SARP: Chemical Recovery of Used Sulfuric Acid Alkylation Catalyst

17

SARP:

Chemical

Recovery

of

Used

Sulfuric

Acid

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on June 29, 2016 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0055.ch017

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

4

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

284

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


17.

GOLDSBY

SARP

285

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



286

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

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


17.

GOLDSBY

SARP

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


287

4

2

4


288

INDUSTRIAL

A N D

L A B O R A T O R Y



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



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



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


296

INDUSTRIAL

A N D

L A B O R A T O R Y



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


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.


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



298

INDUSTRIAL

A N D

L A B O R A T O R Y


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



17.

GOLDSBY

SARP

299

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

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

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

of acid


in

INDUSTRIAL


300

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


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.

Cited

Goldsby, A. R., U.S. Pat. 2,267,458 (Dec. 23, 1941). S t i l e s , R. S., This Book, Chapter 18, 1977. Goldsby, A. R., U.S. Pat. 2,420,369 (May 13, 1947). Goldsby, A. R. and VanGundy, J . C., U.S. Pat. Re 22,146 (July 28, 1942). Goldsby, A. R. and Putney, D. H., Pet. Ref., Sept. 1955. Goldsby, A. R., U.S. Pat. 3,422,164 (Jan. 14, 1969). Goldsby, A. R., U.S. Pat. 3,428,705 (Feb. 18, 1969). Goldsby, A. R., U.S. Pat. 3,448,168 (June 3, 1969). Goldsby, A. R., U.S. Pat. 3,691,252 (Sept. 12, 1972). Goldsby, A. R., U.S. Pat. 3,742,081 (June 26, 1973). Massa, Η. Ε., U.S. Pat. 3,442,972 (May 6, 1969).


17.

12. 13. 14.


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

GOLDSBY

SARP

301

Goldsby, A. R. and Pevere, E. F., U.S. Pat. Re. 22,510 (July 4, 1944). Goldsby, A. R., Pevere, E. F., Clarke, L. A. and Hatch, G. C., U.S. Pat. 2,348,467 (May 9, 1944). Goldsby, A. R. and Clarke, L. Α., U.S. Pat. 3,000,991 (Sept. 19, 1961). Goldsby, A. R. and Gross, Η. H., U.S. Pat. 3,083,247 (March 26, 1963). DeJong, U.S. Pat. 2,381,041 (1945). Hydrocarbon Processing and Petroleum Refiner 14, (1965). O i l and Gas Journal, Jan. 2, 48 (1967). Goldsby, A. R., U.S. Pat. 3,227,774 (Jan. 4, 1966). Goldsby, A. R., U.S. Pat. 3,227,775 (Jan. 4, 1966). Goldsby, A. R., U.S. Pat. 3,234,301 (Feb. 9, 1966). Oil and Gas Journal, Jan. 2, 54 (1967). Goldsby, A.R., U.S. Pat. 3,803,262 (April 9, 1974). Goldsby, A. R., U.S. Pat. 3,683,041 (Aug. 8, 1972). Webb, O., This Book, Chapter 16, 1977. Albright, L. F., Houle, H., Sumutka, A. M. and Eckert, R. E., Ind. Eng. Chem. Proc. Dev. 11, 446, No. 3 (1972).


SARP: Chemical Recovery of Used Sulfuric Acid Alkylation Catalyst

Recommend Documents