Fluid Catalytic Cracking - ACS Publications - American Chemical Society

Chapter 19

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 11, 2015 | http://pubs.acs.org Publication Date: September 12, 1988 | doi: 10.1021/bk-1988-0375.ch019

Development of a Reduced Crude Cracking Catalyst William P. Hettinger, Jr. Ashland Petroleum Company, P.O. Box 391, Ashland, KY 41114 F a c e d w i t h t h e need o f o b t a i n i n g more t r a n s p o r t a t i o n fuels from a b a r r e l o f c r u d e , A s h l a n d d e v e l o p e d t h e Reduced Crude C o n v e r s i o n P r o c e s s ( R C C ® ) . To s u p p o r t this development, a r e s i d u u m o r r e d u c e d c r u d e c r a c k i n g catalyst was developed and o v e r 1,000 tons were p r o d u c e d and employed i n c o m m e r c i a l o p e r a t i o n . The catalyst p o s s e s s e d a l a r g e p o r e volume, d u a l pore structure, an Ultrastable Y zeolite w i t h an a c i d i c m a t r i x e q u a l i n acidity t o t h e acidity of the zeolite, and was partially t r e a t e d w i t h rare e a r t h t o enhance cracking activity and to resist vanadium p o i s o n i n g . While subsequently replaced by further improved catalysts, the c a t a l y s t achieved h i g h selectivity, was metal resistant a t 7,800 ppm nickel p l u s vanadium, and a c h i e v e d d e s i g n p r o j e c t i o n s d u r i n g s t a r t - u p and two months o f c o m m e r c i a l o p e r a t i o n . Development o f the catalyst s e r v e d t o s t i m u l a t e r e s e a r c h e f f o r t s by t h e catalyst i n d u s t r y t o i n t r o d u c e o t h e r advanced r e s i d u u m processing catalysts. In 1974 OPEC imposed an embargo on o i l t o t h e U n i t e d S t a t e s , causing a r a p i d r i s e i n the p r i c e of a b a r r e l of o i l . Ashland P e t r o l e u m , a t r a n s p o r t e r , r e f i n e r and m a r k e t e r o f o i l , p u r c h a s e s most o f i t s c r u d e o i l . A t t h e t i m e o f t h e embargo, A s h l a n d i m p o r t e d much o f i t s o i l from t h e M i d d l e E a s t , thus r a i s i n g t h e question of a v a i l a b i l i t y . As t h e p r o b l e m became s e v e r e , M e s s r s . M y e r s , Busch and Zandona ( 1 - 4 ) o f our company began t o c o n s i d e r a l t e r n a t i v e s o u r c e s o f c r u d e and ways o f s q u e e z i n g more p r o d u c t from a g i v e n barrel. A f t e r c o n s i d e r i n g many p o s s i b i l i t i e s , i n c l u d i n g a number o f p r o c e s s e s t h e n c o m m e r c i a l l y a v a i l a b l e , t h e y c o n c e i v e d a new way t o c o n v e r t t h e 1050 F+ f r a c t i o n o f t h e b a r r e l d i r e c t l y t o gasoline. I f s u c c e s s f u l , t h i s i n e x p e n s i v e new p r o c e s s w o u l d , i n e f f e c t , g i v e them an a d d i t i o n a l volume o f o i l f o r c o n v e r s i o n t o gasoline. They a l s o c o n c l u d e d t h a t i f vacuum f r a c t i o n a t i o n were e l i m i n a t e d , t h e e n t i r e 650 F+ ( r e d u c e d c r u d e ) p o r t i o n o f t h e

0097-6156/88/0375-0308$09.25/0 ° 1988 American Chemical Society

In Fluid Catalytic Cracking; Occelli, M.; ACS Symposium Series; American Chemical Society: Washington, DC, 1988.


19. H E T T I N G E R

Reduced Crude Cracking Catalyst

309

b a r r e l c o u l d be p r o c e s s e d i n one s t e p , t h u s a l s o g r e a t l y r e d u c i n g o p e r a t i n g c o s t s and i n v e s t m e n t s f o r i n t e r m e d i a t e p r o c e s s i n g equipment. A t t h e same t i m e , t h e 650 t o 1050 F f r a c t i o n would p r o v i d e a c a r r i e r o r d i l u e n t f o r t h e 1050 F+ residuum. They began r e d u c e d c r u d e c r a c k i n g e x p e r i m e n t a t i o n i n a s m a l l 12,000 b a r r e l p e r day (B/D) F l u i d C a t a l y t i c C r a c k i n g (FCC) o p e r a t i n g u n i t a t L o u i s v i l l e , Ky. The RCC p r o c e s s was b o r n from t h e s e g o a l s , c o n c e p t s and a s m a l l o p e r a t i n g u n i t . The development and a t t r i b u t e s o f t h i s p r o c e s s have been d e s c r i b e d i n a number o f a r t i c l e s and p a t e n t s ( 1 - 6 ) . F i g u r e 1 shows t h e d i s t r i b u t i o n o f 650 F+ volume p e r c e n t c o n t e n t i n r e d u c e d c r u d e f o r some 50 c r u d e s t h e n a v a i l a b l e t o Ashland. F i g u r e 2 i n d i c a t e s t h e volume p e r c e n t a g e o f 1050 F+ p r e s e n t i n t h e same c r u d e s , r a n g i n g from l e s s t h a n 10% t o more t h a n 30%. C a t a l y s t Development As work began on t h e p r o c e s s , i t q u i c k l y became a p p a r e n t t h a t t h e e x t r a o r d i n a r y c a t a l y s t p r o p e r t i e s r e q u i r e d f o r t h e p r o c e s s were n o t then a v a i l a b l e , and even w i t h a s u p e r i o r c a t a l y s t , consumption would u n d o u b t e d l y be s e v e r e . F i g u r e 3 shows how Ramsbottom Carbon and n i c k e l p l u s vanadium v a r y i n t h e same reduced crude o i l s . A l l l e v e l s a r e v e r y h i g h ; f a r beyond a n y t h i n g n o r m a l l y e n c o u n t e r e d i n a gas o i l f e e d s t o c k . A l t h o u g h t h e y a r e n o t shown h e r e i n d e t a i l , n i t r o g e n , s u l f u r , a s p h a l t e n e s , p o l y n u c l e a r a r o m a t i c s , and h e t e r o c y c l i c s a r e a l l a l s o p r e s e n t i n s i g n i f i c a n t amounts i n r e d u c e d c r u d e s . F i g u r e 4, however, does d e p i c t t h e g e n e r a l r e l a t i o n s h i p between API g r a v i t y , s u l f u r , a s p h a l t e n e and t o t a l m e t a l c o n t e n t o f c r u d e s i n g e n e r a l . C e r t a i n l y none o f t h e s e i n g r e d i e n t s , e s p e c i a l l y i n such l a r g e amounts, c o u l d be c o n s i d e r e d " f r i e n d l y " f o r c a t a l y s t s used i n normal c a t a l y t i c c r a c k i n g . Hardware m o d i f i c a t i o n a l o n e , w i t h o u t s i m u l t a n e o u s c o n s i d e r a t i o n o f how t o meet c a t a l y s t p r o p e r t y r e q u i r e m e n t s , would n o t be enough t o a c h i e v e s u c c e s s . Therefore, a catalyst development program was proposed and approved t o h e l p f o r m u l a t e new c a t a l y s t s t h a t c o u l d d e a l w i t h t h e s e s e v e r e c o n t a m i n a n t s . I t s g o a l was t h e s i m u l t a n e o u s development o f a new p r o c e s s and t a i l o r e d c a t a l y s t s , as b o t h were o b v i o u s l y c r i t i c a l t o t h e u l t i m a t e economic s u c c e s s o f t h e p r o j e c t . Of c o u r s e , t h e r e were c a t a l y s t s on t h e market i n 1977-78 t h a t were b e i n g t a r g e t e d f o r p r o c e s s i n g h e a v i e r s t o c k s , w i t h higher l e v e l s o f metals. C a t a l y s t m a n u f a c t u r e r s such as D a v i s o n and F i l t r o l h a d a l r e a d y been w o r k i n g a l o n g t h e s e l i n e s . However, t h e s e s t r i n g e n t new r e q u i r e m e n t s c r e a t e d a need t o a c c e l e r a t e t h e development o f s p e c i f i c a l l y t a r g e t e d c a t a l y s t s . A s h l a n d d e c i d e d t o i n i t i a t e i t s own c a t a l y s t p r e p a r a t i o n program, c o u p l e d w i t h i n s t a l l a t i o n and development o f advanced t e s t i n g equipment, t o speed t h e e v o l u t i o n o f advanced c a t a l y s t s .


FLUID CATALYTIC CRACKING: R O L E IN M O D E R N REFINING


310

F i g u r e 1. 650 F+ A t m o s p h e r i c Reduced f o r 50 Crudes

20 1025°

F i g u r e 2.

30 F

+ VOL.

Crude O i l V o l . % o f Crudes

40 /. OF

50 CRUDE

1025°F+ Bottoms V o l . % o f Crude f o r 50 Crudes



F i g u r e 3. R e l a t i o n s h i p Between N i c k e l P l u s Vanadium and Ramsbottom Carbon f o r Reduced Crude

F i g u r e 4. R e l a t i o n s h i p Between Crude O i l API, S u l f u r , M e t a l s and A s p h a l t e n e s



312


Equipment Equipment and f a c i l i t i e s f o r b a t c h c a t a l y s t p r e p a r a t i o n and s p r a y d r y i n g and ovens f o r d r y i n g and c a l c i n i n g were r a p i d l y a c q u i r e d and i n s t a l l e d . A v a r i e t y o f c a t a l y s t t e s t i n g r e a c t o r s were a l s o d e s i g n e d , c o n s t r u c t e d , and p l a c e d i n o p e r a t i o n . T e s t i n g began w i t h improved m i c r o a c t i v i t y c a t a l y t i c c r a c k i n g t e s t i n g r e a c t o r s , m o d i f i e d t o o p e r a t e on reduced c r u d e , t o m o n i t o r and e v a l u a t e d e v e l o p m e n t a l , v i r g i n , commercial, and o p e r a t i n g c a t a l y s t s . They f u n c t i o n e d r e m a r k a b l y w e l l . Of c o u r s e , f r e s h c a t a l y s t s were a l s o exposed t o v a r i o u s s e v e r e p r e t e s t i n g c o n d i t i o n s t o p r e p a r e them p r o p e r l y f o r e v a l u a t i o n . H i g h - p u r i t y h y d r o c a r b o n s and r e a c t o r s were a l s o u s e d t o f o c u s i n d e t a i l on c r i t i c a l mechanisms. Advanced t e s t i n g f o r e x t e n s i v e e v a l u a t i o n o f s e l e c t e d c a t a l y s t s and f e e d s t o c k s was c a r r i e d out i n a f i x e d f l u i d bed o f about one l i t e r c r a c k i n g c a t a l y s t c a p a c i t y . T h i s p r o v i d e d us w i t h r e p r e s e n t a t i v e y i e l d s and l a r g e volumes f o r p r o d u c t q u a l i t y t e s t i n g i n c l u d i n g o c t a n e numbers. I n c o n s t r u c t i o n and o p e r a t i o n , t h i s t e s t equipment was s i m i l a r t o t h a t u s e d much e a r l i e r t o d e v e l o p t h e s e m i s y n t h e t i c c a t a l y s t s o f t h e 1950s.(7) C o n s i d e r a b l e m o d i f i c a t i o n was r e q u i r e d , however, t o e n a b l e us t o p r o c e s s r e d u c e d c r u d e r a t h e r t h a n gas o i l . The b e t t e r c a t a l y s t s were f u r t h e r e v a l u a t e d i n two c i r c u l a t i n g bed o p e r a t i o n s . The f i r s t u n i t , complete w i t h r e g e n e r a t o r , was d e v e l o p e d by A s h l a n d p i l o t p l a n t p e r s o n n e l . It was c a p a b l e o f e v a l u a t i n g s p e c i f i c f e e d s t o c k s , or p r o c e s s i n g p a r a m e t e r s , and t e s t i n g f l u i d c a t a l y s t s o v e r l o n g p e r i o d s o f o p e r a t i o n (days and weeks). The u n i t p e r m i t t e d c o n t i n u o u s c a t a l y s t r e p l a c e m e n t and e x t e n s i v e v a r i a t i o n i n o p e r a t i n g c o n d i t i o n s and c a t a l y s t t r e a t m e n t s , w h i l e y i e l d i n g l a r g e volumes o f l i g h t and heavy p r o d u c t s . An even l a r g e r o n e - q u a r t e r b a r r e l p e r day c i r c u l a t i n g u n i t came v e r y c l o s e t o s i m u l a t i n g b o t h t h e 200 B/D d e m o n s t r a t i o n u n i t and l a t e r commercial o p e r a t i o n s . I t a l s o p o s s e s s e d a two-stage r e g e n e r a t o r and v e n t e d r i s e r ( b o t h h a l l m a r k s o f t h e RCC p r o c e s s ) . T h i s a l l o w e d s i m u l a t i o n and e v a l u a t i o n o f a d d i t i o n a l RCC o p e r a t i n g parameters. F i n a l l y a 200 B/D 80 t a l l d e m o n s t r a t i o n u n i t was u s e d f o r s t u d y i n g o p e r a t i n g p a r a m e t e r s , equipment, p r o c e s s v a r i a t i o n s , and f i n a l l y c a t a l y s t s , c a t a l y s t t r e a t m e n t s , and v a r y i n g f e e d s t o c k s . Much o f t h e 200 B/D work has been d e s c r i b e d i n p u b l i s h e d reports.(8-10) In b r i e f , s a t i s f a c t o r y runs w i t h e x c e l l e n t y i e l d s and good c o n v e r s i o n were made on c a t a l y s t s c o n t a i n i n g as much as 12,300 ppm o f n i c k e l p l u s vanadium.(4) 1

C a t a l y s t R e s e a r c h and

P h y s i c a l Chemical E v a l u a t i o n

A number o f a n a l y t i c a l i n s t r u m e n t s h e l p e d us t o probe and u n d e r s t a n d our c a t a l y s t s i n g r e a t e r d e t a i l . A l t h o u g h t h e s e may be s t a n d a r d equipment f o r a l a r g e m a n u f a c t u r e r o r l a r g e p e t r o l e u m r e s e a r c h l a b o r a t o r y , we had t o a c q u i r e them and t r a i n our p e r s o n n e l i n t h e i r use b e f o r e we c o u l d p r o c e e d . Some o f t h e more v i t a l i n s t r u m e n t s i n c l u d e d equipment f o r m e a s u r i n g s u r f a c e a r e a , p o r e volume and p o r e d i a m e t e r d i s t r i b u t i o n , and X - r a y




313

d i f f r a c t i o n , s c a n n i n g e l e c t r o n m i c r o s c o p y , and energy d i s p e r s i v e X - r a y f l u o r e s c e n c e were a l s o u t i l i z e d . H i g h s e v e r i t y f l u i d bed steamers and c a l c i n e r s , and d i f f e r e n t i a l t h e r m a l and t h e r m a l g r a v i t a t i o n a l a n a l y z e r s , and m i c r o - c a l o r i m e t r y a l s o were o f g r e a t value.


C a t a l y s t Development and Scale-Up With t h e c h a l l e n g e w e l l d e f i n e d , c a t a l y s t p r e p a r a t i o n , development, and e v a l u a t i o n began. R e s e a r c h and development took a two-pronged approach. We began w i t h e x a m i n a t i o n and e v a l u a t i o n o f a l l c a t a l y s t s a v a i l a b l e on t h e market. D e t a i l e d a n a l y s i s o f c a t a l y s t s showing p r o m i s i n g performance i n o u r t e s t u n i t s gave us i n s i g h t as t o w h i c h p r o p e r t i e s and i n g r e d i e n t s s h o u l d r e c e i v e g r e a t e r a t t e n t i o n and w h i c h were c o n t r i b u t o r y o r n o n c o n t r i b u t o r y . S e c o n d l y , we began r e s e a r c h and development based on o u r own knowledge and e x p e r i e n c e w i t h commercial c a t a l y s t m a n u f a c t u r e and compositions. We a l s o drew on many y e a r s o f p e r s o n a l e x p e r i e n c e d i r e c t i n g c a t a l y s t r e s e a r c h and development, as w e l l as o u r own s p e c u l a t i o n s a s t o what p r o p e r t i e s might be most i m p o r t a n t . As o u r work g a i n e d momentum, we r e a l i z e d t h a t a c o o p e r a t i v e e f f o r t w i t h a c a t a l y s t m a n u f a c t u r e r would be h i g h l y d e s i r a b l e . T h e r e f o r e , we a r r a n g e d f o r a development program w h i c h l a s t e d f o u r y e a r s . T h i s work l e a d t o s e v e r a l c a t a l y s t s w h i c h showed p r o m i s e and w h i c h were p r e p a r e d c o m m e r c i a l l y i n tonnage q u a n t i t i e s and e v a l u a t e d i n t h e 200 B/D RCC u n i t . F i n a l l y , i n l a t e 1982, j u s t p r i o r t o RCC commercial s t a r t - u p , a more advanced c a t a l y s t was d e v e l o p e d and p r e p a r e d i n s e v e r a l c o m m e r c i a l - s i z e 20-ton b a t c h e s . I t a l s o was t e s t e d i n t h e 200 B/D p i l o t p l a n t u n i t , and shown t o be an e x c e l l e n t catalyst. Over 1,000 t o n s o f t h i s c a t a l y s t , d e s i g n a t e d DZ-40, was produced c o m m e r c i a l l y and used f o r s t a r t - u p and two months s u c c e s s f u l reduced crude o p e r a t i o n . ( 1 1 ) As c a t a l y s t improvements e v o l v e d a l o n g w i t h t h e p r o c e s s , t h e y i e l d s i n t h e 200 B/D u n i t from a t y p i c a l A r a b i a n L i g h t r e d u c e d c r u d e o i l a t t h e "knee" c o n v e r s i o n l e v e l ( t h e p o i n t o f maximum g a s o l i n e y i e l d ) g r a d u a l l y r o s e from 47-48 volume p e r c e n t g a s o l i n e t o 52% and s u b s e q u e n t l y t o as h i g h as 56-57 volume p e r c e n t gasoline, with a corresponding reduction i n h i g h - b o i l i n g s l u r r y o i l product. These y i e l d s have now been w e l l c o n f i r m e d and exceeded i n t h e commercial u n i t ( T a b l e s I & I I ) . A second c a t a l y s t s u b s e q u e n t l y i n t r o d u c e d by a second m a n u f a c t u r e r was a l s o c o n s i d e r e d a c c e p t a b l e and u t i l i z e d successfully. However, t h e s t i m u l u s o f o u r work u n d o u b t e d l y had a f a v o r a b l e impact on commercial p r o d u c e r s , r e s u l t i n g i n a c c e l e r a t e d development and commercial i n t r o d u c t i o n o f new and s u p e r i o r - p e r f o r m i n g RCC c a t a l y s t s , and a t r e d u c e d c o s t . Commercial O p e r a t i o n The RCC p r o c e s s commercial u n i t has been on-stream f o r o v e r f o u r years. E x c e p t f o r a few minor problems d u r i n g s t a r t - u p , i t h a s


FLUID CATALYTIC C R A C K I N G : R O L E IN M O D E R N REFINING

314


Table

I.

D e s i g n and A c t u a l O p e r a t i n g Commercial RCC U n i t

Feedstock Inspection "API N i + V, ppm Ramsbottom Carbon, Wt.% UOP K-Factor Product Y i e l d s Dry Gas, Wt.% Propane/Propylene, V o l % Butanes/Butylenes,Vol% C -430°F G a s o l i n e , V o l % D i s t i l l a t e , 430°-630°F, Vol% Heavy O i l , 630°F, +, V o l % Coke, Wt.%

Intermediate °API And Ramscarbon Feed 21. 3 44. 0 4. 5 11. 8

Low API, High Ramscarbon Feed 19. 2 65. 0 6. 9 11. 8

4. 1 2.5/9. 3 5 .9/10. 9 51. 5 11. 3

3. 3 1.8/8. 7 4.6/10. 1 57. 8 15. 0

4. 1 1.8/8. 3 3.9/9. 9 55. 6 15. 0

10. 4 11. 5

8. 4 8. 4

10. ,9 10. 8

3 6

76. 6 91. 6

74. ,1 89. ,1

7 0

93. ,6 106. ,4

89. ,1 105. ,4

1 0

79.,5 93. ,2

79.,2 93. ,6

Design 18. 6 35. 0 6. 0 11. 8

O p e r a t i n g Parameters Conv. t o 430"F & Coke, V o l % 78. Conv. t o 630°F & C o k e V o l % 89. C~ + E q u i v a l e n t Gaso. + Distillate, Vol% 86. Total Liquid Yield, Vol% 102. Gasoline & D i s t i l l a t e Selectivity, % 70. G a s o l i n e Octane, Rone 93. M e t a l s on C a t a l y s t , N i + V ppm 6,000 ô

Results

7,200


8,000



Table IIA.

°API

40.0

18.6


Thruput MBPD

315

C a t l e t t s b u r g RCC U n i t A c h i e v e s D e s i g n O b j e c t i v e s on U n t r e a t e d F e e d s t o c k s

Feedstock P r o p e r t i e s ItRams Metals Factor Ni + V Carbon PPM Wt.%

11.8

Design 6.0

LPG, E q u i v . Gaso.* + D i s . Yd. Vol.%

35.0

Gaso.** Select.

%

86.1

65.0

Commercial E x p e r i e n c e 47.5

22.1

11.9

4.6

21.0

86.3

69.0

39.8

20.9

11.8

5.8

47.0

88.9

72.0

30.5

21.5

11.9

5.4

55.0

93.2

74.0

28.8

18.5

11.8

7.1

68.0

89.6

77.0

Table IIB.

Octane RONC

C a t l e t t s b u r g RCC U n i t A c h i e v e s D e s i g n O b j e c t i v e s on U n t r e a t e d F e e d s t o c k s

Equilibrium Catalyst Ni + V PPM

Coke Yield Wt.%

Carbon F u n c t i o n s Regenerator Coke P r o c e s s e d MLb./Hr.

Design 93.0

6000

11.4

63

Commercial E x p e r i e n c e 93.4

7200

10.0

67

92.9

7800

10.9

65

92.6

7100

8.4

36

93.6

7700

10^S

44

*

E q u i v a l e n t G a s o l i n e = C.-430 Naphtha + (0.8)(C„/C O l e f i n s ) + C »s ^ * ** G a s o l i n e S e l e c t i v i t y = { ( V o l . % C "430 Naphtha) t ( V o l . % Gas O i l + D i s a p p e a r a n c e ) } χ 100 J

5


FLUID CATALYTIC C R A C K I N G : R O L E IN M O D E R N REFINING

316

r u n a l m o s t c o n t i n u o u s l y and has met o r exceeded a l l t h e d e s i g n p r o j e c t i o n s o b t a i n e d from t h e 200 B/D u n i t ( F i g u r e 5 ) . In a d d i t i o n , p r o c e s s m o d i f i c a t i o n s made d u r i n g c o n s t r u c t i o n and i n o p e r a t i o n have f u r t h e r enhanced t h e p e r f o r m a n c e o f t h e u n i t , e x c e e d i n g e a r l y p r e d i c t i o n s . F i g u r e 6 shows t h e f l o w diagram f o r the process. T a b l e s I and I I show r e s u l t s o b t a i n e d w h i l e o p e r a t i n g on a range o f c a r b o m e t a l l i c f e e d s t o c k s . Note t h e i m p r e s s i v e y i e l d o f g a s o l i n e and o t h e r l i q u i d p r o d u c t s .


Catalyst

Design

K e e p i n g t h e p r o p e r t i e s o f t h e r e d u c e d c r u d e s c l e a r l y i n mind, we drew upon b a s i c c a t a l y s t c o n c e p t s and p r e v i o u s e x p e r i e n c e . The s t a t e o f t h e a r t i n 1978 s u g g e s t e d k e y i n g i n on a number o f c a t a l y s t p r o p e r t i e s . We f o c u s e d on them i n d i v i d u a l l y and c o l l e c t i v e l y i n o r d e r t o o p t i m i z e each p r o p e r t y i n terms o f t h e o v e r a l l o b j e c t i v e . T h i s meant h a r n e s s i n g and o p t i m i z i n g such p r o p e r t i e s as p o r e volume, p o r e d i a m e t e r d i s t r i b u t i o n , z e o l i t e p r o p e r t i e s and a c i d i t y , r a r e e a r t h s t a b i l i z a t i o n , m e t a l r e s i s t a n c e , matrix a c i d i t y , a t t r i t i o n r e s i s t a n c e , burning r a t e , and c o s t . Our g o a l was t o cope w i t h c a r b o n , m e t a l s , asphaltenes, p o l y n u c l e a r a r o m a t i c s and h e t e r o c y c l i c s , η-paraffins, s u l f u r , and n i t r o g e n - c o n t a i n i n g molecules. The f o l l o w i n g i s a d e t a i l e d a c c o u n t o f how some o f t h e more i m p o r t a n t problems were addressed. Pore Volume and

Pore Diameter D i s t r i b u t i o n

I n t h e r e c e n t p a s t , commercial c r a c k i n g c a t a l y s t s have tended t o be h i g h i n d e n s i t y (low i n p o r e volume) i n o r d e r t o r e d u c e a t t r i t i o n and a v o i d a i r p o l l u t i o n problems, w h i c h t e n d t o r e l a t e t o catalyst density. C a t a l y s t s f o r FCC a p p l i c a t i o n a r e n o t c o n s i d e r e d t o be d i f f u s i o n l i m i t e d ; and, t h e r e f o r e , h i g h e r density c a t a l y s t s are quite acceptable. F o r RCC a p p l i c a t i o n , we soon c o n c l u d e d t h a t a h i g h e r p o r e volume c a t a l y s t w h i c h c o u l d a c t as a sponge i n p i c k i n g up n o n v o l a t i l e o r o n l y p a r t i a l l y v o l a t i l e r e s i d u u m l i q u i d , c o u l d be desirable f o r r e s i d processing. Development o f a d u a l p o r e s t r u c t u r e w i t h f e e d e r p o r e s t o t h e z e o l i t e c r y s t a l s would enhance a c c e s s i b i l i t y o f t h e much h i g h e r m o l e c u l a r w e i g h t r e a c t a n t s , found i n t h e 1050 F+ bottom p o r t i o n o f t h e r e d u c e d c r u d e b a r r e l , t o t h e z e o l i t e " p o r t a l s u r f a c e a r e a " * and i n t e r n a l a c i d i t y . In a d d i t i o n , s u c h means might a v o i d p o r e passageway b l o c k a g e by h i g h l y a d s o r b i n g s u p e r - l a r g e a s p h a l t e n e c o l l o i d a l p a r t i c l e s and h i g h m o l e c u l a r w e i g h t a r o m a t i c and b a s i c n i t r o g e n - c o n t a m i n a t i n g molecules. F i g u r e 7 p o r t r a y s t h i s o b j e c t i v e i n an e x a g g e r a t e d f a s h i o n and F i g u r e 8 shows how t h i s r e l a t e s t o t h e o v e r a l l c o m p o s i t i o n o f our p r e f e r r e d r e s i d u a l c r a c k i n g c a t a l y s t . When c r a c k i n g c a t a l y s t s a r e p r e p a r e d w i t h a s i l i c a o r s i l i c a - a l u m i n a g e l base, t h e p o r e volume and a v e r a g e p o r e * The t e r m " p o r t a l s u r f a c e a r e a " has been p r o p o s e d by t h e a u t h o r t o convey t h e c o n c e p t o f t h e o u t e r s u r f a c e o f a z e o l i t e c r y s t a l p r o v i d i n g entrance to the strong a c i d s i t e s w i t h i n the c r y s t a l .




HETTINGER

F i g u r e 5.

A s h l a n d RCC P r o c e s s D e m o n s t r a t i o n

Unit



318


u n u u t U1L CHARGE

F i g u r e 6.

•

n c u c i N .

CTLST.

P r o c e s s Flow Diagram RCC

Unit



19.

HETTINGER


Figure

7.

Catalyst

Structure

-MACRO PORE TO S I E V E LARGE CRUDE

S I L I C A ALUMINA G E L A C I D I C S U R F A C E FOR CRACKING LARGE MOLECULES

REDUCED MOLECULE

F R A G M E N T S OF LARGE REDUCED CRUDE M O L E C U L E GOING TO S I E V E

100-10001 PORE SURROUNDING S I E V E K A O L I N C L A Y TO B U I L D MACRO PORE| STRUCTURE

LARGE ASPHALTENE MOLECULE

-ALUMINA, ΤΙΤΑΝΙΑ, ZIRCONIA, L A N T H A N A GEL METAL RESISTENCE

Figure

8.

Reduced

Crude C a t a l y s t


319


320


d i a m e t e r can be r e a d i l y v a r i e d by c o n t r o l o f g e l concentration, t i m e , t e m p e r a t u r e , and pH. To o b t a i n a d u a l p o r e s t r u c t u r e , however, r e q u i r e s a d i f f e r e n t a p p r o a c h . Some h i s t o r i c a l background i s i n o r d e r , and a r e v i e w o f some e a r l y c a t a l y s t work may p r o v e h e l p f u l . I n t h e e a r l y 1950s, w h i l e i n v o l v e d i n p l a t i n u m on a l u m i n a c a t a l y s t r e s e a r c h s t u d i e s at the l a b o r a t o r i e s of S i n c l a i r O i l (now a p a r t o f ARCO), I d i s c o v e r e d t h a t c r y s t a l l i n e a l u m i n a t r i h y d r a t e was p r e s e n t i n t h e amorphous p s e u d o - B o e h m i t e l i k e a l u m i n a g e l u s e d t o p r e p a r e some new e x p e r i m e n t a l r e f o r m i n g catalysts. F u r t h e r s t u d y showed t h e p r e s e n c e o f s e v e r a l c r y s t a l l i n e a l u m i n a t r i h y d r a t e s , i n c l u d i n g a p r e v i o u s l y unknown t r i h y d r a t e t h a t was dubbed "Randomite".(12) I t was l a t e r o f f i c i a l l y named N o r s t r a n d i t e i n honor o f R o b e r t Van N o r s t r a n d , who was t h e n i n c h a r g e o f p h y s i c a l c h e m i c a l s t u d i e s a t S i n c l a i r and who s p e a r h e a d e d e l u c i d a t i o n o f i t s s t r u c t u r e . Next came development work and some b r i l l i a n t o b s e r v a t i o n s and d e d u c t i o n s by M a r v i n F. L. Johnson, t h e n i n c h a r g e o f s u r f a c e a r e a and p o r e volume s t u d i e s o f t h o s e l a b o r a t o r i e s . He showed t h a t a t an optimum c o n c e n t r a t i o n o f about 75% t r i h y d r a t e i n an e x t r u d a t e , a d u a l and even r a t h e r l a r g e t r i p l e - p o r e d i s t r i b u t i o n s t r u c t u r e formed as t r i h y d r a t e c o n c e n t r a t i o n r e a c h e d a c r i t i c a l l e v e l . T h i s p o r e s i z e d i s t r i b u t i o n was shown t o p r o v i d e an optimum p o r e structure f o r platinum reforming c a t a l y s t a c t i v i t y , s e l e c t i v i t y and c a t a l y s t l i f e . T h i s c a t a l y s t e v e n t u a l l y was c o m m e r c i a l i z e d and became t h e famous RD-150; s t i l l i n use i n o n l y s l i g h t l y m o d i f i e d form. In 1957 I t r a n s f e r r e d t o N a l c o C a t a l y s t D i v i s i o n and became D i r e c t o r o f R e s e a r c h . A t t h a t t i m e N a l c o was f a c e d w i t h s e v e r e competition to t h e i r synthetic s i l i c a - a l u m i n a g e l cracking c a t a l y s t by a r e l a t i v e l y new and low c o s t n a t u r a l c l a y - b a s e d cracking c a t a l y s t containing H a l l o y s i t e clay, introduced and m a n u f a c t u r e d by F i l t r o l C o r p o r a t i o n . I n a t t e m p t i n g t o meet t h i s c o m p e t i t i o n , we c o n s i d e r e d a number o f a l t e r n a t i v e s . Among t h e s e was t h e i d e a o f i n c o r p o r a t i n g some l o w - c o s t , h i g h - p u r i t y K a o l i n (a p l a t e l e t - t y p e c l a y ) as a l o w - c o s t d i l u e n t . If successful, t h i s would r e d u c e t h e amount o f c o s t l y s i l i c a - a l u m i n a g e l required. By r e d u c i n g t h e c o s t , we might a g a i n make our c a t a l y s t competitive. As our e x p e r i m e n t a l work p r o c e e d e d , I r e a l i z e d t h a t we were d e a l i n g w i t h a s i l i c a - a l u m i n a system ( s i l i c a - a l u m i n a g e l and p l a t e l e t c r y s t a l l i n e s i l i c a - a l u m i n a K a o l i n ) t h a t s h o u l d be s i m i l a r t o t h e a l u m i n a g e l / a l u m i n a t r i h y d r a t e c r y s t a l system o f RD-150. I t seemed p o s s i b l e t o a c h i e v e a s i m i l a r p o r e d i a m e t e r s p e c t r u m s t r u c t u r e h e r e by j u d i c i o u s c o m b i n a t i o n o f c r y s t a l s and gel. By a c h i e v i n g random d i s p e r s i o n o f t h e K a o l i n i n t h e sodium s i l i c a t e s o l u t i o n p r i o r to formation of the s i l i c a - a l u m i n a g e l , i t was p o s s i b l e t o d i s p e r s e t h e c l a y c r y s t a l s . They condensed somewhat p e r p e n d i c u l a r t o each o t h e r and were bound t o g e t h e r by silica-alumina gel. I therefore speculated that spray drying, d u r i n g w h i c h t h e g e l system c o n t r a c t s , might c r e a t e a d u a l structure. An a n a l o g y would be a house b u i l t o f c a r d s ( K a o l i n ) , cemented t o g e t h e r w i t h s i l i c a - a l u m i n a g e l .




321


We v a r i e d t h e g e l - f o r m i n g p a r a m e t e r s , t h e c o n t e n t o f K a o l i n c l a y , t h e c r y s t a l s i z e , and t h e t h i c k n e s s - t o - d i a m e t e r ratio i n a s e r i e s o f experiments. A d u a l s t r u c t u r e began t o appear a t about 35-40% K a o l i n . I f t h e c l a y c o n t e n t was i n c r e a s e d t o t o o h i g h a l e v e l , t h e m i c r o s p h e r e s became t o o weak and began t o have poor a t t r i t i o n resistance. The c o s t o f t h e v a r i o u s g r a d e s a l s o a f f e c t e d our choice. F i g u r e 9 shows a comparison o f p o r e volume d i s t r i b u t i o n f o r a t y p i c a l synthetic versus a clay modified catalyst. K a o l i n had l i t t l e o r no c r a c k i n g a c t i v i t y , and c a t a l y s t a c t i v i t y as t e s t e d i n t h e l a b o r a t o r y was d i r e c t l y r e l a t e d t o s i l i c a - a l u m i n a g e l content. However, t h e c a t a l y s t p e r f o r m e d much b e t t e r i n commercial t e s t s t h a n a n t i c i p a t e d from l a b o r a t o r y testing. U n d o u b t e d l y , t h i s open s t r u c t u r e e n c o u n t e r e d much l e s s severe c o n d i t i o n s a t t h e outer s u r f a c e o f the microsphere d u r i n g r e g e n e r a t i o n s and made i n t e r n a l c a t a l y t i c s u r f a c e s more r e a d i l y available. T h i s f i r s t o f t h e s o - c a l l e d " s e m i s y n t h e t i c s " was c a l l e d N a l c o 783, and t h e m a t r i x i s s t i l l used i n many forms some 28 y e a r s l a t e r . ( 7 , 1 3 ) Today i t i s e s t i m a t e d t h a t some 200,000 t o n s / y r . o f k a o l i n c l a y i s used f o r c r a c k i n g c a t a l y s t m a n u f a c t u r e as r e p o r t e d by G e o r g i a K a o l i n C o r p o r a t i o n . ( 2 4 ) F i g u r e 10 shows t h e p o r e volume d i s t r i b u t i o n f o r N a l c o 783 and two o t h e r commercial s e m i s y n t h e t i c s from t h a t p e r i o d . T h i s l o w - c o s t m a t r i x , w i t h i t s u n u s u a l d u a l p o r e s p e c t r a and somewhat u n e x p e c t e d b e n e f i c i a l p r o p e r t i e s , became t h e m a t r i x o f choice f o r the next generation, t h e z e o l i t e - c o n t a i n i n g c a t a l y s t s . T h i s approach continues t o provide a pore s t r u c t u r e t h a t g i v e s r e a c t a n t molecules ready access t o t h e z e o l i t e c r y s t a l s b u r i e d d e e p l y w i t h i n , w h i l e a t t h e same t i m e g r e a t l y r e d u c i n g manufacturing costs.(23) K a o l i n i s a l s o an i n e x p e n s i v e i n g r e d i e n t , t h u s l o w e r i n g raw m a t e r i a l c o s t s by r e p l a c i n g e x p e n s i v e sodium s i l i c a t e , aluminum s u l f a t e , and sodium a l u m i n a t e , p l u s r e d u c i n g u s e o f n e u t r a l i z i n g ammonia o r a c i d . I t g e n e r a t e s much l e s s waste e f f l u e n t and r e d u c e s h i g h - e n e r g y water e v a p o r a t i o n s p r a y d r y i n g r e q u i r e m e n t s and f i n a l d r y i n g c o s t s . T h i s reduces energy c o s t s w h i l e appreciably i n c r e a s i n g manufacturing capacity. The same a p p r o a c h was a p p l i e d t o enhance and e x t e n d r e s i d c a t a l y s t technology. We gave c o n s i d e r a b l e a t t e n t i o n t o s p e c i f i c g r a d e s o f K a o l i n t o a s s u r e a v e r y good p o r e s t r u c t u r e and t o keep c o s t s down. F o r a c o m b i n a t i o n o f low c o s t , good open p o r e s t r u c t u r e , low i r o n c o n t e n t , and low a t t r i t i o n , we p r e f e r r e d t h e smaller, s p h e r i c a l equivalent Kaolin c r y s t a l s with a high diameter-to-thickness ratio. DZ-40 h a s t h e p r o p e r t i e s o f p o r e volume and p o r e d i a m e t e r d i s t r i b u t i o n l i s t e d i n Table III.(11) Note t h e c o n s i d e r a b l e p o r e volume i n t h e 100-1000 Angstroms r a n g e ( F i g u r e 11). F i g u r e 12 a l s o shows some o f o u r d a t a i n d i c a t i n g t h e b e n e f i t o f a l a r g e r p o r e volume. I t appeared t o us t h a t an optimum f o r c a t a l y s t s i n r e s i d c r a c k i n g o c c u r s between 0.40 and 0.55 cc/gm.



•

35-40

40-60

80-100

100-200

200-400

400-1M

1M - 6M

J H i H i HHP

DJ Nalco 783 semi-synthetic

Pore diameter angstroms

60-80

F i g u r e 9. D i s t r i b u t i o n o f Pore Volume v s . Pore D i a m e t e r S y n t h e t i c v s . N a l c o 783 s e m i s y n t h e t i c

13X alumina synthetic

30-35

ΓΤ f i r

Volume X of total pore volume



13% alumina synthetic •

Cat D semi-synthetic

CD Nalco 783 semi-synthetic

Pore diameter angstroms

F i g u r e 10. D i s t r i b u t i o n o f Pore Volume v s . P o r e D i a m e t e r S y n t h e t i c v s . c o m m e r c i a l l y - a v a i l a b l e 1958 s e m i s y n t h e t i c

Β Cat A semi-synthetic

•

Volume % of total pore volume


5

33


324


T a b l e I I I . Pore S i z e D i s t r i b u t i o n c c / g (% o f T o t a l P o r e Volume)

6000A 6000-1000A 1000-400A 400-200A 400-100A 100-80A 80-60A 60-20A S u r f a c e A r e a , m^/g Z e o l i t e A r e a , m ^g E x t e r n a l A r e a , m /g P o r e Volume, c c / g

0.03 0.09 0.18 0.12 0.09 0.03 0.03 0.04 198 99 108 0.59

S k e l e t a l D e n s i t y , g/cc Apparent Bulk D e n s i t y , g/cc

cc/g cc/g cc/g cc/g cc/g cc/g cc/g cc/g

( 0%) (15%) (31%) (21%) (16%) ( 5%) ( 6%) ( 6%)

2.57 0.56

Volume % of total pore volume 50

30-60

60-80

80-100 100-200 200-400 400-1M

1M-6M

Pore diameter angstroms •

Early semi-synthetic

CD RCC

type catalyst

F i g u r e 11. D i s t r i b u t i o n o f Pore Volume v s . Pore D i a m e t e r - E a r l y s e m i s y n t h e t i c v s . r e s i d u u m (RCC) c a t a l y s t


19. HETTINGER


Z e o l i t e A c i d i t y and M a t r i x

Acidity


R e s i d c r a c k i n g c a t a l y s t s must d e a l w i t h a f e e d s t o c k o f h i g h m o l e c u l a r - w e i g h t , h i g h - b o i l i n g , and even n o n b o i l i n g v i s c o u s m o l e c u l e s . T h i s makes e n t r a n c e i n t o a z e o l i t e s t r u c t u r e questionable. On t h e o t h e r hand, much o f i t i s i n t h e FCC f e e d o r gas o i l p o r t i o n o f t h e r e d u c e d c r u d e (600-1050 F ) , where z e o l i t e c r a c k i n g a c t i v i t y , s e l e c t i v i t y , and s t a b i l i t y a r e c r i t i c a l l y required. F u r t h e r m o r e , t h e s e v e r e environment f o r c r a c k i n g and r e g e n e r a t i o n , a l s o c a l l e d f o r a z e o l i t e w i t h good p e r f o r m a n c e i n terms o f r e s i s t a n c e t o h i g h t e m p e r a t u r e and s e v e r e steam c o n d i t i o n s . We worked h a r d t o e v a l u a t e s t r u c t u r e s such as r a r e e a r t h s t a b i l i z e d v e r s u s U l t r a s t a b l e hydrogen Y z e o l i t e s . transfer c h a r a c t e r i s t i c s were a l s o c r i t i c a l . W i t h t o o much r a r e e a r t h c o n t e n t , H~ p r o d u c t i o n i n c r e a s e d w i t h accompanying coke i n c r e a s e ( F i g u r e 11;. U l t r a s t a b l e Y s i e v e s gave good p r o d u c t d i s t r i b u t i o n , h i g h o c t a n e s , and r e d u c e d hydrogen g e n e r a t i o n , b u t had lower a c t i v i t y and were more s u s c e p t i b l e t o m e t a l d e a c t i v a t i o n and a c i d i t y n e u t r a l i z a t i o n . To enhance z e o l i t e p e r f o r m a n c e i n t h e f a c e o f p o i s o n i n g , a s p h a l t e n e b l o c k a g e , and c o k i n g , we t r i e d t o enhance p o r t a l s u r f a c e a r e a by g r i n d i n g o r b r e a k i n g up s i e v e c l u s t e r s t o i n d i v i d u a l s i e v e s and/or by producing very small sieves. Both approaches were r e q u e s t e d o f the manufacturer. F o r t h e s t a r t - u p o f t h e RCC U n i t DZ-AO was u s e d . I t was a c o m b i n a t i o n o f U l t r a s t a b l e hydrogen Y, p a r t i a l l y t r e a t e d w i t h r a r e e a r t h , and ground t o as f i n e a z e o l i t e s t r u c t u r e as c o m m e r c i a l l y a v a i l a b l e and r e a s o n a b l e , and w e l l d i s p e r s e d i n a s p e c i a l l y developed s i l i c a - a l u m i n a c o g e l / K a o l i n matrix. T a b l e IV provides a t y p i c a l a n a l y s i s . Matrix

Acidity

Because we would be d e a l i n g w i t h v e r y l a r g e m o l e c u l e s , i n c l u d i n g some w i t h l o n g p a r a f f i n groups a t t a c h e d , we s p e c u l a t e d t h a t an a c i d i c m a t r i x would be d e s i r a b l e . A t t h a t t i m e , g e n e r a l l y t h e c a t a l y s t s a v a i l a b l e from o u r s u p p l i e r s had been s t r i p p e d o f m a t r i x a c i d i t y , because commercial e x p e r i e n c e on FCC f e e d s t o c k s had shown t h a t z e o l i t e a c i d i t y was g e n e r a l l y q u i t e adequate. However, we s u s p e c t e d t h a t m a t r i x a c i d i t y would p r o v i d e optimum product d i s t r i b u t i o n . L a t e r o p e r a t i o n o f t h e 200 B/D d e m o n s t r a t i o n u n i t and t h e RCC commercial u n i t e s t a b l i s h e d t h a t a c i d m a t r i x c a t a l y s t s a t c o n s t a n t c o n v e r s i o n p r o v i d e d a lower 650 F+ y i e l d and a h i g h e r m i d d l e d i s t i l l a t e t o 650 F end p o i n t r a t i o (see F i g u r e 13). Note t h e d e c r e a s e i n heavy c y c l e o i l a t c o n s t a n t c o n v e r s i o n f o r a c a t a l y s t w i t h m a t r i x a c i d i t y compared t o a n o n a c i d i c m a t r i x c a t a l y s t . More r e c e n t l y c a t a l y s t m a n u f a c t u r e r s have adopted t h i s s t r a t e g y o f m a t r i x a c i d i t y t o d e a l w i t h bottoms c r a c k i n g . T i t r a t i o n techniques f o r i s o l a t i n g o r d e f i n i n g z e o l i t e and m a t r i x a c i d i t y d e v e l o p e d a r e l a t i o n s h i p r e p r e s e n t i n g a b a l a n c e d performance o f t h e two a c i d i t i e s (see Table V ) .


325


326

55H


50H

40®

ACIDIC MATRIC

(N) NON-ACIDIC MATRIX

Ί

I

0.2

I

I

I

Γ

0.3 0.4 0.5 0.6 0.7

VIRGIN CTLST. WATER PORE VOL. CC/Gl

Figure

12. E f f e c t s o f Pore Volume on RCCDS G a s o l i n e

Yield

Table IV.

Chemical Analyses

T y p i c a l A n a l y s i s , Wt.%

Si0 Al 6 Ti6 Fe 0 Na^T REp LalO"

58.3 40.1 0.52 0.43 0.42 1.29 0.74

J 2

0.14

Nd 0 Pr Ο

0.31 0.10

2

J

2

?

Ce6 2

La°OÎ7CeO Ratio n

5.3

Μ δ 8

Phase Composition Z e o l i t e Type Zeolite Lattice Κ Z e o l i t e Content % Int./Na Y I n t e r n a l Std. N i t r o g e n Method Kaolinite

USY 24.58 8.8 7.7 15.0 45.0





Figure

13. L C O / S l u r r y v s C o n v e r s i o n


327



328

T a b l e V.

n-butylamine Total Acidity in the Sieve RCC RCC

C a t a l y s t #1 C a t a l y s t #3

0.25 0.22

tridodecylamine Matrix Acidity 0.00 0.22

Ratio Matrix A c i d i t y Sieve A c i d i t y 0.00 1.00

C a t a l y s t #3

n-butylamine a c i d i t y t o t a l c a t a l y s t n-buytlamine a c i d i t y o f contained s i e v e tridoecylamine a c i d i t y Total accessible acidity T o t a l m i c r o porous a c i d i t y unaccounted f o r and e v i d e n t l y i n t h e m a t r i x

0.77 0.22 0.22 0.44 0.33


meg/gm meg/gm meg/gm meg/gm meg/gm



Silica-alumina best combination o f we chose a g e l w i t h system t o g e t h e r and


Rare E a r t h

329

g e l s c o n t a i n i n g 20-45% a l u m i n a p r o v i d e d t h e a c t i v i t y and a c t i v i t y s t a b i l i t y . Therefore, a c o m p o s i t i o n i n t h i s range f o r b i n d i n g t h e as t h e m a t r i x a c i d i t y i n g r e d i e n t .

Stabilization

Rare e a r t h s t a b i l i z a t i o n , as i t r e l a t e s t o z e o l i t e p e r f o r m a n c e , has a l r e a d y been d i s c u s s e d . However, c a t a l y s t p e r f o r m a n c e a l s o v a r i e s depending on how t h e r a r e e a r t h s a r e d e p o s i t e d w i t h i n t h e z e o l i t e and t h e m a t r i x , and a l s o on how t h e r a t i o o f i n d i v i d u a l s p e c i e s ( s u c h as lanthanum, c e r i u m , and t h e o t h e r r a r e e a r t h s ) are d i s t r i b u t e d . Y t t r i u m c a n a l s o be used t o enhance z e o l i t e c a t a l y s t p e r f o r m a n c e and s t a b i l i t y . These a l s o seem t o h e l p m i t i g a t e t h e d e t r i m e n t a l e f f e c t o f vanadium, t h e most common and c o n t r o v e r s i a l contaminant. We d e v o t e d much e f f o r t t o e x p l o r i n g how much r a r e e a r t h s h o u l d be u s e d i n b o t h t h e z e o l i t e and t h e m a t r i x , how i t s h o u l d be i n t r o d u c e d o r i n c o r p o r a t e d , and w h i c h r a t i o o f r a r e e a r t h elements was p r e f e r r e d . F i g u r e s 14 and 15 r e s p e c t i v e l y show how a c t i v i t y and s e l e c t i v i t y c a n be a f f e c t e d by r a r e e a r t h c o n t e n t i n j u s t one c a t a l y s t p r e p a r a t i o n . Metal

Resistance

Anyone who i s s e r i o u s l y i n v o l v e d i n c a t a l y t i c c r a c k i n g , whether as an o p e r a t o r , a c a t a l y s t m a n u f a c t u r e r , o r a r e s e a r c h e r , soon l e a r n s how s e v e r e l y sodium, vanadium, n i c k e l , i r o n , and copper a c t as p o i s o n s . I n t h e p a s t , FCC f e e d s t o c k p r e p a r a t i o n v i a vacuum d i s t i l l a t i o n was t o a c o n s i d e r a b l e e x t e n t , d e t e r m i n e d by metal carryover. Generally, metal carryover t o the f l u i d u n i t was l i m i t e d t o 0.1 ppm o r l e s s o f e a c h o f t h e s e m e t a l s . I n t h e development o f a p r o c e s s t o c r a c k r e d u c e d c r u d e , i t soon became e v i d e n t t h a t t h e m e t a l s l e v e l s e n c o u n t e r e d i n t h e s e c r u d e s would be c o n s i d e r a b l y h i g h e r . T h e r e f o r e , m e t a l s would be e x p e c t e d t o m a n i f e s t t h e m s e l v e s i n v e r y u n f a v o r a b l e ways. P r e v i o u s l y , n i c k e l was c o n s i d e r e d t h e w o r s t p o i s o n by f a r , i n terms o f H^ and coke make, and poor p r o d u c t d i s t r i b u t i o n . Vanadium was c o n s i d e r e d much l e s s o f a p o i s o n w i t h about 1/5 t h e s e l e c t i v i t y detriment o f n i c k e l . I r o n , e s p e c i a l l y i n t h e absence o f s u l f u r , was c o n s i d e r e d even l e s s o f a p o i s o n . Copper and sodium were o f l i t t l e consequence i f p r o p e r c a r e was t a k e n t o a v o i d them i n FCC f e e d s t o c k p r e p a r a t i o n . N i c k e l and vanadium c a r r y o v e r i s m a i n l y a t t r i b u t e d t o v o l a t i l i z a t i o n o f p o r p h y r i n s c h e m i c a l l y combined w i t h t h e s e two elements. Because v o l a t i l i t y o f t h e two s p e c i e s i s r o u g h l y e q u i v a l e n t , c a r r y o v e r o f n i c k e l and vanadium a r e a p p r o x i m a t e l y equal. However, because t h e s e l e c t i v i t y d e t r i m e n t o f vanadium i s so much lower, n i c k e l has always g e n e r a t e d t h e most c o n c e r n . W i t h r e s i d u u m p r o c e s s i n g , however, t h e s i t u a t i o n changes. M e t a l l e v e l s r i s e d r a m a t i c a l l y . F i g u r e 16 shows t h e m e t a l d i s t r i b u t i o n i n a l o g / l o g s c a l e p l o t o f n i c k e l v e r s u s vanadium f o r some 50 c r u d e s . O b v i o u s l y , many r e d u c e d c r u d e s c o n t a i n



Figure Effect

14. Rare E a r t h Exchanged on A c t i v i t y

g Constant Conversion

Ο

g g

GAS

ο

F i g u r e 15. Rare E a r t h Exchanged E f f e c t s on P r o d u c t Y i e l d s a t

•

ο GASOLINE



19. HETTINGER

331


m e t a l s f a r beyond t h e 0.1 t o 0.2 ppm m e t a l s l e v e l s o f vacuum gas oil. Not o n l y do n i c k e l and vanadium l e v e l s r i s e s i g n i f i c a n t l y , but vanadium c o n t e n t may g r e a t l y exceed n i c k e l . Because o f t h e absence o f vacuum d i s t i l l a t i o n , sodium, i r o n , c o p p e r , and o t h e r p o t e n t i a l p o i s o n s c a n a l s o appear a t v e r y h i g h l e v e l s . These may have been p r e s e n t i n t h e c r u d e o i l o r added by c o n t a m i n a t i o n from c o r r o s i o n , a d d i t i v e s , o r a c c i d e n t a l c a r r y o v e r from d e s a l t i n g . We knew t h e p o i s o n o u s b e h a v i o r o f n i c k e l , sodium, i r o n , and copper, and c o u l d a n t i c i p a t e t h e problems c o n n e c t e d w i t h them. However, vanadium appeared t o o f f e r some new problems. F i r s t of a l l , i t appeared i n o u r r e d u c e d c r u d e s a t one t o t h r e e t i m e s t h e nickel level. I t c o u l d be e x p e c t e d t o show t h e same a d v e r s e p r o d u c t s e l e c t i v i t y as a t lower l e v e l s , b u t w i t h much g r e a t e r severity. I n a d d i t i o n , r e p o r t s had been n o t e d s u g g e s t i n g t h a t vanadium i n c e r t a i n forms, and e s p e c i a l l y i n t h e p r e s e n c e o f sodium, had a low m e l t i n g t e m p e r a t u r e . T h e r e f o r e , i t s l i q u i d form was l i k e l y t o be h a r m f u l t o c a t a l y s t performance. Thus we began a l o n g and i n v o l v e d r e s e a r c h program t o d e t e r m i n e how b e s t t o d e a l w i t h t h e s e p o i s o n s , and e s p e c i a l l y w i t h vanadium. E a r l y i n o u r work, we had sought t o a c h i e v e z e o l i t e s t a b i l i t y a t h i g h t e m p e r a t u r e s and i n t h e p r e s e n c e o f steam. We sought z e o l i t e s t h a t c o u l d r e s i s t t h e extreme d e a c t i v a t i n g c o n d i t i o n s o f t h e RCC p r o c e s s . I n a s e r i e s o f e x p e r i m e n t a l r u n s on v i r g i n commercial c a t a l y s t s and s i e v e s t h e n a v a i l a b l e and some o f o u r e x p e r i m e n t a l c a t a l y s t s , we q u i c k l y l e a r n e d t h a t a c a t a l y s t impregnated w i t h vanadium, and s u b j e c t e d t o h i g h t e m p e r a t u r e s i n steam and a i r deactivated rapidly. Vanadium, e s p e c i a l l y i n t h e +5 v a l e n c e s t a t e , r a p i d l y d e a c t i v a t e d a c a t a l y s t by d e s t r o y i n g z e o l i t e c r y s t a l l i n i t y ( F i g u r e 1 7 ) . I n t h e p r e s e n c e o f sodium, t h e d e a c t i v a t i o n r a t e o f vanadium was even more s e v e r e . (14-17) C a t a l y s t r e p l a c e m e n t c o s t s and y i e l d l o s s c o s t s c a n r i s e r a p i d l y i f p o i s o n i n g o c c u r s . O b v i o u s l y , a h i g h m e t a l s l e v e l must be d e a l t w i t h a p p r o p r i a t e l y . We a c c e l e r a t e d o u r e f f o r t t o d i s c o v e r a way t o d e a l w i t h vanadium p o i s o n i n g . O r i g i n a l l y we e v o l v e d t h r e e b a s i c approaches o r s t r a t e g i e s : 1. S e a r c h f o r an a d d i t i v e t h a t would r e a c t w i t h vanadium so as t o i m m o b i l i z e and d e a c t i v a t e i t . We dubbed t h e s e "vanadium immobilizers". 2. Seek t o t r a p m o b i l i z e d 5+ v a l e n c e vanadium i o n s i n s i e v e s w i t h s m a l l p o r e s , such as A s i e v e , and t h e r e b y i n a c t i v a t e them. These were r e f e r r e d t o as "vanadium t r a p s " . 3. Seek t o d i v e r t vanadium t o l e s s h a r m f u l d e s t r u c t i v e a c t i v i t y by a d d i n g cheap and/or n a t u r a l l y o c c u r r i n g s i e v e s . F o r t h e s e we p r o p o s e d t h e term " s a c r i f i c i a l s i e v e s " . We t r i e d t o e x p l o i t a l l t h r e e a p p r o a c h e s . T h e r e was p r o g r e s s and some s u c c e s s i n each c a s e . A r e v i e w o f t h e c h e m i s t r y o f lower v a l e n c e vanadium o x i d e s showed t h a t t h e y p o s s e s s e d much h i g h e r m e l t i n g p o i n t s t h a n 2 ° 5 * T h e r e f o r e , we d e v e l o p e d a f o u r t h a p p r o a c h , which h a s l e d t o some p a t e n t s and i s p r e s e n t l y a p r a c t i c a l c o n t r i b u t o r t o p a r t i a l vanadium c o n t r o l . The p r o c e d u r e c a l l s f o r m a i n t a i n i n g a s m a l l b u t V



F i g u r e 16. Reduced Crude M e t a l C o n t e n t f o r 50 R e p r e s e n t a t i v e Crudes

F i g u r e 17. C a t a l y s t M e t a l Torture Test Iron, N i c k e l , Sodium, Vanadium E f f e c t s



19. HETTINGER


333

f i n i t e amount o f coke on t h e r e g e n e r a t e d c a t a l y s t t o m i n i m i z e o x i d a t i o n beyond V^O^ t o V^O^. I n t h i s manner, c a t a l y s t consumption due t o vanadium-caused l o s s o f c a t a l y s t a c t i v i t y has been somewhat r e d u c e d w i t h o u t s i g n i f i c a n t l y l o w e r i n g r e g e n e r a t e d c a t a l y s t a c t i v i t y due t o t h e s m a l l amount o f c a r b o n r e m a i n i n g . E f f o r t s t o c o n t r o l n i c k e l proceeded along s i m i l a r l i n e s . N i c k e l a l u m i n a t e , a s p i n e l , has l o n g been known t o t r a p n i c k e l . M e t a l s l i k e a r s e n i c ( 1 9 ) , antimony(20-21) and bismuth(20) a r e known to p a s s i v a t e t r a n s i t i o n elements and c a n be used t o d e c r e a s e H« and coke make. S u l f u r i s a l s o a known i n h i b i t o r f o r n i c k e l ; t h e r e f o r e , h i g h e r s u l f u r - c o n t a i n i n g crudes may be a l i t t l e l e s s s e n s i t i v e t o n i c k e l poisoning. I n our work we a l s o found t h a t n i c k e l a t low c o n c e n t r a t i o n s i s a c t u a l l y a s l i g h t promoter o f t h e c r a c k i n g r e a c t i o n when i n c o r p o r a t e d i n t o a m o l e c u l a r s i e v e ( F i g u r e 1 7 ) . Because o f t h e h i g h c o k e - f o r m i n g t e n d e n c i e s o f reduced c r u d e , m a i n l y due t o a h i g h c o n c e n t r a t i o n o f Ramsbottom Carbon, t h e a d v e r s e e f f e c t s o f n i c k e l appear t o be somewhat moderated i n t h e t r i p up t h e r i s e r . T h e r e f o r e , n i c k e l does n o t appear t o be q u i t e as h a r m f u l as f i r s t a n t i c i p a t e d . We e x p l o r e d v a r i o u s p o s s i b i l i t i e s i n our e f f o r t s t o c o n t r o l nickel. C a t a l y s t s h i g h i n alumina content, e s p e c i a l l y i f a s e p a r a t e i n c l u s i o n o f a l u m i n a g e l i s u t i l i z e d , d i d seem t o show some improvement. I t a l s o appears t h a t i n s e v e r e c o n d i t i o n s such as i n t h e RCC o p e r a t i o n , n i c k e l t e n d s t o a g g l o m e r a t e , t h i s r e d u c i n g exposed s u r f a c e and p o s s i b l y a l s o embeds i n t h e m a t r i x o r z e o l i t e . We e a r l y n o t i c e d t h a t t h e r e s e a r c h o c t a n e number o f RCC g a s o l i n e was h i g h ( s e e our e a r l y paper e n t i t l e d "RCC P r o g r e s s - An I n e x p e n s i v e Route t o H i g h Octane G a s o l i n e " ) ( 5 ) , and we sought an explanation f o r t h i s . One o f t h e v e r y e a r l i e s t r e f o r m i n g c a t a l y s t s , a n i c k e l on steamed 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 , was d e v e l o p e d by t h e l a t e Frank C i a p e t t a . ( 1 8 ) We s p e c u l a t e d t h a t , i n view o f t h e h i g h o c t a n e o f RCC g a s o l i n e , i t s a r o m a t i c n a t u r e ( F i g u r e 1 8 ) , and t h e abundance o f hydrogen p r o d u c t i o n w i t h o u t c o n c u r r e n t h i g h coke f o r m a t i o n , t h i s h i g h o c t a n e number may r e s u l t from r e f o r m i n g r e a c t i o n s such as d e h y d r o g e n a t i o n , i s o m e r i z a t i o n and d e h y d r o c y c l i z a t i o n r e s u l t i n g from t h e h i g h n i c k e l c o n t e n t on t h e a c i d i c s i l i c a - a l u m i n a . T h i s h y p o t h e s i s , however, has n o t y e t been p r o v e n . P u r s u i t o f t h i s p o s s i b i l i t y c o u l d open up a new a r e a o f c r a c k i n g c a t a l y s t development. RCC p r o c e s s c a t a l y s t s w i t h m e t a l s c o n t e n t s as h i g h as 12,300 ppm n i c k e l p l u s vanadium, p l u s 6,000 ppm o f i r o n , have o p e r a t e d i n t h e 200 B/D d e m o n s t r a t i o n u n i t on f e e d s t o c k s c o n t a i n i n g up t o 84 ppm n i c k e l p l u s vanadium.(4,5) P r e s e n t l y i n our r e f i n e r y , when m e t a l s l e v e l s a r e a t s t i l l h i g h e r l e v e l s , t h e reduced c r u d e i s f i r s t p r o c e s s e d i n t h e A s h l a n d ART u n i t , where some 85-95% o f t h e m e t a l s and 75% o f t h e Ramsbottom Carbon a r e removed.(6) I n n o r m a l o p e r a t i o n s , however, t h e RCC u n i t r o u t i n e l y r u n s a t 6-9000 ppm n i c k e l p l u s vanadium on f e e d s t o c k s w i t h as h i g h as 35-75 ppm n i c k e l p l u s vanadium c o n t e n t . P r e s e n t l y s e v e r a l commercial r e s i d u u m - t y p e c a t a l y s t s a r e g i v i n g good p e r f o r m a n c e a t t h e s e levels. C a t a l y s t m a n u f a c t u r e r s c o n t i n u e t o seek f u r t h e r improvement i n p e r f o r m a n c e i n terms o f a c t i v i t y , s e l e c t i v i t y , and c a t a l y s t l i f e , w h i l e a l s o t r y i n g t o h o l d down o r even r e d u c e overall cost.




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R e s i s t a n c e t o H i g h Temperature - H i g h Steam E n v i r o n m e n t s . Because of t h e g r e a t e r amount o f coke d e p o s i t e d i n and on a r e s i d c a t a l y s t , t h e n a t u r e o f t h e coke, and t h e i n t e r n a l t e m p e r a t u r e s experienced i n connection with burning i t o f f , e a r l y h i g h - s e v e r i t y screening t e s t s were used t o s c r e e n c a t a l y s t s . ( 1 6 , 1 7 ) These t e s t s c o n s i s t e d of steaming and c a l c i n i n g a t t e m p e r a t u r e s as h i g h as 1400-1600 F prior to testing. They were a b l e t o p i n p o i n t p r e f e r r e d z e o l i t e s and m a t r i c e s f o r i n c o r p o r a t i o n , where f e a s i b l e , i n t o t h e commercial catalyst. H^ P r o d u c t i o n . The RCC o p e r a t e s w i t h r e c y c l e d gas, and we soon r e c o g n i z e d t h a t r e c y c l e d H^ might s e r v e t o p a r t i a l l y r e v e r s e c o k i n g r e a c t i o n s and p e r h a p s even t o c a t a l y z e r e f o r m i n g r e a c t i o n s . ( 1 8 ) Thus, hydrogen g e n e r a t i o n , i n t h e absence o f a s s o c i a t e d coke f o r m a t i o n , i s n o t n e c e s s a r i l y bad. Those o f us who had worked on f l u i d r e f o r m i n g i n t h e e a r l y 1950s r e c o g n i z e d t h a t a v e r y low, b u t f i n i t e , H^ p a r t i a l p r e s s u r e c o u l d i n d u c e r e f o r m i n g r e a c t i o n s i n c l u d i n g d e h y d r o c y c l i z a t i o n . ( 1 9 ) Thus, we had mixed o p i n i o n s as t o t h e b e n e f i t s and d e t r i m e n t s o f H p r o d u c t i o n . Recycling of h i g h - H ^ - c o n t a i n i n g gas i s more d i f f i c u l t t o a c h i e v e m e c h a n i c a l l y because o f t h e low m o l e c u l a r w e i g h t o f t h e gas. On t h e o t h e r hand, p r o t e c t i o n a g a i n s t c a t a l y s t c o k i n g and p o s s i b l e enhancement o f y i e l d and h i g h o c t a n e p r o d u c i n g r e f o r m i n g r e a c t i o n s h o l d much p r o m i s e f o r even b e t t e r r e s u l t s w i t h h i g h e r H^ r e c y c l e p r e s s u r e . Two s c h o o l s o f thought s t i l l a b i d e on t h i s u n r e s o l v e d i s s u e . The RCC u n i t o p e r a t e s w i t h a s i g n i f i c a n t H^ p a r t i a l p r e s s u r e , g i v e s r a t h e r low coke y i e l d s i n r e l a t i o n s h i p t o Ramsbottom Carbon i n t h e f e e d , and makes an u n u s u a l l y h i g h r e s e a r c h o c t a n e . ( 5 ) ?

Basic Nitrogen. Because o f t h e h i g h b a s i c n i t r o g e n c o n t e n t o f r e d u c e d c r u d e , t h e r e was c o n c e r n about how t o h a n d l e such h i g h l e v e l s o f b a s i c n i t r o g e n , w h i c h have been shown t o p o i s o n a c i d sites. The i s s u e o f c o n s t r u c t i n g a c a t a l y s t w i t h minimum s e n s i t i v i t y t o n i t r o g e n h a s n o t y e t been e n t i r e l y r e s o l v e d . P e r s o n a l l y , I am i n c l i n e d t o b e l i e v e t h a t t h e p r e s e n c e o f an a c i d i c m a t r i x t e n d s t o m i n i m i z e t h e n e u t r a l i z a t i o n o f z e o l i t e a c i d i t y by p a r t i a l a b s o r p t i o n on a c i d i c s i t e s a l o n g t h e w a l l s o f f e e d e r p o r e s . Hence, m a t r i x a c i d i t y may o f f e r an a d d i t i o n a l b e n e f i t i n c a t a l y s t performance. Asphaltenes. Asphaltenes a r e l a r g e polynuclear aromatic c o l l o i d a l p a r t i c l e s t h a t a r e r a p i d l y and e a s i l y c o n v e r t e d t o coke i n y i e l d s o f 50-70% o r g r e a t e r . A n o t h e r a s s e t o f t h e l a r g e p o r e volume, l a r g e f e e d e r p o r e s t r u c t u r e i s t h a t i t may p r e v e n t p l u g g i n g o f f e e d e r p o r e s t o t h e z e o l i t e by a l l o w i n g t h e a s p h a l t e n e s t o d e p o s i t on t h e w a l l s o f l a r g e p o r e s , w h i l e a l l o w i n g s m a l l e r m o l e c u l e s t o p a s s by on t h e i r way t o t h e z e o l i t e p o r t a l s u r f a c e . See F i g u r e 8, w h i c h a l s o seeks t o d e p i c t o v e r a l l c a t a l y s t s t r u c t u r e and t h e r o l e of e a c h i n g r e d i e n t i n a c h i e v i n g a s u p e r i o r c a t a l y s t . Normal P a r a f f i n s . present i n reduced

E a r l y i n o u r work we n o t e d t h a t n - p a r a f f i n s , c r u d e , a r e known t o be r e s i s t a n t t o c a t a l y t i c


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c r a c k i n g . ( 2 2 ) They would p o s s i b l y c a s c a d e down i n t o l i g h t gas o i l , which would g i v e t h e s e gas o i l s a h i g h e r c l o u d and pour p o i n t . W h i l e s u c h d a t a a r e n o t i n c l u d e d i n t h i s r e p o r t , our work has a l s o shown t h a t i n FCC o p e r a t i o n s t h e a c i d i c m a t r i x i s a b l e t o b e t t e r c r a c k and i s o m e r i z e more η-paraffins, t h u s r e d u c i n g t h e n - p a r a f f i n c o n t e n t i n m i d d l e d i s t i l l a t e and t h e r e b y t h e c h a r a c t e r i s t i c h i g h c l o u d p o i n t a s s o c i a t e d w i t h i t , w h i l e a l s o r a i s i n g o c t a n e number by removing o r i s o m e r i z i n g η-paraffins i n t h e g a s o l i n e f r a c t i o n . Burning Rates. The d u a l p o r e s t r u c t u r e and l a r g e p o r e volume, together w i t h contaminated metals t h a t are a l s o o x i d a t i o n c a t a l y s t s , v e r y l i k e l y have a p o s i t i v e e f f e c t on b u r n i n g r a t e s . A t any r a t e , t h e easy a c c e s s i b i l i t y o f oxygen t o an a p p r e c i a b l e coke s t r u c t u r e due t o t h e open p o r e s t r u c t u r e o f t h e s e residuum c a t a l y s t s has u n d o u b t e d l y h e l p e d r e g e n e r a t i o n and r e d u c e d o r e l i m i n a t e d p o r e s i n t e r i n g w i t h accompanying c a t a l y s t c o l l a p s e . The p r e s e n c e o f n i c k e l and vanadium as b u r n i n g promoters i s a l s o h e l p f u l , e s p e c i a l l y when r e g e n e r a t i o n i s a c c o m p l i s h e d i n t h e q u i t e u n i q u e two-stage r e g e n e r a t o r o f t h e RCC p r o c e s s ( F i g u r e 19). S i l i c a - m a g n e s i a m a t r i c e s have n o t y e t been p r o p e r l y e v a l u a t e d as an RCC c a t a l y s t m a t r i x . However, s u c h a m a t r i x i n c o n j u n c t i o n w i t h s t a b i l i z e d z e o l i t e might p r o v i d e an a t t r a c t i v e m a t r i x w i t h a Kaolin-enhanced d u a l pore s t r u c t u r e . Silica-magnesia matrices are n o t o r i o u s f o r t h e i r poor r e g e n e r a t i o n c h a r a c t e r i s t i c s . When p r e p a r e d by t h e d u a l p o r e K a o l i n - e n h a n c e d method, t h e y might be e a s i e r t o r e g e n e r a t e and, t h e r e b y , open up a new f a m i l y o f r e s i d u u m catalysts. Such c a t a l y s t s have n o t y e t been e x p l o r e d . C a t a l y s t Cost. C a t a l y s t replacement c o s t r e p r e s e n t s a l a r g e operating expenditure, i n a d d i t i o n to the e f f e c t that c a t a l y s t performance (good o r bad) can have on y i e l d and a s s o c i a t e d p r o f i t . T h e r e f o r e , i n a d d i t i o n t o a l l t h e o t h e r o b j e c t i v e s , we c o n t i n u a l l y e v a l u a t e d c a t a l y s t c o m p o s i t i o n and method o f manufacture as t h e y impacted on c a t a l y s t c o s t . C a t a l y s t m a n u f a c t u r i n g m o d i f i c a t i o n s as t h e y impacted c o s t were always c a r e f u l l y r e v i e w e d and s u c h r e v i e w was a key p a r t o f t h e c a t a l y s t development program. I n r e t r o s p e c t , we e n v i s i o n e d a number o f a l t e r n a t i v e c a t a l y s t systems. A l t h o u g h some o f them appeared q u i t e p r o m i s i n g , t h e c o s t o f raw m a t e r i a l s , and/or t h e c o m p l e x i t y o f a p r o c e s s , o r t h e u n a v a i l a b i l i t y o f s p e c i f i c m a n u f a c t u r i n g equipment o r p r o c e d u r e s f r e q u e n t l y m i l i t a t e d a g a i n s t many a t t r a c t i v e a l t e r n a t i v e s . Summary Research t o develop a c a t a l y s t s u i t a b l e f o r p r o c e s s i n g of r e s i d u a l f e e d s t o c k s has f o c u s e d on t h e many f a c e t e d r e q u i r e m e n t s o f s u c h a catalyst. T h i s work has shown t h a t s u c h a c a t a l y s t must p o s s e s s v e r y h i g h c r a c k i n g a c t i v i t y t h a t i s s t a b l e i n t h e p r e s e n c e o f steam and h i g h t e m p e r a t u r e , but must have good s e l e c t i v i t y as w e l l . T h i s has been a c h i e v e d by employing U l t r a s t a b l e Y z e o l i t e , p a r t i a l l y enhanced i n a c t i v i t y by a d d i t i o n o f a s m a l l amount o f r a r e e a r t h , b o t h i n t h e z e o l i t e and i n t h e m a t r i x .



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Regenerator



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The c a t a l y s t must a l s o have a c i d i t y i n t h e m a t r i x i n o r d e r t o reduce t h e molecular weight o f molecules t o o l a r g e t o e n t e r t h e z e o l i t e and i n o r d e r t o a l s o c o n v e r t h e a v y - c y c l e o i l t o l i g h t - c y c l e oil. Our s t u d i e s have e s t a b l i s h e d t h a t good b a l a n c e i n a c i d i t y between t h e m a t r i x and t h e z e o l i t e t e n d s t o enhance s e l e c t i v i t y . A s t a b l e m a t r i x a c i d i t y i s a l s o r e q u i r e d , and h e r e a h i g h a l u m i n a s i l i c a - a l u m i n a c o g e l was s e l e c t e d due t o i t s d e m o n s t r a t e d s t a b i l i t y i n t h e p r e - z e o l i t e e r a . C e r t a i n l y many o t h e r a c i d i c m a t r i c e s c o u l d p r o b a b l y be s u b s t i t u t e d . A t t r i t i o n r e s i s t a n t c a t a l y s t s a r e r e q u i r e d , but p r e f e r a b l y s h o u l d p o s s e s s a p o r e volume i n t h e 0.4 t o 0.5 cc/gm range. This i n c r e a s e d p o r e volume a p p a r e n t l y h e l p s i n f a c i l i t a t i n g a c c e s s i b i l i t y t o t h e c a t a l y s t i n t e r i o r by heavy v i s c o u s l i q u i d s , and d u a l p o r e s t r u c t u r e s c o n t a i n i n g p o r e s o v e r 100 Angstroms i n d i a m e t e r a l s o appear t o f a c i l i t a t e a c c e s s i b i l i t y t o t h e z e o l i t e w h i l e k e e p i n g f e e d e r p o r e s open. A p o r o u s system, y e t a t t r i t i o n r e s i s t a n t and i n e x p e n s i v e , was a c h i e v e d by i n c o r p o r a t i o n o f p l a t e l e t kaolin clay. Reduced c r y s t a l l i t e s i z e o f t h e z e o l i t e and/or b r e a k i n g o r grinding of clusters of zeolite crystals to individual crystals, a l s o s e r v e s t o enhance a c c e s s i b i l i t y i n t h e f a c e o f a s p h a l t e n e s , n i t r o g e n - c o n t a i n i n g m o l e c u l e s , d e s t r u c t i v e and h a r m f u l e l e m e n t s , and o t h e r m o l e c u l a r " c l u t t e r a s s o c i a t e d w i t h t h e bottom o f t h e barrel. Vanadium a t h i g h l e v e l s and i n t h e +5 v a l e n c e s t a t e has been shown t o have h i g h l y d e s t r u c t i v e c h a r a c t e r i s t i c s , w h i l e n i c k e l a t high l e v e l s continues to manifest i t s undesirable a b i l i t y to increase and coke make. Much e f f o r t has been d i r e c t e d t o c o n t r o l l i n g vanadium by s e v e r a l s t r a t e g i e s i n c l u d i n g i m m o b i l i z a t i o n , t r a p p i n g , o f f e r i n g s a c r i f i c i a l i n e x p e n s i v e s i e v e s as z e o l i t e s u b s t i t u t e s , and f i n a l l y by v a l e n c e c o n t r o l . Here t h e e f f o r t s were o n l y p a r t i a l l y s u c c e s s f u l , and v a l e n c e c o n t r o l t h r o u g h r e s i d u a l coke l e f t on t h e c a t a l y s t t o d a t e appears t o be t h e most successful. Antimony can h e l p c o n t r o l n i c k e l . W h i l e SO control i s n o t a p r o b l e m a t C a t l e t t s b u r g , due t o t h e p r e s e n c e o f a f l u i d i z e d l i m e s t o n e bed combustor w h i c h c a p t u r e s e f f l u e n t SOx, SO t r a n s f e r c a p a b i l i t y might a l s o be r e q u i r e d i n o p e r a t i o n s i n o t h e r plants. C o s t i s a l s o a most i m p o r t a n t f a c t o r i n d e v e l o p i n g a c o m m e r c i a l l y a c c e p t a b l e c a t a l y s t , and i n c l u d e s c o n s i d e r a t i o n o f b o t h m a n u f a c t u r i n g and raw m a t e r i a l c o s t s . Many c a t a l y s t s w h i c h c o u l d meet o p e r a t i n g r e q u i r e m e n t s were t o o c o s t l y . To keep c o s t s low, b o t h z e o l i t e c o n t e n t as w e l l as t y p e and r a r e e a r t h c o n t e n t had t o be c o n s i d e r e d . K a o l i n as a low c o s t e x t e n d e r and f i l l e r was o f c o n s i d e r a b l e h e l p , b u t a g a i n had i t s l i m i t s . I n a t t e m p t i n g t o o p t i m i z e a c a t a l y s t o f t h i s k i n d , many f a c t o r s and p a r a m e t e r s must be b a l a n c e d one a g a i n s t a n o t h e r . O p e r a t i n g f a c t o r s a r e a l s o so complex t h a t c a t a l y s t e v a l u a t i o n becomes e x t r e m e l y complex and c o s t l y . L i t e r a l l y hundreds o f c a t a l y s t p r e p a r a t i o n s and c o u n t l e s s e v a l u a t i o n s were u n d e r t a k e n b e f o r e a r r i v i n g a t a f i n a l c a t a l y s t f o r manufacture. A sound u n d e r s t a n d i n g o f c a t a l y s t fundamentals and r e a c t i o n mechanisms, an a p p r e c i a t i o n o f c a t a l y s t m a n u f a c t u r i n g r e s t r i c t i o n s , and perhaps i n s t i n c t i v e judgement a r e a l l r e q u i r e d . Even so i t 1 1


19.

HETTINGER


339

s h o u l d be n o t e d t h a t t h e r e i s s t i l l much a d d i t i o n a l p r o f i t t o be g a i n e d by f u r t h e r improvement i n c a t a l y s t p e r f o r m a n c e . Notwithstanding these l i m i t a t i o n s , a very e f f e c t i v e r e s i d u a l c r a c k i n g c a t a l y s t was d e v e l o p e d , p r o d u c e d i n l a r g e c o m m e r c i a l q u a n t i t y and demonstrated t o be v e r y e f f e c t i v e c o m m e r c i a l l y .


Acknowledgements I n c l o s i n g , I would l i k e t o t a k e t h i s o p p o r t u n i t y t o e x p r e s s my a p p r e c i a t i o n to Ashland O i l f o r a l l o w i n g p u b l i c a t i o n of t h i s paper, and f o r t h e o p p o r t u n i t y o f p a r t i c i p a t i n g i n t h i s e x c i t i n g catalytic development. I ' d a l s o l i k e to r e c o g n i z e the outstanding c o n t r i b u t i o n s o f S t e v e K o v a c h , Ron Kmecak, Wayne B e c k , Ted C o r n e l i u s , P a t r i c i a D o o l i n , Chuck Lochow, J i m P a l m e r , and a l l o f t h e o t h e r members o f t h e c a t a l y s t r e s e a r c h s t a f f . My a p p r e c i a t i o n i s a l s o extended t o D r . M a u r i c e M i t c h e l l and t o Don L e e , Roger B e n s l a y and a l l o f t h e members o f t h e p i l o t p l a n t s t a f f f o r t h e i r u n t i r i n g and dedicated contributions. D r . James M a s e l l i and h i s s t a f f a t D a v i s o n C h e m i c a l Company a r e a l s o t o be commended f o r t h e i r v a l u a b l e e f f o r t s on our b e h a l f f o r t h i s u n d e r t a k i n g . In p a r t i c u l a r , I ' d l i k e t o c i t e t h e s t i m u l a t i n g encouragement o f M e s s r s . O l i v e r Zandona, George M y e r s , John H a l l , R o b e r t Y a n c e y , S r . , and R o b e r t Y a n c e y , J r . as b e i n g c r i t i c a l t o t h e s u c c e s s o f our c a t a l y s t work and t o t h e RCC p r o c e s s as w e l l .

Literature Cited 1. Myers, G. D., U.S. Patent 4 332 673, 1982. 2. Myers, G. D.; Busch, L. E.; U.S. Patent 4 299 687, 1981. 3. Myers, G. D., et a l ; "Catalytic Conversion of Residual Stocks", 1979 NPRA Annual Meeting, 1979. 4. Zandona, O. J.; Busch, L. E.; Hettinger, W. P., Jr. "Reduced Crude Conversion Symposium on Production, Characterization and Processing of Heavy Oils, Tar Sand Bitumens, Shale Oils and Coal-Derived Liquids", University of Utah, 1981. 5. Zandona, O. J.; Busch, L. E.; Hettinger, W. P., Jr. "Reduced Crude Conversion - An Inexpensive Route to High Octane Gasoline", 1982 NPRA Annual Meeting, 1982. 6. Hettinger, W. P., Jr.; Busch, L. E.; Krock, R. P. "Heavy Oil Processing Alternatives - The Ashland Approach", Electronics in Oil/World Oil and Gas Exhibition and Conference, 1984. 7. Hettinger, W. P., Jr.; Oleszko, T. J. Petroleum Refiner, 1959, 38, 169. 8. Zandona, O. J.; Hettinger, W. P., Jr. "Reduced Crude Processing with Ashland's RCC Process", 47th Midyear API Meeting, 1982. 9. Zandona, O. J.; Busch, L. E.; Hettinger, W. P., Jr.; Krock, R. P., Oil & Gas Journal, March 22, 1982, 82-91. 10. Busch, L. E.; Hettinger, W. P., Jr.; Krock, R. P., Oil & Gas Journal, December 10, 1984, 79-84. 11. Beck, H. W.; Carruthers, J. D.; Cornelius, E. P.; Kmecak, R. Α.; Kovach, S. M.; Hettinger, W. P., Jr. U.S. Patent 4 588 702, 1986. 12. Van Nordstrand, R. Α.; Hettinger, W. P., Jr.; Keith, C. D. Nature, 1956, 177, 713.



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13. Hettinger, W. P., Jr.; Braithwaite, D. G. U.S. Patent 3 034 994, and U.S. Patent 3 034 995, 1962. 14. Hettinger, W. P., Jr.; et al, U.S. Patent 4 377 470, 1983. 15. Beck, H. W.; et al, U.S. Patent 4 432 890, 1984. 16. Hettinger, W. P., Jr.; et al, Oil & Gas Journal, April 9, 1984, 102-111. 17. Hettinger, W. P., Jr.; et al, "Hydrothermal Screening of Reduced Crude Conversion Catalysts", ACS Meeting, Aug. 1983. 18. Hettinger, W. P., Jr., "Dr. Frank Ciapetta - Pioneer in Catalytic Chemistry", ACS Symposium, March, 1982. 19. Hettinger, W. P., Jr.; et a l , I&EC, 1955, 47, 719. 20. Beckman, S.; Morrell, J. C.; Egloff, G. Catalysis - Inorganic and Organic; Reinhold Pub. Corp.; New York; 1940; p 416. 21. Maxted, Ε. B.; Poisoning of Metallic Catalysts; Advances in Catalysis; Academic Press; New York, 1951; Vol. III. 22. Greensfelder, B. S.; Voge, Η. H.; Goad, G. M., I&EC, 1949, 41 (11), 2573-2584. 23. Anonymous, "Refinery Catalysts are a Fluid Business", Chem. Week, 41, July 26, 1978. 24. Personal communication. RECEIVED February 25, 1988


Fluid Catalytic Cracking - ACS Publications - American Chemical Society

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