SARP: Chemical Recovery of Used Sulfuric Acid Alkylation Catalyst

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Alkylation Catalyst

ARTHUR R. GOLDSBY 76 Marcourt Drive, Chappaqua, NY 10514

In the early days, in the late 1930's and early 1940's, of the alkylation of isobutane with olefins using a s u l f u r i c acid c a t a l y s t , the acid catalyst was low in cost, the production of alkylate was l i m i t e d , and the discarded or used catalyst could be used in other processes, such as naphtha and lube o i l treating (1). Therefore, there was little incentive for the development of a recovery process unique to the alkylation c a t a l y s t . In addition, i t was confirmed early in the development of a l k y l a t i o n that the current, conventional processes for the recovery or conversion of s u l f u r i c acid containing hydrocarbons from t r e a t ing processed could be used for converting the used a l k y l a t i o n catalyst to fresh s u l f u r i c acid of any desired strength. As the production of alkylate increased in the 1940's, largely because of World War I I , a great deal more of the used catalyst became available for recovery. Most of it continues to be used merely as a source of s u l f u r , and is charged to conventional sludge conversion processes for recovery. To most chemists this did not seem to be a good solution to the problem, and i t still does not. The used catalyst has a t i t r a t a b l e a c i d i t y of about 90% H S0 , and a water content of about 2-5%. The fresh charge acid to a l k y l a t i o n is usually white s u l f u r i c acid of about 98.0-99.5% concentration. Currently a large amount of the used catalyst on the order of 5,000 tons per day in the United States is available for recovery, since t y p i c a l l y about 0.5 pound of s u l f u r i c acid i s required for each gallon of alkylate produced. 2

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In view o f t h e f o r e g o i n g , i t i s not s u r p r i s i n g t h a t many attempts have been made by many companies a l m o s t from t h e s t a r t o f a l k y l a t i o n t o d e v e l o p a r e c o v e r y p r o c e s s unique t o t h e used s u l f u r i c acid alkylation catalyst. Most o f t h e e a r l y attempts were n o t i n t e n s i v e and c o n t i n u o u s . Most o f t h e work i s unpubl i s h e d , s i n c e i t was o f a p r e l i m i n a r y n a t u r e and n o t v e r y successful. An added i n c e n t i v e was p r o v i d e d f o r t h e u s e r s and l i c e n s o r s o f t h e S u l f u r i c A c i d A l k y l a t i o n P r o c e s s when i t was d i s c o v e r e d t h a t h y d r o f l u o r i c a c i d was a l s o a good a l k y l a t i o n

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catalyst. S i n c e h y d r o f l u o r i c a c i d u s u a l l y c o s t s on t h e o r d e r o f twenty times t h a t o f s u l f u r i c a c i d , a r e c o v e r y system by d i s t i l l a t i o n was i n c o r p o r a t e d i n the HF d e s i g n . Hence, the f i g u r e s g i v e n f o r a c i d consumption i n HF a l k y l a t i o n are u s u a l l y n e t figures after recovery. The f i g u r e s g i v e n i n H2SO4 a l k y l a t i o n are u s u a l l y g r o s s f i g u r e s w i t h o u t r e c o v e r y . S i n c e t h e hydrocarbons o r c o n j u n c t polymers i n the used s u l f u r i c a c i d c a t a l y s t are u n s a t u r a t e d , attempts have been made t o hydrogenate t h e c a t a l y s t i n an e f f o r t t o s a t u r a t e t h e p o l y m e r s , and thus make them i n s o l u b l e i n t h e a c i d . Attempts have a l s o been made t o conduct t h e a l k y l a t i o n under hydrogen p r e s s u r e . V a r i o u s s o l v e n t s have been used t o t r y t o e x t r a c t the s o l u b l e o r c h e m i c a l l y bound c o n j u n c t polymers from t h e used c a t a l y s t . Attempts have been made t o s e p a r a t e t h e a c i d from the c o n j u n c t polymers by c r y s t a l l i z a t i o n o f t h e a c i d , and washing o f t h e polymers from t h e a c i d c r y s t a l s . T h i s work was p r o m i s i n g and a l a r g e p i l o t u n i t was o p e r a t e d . A paper on t h e p r o c e s s by Mr. S. Robert S t i l e s i s s c h e d u l e d f o r t h i s Symposium ( 2 ) . Background f o r SARP One l i n e o f a t t a c k , which i s the s u b j e c t o f t h i s p a p e r , i s t o c o n v e r t t h e s u l f u r i c a c i d i n the used c a t a l y s t t o d i a l k y l s u l f a t e s , which a r e s o l u b l e i n h y d r o c a r b o n s , and then e x t r a c t the d i a l k y l s u l f a t e s from the c o n j u n c t polymers and w a t e r . Cons i d e r a b l e background i n f o r m a t i o n was a v a i l a b l e p r i o r t o the l a t e 1950's when a s t u d y was s t a r t e d w i t h t h e s p e c i f i c o b j e c t i v e o f d e v e l o p i n g such a r e c o v e r y p r o c e s s . When i t i s c o n s i d e r e d t h a t s u l f u r i c a c i d had a net c o s t o f not o v e r about one c e n t per pound, o r $20.00 per t o n , and a n e t c o s t i n a l k y l a t i o n o f about 0 . 4 t o 0 . 6 c e n t s per g a l l o n o f a l k y l a t e , and t h a t o n l y 5% o r l e s s o f the a c i d was l o s t i n c o n v e n t i o n a l r e c o v e r y p r o c e s s e s , i t was r e a l i z e d t h a t any new r e c o v e r y p r o c e s s would have t o have low c a p i t a l and o p e r a t i n g c o s t s , and h i g h y i e l d s , i f i t were t o be c o m p e t i t i v e s t r i c t l y on a s a v i n g s i n a c i d c o s t . Some o f the background i n f o r m a t i o n gave hope t h a t not o n l y c o u l d such a p r o cess be i n t e g r a t e d w i t h an a l k y l a t i o n u n i t , b u t by u s i n g such a p r o c e s s , an improved a l k y l a t e o f h i g h e r octane v a l u e and lower end p o i n t c o u l d be made. S i n c e t h i s g e n e r a l l i n e o f a t t a c k i s an e x c i t i n g and c h a l l e n g i n g f i e l d f o r c h e m i s t s and c h e m i c a l e n g i n e e r s , and s i n c e such a p r o c e s s i s o f i n t e r e s t t o most o i l companies and many chemical companies f o r commercial o p e r a t i o n , some o f t h e background i n f o r m a t i o n w i l l be d i s c u s s e d b r i e f l y . S u l f u r i c a c i d and o l e f i n s a r e an i n t r i g u i n g p a i r i n t h a t v a s t l y d i f f e r e n t r e s u l t s may be o b t a i n e d depending on the r e a c t i o n c o n d i t i o n s , the p a r t i c u l a r a c i d s t r e n g t h and the o l e f i n involved. Up t o about 1932 one o f t h e most w i d e l y used a n a l y t i c a l methods f o r t h e a n a l y s i s o f o l e f i n m i x t u r e s was the O r s a t

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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analysis. The o l e f i n m i x t u r e i n gaseous form was passed through progressively stronger s u l f u r i c a c i d . T h u s , i s o b u t y l e n e was removed by 62.5% a c i d , p r o p y l e n e and n-butenes by 82.5% a c i d , and e t h y l e n e by 8% fuming a c i d . C o n s i d e r a b l e work was done by many o i l companies on the s o c a l l e d 2-stage a l k y l a t i o n process ( 3 ) . T h i s p r o c e s s had c o n s i d e r a b l e a p p e a l , s i n c e i t o f f e r e d a p o s s i b l e means o f r e d u c i n g t h e amount o f f r a c t i o n a t i o n r e q u i r e d i n a l k y l a t i o n , and f r a c t i o n a t i o n was the most e x p e n s i v e p a r t o f a l k y l a t i o n . In a d d i t i o n t o p i l o t u n i t work, s e v e r a l p l a n t t r i a l s were made. In t h i s p r o c e s s o l e f i n was absorbed i n used o r r e c y c l e a l k y l a t i o n a c i d , the i n e r t s and p a r a f f i n hydrocarbons e l i m i n a t e d i n the a b s o r p t i o n s t e p , and the a c i d - o l e f i n m i x t u r e c o n t a i n i n g t h e c a t a l y s t contaminants charged t o a l k y l a t i o n . The e l i m i n a t i o n o f i n e r t s r e s u l t e d i n a h i g h e r o c t a n e p r o d u c t and a r e d u c t i o n i n t h e amount o f f r a c t i o n a t i o n r e q u i r e d f o r the r e c y c l e o f i s o b u t a n e . However, a weakness i n the p r o c e s s was t h a t i t r e s u l t e d i n a c o n s i d e r a b l y h i g h e r a c i d consumption. One o t h e r weakness o r c o m p l i c a t i o n was t h a t when t h e a b s o r p t i o n s t e p was c a r r i e d o u t a t a f a i r l y h i g h c o n v e r s i o n o f the a c i d to e s t e r s i n the l i q u i d phase, a c o n s i d e r a b l e amount o f the n e u t r a l e s t e r s o r d i a l k y l s u l f a t e s ended up i n t h e h y d r o c a r b o n l i q u i d , r a t h e r than i n t h e a c i d . Fractionation is s t i l l an e x p e n s i v e p a r t o f a l k y l a t i o n i n c a p i t a l and o p e r a t i n g costs. However, i t i s n o t as e x p e n s i v e as o r i g i n a l l y , s i n c e t h e i n t r o d u c t i o n o f e f f l u e n t r e f r i g e r a t i o n ( 4 , 5 ) i n about 1953 and i s o s t r i p p i n g i n about 1956. Both o f t h e s e schemes r e s u l t i n a s m a l l e r d e i s o b u t a n i z e r and a lower o p e r a t i n g c o s t f o r f r a c t i o n a t i o n to f u r n i s h r e c y c l e isobutane. I t was found i n the e a r l y a l k y l a t i o n work t h a t v a r i o u s o l e f i n e s t e r s c o u l d be used i n p l a c e o f o l e f i n s t o a l k y l a t e i s o butane w i t h a s t r o n g H2SO4 c a t a l y s t . I t was a l s o known t h a t d i e t h y l s u l f a t e was an a c c e p t e d e t h y l a t i n g agent i n the c h e m i c a l industry. B e f o r e the days o f t h e s o p h i s t i c a t e d mechanisms such as t h o s e b e i n g p r e s e n t e d i n t h i s Symposium, i t was t h o u g h t t h a t p r o b a b l y t h e o l e f i n f i r s t formed an a l k y l s u l f a t e b e f o r e r e a c t i n g with isobutane. In a l k y l a t i o n , r e a c t i o n c o n d i t i o n s were s e l e c t e d so as t o keep t h e c o n c e n t r a t i o n o f t h e a l k y l s u l f a t e s low. It was s t a n d a r d p r o c e d u r e i n b a t c h l a b o r a t o r y work t o have a f i n i s h i n g p e r i o d , t h a t i s , a p e r i o d a t t h e end o f a run under a l k y l a t i o n c o n d i t i o n s e x c e p t t h a t no o l e f i n was c h a r g e d . E s p e c i a l l y w i t h p r o p y l e n e as t h e o n l y o l e f i n , o r i n a h i g h c o n c e n t r a t i o n i n the o l e f i n f e e d , i t was d i f f i c u l t t o g e t good enough a l k y l a t i o n c o n d i t i o n s so t h a t the a l k y l s u l f a t e c o n c e n t r a t i o n would not become t o o h i g h i n t h e r e a c t i o n m i x t u r e . And even today sometimes i n commercial a l k y l a t i o n n e u t r a l e s t e r s end up i n t h e a l k y l a t e l e a v i n g the r e a c t o r . T h i s has been shown by a n a l y s i s , and i n some c a s e s by a t e m p e r a t u r e r i s e i n t h e s e t t l e r , d e c o m p o s i t i o n i n the f r a c t i o n a t i o n s y s t e m , and poor l e a d s u s c e p t i b i l i t y o f the a l k y l a t e . N e u t r a l e s t e r s are n o t removed from

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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a l k y l a t e by the u s u a l c a u s t i c washing t r e a t m e n t , and t h a t i s t h e main r e a s o n some p l a n t s use b a u x i t e t r e a t i n g o f a l k y l a t e . Numerous p a t e n t s have been i s s u e d on v a r i o u s phases o f an a c i d r e c o v e r y p r o c e s s i n v o l v i n g the a b s o r p t i o n o f o l e f i n s i n r e c y c l e o r used a l k y l a t i o n c a t a l y s t , e x t r a c t i o n o f t h e d i a l k y l s u l f a t e s , and c h a r g i n g o f t h e d i a l k y l s u l f a t e e x t r a c t , a f t e r treatment with H S 0 , to a l k y l a t i o n . R e f e r e n c e w i l l be made t o t h o s e o f p a r t i c u l a r i n t e r e s t i n l a t e r s e c t i o n s o f the p a p e r . The o t h e r s w i t h which t h e a u t h o r i s f a m i l i a r a r e i n c l u d e d i n the L i t e r a t u r e C i t e d f o r convenience ( 6 - 1 6 ) . In t h e November 1965 Hydrocarbon P r o c e s s i n g and P e t r o l e u m R e f i n e r (17)» i t was i n d i c a t e d t h a t the f i r s t commercial p l a n t f o r such a p r o c e s s was b e i n g i n s t a l l e d by C i t i e s S e r v i c e f o r s t a r t - u p i n l a t e 1966, under l i c e n s e from Texaco Development C o r p o r a t i o n . A s t a f f a r t i c l e on the p r o c e s s i n t h e J a n u a r y 2, 1967 O i l and Gas J o u r n a l , (18), was a p p a r e n t l y based on t h r e e p a t e n t s i s s u e d up t o t h a t t i m e ( 1 9 - 2 1 ) . A second commercial p l a n t by Humble O i l & R e f i n i n g Co. went i n t o o p e r a t i o n i n 1969 ( 2 2 ) . To c o n f i r m some o f the above t y p e s o f i n f o r m a t i o n and t o get some q u a n t i t a t i v e d a t a on the a b s o r p t i o n o f p r o p y l e n e and b u t y l è n e s i n r e c y c l e a l k y l a t i o n a c i d , and t h e s o l u b i l i t y o f d i i s o p r o p y l s u l f a t e and d i i s o b u t y l s u l f a t e s i n h y d r o c a r b o n s , some fundamental work, u n p u b l i s h e d , was done by Midwest Research I n s t i t u t e i n Kansas C i t y , M i s s o u r i , i n t h e e a r l y I 9 6 0 ' s f o r Texaco Development C o r p o r a t i o n . I t seemed q u i t e c l e a r from the a l k y l a t i o n p r o c e s s i t s e l f , and some o f the attempts t o e x t r a c t the c o n j u n c t polymer from t h e used a l k y l a t i o n c a t a l y s t , t h a t t h e polymers c o u l d n o t be ext r a c t e d from the s t r o n g s u l f u r i c a c i d , such as used a l k y l a t i o n catalyst. However, t h e r e was no a s s u r a n c e t h a t t h i s would be the case when the a c i d became weak as a r e s u l t o f most o f t h e a c i d being converted to d i a l k y l s u l f a t e . A number o f d i f f e r e n t p r o c e s s e s i n v o l v i n g t h e a b s o r p t i o n o f olefin in recycle sulfuric acid alkylation catalyst, extraction o f t h e d i a l k y l s u l f a t e , t r e a t m e n t o f the e x t r a c t i n some manner, and a l k y l a t i o n o f t h e t r e a t e d d i a l k y l s u l f a t e have been c o n sidered. One such p r o c e s s which has become known i n t h e i n d u s t r y as SARP i s the s u b j e c t o f t h i s p a p e r . SARP s t a n d s f o r S u l f u r i c A c i d Recovery P r o c e s s , which o b v i o u s l y has a r a t h e r g e n e r i c c o n notation. The p r o c e s s i s r a t h e r s p e c i f i c . The w r i t e r p r e f e r s t h e name o r i g i n a l l y g i v e n t o t h e p r o c e s s , namely, E x t r a c t y l a t i o n . However, SARP has t h e advantage o f b e i n g known and i s s h o r t , so SARP w i l l p r o b a b l y p r e v a i l . The i n f o r m a t i o n m a r s h a l l e d and a c q u i r e d i n c o n n e c t i o n w i t h the development o f SARP has been q u i t e h e l p f u l i n g e t t i n g a b e t t e r understanding of H S 0 a l k y l a t i o n i t s e l f . This i s part i c u l a r l y t r u e f o r such a r e a s as r u n - a w a y s , poor l e a d s u s c e p t i b i l i t y o f a l k y l a t e , t r e a t i n g p r o c e d u r e s f o r crude a l k y l a t e , the importance o f low w a t e r c o n t e n t c a t a l y s t and what c o n s t i t u t e s good m i x i n g o r a g i t a t i o n . 2

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Experimental From e a r l y work done f o r o t h e r p u r p o s e s , i t seemed c e r t a i n t h a t a t l e a s t q u a l i t a t i v e l y o l e f i n s c o u l d be absorbed i n r e c y c l e s u l f u r i c a c i d a l k y l a t i o n c a t a l y s t , the r e s u l t i n g d i a l k y l s u l f a t e s e x t r a c t e d w i t h i s o b u t a n e and a l k y l a t e d . E v i d e n c e as t o what would happen t o t h e c o n j u n c t polymer p r e s e n t i n t h e r e c y c l e a c i d and t h e a d d i t i o n a l c o n j u n c t polymer formed i n t h e a b s o r p t i o n s t e p when t h e a c i d phase o f t h e a b s o r p t i o n m i x t u r e was e x t r a c t e d w i t h i s o b u t a n e was m i s s i n g . T h e r e was some c o n c e r n t h a t the c o n j u n c t p o l y m e r , o r a t l e a s t p a r t o f i t , would a l s o be e x t r a c t e d by t h e isobutane. I t was c o n f i r m e d i n t h e work a t Midwest Research t h a t p r o p y l e n e c o u l d be r e a c t e d w i t h r e c y c l e a l k y l a t i o n a c i d t o g i v e a h i g h y i e l d o f d i i s o p r o p y l s u l f a t e ( D I P S ) , and t h a t t h e DIPS c o u l d be e x t r a c t e d w i t h hydrocarbon s o l v e n t s , i n c l u d i n g i s o butane. The i s o p r o p y l a c i d s u l f a t e (IPS) i s q u i t e i n s o l u b l e i n h y d r o c a r b o n s and o n l y a s m a l l amount i s e x t r a c t e d a l o n g w i t h t h e DIPS. S i n c e t h e r e a c t i o n o f p r o p y l e n e w i t h s u l f u r i c a c i d i s an e q u i l i b r i u m r e a c t i o n , some IPS i s always p r e s e n t . I t was found t h a t some o f t h e c o n j u n c t polymer i s a l s o e x t r a c t e d w i t h t h e DIPS. I t was a n t i c i p a t e d t h a t t h e water would s t a y i n t h e a c i d phase o r r a f f i n a t e , and t h i s was found t o be t h e c a s e . I t was f a i r l y o b v i o u s t h a t some method had t o be d i s c o v e r e d t o remove t h e c o n j u n c t polymer from t h e i s o b u t a n e - D I P S e x t r a c t i f i t were t o be charged t o an a l k y l a t i o n u n i t . I t was found t h a t t h e polymer r e a c t s q u a n t i t a t i v e l y w i t h s t r o n g s u l f u r i c a c i d (19,21 ),such as f r e s h 98% a c i d o r r e c y c l e a l k y l a t i o n c a t a l y s t . About an equal w e i g h t o r 50% by volume o f t h e a c i d i n r e l a t i o n t o t h e c o n j u n c t polymer i s r e q u i r e d . The a c i d - p o l y m e r complex forms e a s i l y and q u i c k l y m e r e l y by hand s h a k i n g i n a c e n t r i f u g e tube a t room t e m p e r a t u r e . The complex i s a heavy but f a i r l y f r e e f l o w i n g , v i s c o u s l i q u i d a t room t e m p e r a t u r e . I t may be s e p a r a t e d by g r a v i t y s e t t l i n g . I t i s i n s o l u b l e i n hydrocarbons such as i s o b u t a n e , and s o l u b l e i n H0SO4. DIPS a p p a r e n t l y i s not s o l u b l e i n the complex. However, i f e x c e s s a c i d i s used, some DIPS w i l l d i s s o l v e i n t h e a c i d and a c i d complex. IPS i s a l s o s o l u b l e i n t h e e x c e s s a c i d and a c i d complex. T h u s , the t h r e e s t e p p r o c e s s o f a b s o r p t i o n , e x t r a c t i o n and a l k y l a t i o n became a f o u r s t e p p r o c e s s o f a b s o r p t i o n , e x t r a c t i o n , a c i d t r e a t m e n t o f t h e e x t r a c t , and a l k y l a t i o n . I t was c o n c l u d e d from the r e s u l t s o f t h e work a t Midwest Research and t h e l a t e r work on the removal o f c o n j u n c t polymer from t h e e x t r a c t w i t h H S 0 t h a t a l l f o u r s t e p s were o p e r a b l e . An economic s t u d y i n d i c a t e d t h a t t h e p r o c e s s would be a t t r a c t i v e i f about 90% o f the a c i d i n t h e used a l k y l a t i o n c a t a l y s t c o u l d be c o n v e r t e d t o DIPS, and about 90% o f the DIPS e x t r a c t e d and alkylated. T h i s amounted t o an 80% r e c o v e r y o f t h e a c i d , and a corresponding r e d u c t i o n i n a c i d consumption. In o r d e r t o o b t a i n q u a n t i t a t i v e d a t a on t h e i n d i v i d u a l s t e p s 2

4

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

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17.

GOLDSBY

SARP

289

and o v e r a l l y i e l d s , a b r i e f p i l o t u n i t s t u d y was c a r r i e d out by Texaco Development C o r p o r a t i o n and S t r a t f o r d E n g i n e e r i n g C o r p o r a t i o n i n Kansas C i t y , M i s s o u r i . To e x p e d i t e t h e s t u d y , a v a i l a b l e S t r a t c o C o n t a c t o r s were used f o r the a b s o r p t i o n , a c i d t r e a t i n g and a l k y l a t i o n s t e p s . U s i n g Texaco Development's s o l v e n t r e f i n i n g e x p e r i e n c e , a R o t a t i n g D i s c C o n t a c t o r (RDC) was used f o r the e x t r a c t i o n s t e p . The SARP f l o w i n s i m p l i f i e d form i s shown i n F i g u r e 1. The SARP f l o w as used i n t h e p i l o t u n i t i s shown i n F i g u r e 2. and d e s c r i b e d i n d e t a i l i n U . S . P a t . 3 , 8 0 3 , 2 6 2 ( 2 3 ) . In the f o l l o w i n g example, t h e f e e d s t o c k s shown i n T a b l e 1 were employed i n t h e a p p a r a t u s o f F I G . 2. TABLE I Feed S t o c k s In w e i g h t

Isobutane Ethane Propylene Propane Isobutane n-Butane Isobutylene Butylene-1 Butylene-2 Pentanes Total

6.9 91.1 2.0

100.0

percent

Propanepropylene

Butanebutylène

0.4 62.3 33.7 3.6

100.0

0.1 2.7 34.6 11.0 15.9 9.5 22.9 3.3 100.0

10 c c . p e r minute o f used a l k y l a t i o n a c i d from the s e t t l e r 39 t i t r a t i n g 91.0% was c h a r g e d t o a b s o r b e r 12 a t about 25° F. F r e s h p r o p a n e - p r o p y l e n e f e e d a t t h e r a t e o f 4 5 . 0 c c . per minute was c h a r g e d t o a b s o r b e r 11 a t about 30° F. U n r e a c t e d propanep r o p y l e n e from a b s o r b e r 11 s e p a r a t e d i n s e t t l e r 23 was c h a r g e d t o a b s o r b e r 12. The h y d r o c a r b o n phase o r u n r e a c t e d propanep r o p y l e n e from a b s o r b e r 12 s e p a r a t e d i n s e t t l e r 14 c o m p r i s e d 11.8% d i p r o p y l s u l f a t e . The a c i d phase from a b s o r b e r 11 s e p a r a t e d i n s e t t l e r 23 c o m p r i s i n g 80.6% d i p r o p y l s u l f a t e and 15.3% p r o p y l a c i d s u l f a t e was passed a t a r a t e o f 2 4 . 2 c c . per minute t o a r o t a t i n g d i s c c o n t a c t o r e x t r a c t o r 33 near t h e t o p . 315.0 c c . p e r m i n u t e o f t h e i s o b u t a n e f e e d was c h a r g e d t o t h e r o t a t i n g d i s c c o n t a c t o r near the bottom. A temperature g r a d i e n t was m a i n t a i n e d i n t h e e x t r a c t o r , t h e bottom temperature b e i n g about 55° F and the top t e m p e r a t u r e about 65° F. Overhead from t h e e x t r a c t o r c o m p r i s i n g 83.8% i s o b u t a n e , 5.7 d i p r o p y l s u l f a t e , and

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

Olefin Feed

Used Alkylation Add ^

Xi

iscard dd

Alkylate

Settler

Used Alkvlatlon Add

Fresh Add

Flowsheet for SARP (simplified)

R

ο ο ε

Recycle Add

Alkylatlon Reactor

Isobutane Dialkyl Sulfate

Add Trbater

Figure 1.

Isobutane

*-

C H HS0„ 3 7 4

ί

Wz

i 3 7>2 C

H

S

S

°4

°4

As may be seen i n F i g u r e 2, the S t r a t c o C o n t a c t o r s were o p e r a t e d so as t o g e t p a r t o f the advantage o f c o u n t e r c u r r e n t flow. The c o n t a c t o r s g i v e good m i x i n g and c o n t a c t o f the o l e f i n feed with the a c i d . I n t i m a t e m i x i n g o f t h e o l e f i n f e e d and a c i d is desirable. An e x c e s s o f o l e f i n , low water c o n t e n t o f a c i d , and removal o f d i a l k y l s u l f a t e from the a c i d phase o f the a b s o r p t i o n r e a c t i o n m i x t u r e f a v o r a h i g h c o n v e r s i o n o f the a c i d t o d i a l k y l sulfate. T h i s p r o b a b l y can be a c c o m p l i s h e d b e s t i n a t r u l y c o u n t e r c u r r e n t o p e r a t i o n i n l i q u i d p h a s e , such as i n a t o w e r . I t w i l l be noted from t h e f l o w o f F i g u r e 2 t h a t t h e u n ­ r e a c t e d o l e f i n stream from t h e weaker a c i d a b s o r b e r 11 i s sent to the s t r o n g e r a c i d a b s o r b e r 12. Then t h e u n r e a c t e d o l e f i n stream from s t r o n g e r a c i d a b s o r b e r 12 i s s e n t d i r e c t l y t o a l k y l a t i o n . T h i s f l o w under t h e p r o p e r c o n d i t i o n s p r o b a b l y i n s u r e s t h a t no c o n j u n c t p o l y m e r , or v e r y l i t t l e , i s s e n t t o a l k y l a t i o n i n the u n ­ reacted o l e f i n stream. I t a l s o e n a b l e s a l l o f the o l e f i n not r e ­ a c t e d i n the a b s o r p t i o n s t e p t o be u t i l i z e d i n a l k y l a t i o n . However, t h e u n r e a c t e d o l e f i n stream from weaker a c i d a b s o r b e r 11 may be s u b s t a n t i a l l y s a t u r a t e d w i t h DIPS, and when t h i s stream i s s e n t t o s t r o n g e r a c i d a b s o r b e r 1 2 , i t tends t o r e t a r d t h e e x t e n t o f c o n v e r s i o n o f a c i d and/or a c i d p r o p y l s u l f a t e t o DIPS. Ignor­ i n g the p o s s i b i l i t y t h a t the u n r e a c t e d o l e f i n stream from weaker a c i d a b s o r b e r 11 may c o n t a i n c o n j u n c t p o l y m e r , and j u s t c o n s i d e r ­ i n g the c o n v e r s i o n o f a c i d t o DIPS, i t would be b e t t e r t o send the unreacted o l e f i n d i r e c t l y to a l k y l a t i o n . E i t h e r l i q u i d phase o r vapor phase a b s o r p t i o n , or a com­ b i n a t i o n o f the two may be u s e d . L i q u i d phase was used commer­ cially. As i n a l k y l a t i o n , t h e time r e q u i r e d f o r t h e a b s o r p t i o n s t e p i s d e t e r m i n e d l a r g e l y by t h e c o o l i n g r e q u i r e d and the e f f i c i e n c y of the c o n t a c t i n g . The two c o n t a c t o r s used i n the p i l o t u n i t gave a c o n t a c t or r e s i d e n c e time o f about one hour i n each c o n t a c t o r , which i s p r o b a b l y f a r i n e x c e s s o f what i s needed. A temperature o f 35-40° F was used c o m m e r c i a l l y . In some l a t e r p i l o t u n i t work b e t t e r r e s u l t s were o b t a i n e d a t 50° F. However, the s o l u b i l i t y o f DIPS i n hydrocarbons i s much h i g h e r a t 50° F than a t 35° F, and t h i s may a c c o u n t f o r a h i g h e r c o n v e r s i o n a t 50° F. Conjunct p o l y m e r i z a t i o n s h o u l d be kept t o a minimum, as i t r e p r e s e n t s a l o s s o f o l e f i n and a c i d . Retardation of conjunct p o l y m e r i z a t i o n i s f a v o r e d by a low t e m p e r a t u r e , as i n a l k y l a t i o n , e s p e c i a l l y i n t h a t p o r t i o n o f the a b s o r b e r w i t h t h e s t r o n g e s t

Albright and Goldsby; Industrial and Laboratory Alkylations ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

296

INDUSTRIAL

A N D

L A B O R A T O R Y

A L K Y L A T I O N S

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a c i d , such as t h e upper p o r t i o n o f a c o u n t e r c u r r e n t t o w e r . A s h o r t r e s i d e n c e time and e f f i c i e n t m i x i n g p r o b a b l y a l s o f a v o r minimum c o n j u n c t p o l y m e r i z a t i o n . U s u a l l y t h e r e i s no d i f f i c u l t y i n s e p a r a t i n g t h e a c i d and hydrocarbon phases i n a g r a v i t y s e t t l e r , e s p e c i a l l y i f the temp e r a t u r e o f the s e t t l e r i s c o n t r o l l e d . I f any d i f f i c u l t y i s e n c o u n t e r e d , i t may be s o l v e d by a d d i n g i s o b u t a n e t o the a b s o r p t i o n m i x t u r e , or by c o o l i n g t h e a b s o r p t i o n m i x t u r e t o about 4 0 - 5 0 " F. I f c o o l i n g i s n o t p r o v i d e d i n t h e s e t t l e r , the t e m p e r a t u r e may r i s e , a p p a r e n t l y due t o c o n t i n u e d r e a c t i o n , as o f t e n i s the c a s e in the a l k y l a t i o n s e t t l e r s in propylene a l k y l a t i o n . Extraction. Solvent e x t r a c t i o n processes are u s u a l l y f a i r l y e x p e n s i v e because o f the c o s t i n r e c o v e r i n g t h e s o l v e n t , such as by h e a t i n g or c h i l l i n g , and u s u a l l y w i t h some l o s s o f s o l v e n t . In SARP we have a u n i q u e and q u i t e f a v o r a b l e s i t u a t i o n . The s o l v e n t i s a r e c y c l e stream o f i s o b u t a n e from t h e a l k y l a t i o n s e c t i o n , w h i c h , a f t e r i t i s used t o e x t r a c t DIPS, i s r e t u r n e d a l o n g w i t h t h e DIPS t o a l k y l a t i o n , where t h e i s o b u t a n e i s p r o c e s s e d as u s u a l in a l k y l a t i o n . As w i l l be n o t e d i n F i g u r e 2 , i s o b u t a n e from the p r o d u c t r e c o v e r y f a c i l i t i e s o r d e i s o b u t a n i z e r was used c o m m e r c i a l l y . This i s a v e r y l a r g e stream and i s adequate i n q u a n t i t y . C o u n t e r c u r r e n t o p e r a t i o n and e f f i c i e n t c o n t a c t i n g w i t h i n t h e e x t r a c t o r , a h i g h s o l v e n t d o s a g e , and a t e m p e r a t u r e above about 40° F f a v o r complete e x t r a c t i o n o f the d i a l k y l s u l f a t e . DIPS i n creases in s o l u b i l i t y in isobutane with i n c r e a s i n g temperature. A temperature o f about 50° F was used c o m m e r c i a l l y w i t h a R o t a t i n g D i s c C o n t a c t o r (RDC). The optimum RPM o f the e x t r a c t o r was n o t determined. The volume r a t i o o f i s o b u t a n e t o DIPS s h o u l d be 6 o r higher. A h i g h s o l v e n t dosage a l s o f a v o r s a good s e p a r a t i o n o f the e x t r a c t from the r e a f f i n a t e i n t h e s e t t l e r . A l t h o u g h t h e DIPS seems q u i t e s t a b l e i n i s o b u t a n e s o l u t i o n , i t i s p r o b a b l y a d v a n tageous t o o p e r a t e a t about 50° F r a t h e r than a t about 100° F. The aim o r i d e a l i n the e x t r a c t i o n s t e p i s t o remove a l l o f t h e a v a i l a b l e HpSO, i n the used a l k y l a t i o n c a t a l y s t as DIPS and I P S , and t o l e a v e a l l o f the c o n j u n c t polymer and water i n t h e raffinate. J u s t how near t h e i d e a l i s r e a l i z e d depends on the e f f i c i e n c y o f t h e a b s o r p t i o n s t e p , as w e l l as the e x t r a c t i o n s t e p . I t was o r i g i n a l l y a n t i c i p a t e d t h a t s u b s t a n t i a l l y a l l o f t h e water would s t a y i n the r a f f i n a t e , and no e v i d e n c e o r d a t a have been developed to i n d i c a t e o t h e r w i s e . In g e n e r a l , a low water c o n t e n t and a low c o n v e r s i o n o f a c i d to DIPS f a v o r r e t e n t i o n o f the p o l y mer i n t h e r a f f i n a t e . A r e l a t i v e l y h i g h water c o n t e n t and a h i g h c o n v e r s i o n o f the a c i d t o DIPS f a v o r removal o f polymer i n t h e extract. The r a f f i n a t e o r s p e n t a c i d from t h e e x t r a c t i o n s t e p comp r i s e s w a t e r , a l k y l a c i d s u l f a t e , d i a l k y l s u l f a t e , and t h e c o n j u n c t polymers ( p r o b a b l y a s s o c i a t e d w i t h a c i d ) formed i n t h e a l k y l a t i o n , a b s o r p t i o n and a c i d t r e a t i n g s t e p s . The e x t r a c t comp r i s e s t h e i s o b u t a n e s o l v e n t , d i a l k y l s u l f a t e , a r e l a t i v e l y small

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17.

GOLDSBY

SARP

297

amount o f a l k y l a c i d s u l f a t e , and p a r t o f t h e c o n j u n c t p o l y m e r . The c o m p o s i t i o n o f the SARP r e j e c t a c i d or e x t r a c t o r bottoms w i l l v a r y depending on a l o t o f f a c t o r s , but f o r most o f the work w i t h l e s s than optimum c o n d i t i o n s i n t h e a b s o r p t i o n , e x t r a c t i o n and a c i d t r e a t i n g s t e p s , a f a i r l y t y p i c a l a n a l y s i s i s shown i n T a b l e 2, below. For o r i e n t a t i o n purposes an a n a l y s i s o f used a l k y l a t i o n a c i d i s a l s o shown.

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TABLE

II

SARP R e j e c t

Acid Weight

Alkylation O i l ( c o n j u n c t polymer) Water Sulfuric acid Isopropyl a c i d s u l f a t e Diisopropyl sulfate Total Sulfur Hydrocarbon i n a c i d - o i l complex and a l k y l s u l f a t e s Equivalent H S0 2

4

Acid

Percent SARP A c i d

6.0 3.0 91.0 0.0 0.0

15.0 4.6 28.0 44.8 7.6

100.0

100.0

29.7

20.7

6.0 91.0

31.9 63.5

There i s some q u e s t i o n as t o whether t h e r e i s a c t u a l l y any f r e e s u l f u r i c a c i d i n the SARP a c i d . P r o b a b l y i n most c a s e s t h e r e i s n ' t and p r e f e r a b l y t h e r e s h o u l d not be any. In most c a s e s i t i s b e l i e v e d t h a t a p p r o x i m a t e l y an equal w e i g h t o f a c i d and c o n j u n c t polymer a r e l o o s e l y t i e d up as a complex. Under more n e a r l y optimum c o n d i t i o n s i n a l l f o u r s t e p s o f the p r o c e s s , and a f t e r e q u i l i b r i u m o r s t e a d y s t a t e c o n d i t i o n s have been r e a c h e d , the water c o n t e n t p r o b a b l y would be n e a r e r 2%, o r l e s s , and t h e amount o f a l k y l s u l f a t e s would be c o n s i d e r a b l y l o w e r . The i d e a l or u l t i m a t e would be j u s t c o n j u n c t polymer and w a t e r . It should be noted t h a t t h e hydrocarbon c o n t e n t o f the SARP a c i d i s much h i g h e r than t h a t o f a l k y l a t i o n a c i d . Acid Treatment. Under most c o n d i t i o n s , some o f the c o n j u n c t polymer i s removed by the i s o b u t a n e i n the e x t r a c t i o n s t e p . Just how much and whether i t w i l l be removed depends on the s p e c i f i c c o m p o s i t i o n o f t h e a b s o r p t i o n m i x t u r e and t h e e x t r a c t i o n c o n ditions. In t h e p i l o t u n i t , r e l a t i v e l y weak make-up a c i d o f 97.5% was charged t o the a l k y l a t i o n s t e p , so the r e c y c l e a c i d charged t o t h e a b s o r b e r was r e l a t i v e l y h i g h i n w a t e r . I f f r e s h make-up a c i d o f 99.5% c o n c e n t r a t i o n , the u s u a l o r b e t t e r d r y i n g o f a l k y l a t i o n s t r e a m s , and a s t r i c t l y c o u n t e r c u r r e n t a b s o r b e r were

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u s e d , i t might v e r y w e l l not be n e c e s s a r y t o a c i d t r e a t t h e isobutane-DIPS e x t r a c t . C o m m e r c i a l l y the e x t r a c t was t r e a t e d w i t h used a l k y l a t i o n c a t a l y s t t o remove c o n j u n c t p o l y m e r , s i n c e i t was a n t i c i p a t e d t h a t q u i t e l i k e l y under the c o n d i t i o n s used some c o n j u n c t polymer would be i n the e x t r a c t . I t was shown c o n c l u s i v e l y i n a p i l o t u n i t t h a t when t h e e x t r a c t was not t r e a t e d , the f r e s h make-up a c i d o r a c i d consumption i n a l k y l a t i o n w i t h SARP was no lower than w i t h o u t SARP. F o r t u n a t e l y , used o r d i s c a r d a l k y l a t i o n c a t a l y s t i s s a t i s f a c t o r y f o r the a c i d t r e a t m e n t , and o n l y a s m a l l amount i s r e quired. U s u a l l y about 0 . 0 5 pound p e r g a l l o n o f a l k y l a t e was a r b i t r a r i l y used c o m m e r c i a l l y . S i n c e o p e r a t i n g c o n d i t i o n s i n comm e r c i a l o p e r a t i o n v a r y from day t o d a y , and a n a l y t i c a l t e s t s a r e o f t e n slow and i n f r e q u e n t , an e x c e s s o f a c i d was u s u a l l y u s e d . As i n d i c a t e d e a r l i e r , an e x c e s s o f a c i d causes s o l u t i o n o f DIPS i n the a c i d . T h u s , t o r e c o v e r the DIPS i n the e x c e s s a c i d , the r a f f i n a t e o r a c i d phase from the a c i d t r e a t m e n t s t e p was s e n t t o the extractor. In r e f i n e r i e s o r a r e a s i n which two o r more a l k y l a t i o n u n i t s are o p e r a t e d , one SARP u n i t l a r g e enough t o p r o c e s s the used a l k y l a t i o n a c i d from a l l o f the a l k y l a t i o n u n i t s c o u l d be i n s t a l l e d . The r e c o v e r e d a c i d i n t h e form o f i s o b u t a n e - D I P S e x t r a c t c o u l d be s e n t t o t h e v a r i o u s a l k y l a t i o n u n i t s as needed o r d e s i r e d . Such a l a r g e r SARP u n i t would not o n l y have a lower c o s t per u n i t o f c a p a c i t y , b u t would a l s o have a d d i t i o n a l advantages i f f u r t h e r p r o c e s s i n g o f t h e SARP r e j e c t a c i d were c a r r i e d o u t p r i o r to c o n ventional recovery. Alkylation. In g e n e r a l t h e c o n d i t i o n s f o r a l k y l a t i o n a r e , o r may b e , the same w i t h o r w i t h o u t SARP. A good d i s c u s s i o n o f t h e c o n d i t i o n s and v a r i a b l e s i n a l k y l a t i o n i s g i v e n i n t h e paper by Mr. O r l a n d o Webb ( 2 5 ) s c h e d u l e d f o r t h i s Symposium. Only t h o s e c o n d i t i o n s which have some unique o r p e c u l i a r r e l a t i o n t o SARP w i l l be d i s c u s s e d h e r e i n . About t h r e e f o u r t h s o f the make-up a c i d charged t o a l k y l a t i o n i s i n the form o f a l k y l s u l f a t e s , and o n l y a minor p o r t i o n o r about one f o u r t h o f t h e usual 99.5% c o n c e n t r a t i o n . The c a t a l y s t i s , o r may b e , somewhat d i f f e r e n t w i t h SARP, e s p e c i a l l y as t o i t s w a t e r and c o n j u n c t polymer c o n t e n t . W i t h o u t SARP the c a t a l y s t u s u a l l y c o n t a i n s about 2.5-5.0% w a t e r . With SARP the water c o n t e n t s h o u l d u s u a l l y be i n t h e 0.5-2.0% r a n g e . A low w a t e r c o n t e n t o f t h e c a t a l y s t i s b e l i e v e d t o be d e s i r a b l e ( 2 6 ) . If less drying o f f e e d s t o c k s i n SARP were p r a c t i c e d , the w a t e r c o n t e n t o f the c a t a l y s t might be as h i g h as w i t h o u t SARP. A l a r g e excess o f i s o b u t a n e i s u s e d , e . g . , as much as 60-80% by volume o f t h e h y d r o c a r b o n s i n the a l k y l a t i o n r e a c t i o n m i x t u r e . C o n s e q u e n t l y , a l a r g e q u a n t i t y o f i s o b u t a n e must be r e c o v e r e d and recycled. I t i s a l s o a v a i l a b l e f o r SARP. The i s o b u t a n e c o n c e n t r a t i o n i s one o f the most i m p o r t a n t v a r i a b l e s , as f a r as q u a l i t y o f p r o d u c t and a c i d consumption are c o n c e r n e d . A high c o n c e n t r a t i o n o f i s o b u t a n e tends t o promote a l k y l a t i o n and

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suppress conjunct p o l y m e r i z a t i o n . The i s o b u t a n e c o n c e n t r a t i o n can be i n c r e a s e d by a d d i n g more i s o b u t a n e , o r by r e d u c i n g t h e amount o f i n e r t s , such as propane and n - b u t a n e . In a d d i t i o n t o the p a r t i c u l a r d e s i g n o f t h e a l k y l a t i o n r e a c t o r and the amount o f horsepower g o i n g i n t o t h e m i x i n g , t h e m i x i n g and a l k y l a t i o n r e s u l t s a r e u s u a l l y improved by having 50% o r more by volume o f a c i d c a t a l y s t i n the e m u l s i o n so t h a t the a c i d i s i n the c o n t i n u o u s p h a s e . Recycle o f emulsion c o n t a i n i n g 20-35% hydrocarbon r a t h e r than f l a t a c i d from t h e s e t t l e r t o t h e r e a c t o r a l s o h e l p s t h e m i x i n g and g i v e s improved r e s u l t s , as would be e x p e c t e d . T h i s i s e s p e c i a l l y t r u e a t h i g h t h r o u g h put o r space v e l o c i t y * , e . g . , 0.5 or h i g h e r , or w i t h high p r o p y l e n e c o n tent feeds. I t w i l l be r e c o g n i z e d t h a t r e c y c l e o f e m u l s i o n a l s o i s i n e f f e c t a way o f r e t u r n i n g i s o b u t a n e t o the a l k y l a t i o n r e a c t o r w i t h o u t r e s o r t i n g to f r a c t i o n a t i o n . Lower temperatures down t o about 30° F f a v o r l o w e r a c i d c o n sumption and h i g h e r q u a l i t y p r o d u c t . Most commercial u n i t s a r e o p e r a t e d i n the 40-50 F, w i t h an i n c r e a s e d a c i d c o n s u m p t i o n . T h i s i s n ' t so s e r i o u s i f the used c a t a l y s t from a l k y l a t i o n i s s e n t to t h e SARP r e c o v e r y s e c t i o n . In some c a s e s , t h e s i z e o f t h e r e a c t o r i s determined by the amount o f c o o l i n g s u r f a c e r e q u i r e d f o r the design temperature. With SARP not as much c o o l i n g i s r e q u i r e d i n t h e a l k y l a t i o n r e a c t o r , s i n c e p a r t o f the heat o f the a l k y l a t i o n r e a c t i o n i s evolved in the absorption s e c t i o n . I t has been e s t i m a t e d t h a t 50% o r more o f the heat o f a l k y l a t i o n i s i n the a b s o r p t i o n s t e p . E f f i c i e n t m i x i n g o f the hydrocarbon and a c i d i s d e s i r a b l e t o keep t h e a c i d c a t a l y s t as n e a r l y s a t u r a t e d as p o s s i b l e w i t h i s o b u t a n e , and i n as high a c o n c e n t r a t i o n as p o s s i b l e . The s o l u b i l i t y of isobutane i n the a c i d c a t a l y s t increases with decreased water c o n t e n t (26) and i n c r e a s e d polymer c o n t e n t . Thus, i t should be p o s s i b l e t o have a h i g h e r c o n c e n t r a t i o n o f i s o b u t a n e i n t h e SARP a l k y l a t i o n c a t a l y s t f o r a g i v e n t i t r a t a b l e a c i d i t y , and i t s h o u l d be p o s s i b l e t o m a i n t a i n a h i g h e r c o n c e n t r a t i o n o f i s o b u t a n e i n the c a t a l y s t . Based on a s t u d y o f commercial p l a n t s some y e a r s a g o , i t was c o n c l u d e d t h a t o f t e n t h e m i x i n g was q u i t e poor i n t h a t the e m u l s i o n was not u n i f o r m . T h e r e was u s u a l l y a small amount o f good e m u l s i o n and a l o t o f poor e m u l s i o n . A major p o r t i o n o f t h e r e a c t i o n m i x t u r e was l o o s e , f a s t b r e a k i n g e m u l s i o n , and even l a r g e amounts o f u n e m u l s i f i e d hydrocarbon were p r e s e n t . The d e s i g n and o p e r a t i o n i n many c a s e s a r e s t i l l about t h e same t o d a y , and hence the m i x i n g and e m u l s i o n p r o b a b l y a r e t o o . Although p r o o f i s not a v a i l a b l e , i t i s b e l i e v e d the use o f t h e i s o b u t a n e DIPS stream as p a r t o f the hydrocarbon f e e d i n SARP h e l p s improve the m i x i n g . The p r o p y l e n e r e p r e s e n t e d by t h e DIPS amounts to

* G a l l o n s per hour o f o l e f i n alkylation reactor.

i n f e e d d i v i d e d by g a l l o n s

of acid

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10-25% o f t h e t o t a l o l e f i n f e e d t o a l k y l a t i o n . The r e s t o f t h e o l e f i n f e e d may be p r o p y l e n e , b u t y l è n e s , amylenes o r p o l y m e r s . The a c i d r e p r e s e n t e d by t h e DIPS amounts t o about 65-75% o f t h e t o t a l make-up a c i d . The a l k y l a t i o n r e a c t o r s used i n t h e p i l o t u n i t o p e r a t i o n and a l s o t h e commercial o p e r a t i o n were S t r a t c o C o n t a c t o r s . However, t h e w r i t e r knows o f no r e a s o n , and no e v i d e n c e i s a v a i l a b l e , t o i n d i c a t e t h a t any o t h e r t y p e r e a c t o r , such as t h e cascade and pump and time t a n k , would n o t be s a t i s f a c t o r y . It i s believed t h a t t h e y would g i v e a t l e a s t as good r e s u l t s w i t h SARP as w i t h o u t SARP f o r t h e same o p e r a t i n g c o n d i t i o n s and o l e f i n f e e d s t o c k , and o f c o u r s e w i t h a much lower a c i d c o n s u m p t i o n . Summary and C o n c l u s i o n s A p r o c e s s termed SARP has been d e v e l o p e d f o r t h e r e c o v e r y o f t h e used o r d i s c a r d e d c a t a l y s t from t h e a l k y l a t i o n o f i s o b u t a n e w i t h o l e f i n s u s i n g s t r o n g s u l f u r i c a c i d as t h e c a t a l y s t . The p r o c e s s was used c o m m e r c i a l l y f o r s e v e r a l y e a r s by two companies, b u t c u r r e n t l y i s n o t i n commercial o p e r a t i o n . The used c a t a l y s t i s r e a c t e d w i t h p r o p y l e n e t o c o n v e r t t h e acid to diisopropyl sulfate. The d i i s o p r o p y l s u l f a t e i s e x t r a c t e d w i t h i s o b u t a n e , t h e e x t r a c t t r e a t e d w i t h a s m a l l amount o f used c a t a l y s t , l e a v i n g a weak a c i d c o n t a i n i n g t h e c o n j u n c t polymer and w a t e r . The i s o b u t a n e e x t r a c t f r e e o f c o n j u n c t p o l y mer and w a t e r i s charged t o a l k y l a t i o n , a l o n g w i t h a d d i t i o n a l o l e f i n and f r e s h make-up a c i d . A d i s c u s s i o n o f the r e a c t i o n cond i t i o n s r e q u i r e d and t h e v a r i a b l e s i n v o l v e d i n t h e f o u r s t e p s o f the process are g i v e n . With SARP t h e n e t a c i d consumption i s reduced by about 65 t o 75%, o r t o about 0 . 2 o f a pound o f s u l f u r i c a c i d p e r g a l l o n o f alkylate. The a l k y l a t e p r o d u c t i s o f about t h e same q u a l i t y , o r perhaps somewhat b e t t e r , as a l k y l a t e produced w i t h o u t SARP. A 375° F . E . P . t o t a l a l k y l a t e had a c l e a r o c t a n e o f about 94 and 105 with 3.0 c c . o f TEL. Literature 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

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