Hydrocracking and Hydrotreating 9780841203037, 9780841202535, 0-8412-0303-2

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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

0.2 Ο

Ω

0(

^0-ΟΌΟΌ-Ό-Ό ^°0- - ^ 0

' I

0.1

' I

I

1.6 2 1.4 < 1.2 Œ

_J

Ο

ι 0 PPM S

Ο

ϋ" 0.8

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 ,< ,ι

•

00

m

00

in

m

en

•Η

C7*

CM •H

t

Ο CM

α. c Ό ο Φ en

Η

53 ~ Φ β Φ

U μ eu •Ρ υ Ό

ο

VO CM

vD

•Ρ CT» β -H rd A β CU Ό Λ β Pi rd

rd β eu ,β

eu β 0 ω

Φ β Φ n ^ -Ρ β rd β Φ ,β

(u 0

Ό

>t

,C •H Q

'p , β >i4J rd rd U C 4J φ Φ A EH Λ

Ο H Ό >Λ Λ rd •Ρ U Ο

•

•Ρ β -s rd ^ β fH (DU

4J β — rd ro β rH Φυ

eu Ο Φ

e

M 0 Ό

m H

fH

•

•

r> Tetralin,

Η

•

hrene

ι ft en ε

•

hrene

CM CM

• 1

•

u

Ο Φ u g Ό Ο >i W Κ H

Φ β Φ rH rd si ,β Φ •Ρ β , β rd ftTJ rd β 53 Η

CM

CM ι

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

rH •Η

π σ\ VO CO CN

Ο

rH

rd

Ο

Ο

Ο

ι—ι

Ο

Ο

Ο

. . .

ο

ο

ο

Publication Date: June 1, 1975 | doi: 10.1021/bk-1975-0020.ch005

υ

ω ω U ,α -Ρ C rd G

s

rH I

-ρ

>ι ιη

ιΗ

VD

ο

Ο

Ο

Ο

ΓΜ

Η Η Ο Ο Ο . . .

C

Ο

CO

CL)

—

Ρί -Ρ

W

Λ

H

CU

Ο

-HO

p$

Sffi

H

— —

ïs W

C0 EH 2

-H 03 α

Ζ

Ο

W

§

U

EH

ο

H H H ÎN

-HO -P U •


>

W

Η ΕΗ

EH

CO

S

M

0

«ζ; Ο

ο

β

cx>^ 03

ω ω

«

|D H

S

pq

w « «


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

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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

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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.

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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

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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.

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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

3

2

3

3

150 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

151

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 ) .

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2

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

2

composition was

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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HYDROCRACKING AND HYDROTREATING

( 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

2

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

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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

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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

1

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

1

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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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.

In Hydrocracking and Hydrotreating; Ward, J., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1975.

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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 .

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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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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

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