Near-Critical Separation of Butadiene-Butene Mixtures with Mixtures

Chapter 17

Near-Critical Separation of Butadiene-Butene Mixtures with Mixtures of Ammonia and Ethylene D. S. Hacker

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on May 28, 2018 | https://pubs.acs.org Publication Date: December 16, 1987 | doi: 10.1021/bk-1987-0329.ch017

Amoco Chemicals Company, Naperville, IL 60566

The results of an experimental investigation are presented for the separation of mixtures of 1,3-butadiene and 1-butene at near critical conditions with mixed and single solvent gases. Ammonia was used as an entrainer to enhance the separation. Several non-polar solvents were used which included ethylene, ethane and carbon dioxide, as well as mixtures of each of these gases with ammonia in concentrations of 2, 5, 8 and 10% by volume. Each solvent and solvent mixture was studied with respect to its ability to remove 1-butene from an equimolar mixture of 1,3-butadiene/ 1-butene. Maximum selectivities of 1.4 to 1.8 were measured at a pressure of 600 psia and a temperature of 20 C in mixtures containing 5%-8% by volume of ammonia in ethylene. All other solvents showed little or no success in promoting separation of the mixture. The experimental results are reported for ethylene/ ammonia mixtures and are shown to be in fair agreement with VLE flash calculations predicted independently by a modified two parameter R-K type of equation of state.

A s e p a r a t i o n p r o c e s s i s sought t h a t c a n s a t i s f y b o t h o u r p r e s e n t economic and e n v i r o m e n t a l c o n s t r a i n t s . I t would a l s o p r o v i d e an a l t e r n a t i v e t o p r e s e n t p r a c t i c e t h a t r e l i e s on e x p e n s i v e azeot r o p i c o r e x t r a c t i v e d i s t i l l a t i o n processes used i n the r e c o v e r y o f p r o d u c t s from low r e l a t i v e v o l a t i l i t y streams. As an example, v i r t u a l l y a l l i n d u s t r i a l b u t a d i e n e r e c o v e r y p r o c e s s e s now r e l y on extractive d i s t i l l a t i o n using a c e t o n i t r i l e or other equivalent agent t o enhance t h e r e l a t i v e v o l a t i l i t y o f t h e C4 components. The use o f s u p e r c r i t i c a l o r near c r i t i c a l s e p a r a t i o n o f t h e s e streams may s a t i s f y t h e s e r e q u i r e m e n t s p r o v i d e d c e r t a i n p r e s s u r e , tempera t u r e and r e c o m p r e s s i o n c r i t e r i a c a n be met. Such a p r o c e s s would a l s o reduce t h e need f o r a complex t r a i n o f d i s t i l l a t i o n towers.

0097-6156/87/0329-0213$06.00/0 © 1987 American Chemical Society

Squires and Paulaitis; Supercritical Fluids ACS Symposium Series; American Chemical Society: Washington, DC, 1987.

SUPERCRITICAL FLUIDS


214

L i q u i d ammonia has been s u g g e s t e d as a s o l v e n t f o r t h e C4 separation(l). A drawback t o i t s use i n t h e l i q u i d s t a t e , however, i s t h e need f o r c o s t l y r e f r i g e r a t i o n . I t s u s e as a s u p e r c r i t i c a l s o l v e n t would a l s o be a c c e p t a b l e were i t n o t f o r i t s h i g h c r i t i c a l t e m p e r a t u r e (405.45 K ) . H i g h temperature f a v o r s t h e p o l y m e r i z a t i o n o f t h e b u t a d i e n e ; hence, i t s l i m i t a t i o n i n t h i s r o l e . In this s t u d y , a method was d e v e l o p e d t h a t seeks t o c i r c u m v e n t t h i s problem and y e t a c h i e v e t h e d e s i r e d s e p a r a t i o n o f t h e C4's. Prausnitz(2) d i s c u s s e s t h e u s e o f a m i x t u r e o f s u p e r c r i t i c a l s o l v e n t s whose p r o p e r t i e s provide the optimal p h y s i c a l conditions f o r e f f i c i e n t extraction. I t i s equally p o s s i b l e to prepare mixtures o f solvents t h a t n o t o n l y m o d i f y those c r i t i c a l p r o p e r t i e s o f t h e i n d i v i d u a l s o l v e n t component, b u t a l s o i n t r o d u c e t h e c h e m i c a l f e a t u r e s needed t o maximize t h e s e p a r a t i o n o f t h e f e e d m i x t u r e . I n v i e w o f t h e i n t e r e s t i n t h i s f i e l d , an e x p e r i m e n t a l investig a t i o n was u n d e r t a k e n t o d e t e r m i n e t h e a p p l i c a b i l i t y o f superc r i t i c a l phenomena t o t h e s e p a r a t i o n o f b u t a d i e n e from C4 m i x t u r e s . I n p a r t i c u l a r , t h e s e p a r a t i o n o f 1-butene from 1,3-butadiene i s a key f a c t o r i n t h e s e p a r a t i o n p r o c e s s . Results o f these s t u d i e s are c o n s i d e r e d i n l i g h t o f p r e d i c t i o n s o b t a i n e d from a r e p r e s e n t a t i v e e q u a t i o n o f s t a t e i n t h e r e t r o g r a d e r e g i o n o f t h e SC s o l v e n t - s o l u t e VLE e n v e l o p e . Theoretical

Discussion

The a b i l i t y t o s e p a r a t e s p e c i f i c s o l u t i o n components from t h e l i q u i d phase w i t h a s u p e r c r i t i c a l o r n e a r - c r i t i c a l s o l v e n t component has been d e m o n s t r a t e d f o r a few s e l e c t e d s y s t e m s Q ) . Generally, the s o l v e n t s a r e s i n g l e component i n o r g a n i c gases o r l i g h t h y d r o c a r b o n s . I n common u s e have been c a r b o n d i o x i d e , ammonia, ethane, e t h y l e n e o r propane. W e i n s t o c k and E l g i n ( 4 ) u s e d p r e s s u r i z e d e t h y l e n e t o promote t h e s e p a r a t i o n o f a number o f m i s c i b l e a q u e o u s - o r g a n i c l i q u i d mixtures. More r e c e n t l y , P a u l a i t i s and o t h e r s have u s e d c a r b o n d i o x i d e to dehydrate ethanol(5.6). The s e p a r a t i o n o f a s p h a l t i n e s w i t h s u p e r c r i t i c a l propane has been c o m m e r c i a l l y d e m o n s t r a t e d by Kerr-McGee(7). S t a r l i n g , e t a l . , have s u g g e s t e d t h a t t h e r e t r o g r a d e regime may be e x p l o i t e d by t h e a d d i t i o n o f s u f f i c i e n t s o l v e n t t o separate a l i g h t l i q u i d hydrocarbon mixture(8). I n a d d i t i o n , s e v e r a l e q u a t i o n s o f s t a t e have been d e v e l o p e d t o p r e d i c t t h e VLE b e h a v i o r o f a s u b c r i t i c a l l i q u i d m i x t u r e w i t h a s u p e r c r i t i c a l component. These t h e o r e t i c a l models a r e o f c u r r e n t research interest. I n a d d i t i o n , s e v e r a l approaches have been formu l a t e d t o e x t e n d t h e a n a l y s i s t o multicomponent systems u t i l i z i n g c o n c e p t s o f c o n t i n u o u s thermodynamics(9. 10). R e i d and o t h e r s ( 1 1 . 12) have shown t h a t s u p e r c r i t i c a l s o l v e n t s e x h i b i t v a r y i n g degrees o f s p e c i f i c i t y towards a p a r t i c u l a r s p e c i e . F u r t h e r m o r e , t h e s m a l l number o f SC s o l v e n t s a v a i l a b l e l i m i t s t h e p o t e n t i a l u s e SC e x t r a c t i o n . The use o f e n t r a i n e r s o r m i x t u r e s o f s o l v e n t s , may remove t h e l i m i t a t i o n imposed by t h e narrow c h o i c e o f l i k e l y solvents. Moreover, i t i s p o s s i b l e t h a t t h r o u g h t h e p r o p e r c h o i c e o f entraîner and s o l v e n t t h e d e s i r e d c h e m i c a l a c t i v i t y c a n be a d j u s t e d t o improve t h e s e l e c t i v i t y o f t h e s o l v e n t . F o r example, m i x t u r e s o f s o l v e n t gases w i t h e n t r a i n e r s c a n p e r m i t a m o d i f i c a t i o n o f c r i t i c a l p r o p e r t i e s as w e l l as c h e m i c a l p r o p e r t i e s , so t h a t Ρ and Τ a d j u s t m e n t c a n be u s e d t o maximize some p h y s i c a l p r o p e r t y o f t h e system(2).



17.

HACKER

Separation of Butadiene-Butène

Matures

215

B r u n n e r ( 1 3 ) s t u d i e d t h e i n f l u e n c e o f e n t r a i n e r s on model m i x t u r e s by i n t r o d u c i n g a c e t o n e i n t o a p o l y g l y c e r i d e m i x t u r e , thus enhancing i t s s e p a r a t i o n with carbon d i o x i d e . The entraîner s e r v e d as a s o u r c e o f h y d r o g e n b o n d i n g t o augment t h e s e p a r a t i o n o f t h e d e s i r e d component. The p r i n c i p l e o f t h e entraîner h a s been w i d e l y known i n l i q u i d e x t r a c t i o n p r o c e s s e s i n i m p r o v i n g s e p a r a t i o n and was d e s c r i b e d by T r e y b a l ( 1 4 ) . I t i s known t h a t t h e a d d i t i o n o f a s t r o n g l y i n t e r a c t i v e t h i r d component t o a m i s c i b l e b i n a r y m i x t u r e c a n a l t e r t h e phase b e h a v i o r o f t h i s n o r m a l l y s t a b l e system. T h i s o c c u r s by a m i n i m i z a t i o n o f the G i b b s f r e e energy. By m o d i f y i n g t h e p a i r p o t e n t i a l s between the components c o m p r i s i n g t h e system, changes i n t h e p a i r w i s e activity coefficients w i l l result(15). The a d d i t i o n o f a f o u r t h s o l v e n t component, i f p r o p e r l y s e l e c t e d , c a n f u r t h e r a l t e r t h e a c t i v i t y c o e f f i c i e n t s o f the s o l u t e , p r e f e r e n t i a l l y i n c r e a s i n g i t s c o n c e n t r a t i o n i n a g i v e n phase(16. 17). An e x t e n s i o n o f t h e s e p r i n c i p l e s t o multicomponent s o l i d o r l i q u i d systems i s s t i l l t o be determined i n the s u p e r c r i t i c a l region. We have a p p l i e d some o f t h e s e p r i n c i p l e s t o t h e e x t r a c t i o n o f 1-butene from a b i n a r y m i x t u r e o f 1,3-butadiene/1-butene. V a r i o u s m i x t u r e s o f s c s o l v e n t s ( e . g . , ethane, c a r b o n d i o x i d e , e t h y l e n e ) a r e used i n c o m b i n a t i o n w i t h a s t r o n g l y p o l a r s o l v e n t g a s l i k e ammonia. The p h y s i c a l p r o p e r t i e s o f t h e s e components a r e shown i n T a b l e I . The e x p e r i m e n t a l r e s u l t s were t h e n compared w i t h VLE p r e d i c t i o n s u s i n g a newly d e v e l o p e d e q u a t i o n o f s t a t e ( 1 8 ) . The key f e a t u r e o f t h i s e q u a t i o n i s a new s e t o f m i x i n g r u l e s based on s t a t i s t i c a l m e c h a n i c a l arguments. We have been a b l e t o demonstrate i t s agreement w i t h a number o f b i n a r y and t e r n a r y systems d e s c r i b e d i n t h e l i t e r a t u r e , c o n t a i n i n g v a r i o u s h y d r o c a r b o n compounds, a number o f s e l e c t e d p o l a r compounds and a s u p e r c r i t i c a l component. It predicts quite well vapor-liquid-phase equilibria for a multicomponent system i n t h e r e t r o g r a d e r e g i o n b u t cannot p r e d i c t t h e f o r m a t i o n o f a second l i q u i d phase. The m i x i n g r u l e s u s e d i n t h e e q u a t i o n o f s t a t e a r e d e f i n e d as follows :

a- (a., χ a ) lm 11 mm

1

/

2

(1-k- ) lm

and

(1)

where a and b a r e t h e average Van d e r Waal c o n f i g u r a t i o n a l c o e f f i c i e n t s f o r m i x t u r e s , and 1 and m a r e t h e p a i r w i s e s p e c i e s which can be a d j u s t e d f o r t h e d i p o l e c o n t r i b u t i o n o f ammonia-butene t h r o u g h the i n t e r a c t i o n p a r a m e t e r s , k. and . A l l o t h e r k and b v a l u e s o f t h e i n t e r a c t i o n c o e f f i c i e n t s were s e t t o 0 and 1, r e s p e c t i v e l y . T h i s model h a s some s e r i o u s l i m i t a t i o n s i n r e p r e s e n t i n g t h e e f f e c t s o f p o l a r compounds, s i n c e q u a d r u p o l e and s t r o n g i n t e r a c t i o n f o r c e s are ignored. Nevertheless, one c a n o b t a i n a " b a l l p a r k " e s t i m a t e o f t h e l i k e l y degree o f s e p a r a t i o n .


Squires and Paulaitis; Supercritical Fluids ACS Symposium Series; American Chemical Society: Washington, DC, 1987. l-Butene

of

Ethane

M o l e c u l a r Wt* 30.07 C r i t i c a l Temp>C 3 2 * 2 7 C r i t i c a l Press* MPa 4*88 C r i t i c a l V o l . c c 4.919 N o r m a l BP*C -88*60 S o l u b i l i t y Coeff* 3*9134xE04 D i p o l e Mom.Bebye 0*0 Acentric Factor 0*09896

Property

of

C4

I

Dioxide

4.605xE04 0.0 0.2276

7.38 2.136

44.01 31 .04

Carbon

Solvents

54*09 152*20 4*32? 4*083 -4.411 4*8694xE04 0.0 0*1932 I

11 3 - B u t a d i e n e

Components

3.932xE04 0.0 0.085

5.03 4.601 103*7

28*05 9*21

Ethylene

Properties

M o l e c u l a r Wt. 56.11 C r i t i c a l Temp* C 146.4 C r i t i c a l Press.MPa 4*019 C r i t i c a l Vol» c c / m o l e 4*276 N o r m a l BP.C -0.25 S o l u b i l i t y Param. 4.7504xE04 D i p o l e Mom* D e b y e 0.34 Acentric Factor 0*1867

Property

Properties

TABLE

9.239xE04 1 .47 0.2520

11.27 4.255 -33.43

17.03 132.50

Ammonia


17.

HACKER

Separation of Butadiene-Butène


E x p e r i m e n t a l A p p a r a t u s and

Mixtures

217

Materials

A l l s o l v e n t gases were s u p p l i e d as c y l i n d e r gases h a v i n g a s p e c i f i e d minimum p u r i t y o f 99.0%. Butene, b u t a d i e n e and ammonia were u s e d as r e c e i v e d w i t h o u t f u r t h e r p u r i f i c a t i o n . E x t r a c t i o n e x p e r i m e n t s were c a r r i e d o u t i n a o n e - l i t e r , s t i r r e d , s t a i n l e s s s t e e l A u t o c l a v e v e s s e l ( A ) r a t e d a t 5000 p s i g a t 600 F. A complete s c h e m a t i c o f the assembly i s shown i n F i g . 1. A l l c o n n e c t i o n s w i t h s t a i n l e s s s t e e l 0.025 I.D. t u b i n g were made w i t h Autoclave E n g i n e e r i n g Speedbite f i t t i n g s . The présure v e s s e l was m a i n t a i n e d a t c o n s t a n t temperature by means o f e x t e r n a l e l e c t r i c a l h e a t i n g and an i n t e r n a l c o o l i n g c o i l . C o o l i n g was f u r n i s h e d by water c h i l l e d and c i r c u l a t e d by a Blue-M f r e o n r e f r i g e r a t i o n u n i t . An A u t o c l a v e magnetic s t i r r i n g u n i t powered by an a i r motor (M) was u s e d t o ensure adequate m i x i n g o f the c e l l c o n t e n t s . The p r e s e n c e o f phase i n t e r f a c e s were v i e w e d t h r o u g h the windows o f a 50 c c J e r g u s o n gauge(J) ( r a t e d a t 5000 p s i g a t 72 F ) , i n p a r a l l e l w i t h the main c e l l . The s i g h t g l a s s o f the gauge which a l s o s e r v e s as a l e v e l i n d i c a t o r , had an e t c h e d , d i r e c t r e a d i n g s c a l e , c a l i b r a t e d t o measure the t o t a l volumes o f the l i q u i d s i n the c e l l . Butene and b u t a d i e n e were pumped i n t o the the r e a c t o r t h r o u g h a common LP10 Whitey d i s p l a c e m e n t pump(Cl). A 30-pound n i t r o g e n head was u s e d t o p r e s s u r i z e each h y d r o c a r b o n c y l i n d e r t o m a i n t a i n adequate pumping e f f i c i e n c y . Ammonia was pumped as a l i q u i d t h r o u g h a second Whitey pump(C2), e q u i p p e d w i t h a r e f r i g e r a t e d head t o a v o i d v a p o r i z a t i o n d u r i n g c o m p r e s s i o n . The ammonia l i n e was i n d e p e n d e n t l y c o o l e d t o p r e v e n t v a p o r i z a t i o n d u r i n g t r a n s f e r to the r e a c t o r . A s l i g h t h e l i u m p r e s s u r e was m a i n t a i n e d i n the v e s s e l d u r i n g c h a r g i n g t o f u r t h e r ensure a minimum o f v a p o r i z a t i o n a t the l i q u i d s u r f a c e and ease the measurement o f the l i q u i d l e v e l . E t h y l e n e , c a r b o n d i o x i d e , o r ethane were compressed t o the d e s i r e d p r e s s u r e t h r o u g h a H a s k e l Model AG-62, gas c o m p r e s s o r ( C 3 ) , w i t h a 25-1 c o m p r e s s i o n r a t i o and a maximum r a t e d o u t l e t p r e s s u r e o f 9000 p s i g . The mass o f the gases u s e d i n each r u n was d e t e r m i n e d by w e i g h t l o s s o f the gas c y l i n d e r mounted on a Dayton d i g i t a l s c a l e . A redundant volume check was made by m e a s u r i n g the d i f f e r e n c e between the l i q u i d l e v e l s b e f o r e and a f t e r gas a d d i t i o n to the l i q u i d c h a r g e and the t o t a l volume o f the v e s s e l . The p r e s s u r e o f the system and i n each o f the r e c e i v e r v e s s e l s , E l and E2, was measured w i t h c a l i b r a t e d h i g h p r e s s u r e p r e c i s i o n Bourdon tube gauges o f a p p r o p r i a t e range (G1,G2,G3). The e x t e r i o r o f the A u t o c l a v e v e s s e l w a l l was d i v i d e d i n t o t h r e e h e a t i n g zones, each c o n t r o l l e d by one Eurotherm 103 temperature c o n t r o l l e r ( T C ) . The r e m a i n i n g s e c t i o n s were h e a t t r a c e d w i t h s e l f - l i m i t i n g "Autotrace" h e a t i n g tapes to prevent v a p o r c o n d e n s a t i o n i n the l i n e s . H e a t i n g c o n t r o l s were a d j u s t e d m a n u a l l y and a l l temperatures were measured w i t h c o p p e r - c o n s t a n t a n thermocouples a t t a c h e d t o the c e l l and r e c e i v e r v e s s e l s . The thermocouple o u t p u t v o l t a g e s were i n d i c a t e d on a 1 0 - p o i n t Acromag d i g i t a l v o l t m e t e r . A c a l i b r a t e d p l a t i n u m - 1 0 % rhodium thermocouple was u s e d t o measure the temperature o f the c o n t e n t s i n the autoclave reactor.




218

F i g u r e 1.

Experimental

Apparatus


17.

HACKER

Separation ofButadiene-Butene Mixtures


P r o c e d u r e . Sampling

and

219

Analysis

Each e x p e r i m e n t was c o n d u c t e d as f o l l o w s : The system was e v a c u a t e d to remove r e s i d u a l f l u i d s . N i t r o g e n was t h e n f l u s h e d t h r o u g h the system and the system once a g a i n e v a c u a t e d . The h y d r o c a r b o n and ammonia were t h e n pumped i n t o the c e l l as l i q u i d s . The d e s i r e d l i q u i d was m o n i t o r e d from the l e v e l on the s i g h t g l a s s . The composit i o n was d e t e r m i n e d by volume p e r c e n t o f the h y d r o c a r b o n s and entraîner added. The s o l v e n t gas was t h e n i n t r o d u c e d . The temperat u r e o f the c o n t e n t s i n the c e l l was a d j u s t e d t o the d e s i r e d v a l u e and s t i r r e d v i g o r o u s l y . The p r e s s u r e o f the s o l v e n t gas was s l o w l y i n c r e a s e d u n t i l the l i q u i d i n t e r f a c e d i s a p p e a r e d and an o p a l e s c e n c e regime appeared, i n d i c a t i n g the a t t a i n m e n t o f the c r i t i c a l r e g i o n . The gas p r e s s u r e was t h e n r e d u c e d by a s l i g h t d e p r e s s u r i z a t i o n i n the chamber u n t i l the i n t e r f a c e j u s t r e a p p e a r e d . I t was e s t a b l i s h e d t h a t t h i s p r o c e d u r e p e r m i t t e d the c o n t e n t s t o be a d j u s t e d l e s s t h a n 2 t o 3 p e r c e n t o f the c r i t i c a l p r e s s u r e . S t i r r i n g was d i s c o n t i n u e d about two minutes b e f o r e s a m p l i n g , t o a l l o w the system t o e q u i l i b r a t e the v a p o r and l i q u i d phases. An e s t i m a t e o f the volume o f s o l v e n t added t o the h y d r o c a r b o n m i x t u r e was o b t a i n e d by c a l c u l a t i n g the d i f f e r e n c e i n the l i q u i d l e v e l b e f o r e and a f t e r gas a d d i t i o n , which i s a p p r o x i m a t e l y e q u a l to the volume o f gas d i s s o l v e d i n the l i q u i d phase. This value i s added t o the volume above the l i q u i d i n t e r f a c e t o o b t a i n the t o t a l s o l v e n t volume added t o the system. The r a t i o o f ethylene/ammonia s o l v e n t m i x t u r e added to the volume o f b u t a d i e n e / b u t e n e s o l u t i o n was a p p r o x i m a t e l y 5:1. The c o n t e n t s o f the r e a c t o r were sampled b e f o r e and a f t e r the i n t r o d u c t i o n o f the s o l v e n t gas. T h i s was done by t r a p p i n g approxi m a t e l y 0.5 c c o f the m i x t u r e from the r e a c t o r volume i n a p r e c a l i b r a t e d l o o p o f 1/16 i n c h i . d . sample l i n e l o c a t e d between two h i g h p r e s s u r e v a l v e s ( S ) a d j a c e n t t o the v e s s e l . The volume o f the sample withdrawn was s u f f i e n t l y s m a l l t o m i n i m i z e any changes i n the p r e s s u r e (< 0.1 p s i ) o f the main c o n t e n t s o f the v e s s e l . The h i g h p r e s s u r e sample was f u r t h e r expanded i n t o a p r e - e v a c u a t e d 300 c c Hoke c y l i n d e r ( E l ) t o about 5 atm. T h i s volume o f sample was a g a i n expanded t o about 1 atm i n a p r e - e v a c u a t e d , f i n a l 70-cc Hoke cylinder(E2). P o r t i o n s o f t h i s volume were t h e n i n j e c t e d by means o f an automated V a l c o v a l v e ( V I ) i n t o the V a r i a n 920 gas chromatog r a p h i c ) . A l l sample l o o p s were a l s o h e a t t r a c e d t o p r e v e n t condens a t i o n i n the l i n e s . T h i s p r o c e d u r e was a l s o f o l l o w e d i n s a m p l i n g the l i q u i d phase from the bottom o f v e s s e l as w e l l . S y r i n g e samp l i n g t h r o u g h diaphram p o r t s l o c a t e d a t s t r a t e g i c p o s i t i o n s i n the system p r o v i d e d a d d i t i o n a l checks on the automated s a m p l i n g procedures. A l l samples were a n a l y z e d i n an A l l T e c h 1/8"I.D, 20 f o o t column, packed w i t h VZ-7 r e s i n , u s i n g h e l i u m as the c a r r i e r gas. T h i s column p r o v e d more e f f e c t i v e f o r the measurement o f the C4 components t h a n the Poropak- Ν column. Ammonia was n o t d e t e c t e d by t h i s column and as a r e s u l t some o f the assumptions employed t o t r e a t the s o l v e n t phase a r e d e s c r i b e d i n a l a t e r p a r a g r a p h . The G.C. was r u n w i t h the i n j e c t o r chamber s e t a t 115 C, the column oven temperature a t 60 C and the f i l a m e n t c u r r e n t s e t a t 150 ma. Column a n a l y s e s were p e r formed by an A u t o l a b I n t e g r a t o r . A Leeds and N o r t h r u p s t r i p c h a r t r e c o r d e r was u s e d t o p l o t the o u t p u t o f the i n t e g r a t o r and t o


220


p r o v i d e a v i s u a l d e t e r m i n a t i o n o f the time t r a c e and the magnitude peak h e i g h t s f o r r a p i d c o m p a r i s o n o f the r e l a t i v e e f f e c t i v e n e s s o f the s e p a r a t i o n . A sample s t r i p c h a r t r e c o r d o f the G.C. o u t p u t i s shown i n F i g . 2.


Results T i e l i n e s o f the system can be g e n e r a t e d from the e q u i l i b r i u m c o m p o s i t i o n s f o r each r u n and s e l e c t i v i t i e s computed. The r e s u l t s o f measurements o b t a i n e d f o r the 5% by volume o f ammonia/ethylene a r e r e p r e s e n t e d i n the b i n o d a l diagram i n F i g . 3. Butene i s r e p r e s e n t e d as the d i s t r i b u t e d component between the s o l v e n t phase and the b u t a d i e n e - r i c h phase. The ammonia-solvent gas m i x t u r e was c o n s i d e r e d t o behave as a p s e u d o - s o l v e n t o f f i x e d c o m p o s i t i o n . The r a t i o o f the i n t e g r a t e d peaks f o r b u t e n e ( i ) and b u t a d i e n e ( j ) was u s e d t o compute the s e l e c t i v i t y , Β ( b e t a ) , d e f i n e d on a s o l v e n t f r e e b a s i s , as: ( y . ) s o l v e n t phase χ

(χ.) heavy phase 3

Β (x^)heavy

phase

(2)

v

χ ( j ) s o l v e n t phase

R e p r e s e n t a t i v e r e s u l t s a r e shown i n T a b l e I I and I I I f o r e t h y l e n e and ethylene/ammonia and ethane and ethane/ammonia s o l v e n t m i x t u r e s . S i n c e our d e t e c t i o n c a p a b i l i t y was l i m i t e d t o h y d r o c a r b o n s gases o n l y , ammonia c o u l d n o t be d i r e c t l y measured i n e i t h e r phase. However, the s e l e c t i v i t y as d e f i n e d i n Eqn. 2 can be c o n s i d e r e d as a measure o f the r a t i o o f the d i s t r i b u t e d components o n l y ; hence, i n d e p e n d e n t o f the a b s o l u t e c o n c e n t r a t i o n o f the s o l v e n t components. A l l e x t r a c t i o n runs were made w i t h e q u i m o l a r m i x t u r e s o f b u t e n e / b u t a d i e n e u s i n g e t h y l e n e , ethane o r c a r b o n d i o x i d e as the s o l v e n t w i t h v a r i o u s c o n c e n t r a t i o n s o f ammonia from 0 - 1 0 vol%. I n the absence o f ammonia, s e p a r a t i o n o f the m i x t u r e o f h y d r o c a r b o n s was n e g l i g i b l e . T a b l e IV summarizes the d a t a f o r pure s o l v e n t s and shows a comparison w i t h some s e l e c t e d d a t a f o r ammonia / p u r e gas m i x t u r e s . Ammonia/ethylene m i x t u r e s appear t o be more e f f e c t i v e as s o l v e n t m i x t u r e s , w i t h a marked s e p a r a t i o n o f butene achieved. 2,3-Butadiene i s c o n c e n t r a t e d i n the heavy phase, i n agreement w i t h the f i n d i n g s r e p o r t e d f o r l i q u i d ammonia ( 1 ) . A s e r i e s o f e x p e r i m e n t s was c o n d u c t e d t o d e t e r m i n e whether t h e r e e x i s t s an ammonia c o n c e n t r a t i o n f o r which maximum s e p a r a t i o n c o u l d be a t t a i n e d . A t a p r e s s u r e o f 600 p s i a and 20 degrees C. and between 5 and 8 v o l % ammonia, a maximum i n the s e l e c t i v i t y i s o b t a i n e d and i s shown i n F i g . 4. The s e l e c t i v i t y , however, d e c r e a s e s w i t h i n c r e a s i n g temperature, w i t h o t h e r v a r i a b l e s h e l d c o n s t a n t as shown i n F i g . 5. The t r e n d o b s e r v e d t h e s e e x p e r i m e n t s a r e i n agreement w i t h the f i n d i n g s o f B r i g n o l e , e t a l . ( u ) . An e r r o r o f +/- 5% was e s t i m a t e d i n the c a l c u l a t i o n o f the e x p e r i mental s e l e c t i v i t i e s . The e x p e r i m e n t a l r e s u l t s were compared w i t h p r e d i c t i o n s o b t a i n e d from the e q u a t i o n o f s t a t e , assuming t h a t the i n t e r a c t i o n parameter, k ^ » 0.2 f o r ammonia and 1-butene dominated the n o n - i d e a l i t y o f the system. A c o m p a r i s o n o f the c a l c u l a t e d s e l e c t i v i t i e s o b t a i n e d f o r the ethylene/ammonia m i x t u r e s a r e g i v e n i n T a b l e I I w i t h the r e s u l t s i n T a b l e I I I f o r the ethane system. m


H AC KER

Separation of Butadiene-Butene Mixtures

22

-50 -60


-70 -80 Lower Phase

-90 -100

Upper Phase

CH 2

J

-90

4

'V.IOO Time

F i g u r e 2. T y p i c a l Gas Chromatographs from a VZ-& Column w i t h Column Temperature a t 98 C. Ammonia Not D e t e c t e d i n t h i s Column.

F i g u r e 3. T e r n a r y Phase Diagram f o r the System. 8% Ammonia C o n c e n t r a t i o n i n E t h y l e n e . P r e s s u r e = 600 p s i a , Temp = 20 °C. E x p e r i m e n t a l P o i n t s Shown as Dots.



222


TABLE I I . Butadiene-Butene-Ethylene-Ammonia E q u i l i b r i u m

TEMP C

PRESSURE PSIA

20

600

20

20

800

1100

NH %

3

C H 2

y

4

i

SOLVENT BUTENE y

PHASE BUTADIENE y k

C H 2

X

4

l

Composition

BUTADIENE BUTENE x

PHASE BUTADIENE x fc

BETA β

0 0 0

88. 351 88. 425 69. 694

3. 768 3. 763 14. 932

7. 881 7. 839 15. 374

45.940 38.338 71.997

17. 47 19. 765 13.092

36. 584 41. 901 14. 911

1.00 0.99 1.10

2.3

82. 199

8. 828

8. 973

58.461

17. 483

20. 879

1.17

5.0 5.0 5.0 5.0 5.0 5.0 5.0

89. 063 88.879 76. 970 75. 469 89. 132 90.259 90. 003

6. 936 6. 903 15.069 15. 505 8. 805 8. 066 8. 241

4. 001 4. 218 7. 961 8.448 2.064 1. 675 1. 756

52.675 40.109 58.039 55.886 38.799 34.527 41.657

23. 890 30.149 22. 047 23. 201 47. 751 50. 693 45. 281

23. 435 29. 742 19. 914 20.913 13.450 14.780 13.062

1.70 1.61 1.71 1.61 1.20 1.40 1.35

8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

91.066 85. 908 86. 668 86. 775 69. 579 70. 150 92. 786 92. 468 90.478 90.092 71.455 70. 326 71. 296

2. 629 3. 288 11. 710 11. 737 19.803 19. 600 2. 932 3. 101 7. 865 8. 193 8.,932 8.,981 9.,006

6. 305 8. 151 1. 622 1. 488 10. 618 10. 249 4. 238 4. 430 1. 657 1. 716 19.,613 20.,693 19,.698

46.473 44.928 47.847 49.963 49.100 61.617 48.052 52.335 37.229 38.954 44.076 42.661 40.781

12. 884 13. 157 41. 382 39. 604 27. 951 21. 157 17. 872 16. 484 48. 002 46. 955 13.,800 14.,033 14.424

39. 303 40. 645 10. 771 10.433 22. 949 17. 226 34.075 31. 182 14. 769 14.091 42. 124 43. 306 33.,795

1.27 1.24 1.88 2.08 1.53 1.56 1.30 1.32 1.46 1.43 1.39 1.34 1.42

10.0 10.0 10.0 10.0

59.,583 60,,217 74,.642 74.960

27,.028 26 .028 19 .423 19.222

13,.389 13 .389 5 .984 5.818

39.981 41.815 66.140 65.523

36 .671 35 .692 25 .400 25 .784

23,.348 22.493 8 .451 8 .694

1.29 1.32 1.10 1.10

2.3 2.3

70 .166 69 .498

13 .873 14 .112

15 .960 16 .389

34.716 43.984

28 .791 24 .539

36 .493 31 .477

1.10 1.10

5.0 5.0 5.0 5.0

76 .947 77 .599 85 .538 85 .908

12.740 12 .566 3.497 3 .354

10.312 9.835 10 .965 10.738

74.065 74.093 68.631 68.631

14 .520 14 .494 7 .017 7 .017

11.415 11.413 24.352 24 .392

1.05 1.00 1.11 1.06

10.0 10.0

81 .026 80 .266

7 .044 3 .354

11 .930 12 .183

67.741 67.009

11 .236 11 .767

21 .021 21 .224

1.10 1.12

0 0

69 .694 81 .759

14 .932 8 .583

15 .374 8 .713

71.997 73.607

13.092 12 .124

14 .911 14 .270

0.90 0.86

5.0 5.0

84 .760 84 .074

8 .380 8 .457

6 .860 7.451

77.316 74.816

11 .457 12 .849

11 .227 12 .335

0.84 0.92

40

600

5.0 5.0

85 .128 86 .617

8 .416 7 .812

6 .456 5 .571

34.556 29.325

34.501 37 .302

30 .943 33 .372

1.17 1.25

60

600

5.0 5.0

75 .099 74 .163

11 .814 12 .412

8 .756 9.471

19.215 20.693

42 .621 41 .856

38 .163 37 .451

1.21 1.17


17.

HACKER

TABLE III.

Separation of Butadiene-Butene Mixtures Butadiene-Butene-Ethane-Ammonia Composition

Butadiene Phase


Solvent Phase C2H6 wi

Butene Butadiene wk wj

C2H6 xi

Butene xj

Butadiene Beta xk

4.18 4.18

4.18

76.258 76.505 74.654

10.925 10.834 11.232

12.817 12.661 14.113

74.367 74.993 75.137

11.568 12.079 12.667

14.065 12.929 12.169

1.0 1.09 1.31

620 640 725 725 1060 1060

6.97 6.97 6.97 6.97 6.97 6.97

90.406 90.107 87.224 87.387 88.840 88.90

3.998 4.123 5.220

85.647 83.324 88.497 88.766 93.178 93.086

5.830 6.804 4.817 4.497 2.751

2.801

8.523 9.871 6.686 6.737 4.071 4.113

1.04

4.489 4.443

5.596 5.770 7.556 7.432 6.689 6.657

675 675 600 600 550 600 600 700 700

6.97 6.97

6.97 6.97 6.97 6.97 6.97

85.525 86.137 88.024 87.722 95.867 83.134 82.572 87.532 87.295

7.426 7.105 6.135 6.201 2.252 10.507 10.834 7.907 8.009

7.229 6.758 5.841 6.077 1.977 6.358 6.594 4.561 4.696

88.073 87.789 85.503 85.812 76.208 80.277 80.176 84.122 83.794

6.047 6.295 7.379 7.185 11.624 11.959 12.228 9.834 10.026

5.879 5.914 7.117 7.002 12.168 7.577 6.044 6.044 6.180

1.00 1.00 1.01 1.00 1.19 1.05 1.02 1.06 1.05

Temp Pressure C psia

NH3

20

17

19

18 16

18 20

223

900

%

6.97 6.97

5.181

1.03

1.00 1.05 1.00 1.00

22

525 525 525 1100 1100

1.85 1.85 1.85 1.85 1.85

89.169 93.286 92.362 88.100 87.700

5.166 3.828 3.900 6.345 6.328

5.664 2.886 3.737 5.555 5.973

69.808 67.462 78.235 78.508 78.581

15.252 16.489 11.064 11.205 11.078

14.939 16.049 10.701 10.288 10.341

1.0 1.28 1.01 1.04 1.00

23

550 550 1075 1075

0 0 0 0

82.754 92.243 77.928 77.279

8.164 9.091 10.663 11.078

3.668 4.089 11.438 11.693

53.113 55.308 72.545 75.175

22.449 21.121 13.088 12.095

24.438 23.570 14.367 12.730

1.00 1.00 1.00 1.01

TABLE IV. Separation of Equimolar Mixtures of Butene-Butadiene with Various Solvents Experimental Values TEMP C 6.0 40.0 22.0 22.0 20.0 23.0 18.0 20.0 23.0

PRESSURE psia 750 1100 1000 700 500 1100 700 900 550

SOLVENT C2H4 C02

ft ft

«

C2H6/5* NH3 C2H6/7* NH3 C2H6/4$ NH3 C2H6

SELECTIVITY

1.23 1.0 1.0 1.0 1.0 1.0 1.06 1.09 1.0



224


0 2 4 6 8 10 Entraîner Concentration-% Ammonia; Ethylene-(free basis)

F i g u r e 4. S e l e c t i v i t y as a F u n c t i o n o f Ammonia C o n c e n t r a t i o n a t Temp - 20 C, P r e s s u r e - 600 p s i a .

F i g u r e 5. The I n f l u e n c e o f E x t r a c t i o n Temperature on t h e S e l e c t i v i t y o f 5% Ammonia - E t h y l e n e S o l v e n t on M i x t u r e s o f Butene and B u t a d i e n e .


17. HACKER


225

S o l v e n t t o f e e d r a t i o s as w e l l as t h e e f f e c t o f ammonia c o n c e n t r a t i o n i n t h e s o l v e n t were i n d e p e n d e n t l y v a r i e d t o match t h e e x p e r i m e n t a l d a t a . The e f f e c t o f i n c r e a s i n g ammonia c o n c e n t r a t i o n a t c o n s t a n t p r e s s u r e and temperature i n b o t h ethylene/ammonia and ethane/ammonia s o l v e n t m i x t u r e s a r e shown i n T a b l e V.


Discussion T h i s s t u d y i s by no means comprehensive and c o v e r s o n l y a narrow range o f v a r i a b l e s . However, i t does demonstrate t h e i n f l u e n c e o f entraîner i n t h e improvement o f s e p a r a t i o n o v e r a s i n g l e superc r i t i c a l solvent. The i n c r e a s e i n s e l e c t i v i t y (1.4 t o 1.8) f o r b u t e n e / b u t a d i e n e m i x t u r e s i s compared w i t h t h e v a l u e o f 1.63 o b t a i n e d w i t h l i q u i d ammonia f o r t h e same b i n a r y s y s t e m ( l ) . Moreo v e r , i t has been demonstrated t h a t a m i x t u r e o f a p u r e s o l v e n t and an entraîner p e r m i t s an improvement i n t h e s e p a r a t i o n a t temperatures and p r e s s u r e s lower t h a n would have been o t h e r w i s e p r e d i c t e d w i t h a s i n g l e gas s o l v e n t ( 2 0 ) . F o r m i x t u r e s c o n t a i n i n g a h i g h l y p o l a r component, such as ammonia, m o l e c u l a r s i z e a l o n e cannot a c c o u n t f o r the l a r g e s e l e c t i v i t i e s o b s e r v e d i n t h e s e e x p e r i m e n t s . At present, a l l t h e o r i e s are inadequate i n e x p l a i n i n g the chemical i n t e r a c t i o n s between t h e entraîner and t h e m i x t u r e . The s t a t e o f t h e a r t i s comparable t o l i q u i d phase s o l v e n t e x t r a c t i o n . The d i s t r i b u t i o n o f t h e mixed s o l v e n t s between t h e phases might p r o v i d e some a d d i t i o n a l u n d e r s t a n d i n g o f t h e r e a s o n f o r t h e e f f e c t i v e n e s s o f t h e ammonia as an e n h a n c i n g agent. The s o l u b i l i t y o f l i q u i d ammonia i n t h e l i q u i d h y d r o c a r b o n phase has been shown t o be h i g h ( 2 1 ) because o f i t s s t r o n g b a s i c i t y as compared w i t h t h e n o n - p o l a r h y d r o c a r b o n gases such as ethane and e t h y l e n e a t normal c o n d i t i o n s ( 2 2 ) . A t h i g h e r p r e s s u r e s , however, s o l u b i l i t i e s o f a l l compounds i n c r e a s e d r a m a t i c a l l y and, a c c o r d i n g l y , t h e d i f f e r e n c e s between t h e p o l a r and n o n - p o l a r s o l u b i l i t i e s a r e somewhat reduced(22). N e v e r t h e l e s s , even f o r a r e l a t i v e l y d i l u t e p o l a r m i x t u r e i n a n o n - p o l a r gas, t h e s o l u b i l i t y o f t h e p o l a r component exceeds t h e n o n - p o l a r component. A t t h e s e p r e s s u r e s , i t i s l i k e l y t o be c o m p l e t e l y a b s o r b e d p r e f e r e n t i a l l y i n t o t h e l i q u i d phase. As a r e s u l t , i t i s estimated t h a t the composition o f the s u p e r c r i t i c a l phase w i l l c o n t a i n l i t t l e ammonia and p r e d o m i n a n t l y s o l v e n t gas with extracted solute. F o r t h i s m i x t u r e t h e s o l v e n t phase w i l l c o n s i s t o f e t h y l e n e o r ethane and butene w i t h a s m a l l c o n c e n t r a t i o n o f ammonia. T h i s i s c o n f i r m e d i n t h e VLE f l a s h c a l c u l a t i o n s f o r a 10:1 s o l v e n t e x t r a c t i o n w i t h a e q u i m o l a r m i x t u r e o f e t h y l e n e and ammonia. The d i s t r i b u t i o n o f ammonia t o e t h y l e n e i n t h e l i q u i d phase i s 2.5:1, whereas i n t h e v a p o r i t i s 1:2. The s e p a r a t i o n o f t h e l i q u i d components i n t h e p r e s e n c e o f a s u p e r c r i t i c a l s o l v e n t o c c u r s much as i t does i n l i q u i d e x t r a c t i o n w i t h t h e entraîner, ammonia, c o n c e n t r a t i n g i n t h e l i q u i d t o i n c r e a s e the r e l a t i v e v o l a t i l i t y o f t h e butene t o b u t a d i e n e . The b u t a d i e n e m i g r a t e s t o t h e ammonia-rich phase w h i l e t h e s o l v e n t gas phase o r "vapor" w i l l c o n t a i n t h e butene. The e x p l a n a t i o n f o r the h i g h e r s e l e c t i v i t y o f the e t h y l e n e / ammonia m i x t u r e over the ethane/ammonia system i s somewhat surprising. The e f f i c i e n c y o f s c e x t r a c t i o n o f a g i v e n s o l v e n t toward a p a r t i c u l a r s o l u t e i s r e l a t e d t o the s u p e r c r i t i c a l



226


Table V

S e p a r a t i o n o f 1-Butene 2,3-Butadiene M i x t u r e s C o m p u t a t i o n a l R e s u l t s by t h e E l y - M a n s o o r i Equation of State k.. = 0.2, a l l o t h e r k =0. wèire i = ammonia , j 2 i - b u t e n e n

Mixture Ratio

Solvent-Feed Ratio

NH3/Ethylene 0.25

20 10

0.50

10

NH3/Ethane 0.0 0.50

2 10

20 1.0

10

Temp. P r e s . C psia

27 37 29 32 37 47 57 37 47

22 47 57 77 42 47 117 97

735 735 735 735 735 735 735 588 588

294 588 735 853 588 588 1190.7 955

Vapor yi

0..011 0,.0208 0..0175 0..024 0..0317 0..0332 0..426 0..339 0..433

0..5501 0,.0250 0,.252 0..0348 0,.0129 0,.0173 0,.0331 0 .3636

Liquid xi

0.405 0.460 0.385 0.393 0.407 0.641 0.786 0.635 0.834

0.228 0.544 0.606 0.931 0.579 0.679 0.900 0.512

Selectivity Β

1..54 1..87 1.,29 1.,37 1.,40 2.,86 3.,10 3.,94 4.,29

1.,04 1.,96 1..65 1..10 2..26 2..48 0..91 1,.13



17.

HACKER


227

s o l u b i l i t y parameter, d e f i n e d i n terms o f the r e d u c e d p r o p e r t i e s o f the s o l u t e and s o l v e n t ( 2 3 ) . The r e d u c e d t e m p e r a t u r e , d e f i n e d i n terms o f t h e temperature a t which e x t r a c t i o n i s c a r r i e d o u t , s h o u l d be c l o s e t o u n i t y t o maximize s e p a r a t i o n ( 2 4 ) . S i n c e b o t h e t h y l e n e and ethane have r e d u c e d t e m p e r a t u r e s n e a r l y e q u a l t o u n i t y a t t h e e x t r a c t i o n c o n d i t i o n s o f 20 C, (T = .98) and e t h y l e n e (T — 1.04), t h e i r r e s p e c t i v e s o l v e n t capaciïies f o r butene s h o u l d be about t h e same. T h i s i s t h e c a s e as i s r e f l e c t e d i n t h e same v a l u e s f o r t h e s e l e c t i v i t y a g a i n s t b u t e n e f o r a l l pure s o l v e n t gases. One c a n c o n c l u d e t h a t t h e p r i m a r y e f f e c t o f t h e n o n - p o l a r s o l v e n t i s t o i n c r e a s e t h e c a p a c i t y o f t h e "vapor" phase f o r t h e e x t r a c t e d s o l u t e n e a r t h e c r i t i c a l . The i n f l u e n c e o f the second s o l v e n t p r o v i d e s o n l y t h e o p t i o n o f m o d i f y i n g t h e p h y s i c a l p a r a m e t e r s ; namely, p r e s s u r e and t e m p e r a t u r e , under which the o p t i m a l e x t r a c t i o n i s t o be c o n d u c t e d . The e v i d e n c e f o r t h i s i s t h e e f f e c t o f t h e ammonia on the s e l e c t i v i t y as c a l c u l a t e d by the EOS i n T a b l e V. The h i g h e r v a l u e s f o r t h e s e l e c t i v i t i e s i n t h e e t h y l e n e m i x t u r e s a r e pronounced. I t c a n be c o n c l u d e d t h a t t h e s o l v e n t m i x t u r e i n t e r a c t i o n p a r a m e t e r s must dominate t h e s o l u b i l i t y o f butene i n t h e v a p o r phase. The s i m p l e model u s e d i n t h e EOS, however, does n o t c o m p l e t e l y i n d i c a t e t h e p r e s e n c e o f a maximum i n t h e q u a n t i t y o f ammonia u s e d as an entraîner. That t h i s i s i n c o n t r a s t t o o u r e x p e r i m e n t a l o b s e r v a t i o n s s u g g e s t s t h a t o t h e r f a c t o r s such as c h e m i c a l synerg i s t i c e f f e c t s cannot be i g n o r e d and a r e l i k e l y t o have a g r e a t e r e f f e c t t h a n a n t i c i p a t e d . While t h i s f e a t u r e o f t h e system was e n t i r e l y unexpected, i t does s u g g e s t t h a t t h e Η-bonding o r o t h e r s t r o n g p o l a r i n t e r a c t i o n t h a t o c c u r s w i t h many s e l e c t i v e s o l v e n t s and s o l u t e s i n l i q u i d e x t r a c t i o n , may be e q u a l l y a p p l i c a b l e i n s c e x t r a c t i o n where s t r o n g p o l a r - p o l a r i n t e r a c t i o n s (as between ammonia and 1-butene) e x i s t . Conclusions 1.

3.

A maximum v a l u e i n t h e s e l e c t i v i t y o f 1.4 - 1.8 c a n be a c h i e v e d w i t h a 5 - 8 v o l % ammonia c o n c e n t r a t i o n i n e t h y l e n e f o r t h e b u t a d i e n e - butene s e p a r a t i o n . The h i g h e r s e l e c t i v i t y found i n the s u p e r c r i t i c a l e x t r a c t i o n i s comparable t o the s e l e c t i v i t y r e p o r t e d f o r the same s e p a r a t i o n w i t h l i q u i d ammonia. Ethylene/ammonia m i x t u r e s appear t o be a more e f f e c t i v e as s o l v e n t s f o r the s e p a r a t i o n o f a b u t a d i e n e - b u t e n e m i x t u r e t h a n are ethane/ammonia m i x t u r e s w i t h t h e same c o n c e n t r a t i o n o f ammonia. T h i s i s v e r i f i e d i n d e p e n d e n t l y by t h e p r e d i c t i o n s o f the E l y - M a n s o o r i e q u a t i o n o f s t a t e . The c o m b i n a t i o n o f enhanced s o l u b i l i t y o f t h e ethylene/ammonia m i x t u r e , a c c o r d i n g to J o s h i and P r a u s n i t z , as a s o l v e n t and t h e s y n e r g i s t i c c h e m i c a l e f f e c t between t h e h i g h l y p o l a r ammonia and e t h y l e n e may e x p l a i n the o b s e r v e d o v e r a l l i n c r e a s e d e f f e c t i v e n e s s o f the solvent mixture.



228 Acknowledgments

I would l i k e t o e x p r e s s my a p p r e c i a t i o n t o t h e Amoco C h e m i c a l s Co. f o r t h e i r s u p p o r t f o r t h i s work. I n p a r t i c u l a r , I w i s h t o e x p r e s s my thanks f o r t h e i n t e r e s t shown i n t h i s work b y D. E. Hannemann and P. G. T h o r n l e y and t o Franke Brooks, my t e c h n i c i a n , f o r h i s i n d u s t r y and c a r e i n c o n d u c t i n g t h e s e e x p e r i m e n t s .


Literature Cited 1. Poffenberger, N.; Horsley, L. H.; Nutting, H. S.; Trans. AIChE, 42:815, (1946) 2. Joshi, D. K.; Prausnitz, J . M.; AIChE Jour. 30:522, (1984) 3. Todd, D. B.; Elgin, J . C.; AIChE Jour. 1:20, (1955) 4. Weinstock, J . J.; Elgin, J . C.; Jour Chem Engr. Data, 4:3, (1959) 5. Paulaitis, M. E.; Kander, R. G.; DiAndreth, J . R.; Berichte der Bunsen-Gesellschaft f. Phy. Chem. 9:869 (1984) 6. Fogel, W.; Arlie, J . P.; Revue Francais Petrole. 39:617, (1984) 7. Brule, M. R.; Corbett, J . C.;, Hydrocarbon Process, 73, (1984) June 8. Starling, Κ. E.; Khan, Μ. Α.; Watanasiri, S.; Fundamental Thermodynamics of Supercritical Extraction, Presented Annual Mtg. AIChE, San Francisco, CA, (1984) 9. Prausnitz, J . M.; Fluid Phase Equil., 14, 1, (1983) 10. Cotterman, R. L.; Dimitrelis, D.; Prausnitz, J . M.; Ber. Bunsen Gelsch. Phy. und Chem., 9, 796, (1984) 11. Reid, R. C.; Schmitt, N. J.; J . Chem Engr. Data, 31:204, (1986) 12. Vasilakos, N. P.; Dobbs, J . M.; Parisi, A. S.; IEC Process Design, 24, 121, (1985) 13. Brunner, G.; Fluid Phase Equil., Part II, 10, 289, (1983) 14. Treybal, R. Ε.;, "Liquid Extraction", 2nd Ed., McGraw-Hill, NY (1963) 15. Prigogine, I.; Bull Soc. Chem, Belg., 52, 115, (1943) 16. Eckert, C. Α.; Greiger, R. Α.; I&EC Process Design. 6, 250, (1967) 17. Rowlinson, J . S.; Liquids and Liquid Mixtures, 2nd Ed., Plenum Press London, (1969) 18. Mansoori, G. Α.; Ely, J . F.; Density Expansion Mixing Rules, Unpublished, (1984) 19. Brignole, Ε. Α.; Skjold-Jorgensen, S.; Fredenslund, J . M.; ibid. 9:801 (1984) 20. Brunner, G; Fluid Phase Equilibria, 10:289, (1983) 21. Patyi, L.; et a l . , Zhur. Priklad. Khimii., 51:1296 (1978) 22. Prausnitz, J . M.; "Molecular Thermodynamics of Fluid Phase Equilibria", Chap.10, Prentice Hall, NY (1969) 23. Gidding, J . C.; Myers, M. N.; et a l . , Science 162:67, (1968) 24. Paul, P. M. F.; Wise, W. S.; The Principles of Gas Extraction. Mills & Boon, Ltd., Monograph CE/5, (1971) RECEIVED October 3, 1986


Near-Critical Separation of Butadiene-Butene Mixtures with Mixtures

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