Higher Linear Oxo Alcohols Manufacture - ACS Symposium Series

10 Higher Linear Oxo Alcohols Manufacture

Downloaded by MICHIGAN STATE UNIV on February 18, 2015 | http://pubs.acs.org Publication Date: June 15, 1981 | doi: 10.1021/bk-1981-0159.ch010

R. E. VINCENT Shell Oil Company, P.O. Box 3105, Houston, TX 77001

Most synthetic higher alcohol production today utilizes either a variation of the original Oxo technology or the Ziegler technology. This paper presents an example of the Shell process which is a modified Oxo process. This process is very flexible and with associated processes has been developed and utilized by Shell through an integrated package that yields high quality biodegradable detergent materials based on hydrocarbon distillates. This series of processes includes the following: •

Ethylene production via cracking of hydrocarbons from crude oil fractions. This process is in general use.

•

Oligomerization of ethylene to higher even carbon number alpha olefins. This is the growth part of the Shell Higher Olefin Process (SHOP) Unit.

•

Production of higher olefins from lower and higher linear alpha olefins via isomerization and disproportionation (I/D). This is the detergent olefin production part of the SHOP unit.

•

Hydroformylation of the internal olefins from the above processes to alcohols utilizing a proprietary catalyst system. This is the part covered in this paper. It can utilize many possible feed stocks, including those from the SHOP unit.

•

Ethoxylation of the alcohols to biodegradable detergent species using ethylene oxide from direct ethylene oxidation. This process is also in wide use.

The processes are flexible and efficient and the alpha olefin products from the SHOP unit can be reacted in either the SHOP I/D unit or in the hydroformylation process depending on which is most desirable. This then avoids the problem of low value byproducts. 0097-6156/81/0159-0159$05.00/0 ©

1981 American Chemical Society

In Monohydric Alcohols; Wickson, E.; ACS Symposium Series; American Chemical Society: Washington, DC, 1981.


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Some aspects of these processes are covered by patents owned by S h e l l O i l Company (±,2^,3)* The o r i g i n a l Oxo process ( o r more a c c u r a t e l y / hydroformyl a t i o n process) i s based on r e a c t i n g a mixture of 1:1 hydrogen and carbon monoxide ( s y n t h e s i s gas) w i t h an o l e f i n t o produce an aldehyde one carbon number higher than the o l e f i n . This aldehyde i s then converted t o the a l c o h o l by hydrogenation a f t e r c o b a l t c a t a l y s t removal. Disadvantages of the o r i g i n a l Oxo c o b a l t c a t a l y s t system i n c l u d e d a requirement of about 200 atmospheres p r e s s u r e , and t h a t the c a t a l y s t be decomposed and r e d i s s o l v e d f o r r e c y c l e . V a r i o u s improvements have been made i n t h i s technology by d i f f e r e n t companies. S h e l l ' s c a t a l y s t system has f i v e primary advantages over the o r i g i n a l Oxo c a t a l y s t system. These are: 1.

I t i s q u i t e s t a b l e and a f t e r crude product s e p a r a t i o n can be r e c y c l e d d i r e c t l y t o the r e a c t o r system. T h i s e l i m i n a t e s the need f o r the c a t a l y s t decomposition and r e d i s s o l v i n g s t e p s , thus e l i m i n a t i n g the a s s o c i a t e d l o s s e s , o p e r a t i n g c o s t s , and some c a p i t a l investment.

2.

I t r a p i d l y achieves e q u i l i b r i u m i s o m e r i z a t i o n of the double bond and r e a c t s the alpha o l e f i n t o a l c o h o l . T h i s allows many feed source p o s s i b i l i t i e s .

3.

I t has a h i g h hydrogenation a c t i v i t y so t h a t the main product of the r e a c t i o n system i s a l c o h o l , not aldehyde. This assures low make of heavy byproducts and minimizes a d d i t i o n a l hydrogenation requirements. I t a l s o u t i l i z e s commercially a v a i l a b l e 2:1 s y n t h e s i s gas.

4.

I t g i v e s a high r a t i o of l i n e a r t o i s o - a l c o h o l i n the product from l i n e a r feeds. This provides both d e s i r a b l e detergent p r o p e r t i e s and r a p i d b i o d e g r a d a b i l i t y .

5.

I t a l l o w s o p e r a t i o n at lower pressure, which saves both c a p i t a l investment and o p e r a t i n g c o s t s .

There are some precautions necessary i n order t o maintain good c a t a l y s t a c t i v i t y . Since i t i s a reduced metal l i g a n d complex i t i s s e n s i t i v e t o o x i d a t i o n . I t a l s o must be kept balanced f o r good performance and s t a b i l i t y . This i s achieved by a d j u s t i n g the makeup of the c a t a l y s t components. Process Scheme The r e a c t i o n p a r t of the process i s shown s c h e m a t i c a l l y i n Figure 1. I t c o n s i s t s of f e e d i n g a mixture of o l e f i n , s y t h e s i s gas and r e c y c l e ( p l u s makeup) c a t a l y s t t o a m u l t i s t a g e r e a c t o r system. The r e a c t o r product i s c o o l e d , degassed and fed t o vacuum evaporators f o r crude a l c o h o l recovery.



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The crude a l c o h o l i s d i s t i l l e d i n f a l l i n g f i l m evaporators. These u n i t s are designed t o provide very low residence time and a l s o low absolute pressures. T h i s assures low product and c a t a l y s t decomposition l o s s e s w h i l e minimizing a l c o h o l r e c y c l e , thereby m i n i m i z i n g a l c o h o l l o s s e s t o the heavy ends bleed. The evaporator bottoms can be r e c y c l e d d i r e c t l y t o t h e r e a c t i o n system w i t h only a very s m a l l bleed r e q u i r e d f o r r e j e c t i o n of c a t a l y s t decomposition products and heavy ends. The c a t a l y s t i s s t a b l e under evaporator c o n d i t i o n s . P u r i f i c a t i o n of the crude a l c o h o l takes place i n f i v e s t e p s . A schematic drawing i s shown i n F i g u r e 2. The s m a l l amounts o f e s t e r formed a r e r e v e r t e d with a c a u s t i c - t r e a t i n g p l u s water wash. D i s t i l l a t i o n i n a l i g h t ends column removes unreacted o l e f i n s , p a r a f f i n byproduct, plus other l i g h t components present i n the crude a l c o h o l . A second d i s t i l l a t i o n i s used t o remove t r a c e heavy components. Hydrogenation e l i m i n a t e s t r a c e unsaturat i o n , aldehydes, e t c . F i l t r a t i o n assures c l e a r , s o l i d s f r e e product. The process scheme i s not complicated and y i e l d s on o l e f i n feed are good. The major byproduct i s p a r a f f i n from o l e f i n hydrogenation i n t h e r e a c t o r system. However p a r a f f i n make i s low. A l s o some o l e f i n remains unconverted, some dimer i s formed, and t r a c e s of other byproducts are made. These i n c l u d e a c e t a l s , e s t e r s and d i o l s . These other l o s s e s ( e x c l u d i n g p a r a f f i n s ) t o t a l l e s s than 5%. The equipment i s almost a l l carbon s t e e l . Some a l l o y i s used, where c a u s t i c i s present, t o minimize the r i s k of s t r e s s cracking. The p a r a f f i n s made can be separated and a f t e r s u i t a b l e treatment, r e c y c l e d t o a dehydrogenation u n i t such as a c h l o r i n a t i o n - d e h y d r o c h l o r i n a t i o n u n i t t o reform the o l e f i n . T h i s improves the o v e r a l l y i e l d . Product Q u a l i t y and Uses The a l c o h o l q u a l i t y i s e x c e l l e n t . The r e a c t i o n i s c l e a n i n t h a t minimal byproducts a r e formed. The chemical cleanups w i t h c a u s t i c and l a t e r w i t h hydrogen e s s e n t i a l l y e l i m i n a t e c l o s e b o i l i n g i m p u r i t i e s . The heart c u t t i n g removes l i g h t ends and heavy end i m p u r i t i e s . The r e s i d u a l hydrocarbons are separated with the l i g h t ends, and the dimers and d i o l s w i t h the heavy ends. T y p i c a l p r o p e r t i e s of the a l c o h o l products a r e good. The a l c o h o l p u r i t y i s t y p i c a l l y above 99%. The products are c l e a r and water white. A c i d i t y , u n s a t u r a t i o n and e s t e r content are low. Residual hydrocarbons are t y p i c a l l y below 0.3%w. Some branched a l c o h o l i s produced but l i n e a r o l e f i n s y i e l d about 80% l i n e a r a l c o h o l s . The carbon number d i s t r i b u t i o n of t h e a l c o h o l w i l l be d i s p l a c e d from the o l e f i n feed d i s t r i b u t i o n by about one carbon number. O l e f i n feed c o n t a i n i n g up t o three adjacent carbon numbers can be used; more than three carbon numbers make


MONOHYDRIC ALCOHOLS

REACTORS

EVAPORATORS


X

X

SYNTHESIS GAS

1

CRUDE

'II

ALCOHOL

x Figure 1.

CAUSTIC TREATING

Alcohol reaction and recovery system

L^g^-NOS

r

HEAVY^ENDS

HYDROGENATION

LIGHT - ENDS

FILTRATION FINISHEO ALCOHOL

r ~ \ i

J

CAUSTIC WATER

( J

Figure 2.

Alcohol purification system


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p u r i f i c a t i o n d i f f i c u l t . With narrower ranges, i t i s p o s s i b l e t o switch feeds without emptying the system i f t h e product mix can be used. These a l c o h o l s are r e a d i l y e t h o x y l a t e d o r s u l f a t e d t o a c t i v e biodegradable detergent s p e c i e s . The p o s s i b l e v a r i a t i o n s i n a l c o h o l s , t h e i r mixtures and the amount of ethylene oxide o r s u l f a t i o n agent used provides a very wide range o f p o s s i b l e detergent m a t e r i a l s . Many d i f f e r e n t products are now being produced u s i n g t h i s technology.


Feed Sources Many types of feed have been used s u c c e s s f u l l y i n t h i s p r o c e s s . Since t h e feed i s narrow i n b o i l i n g range and t h e r e s u l t i n g a l c o h o l i s h i g h e r b o i l i n g , t h e process i s not s e n s i t i v e t o hydrocarbon feed i m p u r i t i e s . Wax cracked o l e f i n s have been used over both the p l a s t i c i z e r range (Cg t o C ^ Q ) detergent range(C

Higher Linear Oxo Alcohols Manufacture - ACS Symposium Series

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