U N D TYPE A N D
SULFUR
CONVERSION
REACTOR
CONDITIONS
FEED
CONTENT
WITH
LEVEL
CATALYST
Τ
CATALYST R
TEMPERATURE, *F
65 5
655
709
665
670
710
PRESSURE,
800
1292
1292
800
1292
1292
0.5
0.3
0.3
0.5
0.3
0.3
74
83
92
74
85
94
psig
LHSV, V O L . / ( V O L . ) CONVERSION COMPOUND
(HR)
LEVEL, TYPE,'/.
SATURATES
30.6
36.8
42.8
43.1
37.5
39.7
45.5
AROMATICS
45.8
47.6
46.8
43.5
47.6
46.4
44.3
POLAR
17.3
10.7
6.2
10.3
10.8
11.3
8.2
6.3
4.9
4.2
3.1
4. 1
2.6
2.0
3.66
0.95
0.63
0.29
0.96
0.55
0.23
AROMATICS
ASPHALTENES TOTAL
SULFUR, %
ABSOLUTE RELATIVE
ASPHALTENIC ASPHALTENIC
SULFUR, % SULFUR, %
0.45 12
0.32 34
0.26 41
0.18 62
0.24 25
0.15 27
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
0.09 39
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9.
RICHARDSON
A N D A L L E Y
Desulfurization of Resids
143
crease, aromatics remain f a i r l y constant and both p o l a r aromatics and asphaltenes decrease. Adsorption chromatography i s the b a s i s f o r type s e p a r a t i o n : pentane e l u t e s the s a t u r a t e s , ether e l u t e s the aromatics, and benzene-methanol e l u t e s the p o l a r aromatics. Quite c l e a r l y , the r e l a t i v e amount of a s p h a l t e n i c s u l f u r increases as the product t o t a l s u l f u r decreases. This i s depicted i n F i g u r e 3. Whereas the r e l a t i v e amount of aromatics remained f a i r l y constant as s u l f u r conversion l e v e l was increased to 92-94%, the r e l a t i v e amount of s u l f u r i n the aromatic f r a c t i o n decreased markedly. T h i s a l s o i s depicted i n F i g u r e 3. P o l a r aromatics are intermed i a t e to the aromatics and asphaltenes i n regard to t h i s behavior. These d i f f e r e n t d i s t r i b u t i o n s of s u l f u r with conversion l e v e l resemble those reported by Drushel f o r Safaniya r e s i d (8). The removal of metals with the a s p h a l t e n i c s u l f u r i s observed i n F i g u r e 4. T h i s response i s c o n s i s t e n t with an asphaltene model i n which vanadium and n i c k e l are b u r i e d as porphyrins or sandwich compounds (9). The s l i g h t l y higher removal of vanadium r e f l e c t s a general tendency f o r vanadium to deposit on the c a t a l y s t more r e a d i l y than n i c k e l . EFFECT OF COKE DEPOSITION ON PORE SIZE DISTRIBUTION A f i r s t step toward c a t a l y s t design i s to r e l a t e pore s t r u c ture roughly to asphaltene dimensions. Another step i s to c o n s i der pore s t r u c t u r e of the used c a t a l y s t and the probable s i z e of asphaltenes at r e a c t o r temperature. Figure 5 i s a histogram showing the d i s t r i b u t i o n of pore v o l ume v s . pore diameter f o r alumina c a r r i e r , f r e s h c o b a l t molybdenum c a t a l y s t and used cobalt molybdenum c a t a l y s t . There was a s l i g h t change i n mode diameter when the c a r r i e r was loaded with about 20% a c t i v e metal oxides. The pore volume was reduced from 0.60 to 0.53 m l / g . However, accumulation of about 17% coke during the p r o c e s s i n g of West Coast r e s i d g r e a t l y s h i f t e d the mode downward and reduced the t o t a l pore volume from 0.53 to 0.30 m l / g . ( A l l of these pore volumes have been normalized to 1.0 gram of alumina). A d d i t i o n a l comparisons of f r e s h v s . used c a t a l y s t are shown i n Table V I I . The coke laydown occurred mainly i n the micropore r e g i o n , causing a s u b s t a n t i a l l o s s of surface a r e a . Coke laydown a l s o was observed i n the macropore r e g i o n of the bimodal c a t a l y s t shown at the bottom of the t a b l e . ASPHALTENE EXCLUSION AS A FUNCTION OF TEMPERATURE The e x c l u s i o n of asphaltenes f i r s t was approached by the simp l e method of immersing a given amount of c a t a l y s t i n a volume of r e s i d equal to 3 times the pore volume of the c a t a l y s t . If asphaltene e x c l u s i o n were to occur to a s i g n i f i c a n t degree, then there
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
144
HYDROCRACKING
A N D HYDROTREATING
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
CATALYST R -CATALYST Τ
SATURATES
, 0
20 7.
•^ • 40
60
80
DESULFURIZATION
100 Figure 3. Distribution of sulfur with conversion level
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
9.
RICHARDSON
Desulfurization of Resids
A N D A L L E Y
20
145
140
60 80 100 PORE DIAMETER, Â
40
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
Figure 5. Histograms of pore volumes vs. pore diameter for carrier, fresh catalyst, and used catalyst
TABLE VII
CHANGE
IN
PORE
DUE TO COKE
SAMPLE AND
DESCRIPTION DESIGNATION
PORE
STRUCTURE
DEPOSITION
VOLUME, ml/g
MODE
SURFACE
DIAMETER
AREA
A
m /g
MACRO
MICRO
TOTAL
S - 0293 - A
0.03
0.3 6
0.39
90
207
USED S - 0 2 9 3 - A
0.04
0.13
0.17
55
164
V-8477-Β
0.02
0.35
0.37
85
136
USED
0.02
0.15
0.17
60
102
X - 02 34 - A
0.02
0.41
0.43
90
167
USED X - 0234 - A
0.02
0.21
0.23
60
140
H-6013
0.70
0.4 5
1.15
95, 350
350
USED
0.39
0.30
0.69
80, 400
174
V-8477-Β
H-6013
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
2
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146
HYDROCRACKING A N D H Y D R O T R E A T I N G
would be an enrichment of asphaltenes i n the e x t e r n a l l i q u i d . Using a 24-hour e q u i l i b r a t i o n p e r i o d of 2 1 2 ° F , the four samp l e s shown i n Table V I I I a l l give an enrichment of asphaltenes. The e x t e r i o r l i q u i d s contained 12.0-13.8% asphaltenes compared to 6.3% i n the Kuwait feed. These r e s u l t s q u a l i t a t i v e l y agree with observations of Drushel who used a d i f f e r e n t technique w i t h Safani y a r e s i d at room temperature (8). The e x c l u s i o n of asphaltenes as a f u n c t i o n of temperature subsequently was approached w i t h the a i d of g e l permeation chromotography (GPC) i n a manner s i m i l a r to that described by D r u s h e l . C a t a l y s t was e q u i l i b r a t e d 4 hour at constant temperatures w i t h a volume of r e s i d equal to 3 times the pore volume of the c a t a l y s t . During t h i s time, the system was n i t r o g e n blanketed and a g i t a t e d every 1/2 hour. The e x t e r n a l l i q u i d subsequently was drained through a screen and submitted f o r GPC analyses and metals content. The i n t e r n a l l i q u i d was e x t r a c t e d from the c a t a l y s t pores f i r s t by benzene and then 50/50 methanol-benzene. A f t e r evaporation of these s o l v e n t s , the i n t e r n a l l i q u i d was submitted f o r i d e n t i c a l analyses. The GPC curves i n Figure 6 show asphaltene or "large molecule" e x c l u s i o n at the nominal temperatures of 200, 400 and 6 0 0 ° F . The e f f e c t decreases with i n c r e a s i n g temperature: planimeter areas f a l l i n the r a t i o of 1.00, 0.65, and 0.40. Metals d i s t r i b u t i o n , which i n some degree should r e l a t e to asphaltene d i s t r i b u t i o n , are shown f o r the a c t u a l e q u i l i b r a t i o n temperatures i n Table IX. N i c k e l showed the expected enrichment at a l l temperatures. Vanadium responded s i m i l a r l y except at 403 and 6 0 3 ° F . Progressive s u l f i d i n g (0.6, 0.7, 1.4% S) and coke l a y down (0.8, 1.5, 7.8% C) were observed f o r the used c a t a l y s t s and hence represent an experiment c o m p l i c a t i o n . CONCLUSIONS The p o i n t s to be emphasized i n c l u d e the f o l l o w i n g : 1. The r e f r a c t o r i n e s s of r e s i d feeds has been considered from the standpoint of process s e v e r i t y and d i v i s i o n between "hard" and "easy" s u l f u r . 2. For lower conversions l e v e l s , where a s p h a l t e n i c s u l f u r removal i s not deep, r e f r a c t o r i n e s s appears to be l a r g e l y i n f l u enced by a l a r g e p r o p o r t i o n of s t e r i c a l l y hindered aromatic s u l fur compounds. S u b s t i t u t e d thiophenes, benzothiophines and d i benzothiophenes are r e p r e s e n t a t i v e compounds. 3. A s p h a l t e n i c s u l f u r i s the most r e f r a c t o r y specie i n r e s i d s and the removal of metals, p a r t i c u l a r l y n i c k e l , c o r r e l a t e s w e l l with removal of a s p h a l t e n i c s u l f u r . 4. Coke d e p o s i t i o n a l t e r s c a t a l y s t pore s i z e d i s t r i b u t i o n s s i g n i f i c a n t l y and i s an e f f e c t to be followed i n regard to c a t a l y s t aging. 5. The e x c l u s i o n of asphaltenes i n Kuwait r e s i d i s observed by an autoclave technique at 2 1 2 ° F with s e v e r a l c a t a l y s t s having
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
A N D
A L L E Y
Desulfurization of Resids
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
RICHARDSON
Figure 6. GPC molecular size distributions at various temperatures
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
148
HYDROCRACKING AND HYDROTREATING
TABLE VIII
ASPHALTENE
EXCLUSION EXPERIMENTS
AT 212 *F A N D Ί ATMOS. .
CATALYST RESID
WEIGHT, g
WEIGHT, g
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
ASPHALTENE
24.00
23.00
25.50
26-60
36.49
35.00
35.07
47.00
CONTENT
INITIAL, % FINAL, OBS., % PORE
CATALYST
6.3
6.3
6.3
6.3
13.8
12.8
12.0
13.4
V O L U M E , ml/g
0.50
0.52
0.47
1.15
MICROPORE VOLUME, ml/g
0.42
0.50
0.44
0.45
MODE
DIAMETER,
65
λ
60
75
TABLE IX
METALS DISTRIBUTION IN RESID FRACTIONS Ni
e
V (PPM)
9
40
INTERNAL
4
18
FEED 197 F
(PPM)
EXTERNAL
15
58
e
INTERNAL
2
48
e
EXTERNAL
12
35
INTERNAL
5
49
EXTERNAL
10
27
e
197 F 403 F 403 F e
603 F e
603 F
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
95
9.
RICHARDSON AND A L L E Y
Desulfurization of Resids
149
mode diameters of 60-95 Â. 6. Exclusion of asphaltenes and/or large molecules i s also observed at 200, 400 and 600°F by similar technique involving GPC. The effect diminishes moderately with increasing temperature due to thermal dissociation into smaller particles. 7. The exclusion of asphaltenes is matched by the distribution of nickel inside and outside the catalyst pore structure. Vanadium distribution is inconsistent, probably influenced by coke deposition at the higher temperatures. ACKNOWLEDGEMENT
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch009
The authors acknowledge Dr. Dennis L . Saunders for the GPC analytical work and many useful discusssions. LITERATURE CITED (1) (2) (3) (4) (5) (6) (7) (8) (9)
Larson, O. Α . , Pittsburgh Catalysis Society, Spring Symposium, (April, 1972). US 3,509,044 (Esso) US 3,531,398 (Esso) US 3,563,886 (Gulf) UK 1,122,522 (Gulf) NPA 6,815,284 (Hydrocarbon Research) German 1,770,996 (Nippon Oil) Drushel, Η. V., Preprints, Div. Petrol. Chem., ACS, 17, No. 4, F-92 (1972). Dickie, J. P . , Yen, T. F., Preprints, Div. Petrol. Chem., ACS, 12, No. 2, B-117 (1967).
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
10 The Structural Form of Cobalt and Nickel Promoters in Oxidic HDS Catalysts R. MONÉ and L. MOSCOU
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
Akzo Chemie Nederland bv, Research Centre Amsterdam, P. O. Box 15, Amsterdam, The Netherlands
H y d r o d e s u l f u r i z a t i o n c a t a l y s t s c o n s i s t of CoO and M o O or NiO and M o O on a -Al O c a r r i e r ( 1 - 3 ) . The c a t a l y s t s are produced i n the o x i d i c form; t h e i r a c t u a l a c t i v e s t a t e is obtained by s u l f i d i n g before or during usage i n the r e a c t o r . Molybdenum oxide - alumina systems have been s t u d i e d i n d e t a i l (4-8). Several authors have pointed out that a molybdate surface l a y e r is formed, due to an i n t e r a c t i o n between molybdenum oxide and the alumina support (9-11). Richardson (12) s t u d i e d the s t r u c t u r a l form of c o b a l t i n s e v e r a l o x i d i c cobalt-molybdenumalumina c a t a l y s t s . The presence of an a c t i v e cobalt-molybdate complex was concluded from magnetic s u s c e p t i b i l i t y measurements. Moreover c o b a l t aluminate and c o b a l t oxide were found. Only the a c t i v e c o b a l t molybdate complex would c o n t r i b u t e to the a c t i v i t y and be c h a r a c t e r i z e d by o c t a h e d r a l l y coordinated c o b a l t . L i p s c h and Schuit (10) s t u d i e d a commercial o x i d i c h y d r o d e s u l f u r i z a t i o n c a t a l y s t , c o n t a i n i n g 12 wt% M o O and 4 wt% CoO. They concluded that a c o b a l t aluminate phase was present and could not f i n d i n d i c a t i o n s f o r an a c t i v e c o b a l t molybdate complex. Recent magnetic s u s c e p t i b i l i t y s t u d i e s of the same type of c a t a l y s t (13) confirmed the c o n c l u s i o n of L i p s c h and Schuit. Schuit and Gates (30 proposed a model f o r the o x i d i c c a t a l y s t , i n which the promotor ions l a y j u s t below the molybdate l a y e r . These c o b a l t ions would s t a b i l i z e the molybdate l a y e r on the c a t a l y s t surface. The promoting a c t i o n of c o b a l t on the a c t i v i t y f o r hydrodesulf u r i z a t i o n has been shown already i n the p i o n e e r i n g work of Byrns, Bradley and Lee ( 1A). This promoting a c t i o n might be l i n k e d with the s u l f i d i n g step, s i n c e the a c t u a l c a t a l y s t i s the s u l f i d e d form of c o b a l t - or nickel-molybdenum-alumina. Voorhoeve and S t u i v e r (15) and Farragher and Cossee (lj3) demonstrated the promoting a c t i o n f o r the unsupported N1-WS2 system. T h e i r i n t e r c a l a t i o n model was based on these experiments. I t i s expected that the a c t i v a t o r system i n the o x i d i c c a t a l y s t has a s t r u c t u r e from which the r i g h t c o n f i g u r a t i o n i s obtained on s u l f i d i n g . We f e e l that the promotor ions have to be 3
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present i n the neighbourhood of the surface molybdate l a y e r and that the assumption of a cobalt-aluminate phase might be an i n s u f f i c i e n t d e s c r i p t i o n of the o x i d i c h y d r o d e s u l f u r i z a t i o n c a t a l y s t . Therefore we have examined the presence of i n t e r a c t i o n s between c o b a l t and molybdenum from which a more d e t a i l e d p i c t u r e of the o x i d i c c a t a l y s t can be deduced. We have s t u d i e d t h e r e f o r e UV-VIS r e f l e c t a n c e s p e c t r a of adsorbed p y r i d i n e , a technique that has been used before f o r t h i s type of c a t a l y s t s by K i v i a t and P e t r a k i s (19). Experimental Methods. C a t a l y s t Preparation. The c a t a l y s t s were prepared by impregn a t i o n of îf-alumina extrudates ( SA=253 m /g ). Each impregnation was followed by drying overnight at 120°C and c a l c i n a t i o n at the i n d i c a t e d temperatures during one hour. Molybdenum was brought on the support as an ammonium molybdate s o l u t i o n ; c o b a l t and n i c k e l as n i t r a t e s o l u t i o n s . Each component was impregnated s e p a r a t e l y . The impregnation of c o b a l t on the blanc support took place stepwise (1 wt% CoO i n each s t e p ) .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
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C a t a l y s t s . MoCo-124: Alumina was impregnated f i r s t w i t h molybdenum, then c a l c i n e d at 650°C, followed by the c o b a l t impregn a t i o n . The f i n a l c a l c i n a t i o n was v a r i e d from 400 - 700°C. Composition:
12 wt%
M0O3 and 4 wt%
CoO.
MoCo-122 and MoCo-123 were obtained by impregnation as c a r r i e d out f o r MoCo-124. Only 2 and 3 wt% CoO resp. were brought on the c a t a l y s t . F i n a l c a l c i n a t i o n temperature 650 C. CoMo-124: Alumina was impregnated f i r s t with c o b a l t stepwise. The sample was d r i e d at 120°C and c a l c i n e d at 650 C a f t e r each impregnation step. Afterwards the c a t a l y s t was impregnated w i t h molybdenum. F i n a l c a l c i n a t i o n temperature 650°C. The composition was the same as f o r MoCo-124. CoMo-124 B: Cobalt was brought on uncalcined boehmite, 4 wt% i n one step. Afterwards the sample was c a l c i n e d at 650°C, impregnated w i t h molybdenum oxide (12 wt%) and c a l c i n e d at 650°C f o r a second time. The surface area was 241 m /g. MoCo-153: Alumina was impregnated f i r s t w i t h molybdenum, d r i e d and c a l c i n e d at 650°C. Then the c o b a l t was brought hereupon. Two f i n a l c a l c i n a t i o n temperatures were a p p l i e d , 480 and 650*C. The e
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15 wt%
M0O3 and
3 wt%
CoO.
NiMo-124: The c a t a l y s t s were prepared according to the Dutch Patent 123195 (17). The alumina c a r r i e r was impregnated f i r s t w i t h n i c k e l . Two f i n a l c a l c i n a t i o n temperatures were a p p l i e d , 480 and 650°C. These samples were impregnated w i t h molybdenum. F i n a l c a l c i n a t i o n temperatures 480 and 650°C. The composition of the four c a t a l y s t s , which were obtained was 12 wt% M0O3 and 4 wt% NiO, The c a t a l y s t s are i n d i c a t e d by the a p p l i e d c a l c i n a t i o n temperatures a f t e r each impregnation; e.g. NiMo-124 480/480. MoNi-153: Molybdenum was brought on the alumina c a r r i e r f i r s t ,
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( c a l c i n a t i o n temperature 650°C), followed by the n i c k e l impregn a t i o n . The f i n a l c a l c i n a t i o n temperature was v a r i e d . The composit i o n was 15 wt% M0O3 and 3 wt% NiO.
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
R e f l e c t i o n Spectroscopy. The r e f l e c t i o n s p e c t r a were r e c o r ded with an O p t i c a Milano CF 4 spectrophotometer, using magnesium oxide as the r e f e r e n c e . The samples were m i l l e d i n a mortar during 20 minutes. The r e f l e c t a n c e d i d not change s i g n i f i c a n t l y when t h i s m i l l i n g time was increased. The s p e c t r a of the c o b a l t c o n t a i n i n g samples are shown, as they have been recorded (% r e f l e c t a n c e against wavelength). The s p e c t r a of the n i c k e l c o n t a i n i n g samples are p l o t t e d as a remission f u n c t i o n (18) against wavenumber. I n f r a r e d Spectroscopy. The procedure of K i v i a t and P e t r a k i s (19) was followed f o r the greater p a r t . The s p e c t r a of adsorbed p y r i d i n e were recorded with a Perkin Elmer 621 spectrophotometer. The d i s c s (15 mg/cm ) were pressed i n a RIIC d i e , using a pressure of 1000 kg/cm . These d i s c s were rehydroxylated f i r s t on standing i n humid a i r during two days before they were placed i n the IR c e l l . Outgassing took place at 420*C. P y r i d i n e was adsorbed at room temperature and the excess was removed by evacuation at 150, 250 and 350°C during one hour. 2
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Pore s t r u c t u r e . The surface area and pore volume were determined by N2 adsorption. No s i g n i f i c a n t changes were observed when the c a t a l y s t was c a l c i n e d i n the temperature r e g i o n of 400 - 700°C i n d i c a t i n g that no s t r u c t u r a l c o l l a p s e took place i n t h i s temperature range. Results. V i s i b l e R e f l e c t i o n Spectra. The f i n a l c a l c i n a t i o n temperature of MoCo-124 samples has been v a r i e d i n order to study i t s i n f l u e n c e on the c o o r d i n a t i o n of the c o b a l t i o n s . The r e f l e c t i o n s p e c t r a are shown i n F i g u r e 1. The s p e c t r a of MoCo-124, c a l c i n e d at 400 and 500°C show a broad absorption band, covering the whole s p e c t r a l region, with a weak s u p e r p o s i t i o n of the c h a r a c t e r i s t i c t r i p l e t of c o b a l t aluminate. T h i s i n d i c a t e s that the c o b a l t ions are f o r the greater part s t i l l on the c a t a l y s t surface and not i n the alumina l a t t i c e . The s p e c t r a of the MoCo-124 samples, c a l c i n e d at 650-700 °C show a strong increase i n i n t e n s i t y of the t r i p l e t band, while the broad absorption band has disappeared. T h i s i n d i c a tes the formation of a c o b a l t aluminate phase. I n f r a r e d Spectra. F i g u r e 2 shows the s p e c t r a of p y r i d i n e adsorbed on /-alumina. Two types of Lewis a c i d s i t e s are present; strong Lewis a c i d s i t e s , which s t i l l bind p y r i d i n e on evacuation at 350°C and c h a r a c t e r i z e d by the 1622 and 1454 cm" bands and weak Lewis a c i d s i t e s , c h a r a c t e r i z e d by the 1614 and 1450 cm" bands. BrSnsted a c i d s i t e s , which have c h a r a c t e r i s t i c bands around 1
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1636 and 1540 cm~l (19,21) are not observed i n t h i s spectrum. The spectrum of p y r i d i n e adsorbed upon cobalt-alumina (4 wt% CoO) i s shown i n F i g u r e 2d. No change i n the p y r i d i n e spectrum i s observed i n comparison with the spectrum of p y r i d i n e on y-alumina, i n d i c a t i n g that the surface a c i d i t y i s not markedly changed. A same behaviour has been observed f o r n i c k e l alumina. These r e s u l t s agree w i t h those o f K i v i a t and P e t r a k i s (19). The adsorption of p y r i d i n e on molybdenum-alumina (12 wt% M0O3) has been i n v e s t i g a t e d f o r samples i n both o r i g i n a l and rehydroxylated form. The s p e c t r a are shown i n F i g u r e 3. I t appears that BriSnsted a c i d s i t e s , c h a r a c t e r i z e d by the 1636 and 1540 cm"" bands are observed only, when the d i s c s are rehydroxylated i n wet a i r before the c a l c i n a t i o n under high vacuum i n the IR c e l l takes p l a c e (Figure 3b). By consequence a l l s p e c t r a have been recorded for such rehydroxylated samples. Only one Lewis band i s observed for the molybdenum-alumina sample, opposite t o the observations of K i v i a t and P e t r a k i s (19), who have observed two Lewis bands f o r t h e i r samples. Spectra of adsorbed p y r i d i n e have been recorded f o r the MoCo-124 c a t a l y s t s , f o r which the f i n a l c a l c i n a t i o n temperature a f t e r the c o b a l t impregnation has been v a r i e d . I t turns out that the 400 and 500°C c a l c i n e d samples and the 650 and 700°C c a l c i n e d samples show very s i m i l a r s p e c t r a . Therefore we show only the s p e c t r a o f the 400°C (low c a l c i n e d ) and the 650°C (high c a l c i n e d ) samples. F i g u r e 4 shows s p e c t r a a f t e r desorption at 150 and 250°C. Few BrSnsted a c i d s i t e s are observed i n the low c a l c i n e d MoCo-124 samples. The r e f l e c t i o n s p e c t r a ( F i g u r e 1) i n d i c a t e f o r these low c a l c i n e d samples the presence of c o b a l t on the c a t a l y s t s u r f a c e , because no c o b a l t aluminate phase could be detected. The high c a l c i n e d samples do show the presence of BrSnsted a c i d s i t e s ; the presence of a c o b a l t aluminate phase i s concluded from the r e f l e c t i o n s p e c t r a (Figure 1) f o r these samples. These experiments i n d i c a t e that at low c a l c i n a t i o n tempera tures the c o b a l t ions are present on the c a t a l y s t surface and n e u t r a l i z e the BrBnsted a c i d s i t e s of the molybdate surface l a y e r . At the higher c a l c i n a t i o n temperatures, the c o b a l t ions move i n t o the alumina l a t t i c e . The BrGnsted a c i d s i t e s reappear, i n d i c a t i n g that the s i t u a t i o n on the molybdate surface i s r e s t o r e d . However, the molybdenum-alumina and the high c a l c i n e d c o b a l t molybdenum-alumina samples s t i l l show an important d i f f e r e n c e . The p y r i d i n e s p e c t r a of MoCo-124 i n d i c a t e a second Lewis a c i d s i t e , c h a r a c t e r i z e d by the 1612 cm" band. T h i s band d i f f e r s from the weak Lewis a c i d s i t e s of the alumina support (1614 cm* ) because the p o s i t i o n i s s i g n i f i c a n t l y d i f f e r e n t . I t a l s o appears that the s t r e n g t h of the bond between p y r i d i n e and the c a t a l y s t i s stronger, for the 1612 cm" band i s s t i l l present a f t e r evacuation at 250°C, w h i l e the weak Lewis band (1614 cm" ) o f the alumina has d i s a p peared at t h i s desorption temperature. Obviously the second Lewis band f o r the MoCo-124 c a t a l y s t i s introduced by the i n t e r a c t i o n of c o b a l t with the surface molybdate l a y e r . T h i s i n t e r a c t i o n i s
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
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In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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Or
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Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
Figure 1. Reflectance spectra of MoCo-124 catalysts, calcined at different temperatures, a) 400°C, b) 500°C, c) 600°C, d) 650°C, and e) 750°C.
170Ô 1600 1500 1400 WAVENUMBER (cm-1)
Figure 2. Spectra of adsorbed pyridine a) on y-Al O evacuated 1 hr, 150°C; b) as a), evacuated 1 hr, 250°C; c) as a), evacuated 1 hr, 350° C; d) on CoO-y-Al O , evacuated 1 hr, 150° C 2
s
z
s
1700 1600 1500 1400 WAVENUMBER (cm-1)
Figure 3. Spectra of adsorbed pyridine a) on MoO -y-Al 0 , evacuated 1 hr, 150°C; b) on rehydroxylated MoCVyAl O , evacuated 1 hr, 150° F; c) as b), evacuated 1 hr, 250°C; d) as b), evacuated 1 hr, 350°C s
z
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In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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c l e a r l y s t i l l present i n the high c a l c i n e d c a t a l y s t s , where c o b a l t i s present i n the alumina l a t t i c e . Reversed Impregnation. The reversed impregnation has been s t u d i e d too. Impregnation of 4 wt% CoO on y-alumina i n one step g e n e r a l l y leads t o the formation of C03O4 on c a l c i n a t i o n (black extrudates (22,23)). A stepwise impregnation r e s u l t s i n c o b a l t aluminate formation (blue extrudates), showing i t s c h a r a c t e r i s t i c t r i p l e t i n the r e f l e c t i o n spectrum (Figure 5a). Impregnation of molybdenum on the c o b a l t c o n t a i n i n g support does not i n f l u e n c e the r e f l e c t i o n spectrum of the c o b a l t i o n s , as shown i n F i g u r e 5b. Spectra of p y r i d i n e , adsorbed on t h i s CoMo-124 sample are shown i n F i g u r e 6. The second Lewis band (1612 cm"" ) i s present, i n d i c a t i n g that the i n t e r a c t i o n between the c o b a l t ions and the s u r f a c e molybdate l a y e r i s present too. Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
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Boehmite Based .Catalysts. Hedvall (24) has discussed the f o r mation of c o b a l t aluminate from CoO and AI2O3. He has shown that a r e l a t i v e l y f a s t s o l i d s t a t e r e a c t i o n takes place when the alumina undergoes a phase change, v i z . y-Al2C>3-> rt-A^Og. T h i s phenomenon i s known as the Hedvall e f f e c t . Such an e f f e c t might be expected when boehmite supported c o b a l t i s being c a l c i n e d , v i z . during the phase t r a n s i t i o n AIO(OH) - * y - A l 0 3 . F i g u r e 7 shows s p e c t r a of p y r i d i n e , adsorbed on the sample CoMo-124 B, which has been prepared i n t h i s way. Spectra f o r MoCo-122, -123 and -124, c o n t a i n i n g 2, 3 and 4 wt% CoO resp. are shown f o r comparison. A l l these c a t a l y s t s have had a f i n a l c a l c i n a t i o n of 650°C. Comparison of the s p e c t r a of CoMo-124 Β and MoCo-124 i n d i c a t e s that the i n t e n s i t y of the 1612 cm" band, which i s introduced by the i n t e r a c t i o n of the c o b a l t ions and the molybdate l a y e r , i s lower f o r CoMo-124 Β than f o r MoCo-124. The spectrum f o r CoMo-124 Β resembles that of CoMo-123, i n d i c a t i n g that a part of the c o b a l t ions does not p a r t i c i p a t e i n t h i s i n t e r a c t i o n . 2
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N i c k e l Promoted C a t a l y s t s . N i c k e l c o n t a i n i n g c a t a l y s t s are known to be s e n s i t i v e f o r too high temperatures. The Dutch patent 123195 (17) claims that a c t i v e nickel-molybdenum-alumina c a t a l y s t s are obtained, when n i c k e l i s impregnated f i r s t . The c a l c i n a t i o n i s c r i t i c a l however. According t o t h i s patent, c a t a l y s t s c a l c i n e d at 4 8 0 a r e twice as a c t i v e as c a t a l y s t s , c a l c i n e d at 650°C. C a t a l y s t s NiMo-124 have been prepared according t o t h i s patent and have been i n v e s t i g a t e d . The h y d r o d e s u l f u r i z a t i o n a c t i v i t y showed indeed a pronounced decrease on c a l c i n a t i o n at 650°C i n comparison w i t h the 480°C c a l c i n e d sample. The s p e c t r a of adsorbed p y r i d i n e are shown i n F i g u r e 8. The spectrum of the sample NiMo-124 480/480, which has been c a l c i n e d twice at the lowest c a l c i n a t i o n temperature shows a c l e a r 1612 cm" Lewis band. This band has a f a r weaker i n t e n s i t y f o r the 650/650 c a t a l y s t . The 480/650 sample shows a more intense 1612 cm" band than the 650/650 and 650/480 samples. T h i s might i n d i c a t e that the 1
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
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1700 1600 1500 1400 WAVENUMBER (cm-1)
Figure 4. Spectra of adsorbed pyridine a) on MoCo-124,finalcalcination 400°C, evacuated 1 hr, 150°C; b) as a), evacuated 1 hr, 250°C; c) on MoCo-124, final calcination 650°C, evacuated 1 hr, 150°C; d) as c), evacuated 1 hr, 250°C
Figure 5. Reflectance spectra: a) CoO-y-Al O , calcined at 650°C; b) of CoMo-124,finalcalcination, 650°C 2
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In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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Figure 6. Spectra of adsorbed pyri dine a) on CoMo-124, evacuated 1 hr, 150°C; b) as a) evacuated 1 hr, 1700 250°C
1600 1500 WAVENUMBER (cm-1)
1400
1700 1600 1500 1400 WAVENUMBER (cm-1)
1700 1600 1500 1400 WAVENUMBER (cm-1)
Figure 7. Spectra of ad sorbed pyridine a) MoCo-122; b) MoCo-123; c) MoCo-124; d) CoMo124 B. All after evacua tion 1 hr, 150°C.
Figure 8. Spectra of ad sorbed pyridine NiMo124: a) 480/480; b) 480/ 650; c) 650/480; d) 650/ 650. All after evacuation 1 hr, 150°C.
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n i c k e l i o n s , which are s t i l l present i n the neighbourhood of the alumina surface a f t e r the f i r s t c a l c i n a t i o n at 480°C, remain t i e d to the molybdate l a y e r to some extent a f t e r the second c a l c i n a t i o n at 650°C. The s p e c t r a of adsorbed p y r i d i n e f o r MoCo-153 and MoNi-153 are compared i n F i g u r e 9. Two f i n a l c a l c i n a t i o n temperatures have been a p p l i e d , 480 and 650 C. The s p e c t r a of the 480°C samples ( F i gure 9a and 9b) are n e a r l y i d e n t i c a l . The Brtfnsted a c i d bands are weak, while the 1612 cm"l Lewis bands are strong. The i n t e n s i t y of the Bro'nsted a c i d bands i n c r e a s e s f o r both 650 °C c a l c i n e d samp l e s (Figure 9c and 9d). The Lewis a c i d bands show a marked d i f f e rence now. The 1612 band remains high i n i n t e n s i t y f o r the MoCo153 c a t a l y s t , but t h i s Lewis band decreases a p p r e c i a b l y i n i n t e n s i t y f o r the MoNi-153 c a t a l y s t . R e f l e c t i o n s p e c t r a f o r the MoNi-153 c a t a l y s t s are shown i n F i g u r e 10. The 480°C c a l c i n e d c a t a l y s t shows the c h a r a c t e r i s t i c a b s o r p t i o n band (25) of o c t a h e d r a l l y coordinated n i c k e l i o n s . The 650°C c a l c i n e d c a t a l y s t shows the c h a r a c t e r i s t i c spectrum of n i c k e l aluminate. These r e f l e c t i o n s p e c t r a i n d i c a t e that the n i c k e l ions migrate from the c a t a l y s t surface i n t o the alumina, as has been observed a l s o f o r the cobalt-molybdenum-alumina c a t a l y s t s .
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
e
Discussion. R u s s e l l and Stokes (9) and Sonnemans and Mars (11) have presented strong evidence f o r the formation of a molybdate monolayer. I t appears from t h e i r experiments that each molybdate group covers 20-25 Â of the alumina surface.The surface of the alumina support, which has been used i n t h i s study, i s high enough f o r a complete spreading of 15 wt% M 0 O 3 , so no bulk molybdenum oxide i s expected to be present. T h i s has been confirmed by X-ray d i f f r a c t i o n measurements. The molybdate surface l a y e r i n the molybdenum-alumina samples i s c h a r a c t e r i z e d by the presence of Bro'nsted a c i d s i t e s ( 1545 cm" ) and one type of strong Lewis a c i d s i t e s (1622 cm" ). Cobalt or n i c k e l ions are brought on t h i s surface on impregnation of the promotor. The absence of BrSnsted a c i d s i t e s i s observed f o r both c o b a l t and n i c k e l impregnated c a t a l y s t s , c a l c i n e d at the lower temperatures (400-500°C). A l s o a second Lewis band i s observed at 1612 cm" .The r e f l e c t i o n s p e c t r a of these c a t a l y s t s i n d i c a t e that no c o b a l t or n i c k e l aluminate phase has been formed at these temperat u r e s . T h i s i n d i c a t e s that the c o b a l t and n i c k e l ions are s t i l l present on the c a t a l y s t surface and n e u t r a l i z e the BrSnsted a c i d s i t e s of the molybdate l a y e r . These c o n f i g u r a t i o n s w i l l be c a l l e d " c o b a l t molybdate" and " n i c k e l molybdate" and are shown schematica l l y i n F i g u r e 11a. For the high temperature c a l c i n e d cobalt-molybdenum-alumina c a t a l y s t s , the presence of a c o b a l t aluminate phase has been concluded from the r e f l e c t i o n s p e c t r a . The Bro'nsted a c i d s i t e s reappear i n the spectrum of absorbed p y r i d i n e , i n d i c a t i n g that the 2
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In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
10.
M O N É
A N D
Moscou
Cobalt and Nickel Promoters
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1612
1700 1600 1500 1400 WAVENUMBER (cm-1)
Figure 9. Spectra of adsorbed pyridine on MoC0-153,finalcalcination: a) 480°C; c) 650°C; MoNi-153,finalcalcination: b) 480°C; d) 650°C
1
1
15
10
WAVENUMBER
3
(cm-1)
H Ο ι
/
-Moalumina
-Mo-
Nickel
Cobalt
impregnation Co Cr
calcining 5 0 0 ° C
(5)
2
Ni^
+
-Mo
-Co
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MoΘ-some surface -NiAl^Oj ^^buTk^NiAl^^^
H Ο -Ao<-
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-MoΗ
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-Mosurface CoA^Qj
boehmite based CoMo-124
. χ 10
Figure 10. Reflectance spectra of MoNi153: a)finalcalcination, 480°C; b)finalcal cination, 650°C
molybdate surface layer characterized by Brônsted and Lewis acid sites
calcining 6 5 0 ° C
I 20
-Mo-
^ Î 5 % ζ»\ν€ο&\$£> Figure 11. Schematic representation of the different surface structures
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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HYDROCRACKING AND HYDROTREATING
bond between c o b a l t and the molybdate l a y e r i s broken. S t i l l the presence of two types of Lewis a c i d s i t e s i s observed (1622 and 1612 cm" ). T h i s suggests that no bulk aluminate phase i s formed, but that the c o b a l t ions remain present i n the f i r s t l a y e r of the alumina l a t t i c e , s t i l l having an i n t e r a c t i o n with the surface molybdate l a y e r . The optimal a c t i v i t y f o r a cobalt-molybdenum-alumina c a t a l y s t i s obtained by c a l c i n a t i o n at the higher temperatures. This means that the c o b a l t i o n s , present as a c o b a l t aluminate phase according to the r e f l e c t a n c e s p e c t r a and the magnetic s u s c e p t i b i l i t y measure ments, s t i l l have a pronounced promoting a c t i o n a f t e r t h i s c a l c i n a t i o n . The assumption of c o b a l t present i n the surface l a y e r of the alumina l a t t i c e e x p l a i n s both the high a c t i v i t y due to the c o b a l t promotion as w e l l as the presence of the second Lewis band. T h i s c o n f i g u r a t i o n i s shown s c h e m a t i c a l l y i n F i g u r e l i b . Some bulk c o b a l t aluminate formation i s expected to take place f o r the boehmite based c a t a l y s t , owing to a Hedvall e f f e c t (24).The spectrum of adsorbed p y r i d i n e on CoMo-124 Β shows indeed a weaker 1612 cm" band, comparable with the i n t e n s i t y of t h i s band f o r the MoCo-123 c a t a l y s t . This i n d i c a t e s that about 25 % of the c o b a l t ions has disappeared in the bulk of the alumina. (Figure lid). The reappearance of Bro'nsted a c i d s i t e s has been observed f o r the high c a l c i n e d nickel-molybdenum-alumina c a t a l y s t s . The presence of a n i c k e l aluminate phase has been concluded from the r e f l e c tance s p e c t r a . The second Lewis band (1612 cm" ) has a very low i n t e n s i t y , i n comparison with the c o b a l t c o n t a i n i n g c a t a l y s t s of a same composition and a f t e r the same c a l c i n a t i o n c o n d i t i o n s . N i c k e l aluminate i s a p a r t l y inverse s p i n e l (26) i n which the n i c k e l ions occupy both t e t r a h e d r a l and octahedral holes, opposite to c o b a l t aluminate, which i s a normal s p i n e l . Romeyn (26)has shown f o r the compound NIAI2O4 and Lo Jacono e t . a l . (25) f o r n i c k e l alumina systems that the n i c k e l ions occupy only a f r a c t i o n of the t e t r a h e d r a l s i t e s , never exceeding 25 %. The strong reduc t i o n i n i n t e n s i t y of the 1612 cm" Lewis band might be due to the octahedral p o s i t i o n of the greater part of the n i c k e l ions i n the surface l a y e r of the alumina l a t t i c e . However i t i s a l s o known that the a c t i v i t y decreases s t r o n g l y f o r the high c a l c i n e d n i c k e l molybdenum-alumina c a t a l y s t s (17), at temperatures normally a p p l i e d i n the cobalt-molybdenum-alumina c a t a l y s t p r e p a r a t i o n . This i n d i cates that only a f r a c t i o n of the n i c k e l ions are a v a i l a b l e f o r a promoting a c t i o n i n the high c a l c i n e d c a t a l y s t s . We suggest that t h i s i s due to bulk n i c k e l aluminate formation, by which the n i c k e l ions are l o s t i n the alumina l a t t i c e . T h i s i s s c h e m a t i c a l l y shown i n F i g u r e 11c. K i v i a t and P e t r a k i s (19) have shown that the c o b a l t and n i c k e l ions i n f l u e n c e the s p e c t r a of p y r i d i n e adsorbed on aolybdenumalumina. They have concluded that the i n t r o d u c t i o n of these ions r e s u l t s i n a change of the r a t i o of the i n t e n s i t i e s of the bands of the Lewis and Bro'nsted a c i d s i t e s . Our observations show that t h i s
Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch010
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ΜΟΝΕ AND MOSCOU
Cobalt and Nickel Promoters
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r a t i o i s s t r o n g l y dependent on the c a l c i n a t i o n temperature. T h i s temperature determines the i n t e r a c t i o n between the surface molyb date l a y e r and the promotor ions and might be c o r r e l a t e d w i t h the h y d r o d e s u l f u r i z a t i o n a c t i v i t y of the c a t a l y s t s . Concerning the a c t i v i t y of the cobalt-molybdenum-alumina c a t a l y s t s , i t i s the experience i n t h i s l a b o r a t o r y that the o p t i mal a c t i v i t y i s obtained by c a l c i n a t i o n at high temperatures. The high c a l c i n e d form i s probably p r e f e r r e d , because i n t h i s form the c o b a l t ions are hidden i n the f i r s t l a y e r of the alumina l a t t i c e and are not very s u s c e p t i b l e f o r reducing c o n d i t i o n s i n t h i s con f i g u r a t i o n . I t i s w e l l known that t h i s i s the case f o r the ( low c a l c i n e d ) nickel-molybdenum-alumina c a t a l y s t s . T h i s might be expected from the f a r more exposed form of the n i c k e l ions (Figure 11a). No c o r r e l a t i o n s between a c t i v i t y and the presence of a c o b a l t aluminate complex as i n d i c a t e d by Richardson (12) can be concluded. The low c a l c i n e d cobalt-molybdenum-alumina c a t a l y s t s do show the presence of a " c o b a l t molybdate" phase; however t h i s phase disappears on c a l c i n a t i o n at 650-700°C, where the c a t a l y s t s s t i l l have a high a c t i v i t y . T h i s shows that the c o b a l t ions are not l o s t i n the alumina l a t t i c e . Conclusions.. I t has been found by measuring s p e c t r a of adsorbed p y r i d i n e on various C0O-M0O3-AI2O3 systems that there i s a c l e a r i n t e r a c t i o n of the c o b a l t ions w i t h the M0O3-AI2O3 s u r f a c e l a y e r . T h i s c o n c l u s i o n i s based upon the occurence of a second Lewis band i n the spectrum of adsorbed p y r i d i n e , which has been observed i n the whole r e g i o n of the c a l c i n a t i o n temperatures a p p l i e d . A p i c t u r e has been formed of the way i n which the promotor ions are b u i l t i n the M0O3-AI2O3 system. The n e u t r a l i z a t i o n of the Bro'nsted a c i d s i t e s , as o r i g i n a l l y present i n M0O3-AI2O3 systems by the c o b a l t ions f o r the c a t a l y s t s c a l c i n e d at low tempera tures (^500°C) i n d i c a t e s that the c o b a l t ions are present on the c a t a l y s t s u r f a c e . The l i b e r a t i o n of these s i t e s i n c a t a l y s t s c a l c i n e d at high temperatures (~650°C) and the o b s e r v a t i o n of the c h a r a c t e r i s t i c r e f l e c t a n c e spectrum of C0AI2O4 show that the c o b a l t ions enter the alumina l a t t i c e . However the i n t e r a c t i o n between c o b a l t and molybdenum, as i n d i c a t e d by the second Lewis band remains present. T h i s leads to the c o n c l u s i o n that the c o b a l t ions are present i n the surface l a y e r s of the alumina l a t t i c e . S i m i l a r i n t e r a c t i o n s have been observed f o r the n i c k e l promo t e d c a t a l y s t . However, the degree of i n t e r a c t i o n depends on the c a l c i n a t i o n temperature. T h i s i n t e r a c t i o n disappears f o r a great p a r t at i n c r e a s i n g temperatures. T h i s i s a s c r i b e d to bulk n i c k e l aluminate formation. These observations might c o n t r i b u t e to the understanding of the d i f f e r e n c e s i n c a t a l y t i c performance between c o b a l t and n i c k e l promoted h y d r o d e s u l f u r i z a t i o n c a t a l y s t s .
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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Literature Cited. 1) 2) 3) 4) 5) 6) 7) 8)
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9) 10) 11) 12) 13) 14) 15) 16)
17) 18) 19) 20) 21) 22)
23) 24) 25) 26)
McKinley, J.B., i n "Catalysis", P.H. Emmett,(ed), Vol 5, ρ 405, Reinhold, New York 1957. Schuman, S.C. and Shalit, Η., Catal. Rev., (1970),4, 245. Schuit, G.C.A. and Gates, B.C., AIChE, (1973),19, 417. Seshadri, K.S. and Petrakis, L., J.Catal. (1973),30, 195. Massoth, F.E., J. Catal. (1973),30, 204. Dufaux, Μ., Che, M. and Naccache, C., J. Chim. Phys. Physicochim. B i o l . , (1970),67, 527. Masson, J. and Nechtstein, J., B u l l . Soc. Chim. Fr., (1968), 3933. Miller, A.W., Atkinson, W., Barber, M. and Swift, P., J. Catal. (1970),22, 140. Russell, A.S. and Stokes, J.J., Ind. Eng. Chem., (1946),38, 1071. Lipsch, J.M.J.G. and Schuit, G.C.A., J. Catal., (1969),15, 174. Sonnemans, J. and Mars,P., J. Catal., (1973),31, 209. Richardson, J.T., Ind. Eng. Chem. Fundamentals, (1964),3, 154. Roelofsen, J.W., unpublished results. Byrns, A.C., Bradley, W.E., and Lee, M.W., Ind. Eng. Chem., (1943), 35, 1160. Voorhoeve, R.J.H. and Stuiver, J.C.M., J. Catal., (1971),23, 228,236,243 (1971). Farragher, A.L. and Cossee, P.,Proc F i f t h Intern. Congr. Catal., Palm Beach, ρ 1301, North-Holland Publishing Company, 1973. Chevron Researh Company, Dutch Patent 123195. Wendlandt, W.Wm. and Hecht, H.G., "Reflectance Spectroscopy", Interscience Publishers, New York, 1966. Kiviat, F.E. and Petrakis, L., J. Phys. Chenu,(1973),77, 1232. Parry, E.P., J. Catal., (1963),2, 317. Grimblot, J., Pommery, J. and Beaufils, J.P., C.R. Acad. S c i . , Ser. C., (1973),276, 331. Tomlinson, J.R., Keeling, R.O., Rymer, G.T. and Bridged, J.M., Actes du deuxième Congr. Intern, de Catalyse, ρ 1831, Ed. Technip, Paris (1961). Nishina, R., Yonemura, M. and Kotera, Y., J. Inorg.Nucl.Chem., (1972),34, 3279. Hedvall, J.A. and L e f f l e r , L.,Z, Anorg. A l l g . Chem., (1937), 234, 235. Lo Jacono, M., Schiavelo, M. and Cimino, Α., J. Phys. Chem., (1971),75, 1044. Romeyn, F.C., Thesis, university of Leiden, 1953.
In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
INDEX
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A
Acid function of the catalyst 29 Acid sites, Bronsted 158 Acidic halides 29 Activation energies, Arrhenius 94 Activity, hydrogénation 1, 11, 30 n-Alkanes 1, 2, 18 Alkylbenzenes 82 Alkylcarbenium ions 2 γ-Alumina 151 Alumina catalyst, chromia66,72 Amorphous catalysts 42 Anthracene 83,92 Argon 133 Aromatic structures, complex 82 Aromatics, condensed ring 65 Arrhenius activation energies 94 Arrhenius plots 95 Asphaltenes 112, 121, 139, 143 Asphaltenic sulfur 136 Β Batch distillation 103 Batch stirred tank reactor 84 Benzene 88,126 insolubles 114 Berguid process 123 Bifunctional catalysts 1,9 Blending, products from 105 Boehmite based catalysts 155 Branched isomers, multiple 8 Branching in the cracked products .... 19 Bronsted acid sites 158 Burner fuels 99, 108 η-Butane hydrocracking, isobutane/ .39,41 C C yield hydrocracking C - 180°F product C M , conversion to California gas oil Carbenium ions Carbon balance Carbon number Carbonization of coal Catalyst(s) acid function of aging effects amorphous bifunctional boehmite based 5
5
40,44 36 67 34,37 5 131 11, 79 82 29 42 42 1,9 155
Catalysts (continued) chromia-alumina 66,72 deactivation 46 Ε hydrocracking 45 effects on yields and product prop erties 28 experimental 34 faujasite 46 fouling 45 hydrocracking 29 hydrodesulfurization 150 hydrogenation-dehydrogenation component of 29 monofunctional 7 nickel-molybdena 102 nickel promoted 155 NIS-H-zeolon 88 noble metal 29 nonacidic 65 oxidic HDS 150 palladium-nickel containing syn thetic mica-montmorillonite .... 52 preparation and processing 53, 151 presulfided cobalt moly 136 pore structure 136 Pt/Ca-Y-zeolite 2 reduced 60 sulfided 57 sulfided metal 29 treatment on LPG yields, effect of 61 Catalytic cracking 5 Catalytic sites 40 Cation, mono-branched decyl 20,22 Cation, primary 18 Cetane index 105 Centrifuged liquid product 114, 116 Chain length 1,3 Char feed analysis 127 Chemisorption, competitive 7 Chromia-alumina catalysts 66 Chromia-alumina reactor 72 City bus diesel fuel 104 Cleavage 9,18 Coal 93 carbonization of 82 -derived fuels Ill feed analysis 113, 127 feed rate 132 hydrocracking of 83, 84 hydrogénation tubular reaction experiment
165 In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.
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166
HYDROCRACKING A N D H Y D R O T R E A T I N G
Coal (continued) liquefaction 114, 123 New Mexico sub-bituminous 125 oil 83, 85, 93 particle residence time 128, 130 particle size distribution 130 properties of 85 solvent refined 65 Cobalt moly catalyst, presulfided 136 -molybdate complex 150 promotors 150 Coke deposition 143 Competitive chemisorption 7 Condensed-ring aromatics 65 Cracked products, branching in the .. 19 Cracked products, distribution of 11,12 Cracking catalytic 5 primary •••• 13 reactions, overall 14 Crude in situ 103 Kuwait 136 oil, distillation of 140 oils, synthetic 99 residuum fraction of 136 shale oil feedstock 103 CycloparafEns 36
Free radical mechanisms 67 Fuel(s) burner 99 coal-derived Ill diesel 99, 103, 106, 107 distillate burner 108 oil 106 G Gas from hydrocracking in situ crude .... 103 oil, California 34,37 oil, mid-continent 47 phase hydrogénation, rapid 123 GPC molecular size distributions 147 H
Halides, acidic 29 HDS catalysts, oxidic 150 η-Heptane 24 n-Hexane hydrocracking, isohexanes/ 38 Hydrocarbons, polynuclear aromatic .. 82 Hydrocracked oil 103 Hydrocracked products 89 Hydrocracking 2 of n-alkanes, ideal 1,18 anthracene 83 C liquid yield 44 of California gas oil 37 D catalysts 29 of coal 83, 84 n-Decane 11 coal oil 83 Decyl cations, mono-branched 20,22 condensed-ring aromatics 65 Dehydrogenation 11,29 extinction recycle 31 Desorption 7 ideal 1 Desulfurization of resids 136 incorporating sulfur on 58 Diesel fuels 99, 103, 104, 106, 107 in situ crude, gas from 103 9,10-Dihydrophenanthrene 66 in situ shale oil 99 Distillate burner fuels 108 product yields from 28,59 Distillation ionic 19 of crude oil 140 isobutane/n-butane 41 of the hydrocracked oil, batch 103 isohexanes/n-hexane 38 product from 105 isopentane/n-pentane 38 of phenathrene 79,83 £ raffinate 52,56 Entrained down-flow tubular reactor 124 Hydrogénation Extinction recycle hydrocracking 31 activity 1, 30 acidity 30 /dehydrogenation activity 11 F /dehydrogenation component of a Faujasite catalyst 46 catalyst 29 Feed(s) 32 product ratios 74 char 127 rapid gas 123 coal 113, 127, 132 reactions 76 properties 33 tubular reaction experiment 127 sulfur level 57,60 unit 101 Feedstocks 90, 103, 136 Hydrogenolysis 7,21 First order rate constants 94 Hydroisomerization 1, 2, 7, 11 Fractionation scheme 116 Hydrodesulfurization catalysts 150 5
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INDEX
I
Ν
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Infrared spectroscopy 152 Ionic hydrocracking 19 Isoalkanes 16 Isobutane 52 /n-butane hydrocracking 41 /n-butane ratio 39 production 60 yields 62 Isohexanes/n-hexane hydrocracking .. 38 Isomer (s) distributions 61,63 from hydroisomerization of noctane and n-nonane 10 monomethyl 11 multiple branched 8 Isoparaffins 36 Isopentane/n-pentane hydrocracking 38 J Jet product Jet yield
46 40 Κ
Kinetics Kuwait crude
91 136 L
LPG yields Lewis band Lignite, North Dakota Liquefied petroleum gas Liquid product, centrifuged Liquid ( C + ) yield 5
61 158 125 52 114,116 40, 44
M
Metal catalysts 29 Metals, removal of 144 Methylnonane 11 Mica-montmorillonite catalysts, palladium nickel-containing synthetic 52 Microreactor, steady state 72 Mid-continent gas oil 47 Molecular size distributions, GPC 147 Moly catalyst, presulfided cobalt 136 Molybdate complex, cobalt150 Molybdate monolayer 158 Molybdena catalyst, nickel102 Mono-branched decyl cations 20, 22 Monofunctional catalysts 7 Monolayer, molybdate 158 Monomethyl isomers 11 Montmorillonite catalysts, palladium nickel-containing synthetic mica 52
NIS-H zeolon catalyst 88 New Mexico sub-bituminous coal 125 Nickel 143 containing synthetic mica-montmorillonite catalysts 52 molybdena catalyst 102 promoted catalysts 155 promotors in oxidic HDS catalysts .. 150 Noble metal catalysts 29 Nonacidic catalysts 65 n-Nonane 10 North Dakota lignite 125 Ο
η-Octane Octane number
4, 9,19, 24 28
Palladium nickel-containing synthetic mica-montmorillonite catalysts .. 52 Paring reaction 39 n-Pentane hydrocracking, isopentane/ 38 Pentane insolubles 136 Phenanthrene 67, 79, 83, 92 Poisoning of catalytic sites 40 Polynuclear aromatic hydrocarbons .... 82 Pore size distribution 143 structure, catalyst 136, 152 volume vs. pore diameter 145 Power generation, fuel oil for Ill Preferential poisoning of catalytic sites 40 Primary cation 18 Primary cracking 13 Product 78 analysis Ill composition 45 distributions 34, 62, 78, 79 properties 28 yields 59 Promotor ions 150 Promotors, cobalt and nickel 150 Pt/Ca-Y zeolite catalyst 2 Pyridine 114, 181, 151, 154
Raffinite analysis 54 Raffinitate hydrocracking 52, 56 Rate constant, first order 94 Rate constant, variation of 97 Reaction rates 3 Reaction zone 128 Reactor, entrained down-flow tubular 124 Recycle hydrocracking, extinction 31 Reflection spectroscopy 152, 154 Reforming stock 106
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HYDROCRACKING A N D H Y D R O T R E A T I N ^
Refractoriness of asphaltenes Resid (residuum fraction) Residence time, coal particle 128, Reversed impregnation γ-Ring opening of a saturated termi nal
139 136 130 155 73
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S
β-Scission 7, 18, 20, 22 Shale oil, in situ 99, 103 Solvent refined coal 65 Stationary-marine diesel fuel 104 Steady state microreactor 72 Steric hindrance 139 Sulfur distribution of 144 in the desulfurization of resids 136 in hydrocracking 58 level 57, 59, 60, 61 in raffinate hydrocracking 56 Sulfided catalysts 29,57 Supports for hydrocracking catalysts 29 Surface structures, different 159 Sym-octahydrophenanthrene 73 Synthetic crude oils 99 Synthoil process Ill
Τ Tank reactor, batch stirred 84 Temperature on product distribtuion, effect of 78 Terminal ring, saturated 73 Tetrahydrophenanthrene 73 Tetralin 73 Toluene 91, 126 insolubles 114, 121 Truck-tractor diesel fuel 104 Tubular reactor, entrained down-flow 124 Tubular reaction experiment, coal hydrogénation 127 U n-Undecane
9 V
Vanadium
143 X
Xylene
126
Y Yields in hydrocracking
28
Ζ Zeolites
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