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Reactive Polymers 2 0 (1 9 9 3 ) 1 -4 5 1
E l s e v i e r S c i e n c e P u b l i s h e r s B . V . , A m s t e r d a m
State of the Art Report
C a t i o n i c i o n e x c h a n g e r e s i n s a s c a t a l y s t
A n i m e s h C h a k r a b a r t i a n d M . M . S h a r m a *
Department of Chemical Technology University of Bom bay Matunga Bombay-400 019 India
( R e c e i v e d N o v e m b e r 2 5, 1 9 92 ; a c c e p t e d F e b r u a r y 2 , 1 99 3)
b s t r a c t
Th is paper prese nts a review of the l i te ra tu re pe r ta in ing to ca ta lysis by ca tion exchange
re s ins . Emp has i s ha s been g iven to the l i t e ra tu re tha t ha s ap pea red du r ing the l a s t seven
years . A var ie ty of reac t ions ca ta lyzed by ca t ion exchange resins have been tabula ted
according to the i r broad c lass if ica tion; indust r ia l ly im porta nt rea c t ions have bee n de l in-
ea ted . Examples , where the use of ion exchange resin ca ta lysis has led to an improvement
in the se lec tiv i ty of the desi red products , h ave a lso been d iscussed . App roach es for the
in te rp re t a t ion o f k ine t ic da ta and mode l ing have been rev iewed .
The type o f r eac to r to be employed fo r c a r ry ing ou t ion exchange re s in ca t a lyzed
reac t ions ha s been d i scussed . A new em erg ing a rea i s t he adop t ion o f d i s ti l la t ion co lumn
reac tors e . g . , methy l t e r t - b u t y l e the r f rom i sobu ty lene and me thano l .
Some a spec t s o f the deac t iva t ion and regene ra t ion o f the se ca t a lys t s have been b r i e f ly
discussed.
The use o f ion exchange re s ins fo r the remova l o f impur i t i e s f rom mix tu re s and the
separa t ion of c lose-boi l ing compounds by explo i t ing the i r d i f fe rent c h em i c a l reac t iv ity has
been h igh l igh ted .
Sugges t ions have been mad e fo r fu r the r work .
Keywords: ca ta lysis ; ca t ion exchange resin ; a lkyla t ion; e ther i f ica t ion; es te r i f ica t ion; Am-
berlyst-15
C o n t e n t s
A b s t r a c t 1
1 . I n t r o d u c t i o n 2
2 . P r e v i o u s r e v i e w s 3
3 . P r e p a r a t i o n o f i o n e x c h a n g e r e s i n c a t a l y s t s 3
4 . R e s i n s t r u c t u r e a n d i t s c a t a l y t ic c o n s e q u e n c e s 4
* C o r r e s p o n d i n g a u t h o r .
0 9 2 3 - 1 1 3 7 / 9 3 / 0 6 . 0 0 1 99 3 - E l s e v i e r S c i e n c e P u b l i s h e r s B . V . A l l r i g h t s r e s e r v e d
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2 A. Chakrabarti, M.M. Sh arm a/R eac t. Polym. 20 1993) 1-4 5
5. Catalysis by ion exchange resins 5
6. Adv antages and limitations of ion exchange resins as catalyst 6
7. Selectivityof ion exchange resin catalysts 7
8. Kinetics of ion exchange resin catalysis 8
8.1. Role of ma ss transfer 8
8.2. Kinetic mod el 9
8.3. Dis tribution coeffic ient 11
9. Reactions catalyzed by cation exchange resins: Reactions of industrial importance 12
10. Reactors used for ion exchange resin catalyzed reactions 22
11. So m e important observations on ion exchange resin catalysis 23
12. Separation of close-boilingcom pounds through reactions catalyzed by ion exchange resin 25
13. Rem oval of impurities from a mixture by reaction catalyzed by ion exchange resin 26
14. M odified ion exchange resin s and supported perfluorinated resin sulfonic acid 27
15. Deactivation and regeneration of ion exchange resin catalysts 29
16. I on exchan ge resin s versus clays versus othe r catalysts 30
17. Co nclus ions 31
18. Futu re scop e 32
References 32
1. I n t r o d u c t i o n a c id s , b u t t h e u s e o f a c i d i o n e x c h a n g e r e s i n
p r o v i d e d r e a s o n a b l y h i g h r e a c t i o n r a t es a t
A n i o n e x c h a n g e m a t e r i a l m a y b e b r o a d l y t h e lo w t e m p e r a t u r e s e m p l o y e d [ 3 ]. I n t h e
d e f i n e d a s a n i n s o lu b l e m a t r i x c o n t a i n i n g c a s e o f d e h y d r a t i o n o f t e r t - b u t a n o l , s u l f o n i c
l a bi le i o n s c a p a b l e o f e x c h a n g i n g w i t h i o n s i n a c i d re s i n c at a ly s ts w e r e f o u n d t o b e m u c h
t h e s u r r o u n d i n g m e d i u m w i t h o u t m a j o r p h y s - m o r e e f f ec t iv e t h a n t h e s o l u b l e a c i d c a ta l ys t s
i ca l c h a n g e t a k i n g p l a c e i n i ts s t r u c t u r e . T h e [ 4] . S i m i l a rl y , a c t i v it i e s h i g h e r t h a n s o l u b l e
r e si n s t yp ic al ly e m p l o y e d a r e su l fo n i c a c id p - t o l u e n e s u l f o n i c a c id p - T S A ) h a s b e e n r e-
c a t i o n e x c h a n g e r s i n t h e h y d r o g e n f o r m o r p o r t e d f o r t h e a d d i t i o n o f a l c o h o l s t o o l e f in s
q u a t e r n a r y a m m o n i u m a n i o n e x c h a n g e r s i n u s i n g i o n e x c h a n g e r e s i n c a ta l ys t s [ 5] . F o r t h e
t h e h y d r o x i d e f o r m . T h e i d e a t h a t i o n e x - e t h e r i f i c a t io n o f e t h y l e n e a n d p r o p y l e n e g ly -
c h a n g e r s c a n b e u s e d a s a s u b s t i t u t e fo r c o ls w i t h i s o b u t y l e n e , i t w a s o b s e r v e d t h a t
m i n e r a l a c i ds a n d b a s e s , d a t e s b a c k t o 1 91 1 t h e r a t e s o f r e a c t i o n w i t h c a t i o n e x c h a n g e
[1 ]. T h e f ir s t c o m m e r c i a l p r o c e s s , f o r e s t er i fi - r e s i n c at a ly s t w e r e m u c h h i g h e r t h a n t h o s e
c a t i o n a n d e s t e r h y d r o ly s i s o v e r W o f a t i t p h e - w i t h s o lu b l e p - T S A c a t a ly s t [ 6 ]. I n t h e c a se
n o l s u l p h o n i c a c i d - f o r m a l d e h y d e c o n d e n s a - o f e t h e ri f ic a t io n o f t h e p h e n o l s w i t h i so b u ty -
t i o n p o l y m e r s , w a s d e v e l o p e d b y I . G . F a r - l e n e , t h e y i e ld s o f t h e c o r r e s p o n d i n g t e r t -
b e n i n d u s t r i e in t h e 1 9 40 s i n t h e c o n t e x t o f b u t y l e t h e r s w e r e r e m a r k a b l y h i g h c o m p a r e d
t h e G e r m a n w a r ef f o rt [ 2 ]. A l t h o u g h io n t o t h a t w i t h p - T S A [7a]. B e c a u s e o f t h e
e x c h a n g e c a ta l ys is i n v ol v e s t h e u s e o f i o n i m p r o v e d s e l e c ti v it y o f t h e i o n e x c h a n g e
e x c h a n g e r e si n s t o p r o m o t e r e a c t i o n s t h a t r e si n s , t h e c u r r e n t i o n e x c h a n g e r e s i n c a t a-
a r e n o r m a l l y c a t a ly z e d b y m i n e r a l a c i d s a n d l ys t c a p a c i ty o f a b o u t 4 00 0 m 3 / y r o f r e s i n i s
b a s e s, t h e r e a r e m a n y i n s t a n c e s w h e r e t h e e x p e c t e d t o d o u b l e o v e r t h e n e x t f iv e y e a r s,
u s e o f i o n e x c h a n g e r e s i n c a ta l y st s h a s l e d t o e s p e c ia l l y d u e t o t h e i r h i g h c o n s u m p t i o n i n
i m p r o v e d a ct iv it y a n d / o r y i el d o v e r t h e h o - m e t h y l t e r t - b u t y l e t h e r M T B E ) p l a n t s [7 b].
m o g e n e o u s c a ta l ys ts . F o r t h e r e a c t i o n o f l in - T h i s p a p e r t a k e s i n t o c o n s i d e r a t i o n a ll t h e
e a r k e t o n e s a n d a l c o h o ls t o g i ve k e t al s , t h e p r e v i o u s r e v ie w s w h i c h h a v e a p p e a r e d i n t h e
r a t e s w e r e i m p r a c t i c a b l y l o w w i t h t h e s o l u b l e l i t e ra t u r e . I n t h is r e v ie w , e m p h a s i s h a s b e e n
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A. Chakrabarti, M.M. Sharma /Re ac t. Polym . 20 1993) 1-45 3
e s p e c i a ll y g i v e n t o t h e l i te r a t u r e o f t h e l a st t a g e t h a t t h e d e g r e e o f c r o s s li n k i n g a n d t h e
s e v e n y e a rs . A n a t t e m p t h a s b e e n m a d e t o p a r t i c l e s i ze o f t h e re s i n s a r e m o r e re a d i l y
f o c u s a t t e n t i o n o n i m p o r t a n t a s p e c t s o f c a t a l- a d j u s t e d [ 16 ].
y s is b y i o n e x c h a n g e r e s in s . T h e n e w d e v e l - T h e m o s t i m p o r t a n t r e s i n s o f t h is t y p e a r e
o p m e n t s i n p r e p a r i n g t a i l o r - m a d e r e s i n c a t a - c r o s s l i n k e d p o l y s t y re n e s w i t h s u l fo n i c a c id
l ys ts h a v e a l so b e e n d i s c u ss e d . T h e u s e o f g r o u p s w h i c h h a v e b e e n i n t r o d u c e d a f t e r
c a t i o n e x c h a n g e r e s i n s f o r a v a r i e ty o f a c i d- p o l y m e r i z a t i o n b y t r e a t m e n t w i t h c o n c e n -
c a t a l y z e d r e a c t i o n s h a s b e e n c o v e r e d ; s p e c ia l t r a t e d s u l fu r ic a c i d o r c h l o r o s u l f o n ic a c i d
a t t e n t io n h as b e en g iv en to in d u s t r i a l ly im- [1 7 -1 9 ]. A s a ru l e , d iv in y lb en z en e i s u sed as
p o r t a n t r e a c t io n s . T h e p o t e n t i a l o f e x p e n s i v e t h e c r o s s li n k i n g a g e n t ( c o m m e r c i a l m i x t u r e
p e r f l u o r i n a t e d s u lf o n ic a c i d b a s e d i o n e x - o f d i v i n y l b e n z e n e a n d e t h y l s t y r e n e i s u s e d
c h a n g e r e s i n a s s u p p o r t e d c a t al y st s h a s b e e n f o r t h is p u r p o s e ) .
c o n s i d e r e d . T h e c o p o l y m e r b e a d s a r e p r e p a r e d b y t h e
s o - c a l l e d p e a r l p o l y m e r i z a t i o n t e c h n i q u e
[2 0,2 1]. T h e m o n o m e r s ( f r o m w h i c h p o l y m e r -
2.
Previous reviews
i z a t i o n i n h i b i t o r s h a v e b e e n r e m o v e d ) a r e
m i x e d a n d a p o l y m e r i z a t i o n c a ta l y st s u c h a s
B h a g a d e a n d N a g e s h w a r h a v e p u b l i s h e d b e n z o y l p e r o x i d e is a d d e d . T h e m i x t u r e is
r e v ie w s o n d i f f e r e n t r e a c t i o n s, n a m e l y , hy - t h e n a d d e d t o a t h o r o u g h l y a g i t a t e d a q u e o u s
d r a t i o n , d e h y d r a t i o n , e s t e r i fi c a t i o n , e s t e r h y - s o l u t i o n w h i c h is k e p t a t t h e t e m p e r a t u r e
d ro lys i s an d a lk y la t io n , ca t a ly zed b y io n ex - r eq u i re d fo r p o ly m er i za t io n (u su a l ly 8 5 to
ch a n g e r es in s [8 -1 2 ] . In a l l t h e cases , t h ey 1 00 C ). T h e mix tu re fo rm s smal l d ro p le t s
h a v e t a b u l a t e d t h e r e a c t a n t s a n d t h e c a t al y st w h i c h r e m a i n s u s p e n d e d . A s u s p e n s i o n s t a bi -
u sed . W id d ec k e [1 3 ], i n an ex h au s t iv e r ev iew , l i ze r (g e l a t in , p o ly v in y l a l co h o l , so d iu m
h a s d i s c u s s e d t h e w o r k i n g c o n c e p t s o f i o n
e x c h a n g e r e s i n s a s c a ta l ys t . S o m e i m p o r t a n t o l e a t e , s o d i u m m e t h a c r y l a t e , m a g n e s i u m s il i-
p o i n t s a b o u t t h e d e s i g n a n d i n d u s t r ia l a p p li - c a t e ,
e t c .
i n t h e a q u e o u s p h a s e p r e v e n t s
a g g l o m e r a t i o n o f t h e d r o p l e t s . T h e s i ze o f
c a t i o n s o f t h e c a ta l y st s h a v e a ls o b e e n h i g h - t h e d r o p l e t s d e p e n d s c h i e fl y o n t h e n a t u r e o f
l ig h te d b y h im . R ec en t ly , N e ie r [1 4 ] h as p u b - th e su sp e n s io n s tab i l i ze r, v i scos i ty o f t h e so -
l i s h e d a c o m p r e h e n s i v e r e v i e w o n t h e i o n
l u t io n , a n d a g i t a t io n a n d c a n b e v a r i e d w i t h in
ex ch an g er s a s ca t a ly s t . O lah e t a l . [ 1 5 ] h a v e w i d e l im i ts . T h e p o l y m e r i s o b t a i n e d i n t h e
p u b l i s h e d a r e v i e w a r t ic l e o n p e r f l u o r i n a t e d f o r m o f f a ir ly u n i f o r m s p h e r i c a l b e a d s . F o r
su l fo n ic ac id r e s in ca t a ly zed reac t io n s . T h e mo s t p u rp o se s , a b e ad s i ze o f 0 .4 to 1 .1 m m
p r e s e n t r e v i e w c o v e r s s o m e a d d i t i o n a l a n d is p r e f e r r e d , b u t b e a d s f r o m 1 ~ m to 2 m m
n e w a s p e c t s o f c a ta l ys i s a n d a ls o h i g h l ig h t s i n d i a m e t e r c a n b e p r e p a r e d w i t h o u t m a j o r
m a n y o f t h e i n d u s t ri a l ly i m p o r t a n t r e a c t i o n s .
d i f f i cu l t i e s . P o ly mer i za t io n in aq u eo u s su s -
p e n s i o n i s p o s s i b l e i f t h e m o n o m e r s a r e i n -
3. Preparat ion of ion exchange res in cata so lu b le in w a te r . T h i s is n o t a lw ay s th e case .
lysts H o w e v e r , w a t e r - s o l u b l e m o n o m e r s s u c h a s
ac ry l i c ac id can b e mad e in so lu b le , fo r ex am-
M o s t p r e s e n t d a y i o n e x c h a n g e r e s i n s a r e p i e , b y e s t e r if i c a t io n . T h e e s t e r g r o u p s a r e
a d d i t i o n c o p o l y m e r s p r e p a r e d f r o m v i n yl t h e n h y d r o l y z e d a f t e r p o l y m e r i z a t i o n . A l t e r -
m o n o m e r s . T h e s e p o l y m e r s h a v e a h i g h e r n a t iv e ly , t h e w a t e r - i n - o i l t e c h n i q u e ( in -
c h e m i c a l a n d t h e r m a l s t a bi li ty t h a n t h e i r v e r s e s u s p e n s i o n p o l y m e r i z a t i o n ) c a n b e
f o r e r u n n e r s , t h e c o n d e n s a t i o n p o l y m e r s , u s e d . H e r e , t h e c o p o l y m e r i s f o r m e d e x c lu -
A l s o , a d d i t i o n p o l y m e r i z a t i o n h a s t h e a d v a n - s iv e ly f r o m h y d r o p h i l i c m o n o m e r s . T h e
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d r o p l e t s o f th e p o l y m e r i z a t i o n m i x t u r e a r e u n i f o r m s iz e . I f s u i t a b le m e t h o d s a r e u s e d t o
s u s p e n d e d i n a n i n e r t o r g a n i c s o l v e n t in p r e v e n t t h e m f r o m c o a l e s c i n g t o f o r m l a r g e r
w h i c h t h e m o n o m e r s a r e i n so l u bl e , d r o p l et s , m o n o d i s p e r s e b e a d s a r e f o r m e d ,
T h e p o l y m e r i z a t i o n p r o c e d u r e d e s c r i b e d y i e l d i n g m o n o d i s p e r s e r e s in s a f t e r f u n c t i o n -
a b o v e is g e n e r a l l y a d o p t e d f o r m a n u f a c t u r i n g a l iz a t io n . U s i n g t h e p r o c e s s d e v e l o p e d b y
g e l -t y p e r e si n s. H o w e v e r , t h e c o n v e n t i o n a l B a y e r A G , L e v e r k u s s e n , i t is p o s s ib l e t o p r o -
p e a r l p o l y m e r i z a t i o n t e c h n i q u e c a n b e s u it - d u c e b o t h g e l a n d m a c r o p o r o u s r e s in s . F o r
a b ly m a n i p u l a t e d t o g e t h i g h l y p o r o u s , t h e m o n o d i s p e r s e r e s i n t h e r e i s n o G a u s s i a n f r e -
s o - c a ll e d m a c r o r e t i c u l a r o r m a c r o p o r o u s , i o n q u e n c y d i s t ri b u t io n . T h u s , m o n o d i s p e r s e
e x c h a n g e r e si n s . A n o r g a n i c s o l v e n t w h i c h is r e f e r s t o p r o d u c t s w h e r e a t l e a s t 9 0 % o f a ll
a g o o d s o l v en t f o r t h e m o n o m e r s , b u t a p o o r b e a d s a r e o f t h e s a m e s iz e w i t h a t o l e r a n c e
s o l v en t f o r t h e p o l y m e r , is a d d e d to t h e p o ly - o f + 0 .1 m m . H o w e v e r , t h e b e a d s a r e u s u a l ly
m e r i z a t i o n m i x t u r e . A s p o l y m e r i z a t i o n p r o - w i t h i n a n e v e n n a r r o w e r t o l e r a n c e ,
e.g.
9 0 %
g r e s se s , t h e s o l v e n t i s s q u e e z e d o u t b y t h e w i t h i n + 0 . 0 5 m m d i a m e t e r .
g r o w i n g c o p o l y m e r r e g i o n s. I n t h is W a y , o n e A n o t h e r t y p e o f i o n e x c h a n g e r e s in ,
c a n o b t a i n s p h e r i c a l b e a d s w i t h w i d e p o r e s n a m e l y , p e r f l u o r i n a t e d s u l fo n i c a c i d re s i n
( s e v e ra l h u n d r e d A n g s t r o m u n i t s) w h i c h a l- ( N a t i o n ) , i s p r e p a r e d fr o m a c o p o l y m e r o f
l o w a c c e ss t o t h e i n t e r i o r o f t h e r e s i n e v e n t e t r a f l u o r o e t h e n e a n d p e r f l u o r o [ 2 -( f l u o r o -
w h e n n o n - p o l a r s o l v e n t s a r e u s e d [ 22 ]. s u l f o n y le t h o x y ) ] p o ly v i n y l e t h e r . T h e p e r f l u o -
T h e s u lf o n a t i o n o f t h e r e s in s p r e s e n t s n o r i n a t e d v i ny l e t h e r i s p r o d u c e d by r e a c t i n g
p r o b l e m s i f p r o p e r p r e c a u t i o n s a r e t a k e n , t e t r a f l u o r o e t h e n e w i t h S O 3 t o f o r m a c y c li c
S u l f o n a t i o n p ro g r e s s e s f r o m t h e o u t e r s h e ll s u l f o n e w h i c h s u b s e q u e n t l y r e a r r a n g e s t o f lu -
t o w a r d s th e c e n t r e o f t h e p a r t i c le a n d is o r o c a r b o n y l m e t h a n e s u lf o n y l f l u o r id e . T h e
a c c o m p a n i e d b y c o n s i d e r a b l e s w e l li n g a n d l i n e a r a n a l o g r e a c t s w i t h t w o m o l e s o f h e x a -
e v o l u t i o n o f h e a t . T h e m a t r ix is s t r a i n e d f l u o r o p r o p y l e n e o x i d e t o y i e l d a c o m p o u n d
r a t h e r s e v e re l y , a n d t h e b e a d s m a y c r a c k , w i t h a t e r m i n a l 1 - f l u o r o c a rb o n y l t r if l u o r o -
S u c h d i s i n t e g r a t i o n c a n b e a v o i d e d b y l e t ti n g e t h o x y g r o u p . T h i s g r o u p l o s es c a r b o n y l f l uo -
t h e b e a d s s w e ll , p r i o r t o s u l f o n a t io n , i n s o l- r i d e o n h e a t i n g w i t h N a 2 C O 3 t o g i v e t h e
v e n t s s u c h a s t o l u e n e , n i t r o b e n z e n e , m e t h y l - p e r f l u o r i n a t e d v in y l e t h e r . T h e c o p o l y m e r
e n e c h l o r i d e o r t r i c h l o r o e t h a n e [1 9]. S i m i l a r r e s i n i n t h e s u l f on y l f l u o r i d e f o r m i s b a s e
s t ra i n s d e v e l o p w h e n t h e s u l f o n a t e d b e a d s h y d r o l y z e d t o t h e a l k al i f o r m a n d t h e n a c id i -
a r e t r a n s f e r r e d i n t o a d i l u t e a q u e o u s s o l u t i o n f l e d t o t h e s u l f o n i c a c i d f o r m [2 4].
o r p u r e w a t e r . T h e r e f o r e , i t i s a d v i s a b l e t o
t r a n s f e r t h e b e a d s a t f i rs t i n t o a h i g h l y c o n -
c e n t r a t e d e l e c t r o l y t e s o l u t io n w h i c h c a u s e s 4 . R e s i n s t r u c t u r e a n d it s c a t a l y ti c c o n s e -
l es s s w e l li n g , a n d t h e n t o d i l u t e t h e s o l u t io n q u e n e e s
prog ress ive ly [19].
T h e c o m m e r c i a l r e s in s a v a i la b l e a r e h e t - T h e r e s in s c a n b e d i v i d e d i n t o t w o g r o u p s
e r o d i s p e r s e a n d h a v e p r o p e r t i e s w h i c h c a n h a v i n g m a j o r s t r u c t u r a l d i f f e r e n c e s , g e l a n d
b e a t t r i b u t e d d i r e c tl y t o t h e b a n d w i d t h , m a c r o r e t i c u l a r r e s in s . O n a m i c r o s c o p i c
w i t h i n w h i c h t h e b e a d s iz e s f al l. T h e s e i r re g - s c a le , t h e t h r e e - d i m e n s i o n a l p o l y m e r i c g e l
u l a r it i e s c a n b e o b s e r v e d i n t h e m e c h a n i c a l m a t r i x i s h o m o g e n e o u s w i t h n o d i s c o n t i n u -
s t a b il i ty , h y d r a u l i c p r o p e r t i e s , a n d k i n e t i c i t ie s . I f t h e g e l b e a d s a r e t o t a l l y d r y , t h e n t h e
p h e n o m e n a i n c o l u m n s [2 3]. p o l y m e r i c m a t r i x c o l la p s e s a n d t h e p o ly s ty -
I n t h e p a s t f e w y e a r s i t h a s b e e n p o s s ib l e r e n e c h a i n s w i l l b e as c l o s e a s a t o m i c f o r c e s
t o d i s p e r s e l i q u id m o n o m e r s i n t o d r o p l e t s o f a l lo w . I n t h is c o n d i t i o n , u n l e s s a r e a c t a n t i s
-
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i t s e l f c a p a b l e o f s w e l l in g t h e m a t r ix , t h e c o l- m e d i u m a n d p r e s e n t u n i f o r m l y t h r o u g h o u t
l a p s e d g e l b e a d e x h i b it a l m o s t n o c a ta l y ti c t h e s ys t e m . T h i s i s n o t t h e c a s e w i t h r e s i n
ac t iv i ty b ec au se o n ly th e s i t e s o n th e b ea d ' s ca t a ly s i s. T h e ca ta ly t i ca lly ac t iv e g ro u p s a re
s u r f a c e ( w h i c h a r e i n s i g n if i c a n t i n n u m b e r a n c h o r e d t o t h e m a t r i x a n d , i n t h e s o l v e n t -
c o m p a r e d t o t h e t o t a l a c t iv e s i te s w i t h i n t h e r e s i n s y s te m , a re l o c a t e d a t t h e s u r fa c e o f
b o d y o f t h e b e a d ) a r e a v a il a b le t o t h e re a c - a n d w i th i n t h e b o d y o f t h e r e s in b e a d o n l y.
t a n t s [ 2 5 ]. T h e r e f o r e , t h e s w e l l i n g a b il it y o f T h e b u l k s o l u t i o n i s c o m p l e t e l y f r e e o f c a t a -
th e r eac t a n t s i s a p re r eq u i s i t e fo r ca t a ly s i s b y lys t an d co n seq u en t ly ca t a ly ti ca l ly in e r t .
g e l re s i n s. G e l r e s i n s a r e c h a r a c t e r i z e d b y H o w e v e r , i n p o l a r s o l ve n t s , a c i d l e a c h i n g m a y
d i v i n y l b e n z e n e c o n t e n t g e n e r a l l y b e l o w 1 2 % . b e o b s e r v e d l e a d i n g t o t h e p r e s e n c e o f c a t -
T h e l im i t a t io n o f t h e g e l r e s in s w as l a rg e ly a ly ti ca lly ac t iv e sp ec ies in th e b u lk so lu t io n
o v e r c o m e , a r o u n d 1 9 60 , w i t h t h e a d v e n t o f a s w e l l a s i n t h e r e s in .
t h e m a c r o p o r o u s i o n e x c h a n g e r e s i ns [ 2 6 - I o n e x c h a n g e r s a r e , i n e f f e c t, p a r t i c u l a t e
3 0] . T h e y co n s i s t o f ag g lo m era te s o f v e ry ac t iv e sp ec ies an d w h e n u se d as ca t a lys t s
s m a l l m i c r o s p h e r e s i n t e r s p e r s e d w i t h m a c r o - o f f e r t h e c h e m i c a l b e n e f i t s o f h o m o g e n e o u s
p o r e s . R e a c t a n t s m a y m o v e e a s il y i n t o th e c a ta l ys is c o m b i n e d w i t h t h e p h y s ic a l a n d m e -
i n t e r i o r o f t h e b e a d t h r o u g h t h e s e m a c r o - c h a n i c a l b e n e f i t s o f h e t e r o g e n e o u s c a ta l ys t s
p o res . T h e s ig n i f i can t co n seq u e n ce i s t h a t , [25 ].
w h e r e a s g e l r e s i n s c a n o n l y f u n c t i o n e f f e c - D e p e n d i n g o n t h e n a t u r e o f t h e r e a c t a n t s
t iv e ly a s ca t a ly s ts i n a sw e l l in g m ed iu m , mac - an d so lv en t , a l l t h e r e s in -ca t a ly ze d r eac t io n s
r o r e t i c u l a r r e s i n s c a n f u n c t i o n a l so i n n o n - f a ll in t o o n e o f t w o m a j o r ty p e s , n a m e l y ,
s w e l li n g s o l ve n t s, t h e r e b y g r e a t l y e x p a n d i n g T y p e A a n d T y p e B [ 2 5 ] . T y p e A c a n b e
th e p o ss ib i l i ti e s o f r e s in ca t a lys i s [3 1 -3 4 ]. su b d iv id ed in to tw o g ro u p s : (A 1 ) ca t a ly s i s b y
f u ll y w a t e r - s w o l l e n r e s i n s i n a q u e o u s s y s te m s
a n d ( A 2 ) ca ta ly si s in m i x e d w a t e r / o r g a n o
5 . C a ta ly s i s b y io n ex ch an g e r es in s so lv en t s. In th e f i rs t case , t h e h y d ra t ed p ro -
to n i s t h e ca t a ly t i c ag en t an d th e r e s in i s
T h e p r i n c i p a l d i f f e r e n c e s b e t w e e n c a ta l y- f o u n d t o b e m o r e e ff e c t iv e t h a n h o m o g e -
s is b y d i s so lv ed e l ec t ro ly t es an d b y r es in s a re : n eo u s ac id . D av i s an d T h o m as [37 ] sh o w e d
i )
w i th r e s in s a s ca ta ly s ts , t h e ca t a ly s i s t h a t t h e r e s in -ca t a ly ze d h y d ro ly s is o f a se r i e s
o v e r l a p s w i t h d i f fu s i o n , a d s o r p t i o n a n d d e - o f e s t e r s u s i n g p u r e w a t e r a s a s o l v e n t w a s
s o r p t i o n p r o c e s s e s [ 3 5 ]; a n d t h e c o n c e n t r a - m o r e e f f e c t i v e t h a n h y d r o c h l o r i c a c i d .
t i o n o f t h e r e a c t a n t s i n s i d e t h e c a t al y s t ( w h e r e H a s k e l l a n d H a m m e t t [3 8] u s e d 7 0 % a c e t o n e
t h e r e a c t i o n t a k e s p l a c e ) m a y b e d i f f e r e n t a s t h e s o l v e n t i n t h e h y d r ol y s is o f d i f f e r e n t
f r o m t h a t i n t h e b u l k s o l u ti o n , d e p e n d i n g o n e s t e r s c a t a l y z e d b y i o n e x c h a n g e r e s i n a s t h e
t h e n a t u r e o f t h e m a t r i x, fi x e d i o n i c g r o u p , c a t al y st ( T y p e A 2 ) a n d f o u n d t h a t h y d r o c h l o -
t h e r e a c t a n t s , a n d t h e s o lv e n t s. F o r a p a r t ic u - r ic a c i d w a s m o r e e f f i c ie n t t h a n t h e r e s in .
l a r c a t a ly s t a n d r e a c t a n t s y s te m , t h e d i s tr i b u - H e r e t h e p r e s e n c e o f a c e t o n e c h a n g e s t h e
t i o n o f t h e r e a c t a n t s b e t w e e n t h e r e s i n p h a s e d i s t r ib u t i o n o f t h e e s t e r i n f a v o u r o f t h e b u l k
a n d t h e b u l k s o l u t i o n m a y b e c h a n g e d b y s o l u t i o n w h i c h i s r i c h i n a c e t o n e (i o n e x -
c h a n g i n g t h e s o l v e n t [3 6]. c h a n g e r i s e n r i c h e d b y w a t e r d u e t o i ts h i g h e r
i i )
t h e m a t r i x w i t h t h e f i xe d i o n i c g r o u p d i e l e c t r ic c o n s t a n t ) l e a d i n g t o a l o w e r e f fi -
m a y h a v e s o m e i n f l u e n c e ( w h i c h i s n o t p u r e l y c i e n c y o f t h e re s i n . T h e a b o v e d i s c u s si o n a l so
p h y s ic a l ) o n t h e c o u r s e o f t h e r e a c t i o n , s h o w s t h e i m p o r t a n c e o f r e a c t i o n c o n d i t i o n s
In h o m o g en eo u s ca t a ly s i s, t h e ca t a ly t i ca lly in ach iev in g su ccess in r e s in ca t a ly s i s. T y p e B
ac t iv e sp ec ies is d i s so lv ed in th e r eac t io n i s d iv id ed in to tw o su b g ro u p s : (B 1 ) ca t a ly s i s
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b y w a t e r - f r e e ) r e s in s i n n o n - a q u e o u s sy s- c a p i t a l a n d p r o c e s s i n g c o s ts b y e l i m i n a t i n g
t e m s w h e r e w a t e r is n o t a p r o d u c t o f t h e t h e s te p s a n d e q u i p m e n t r e q u i r e d f o r c a t a-
r e a c t i o n a n d B 2 ) n o n - a q u e o u s c a ta l y si s i n l ys t r e m o v a l i n a n a l o g o u s h o m o g e n e o u s p r o -
w h i c h w a t e r i s a b y - p r o d u c t o f r e a c t i o n , c e s se s . T h e w a s t e d i s p o s al p r o b l e m i s o b v i-
A l k y l a t i o n o f p h e n o l w i t h o l e f in s is a t y p ic a l a t e d . P r o d u c t p u r i ty a n d y ie l d a r e im p r o v e d
e x a m p l e o f t h e B l - t y p e r e a c t i o n . W a t e r h a s a i n m a n y c a s es . R e s i n s c a n o f t e n b e u s e d , i n
d e t r i m e n t a l e f f e c t o n th e B l - t y p e r e a c t i o n s h u n d r e d s o f c a t a ly t ic c y c le s w i t h o u t r e g e n e r -
w h i c h a r e c a ta l y z e d b y u n d i s s o c i a t e d s ul - a t i o n i n w e l l - d e s i g n e d p r o c e s s es . T h e r e f o r e ,
f o n i c a c i d g r o u p s ) . T h e c a u s e f o r t h e d e t r i - t h e c o s t o f t h e r e s i n i s s p r e a d o v e r t h e l if e o f
m e n t a l e f f e c t o f w a t e r o n B l - t y p e r e a c t i o n t h e r e s in , m a k i n g t h e c a t al y s t c o s t p e r u n i t
w a s g i ve n b y Z u n d e l [3 9]. W a t e r c o m p e t e s p r o d u c t i o n l o w e r t h a n t h e i r h o m o g e n e o u s
w i t h t h e r e a c t a n t f o r t h e a c t iv e s i te s a n d is c o u n t e r p a r t i n r e a l t e r m s .
s t ro n g l y b o n d e d t o s u l f o n ic a c i d g r o u p s . O n e T h e a b i li ty o f i o n e x c h a n g e r e s in s t o w o r k
w a t e r m o l e c u l e a t t a c h e s i ts e l f t o f o u r s u l- i n b o t h a q u e o u s a n d n o n - a q u e o u s s y s te m s
f o n i c a c i d g r o u p s le a d i n g t o a r e d u c t i o n i n c o n f e r s u n i q u e a d v a n t a g e s . H y d r o p h o b i c sy s-
t h e n u m b e r o f a v a i la b l e a c i d g r o u p s w h i c h i n t e m s c a n b e c a ta l y z e d b y d r y m a c r o r e t i c u l a r
t u r n d e c r e a s e s t h e r a t e o f t h e r e a c t i o n . E x - r e si n s. T h e d r y i n g o f t h e r e s in s is m u c h e a s -
a m p l e s o f t y p e B 2 r e a c t i o n s a r e t h e d e h y d r a - i e r t h a n t h a t o f p - T S A . R e s i n s e v e n h a v i n g
t i o n o f a n a l c o h o l, t h e e s t e r i f ic a t i o n o f a c i d t h e e q u i v a l e n t s t r e n g t h o f s t r o n g m i n e r a l a c i d
wi t h a l c o h o l , e tc . H e r e a s t h e r e a c t io n p r o - c a n b e h a n d l e d w i t h o u t d a n g e r t o p e r s o n n e l.
c e e d s , t r a n s i ti o n f r o m B 2 t o A 1 t a k e s p l a c e D u e t o i ts h e t e r o g e n e o u s n a t u r e t h e r e s in ,
wi t h r e s u l t i n g d r o p i n t h e c a t a l y t i c a c ti v it y , t h o u g h i t c o n t a i n s a c i d a t h i g h c o n c e n t r a t i o n ,
T h e r e f o r e to m a i n t a i n t h e B - t y p e c h a r a c t e r , c a n b e u s e d c o n v e n i e n t l y i n m i l d s t e e l e q u i p -
i . e . , t o m a i n t a i n h ig h c a t a ly t i c a c ti v it y, w a t e r m e n t : t h e n u m b e r o f a c i d g r o u p s a t t h e s u r -
n e e d s to b e r e m o v e d f r o m t h e s y s t em a s s o o n f a c e o f t h e b e a d i n c o n t a c t w i t h e q u i p m e n t is
a s i t is g e n e r a t e d , a v e r y s m a l l p e r c e n t a g e o f t h e t o t a l n u m b e r
o f a c i d g r o u p s p r e s e n t , t h u s o b v i a t i n g t h e
p r o b l e m o f c o r r o s i o n . A g i t a t i o n c a n f u r t h e r
6 . A d v a n t a g e s a n d l i m i t a ti o n s o f i o n e x
r e d u c e a n y c o r r o s i o n b y m i n i m i z i n g t h e c o n -
c h a n g e
r e s i n s a s c a t a l y s t
t a c t b e t w e e n t h e r e s i n p a r t i c l e s a n d t h e
e q u i p m e n t .
T h e p a r t ic u l a t e n a t u r e o f t h e i o n e x c h a n g e T h e m a j o r d i s a d v an t a g e o f i o n e x c h a n g e
r e s i n s p e r m i t s m e c h a n i c a l s e p a r a t i o n o f t h e r e s i n s i n c a t a l y s is i s t h e i r r e l a t i v e l y l o w t h e r -
c a t a ly s t a n d t h e r e a c t a n t - p r o d u c t m i x t u r e b y m a l st a bi li ty . I o n e x c h a n g e r e s in s c a n w i t h -
f i lt r a ti o n o r d e c a n t a t i o n , t h u s e l i m i n a t i n g s t a n d t e m p e r a t u r e s b e l o w 1 25 C f o r l o n g p e -
d i s ti l la t i o n o r e x t r a c t i o n p r o c e d u r e s f o r r io d s . F o r m a c r o r e t i c u l a r r e s in s , o p e r a t i o n a t
p r o d u c t i s o la t io n . R e s i n s c a n b e u s e d a s c a ta - 1 5 0 C f o r a lo n g t i m e m a y c a u s e d e s u l f o n a -
l ys t i n c o n t i n u o u s p r o c e s s e s i n f i x ed b e d r e - t i o n l e a d i n g t o a r e l e a s e o f s u l f o n i c a c i d a s
a c t o r s . I n t h i s c a s e , s i z e o f t h e i o n e x c h a n g e we l l a s a d r o p i n t h e a c t iv i ty . I t is r e c o m -
r e s i n m a y n e c e s s i t a t e t h e u s e o f s p e c i al s u p - m e n d e d t h a t s u c h c a t a l ys t s a r e n o t u s e d
p o r t t r a y s [ 40 ]. P a r t i c l e s s h o u l d p r e f e r a b l y b e a b o v e 1 20 C . R e s e a r c h i s g o i n g o n t o d e -
o f u n i f o r m s iz e . O t h e r w i s e , s m a l l e r p a r t i c le s v e l o p i o n e x c h a n g e r e s i n s h a v i n g h i g h e r t h e r -
m a y f il l u p t h e s p a c e b e t w e e n l a r g e r p a r t i c l e s m a l s t a b il i ty , a n d t h i s w i l l b e d i s c u s s e d l a t e r
c a u s i n g i m p r o p e r d is t r ib u t i o n o f t h e re a c - i n t h e t e xt . N a t i o n c a n w i t h s t a n d t e m p e r a -
t a n t s i n t h e r e s i n b e d [4 1] . t u r e u p t o 2 0 0 C , b u t u n f o r t u n a t e l y s u c h
C a t a ly s i s b y i o n e x c h a n g e r e s i n s l o w e r s m a t e r i a l s a r e e x p e n si v e ; t h e u s e o f s u p p o r t e d
-
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p e r f l u o r i n a t e d s u l f o n ic a c i d m a y h o w e v e r r e - w i t h p - T S A , A m b e r l y s t- 1 5 a n d N a f i o n - H as
d u c e o v e r a l l o p e r a t i n g c o s t s, t h e c a t a ly s t , r e s p e c t i v e l y [ 42 ]. E t h e r i f i c a t i o n
o f p h e n o l w i t h i s o a m y l e n e w a s t r i e d a t l o w
t e m p e r a t u r e w i t h p - T S A a s t h e c a t a l y s t [ 7 ] .
7 . e lec t iv i ty o f ion exchange res in ca ta lys ts O n l y C - a l k yl a te d p r o d u c t w a s f o r m e d . H o w -
e v e r , e t h e r i f i c a t i o n p r o c e e d e d w e l l a t t h e
T h e se l e ct iv i ty o f i o n e x c h a n g e r c a t al y st s s a m e t e m p e r a t u r e w i t h A m b e r l y st - 1 5 a s t h e
o f t e n l e a d s t o y i e l d s w h i c h a r e c o n s i d e r a b l y c a t a ly s t .
h i g h e r t h a n t h o s e o b t a i n e d w i t h c a ta l y si s b y I n t h e a l k y l a ti o n o f p h e n o l w i t h o l e fi n s ,
d i s so l v e d e l e c t r o l y te s [1 6]. T h e i o n e x c h a n g e r s o m e r e m a r k a b l e d i f f e r e n c e s w e r e o b s e r v e d
d i s ti n g u i s h e s m o r e s h a r p l y b e t w e e n t h e v a r i- w i t h i o n e x c h a n g e r e s i n a s t h e c a t a ly s t i n t h e
o u s r e a c t a n t m o l e c u l e s . I o n e x c h a n g e r s a s
o - / p - p r o d u c t
d i s t r ib u t i o n [ 7 4 ]. W i t h a - m e t h -
c a t al y s ts a r e p e r h a p s a b o u t h a l fw a y b e t w e e n y l s t y re n e ( A M S ) a s t h e a l k y la t in g a g e n t , t h e
t h e n o n - s e l e c t i v e d i s s o l v e d e l e c t r o l y t e s a n d o - / p - d i s t r i b u t i o n w a s 1 6 : 8 4 a n d 3 : 9 7 w i t h
t h e e x t r e m e l y s e l e c ti v e e n z y m e s . I o n e x- p - T S A a n d A m b e r l y st - 1 5 a s t h e c a t al y st , r e -
c h a n g e r e s in s c a n b e t a i l o r - m a d e t o u s e a s a s p e ct iv e ly ; w i t h d i i s o b u t y l e n e ( D I B ) a s t h e
m e a n s f o r s e l e c t i v e c a t a l y si s o f s m a l l a l k y la t in g a g e n t , t h e v a l u e s w e r e 4 1 : 5 9 a n d
m o l e c u l e s i n t h e p r e s e n c e o f l a r g e m o l e c u l e s . 5 9 5 w i t h p - T S A a n d A m b e r l y st - 1 5 a s t h e
A c r o s s l i n k d e n s i t y m a y b e c h o s e n t o i n h i b i t c a t a ly s t , r e s p e c t i v e l y ; a n d w i t h 1 - o c t e n e a s
ma t r i x e x p a n s i o n s u f f i c i e n tl y s o t h a t l a r g e t h e a l k y l a t i n g a g e n t , t h e r a t i o w a s 7 2 2 8 a n d
m o l e c u l e s a r e e x c l u d e d f r o m t h e i n t e r i o r o f 5 9 : 4 1 w i t h p - T S A a n d A m b e r l y st - 1 5 a s t h e
t h e b e a d b y s i e v e a c t i o n w h i l e s m a l l c a ta l y st , r e s p ec t iv e l y . R e c e n t l y , C h a n d r a a n d
m o l e c u l e s m a y e n t e r t h e m a t r i x t h u s f a v o u r- S h a r m a [ 4 4 ] h a v e o b s e r v e d t h a t m e t h y l
t e r t -
i n g t h e r e a c t i o n o f t h e s m a l l m o l e c u l e s o n l y b u t y l e t h e r ( M T B E ) c a n b e a d v a n t a g e o u s l y
[2 5]. O t h e r s p e c if i c e x a m p l e s o f s e l e ct i v e r e s i n u s e d f o r t h e b u t y l a t i o n o f p h e n o l w i t h A m -
c a t a ly s i s , w h i c h c a n n o t b e e x p l a i n e d s imp l y b e r l ys t - 15 a s c a t a ly s t . T h e s e le c t i v it y f o r 2 -
i n t e r m s o f m o l e c u l a r s i z e a n d s i e v e a c t i o n , t e r t - b u t y l p h e n o l c a n b e i m p r o v e d b y c ar e f u l ly
i n c l u d e c o n d e n s a t i o n o f f u r f u r a l w i t h a n s e l e c t in g t h e t e m p e r a t u r e a n d t h e l e ve l o f
a l d e h y d e . S u c h e f f e c t s m a y b e t e n t a t i v e ly c o n v e r s i o n . F o r t h e a l k y l at i o n o f s u b s t i t u t e d
e x p l a i n e d b y d i f f e r e n c e s i n s o r p t io n o f v a r i- h y d r o q u i n o n e s s u c h a s m e t h y l h y d r o q u i n o n e ,
o u s r e a c ta n t s . T h e p r e f e r e n t ia l s o r p ti o n o f p h e n y l h y d r o q u i n o n e a n d
t e r t - b u t y l h y d r o -
o n e o f t h e r e a c t a n t s i n t h e r e s i n m a y f a v o u r q u i n o n e , K i m e t a l . [ 1 7 7 ] h a v e r e p o r t e d b e t -
a r e a c t i o n w h i c h i s i n s i g n i f i c a n t i n c a t a ly s i s t e r s e l e c ti v i ty t o 2 , 5 - d i - t e r t - b u t y l h y d r o q u i -
b y d i s so l v e d e l e c tr o l y te s . I n t h e a b o v e - m e n - n o n e s w i t h A m b e r ly s t -1 5 c at a ly s t t h a n 7 0
t i o n e d c a s e , d i s s o l v e d b a s e s u n d e r o t h e r w i s e s u l p h u r i c a c i d . T h e s e l e c ti v i t y o f 2 ,5 - s ub -
i d e n t i c a l c o n d i t i o n s a lm o s t e x cl u si v el y g i ve s t i t u te d h y d r o q u i n o n e s w a s i n t h e d e s c e n d -
s e l f - c o n d e n s a t i o n o f t h e a l d e h y d e , i n g o r d e r o f
t e r t - b u t y l ,
p h e n y l , a n d m e t h y l h y -
I o n e x c h a n g e r e s in s s h o w e d h i g h e r s e l ec - d r o q u i n o n e s .
t iv i ty f o r t h e d e s i r e d p r o d u c t i n m a n y r e a c - I n t h e a c i d - c a ta l y z e d c r a c k i n g o f M T B E ,
t io n s . I n th e a l k y l a t i o n o f b e n z e n e w i t h c o n s i d e r a b l e i m p r o v e m e n t i n t h e s e le c t iv i ty
s t y r e n e , t h e p e r c e n t a g e y i e ld o f a l lo y la te d f o r t h e d e s i r e d p r o d u c t c o u l d b e r e a l i z e d b y
p r o d u c t w a s 0 , 1 0.7 a n d 1 3.7 w i t h p - T S A , u s i n g a s u r f a c e - s u l p h o n a t e d p o r o u s p o l y s ty -
A m b e r l y st - 1 5 a n d N a f i o n - H a s t h e c a ta l y st , r e n e c a t a ly s t i n s t e a d o f t h e c o m m e r c i a l l y
r e s p e c t i v e l y [4 2] . I n t h e a ll o y la t io n o f t o l u e n e a v a i l a b l e re s i n s . T h i s m a y b e a t t r i b u t e d t o
w i t h s t y r e n e , t h e p e r c e n t a g e y i e l d o f t h e t h e f o r m a t i o n o f b y - p r o d u c t s i n t h e s o l id
a l k y l a t e d p r o d u c t w a s 5 1 .5 , 6 1.5 a n d 8 6. 2 m a t r i x r e g i o n s o f t h e c o m m e r c i a l c a t a l y s ts
-
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w h i c h is i n h i b i t e d b y p r o v i d i n g t h e - S O 3 H o b v i o us l y b e r a t e - c o n t r o l l in g s i n ce i n t h is l im -
g r o u p s o n l y o n t h e s u r f a c e o f t h e c a t a ly s t i ti n g c a s e a ll r e a c t a n t m o l e c u l e s r e a c t a s
[4 5] . s o o n a s t h e y r e a c h t h e s u r f a c e o f t h e c a t a l y s t
p a r t i c l e . I f t h e c h e m i c a l r e a c t i o n i s m u c h
s l o w e r t h a n t h e d i f f u s i o n p r o c e s s e s , s o r p t i o n
8. i n e t i cs o f io n e x c h a n g e r e s i n c a t a l y s i s e q u i l i b r i u m o f t h e r e a c t a n t s i s e s t a b l i s h e d
a n d u p h e l d t h r o u g h o u t t h e c a t a l y s t p a r t i c l e
8 .1 . R o l e o f m a s s t r a n s fe r
s i n c e d i f f u s i o n i s e n o u g h t o m a k e u p f o r t h e
d i s a p p e a r a n c e o f r e a c t a n ts b y c h e m i c a l r ea c -
T h e t h e o r y o f c a t al y s is b y i o n e x c h a n g e r s t io n . T h e o v e r a l l r a t e is t h u s c o n t r o l l e d b y
h a s n o t y e t b e e n w e l l - e s ta b l i s h e d . I n a ll c a s e s t h e r a t e o f t h e c h e m i c a l r e a c t i o n t h r o u g h o u t
w h i c h h a v e s o f a r b e e n s t u d i e d a n d i n w h i c h t h e p a r t ic l e . I f i n t r a p a r t i c l e d i f fu s i o n is m u c h
l i m i t a ti o n s d u e t o s l ow d i f fu s i o n p r o c e s s c a n s l o w e r t h a n th e a c t u a l c h e m i c a l r e a c t i o n , t h e
b e r u l e d o u t , t h e k i n e t i c o r d e r o f t h e c h e m i - r e a c t a n t m o l e c u l e s w i ll r e a c t b e f o r e t h e y h a v e
c a l r e a c t i o n i n t h e p a r t i c le s w a s f o u n d t o b e t i m e t o p e n e t r a t e i n t o t h e i n t e r i o r o f t h e
t h e s a m e a s i n h o m o g e n e o u s c a t a l y si s b y a c a t a l y s t p a r t i c l e . I n t h i s l a t t e r l i mi t i n g c a s e ,
d i s s o l v e d e l e c t r o l y t e . T h i s is s t r o n g e v i d e n c e t h e r e a c t i o n o c c u r s o n l y i n a t h i n l a y e r a t t h e
i n s u p p o r t o f th e v i e w t h a t t h e r e a c t i o n s u r f a c e a n d i ts r a t e is c o n t r o l l e d b y e i t h e r
m e c h a n i s m i s e s s e n t ia l l y t h e s a m e in b o t h f il m d i f fu s i o n o r c h e m i c a l r e a c t i o n a t t h e
c a s e s . H o w e v e r , t h e r e a r e d i f f e r e n c e s i n r e - s u r f a c e . If t h e f i lm d i ff u s i o n i s s u f f i c i e n t ly
a c t i o n r a t e s, e v e n w h e n t h e a m o u n t o f c a t a - f as t, t h e p r o c e s s is c o n t r o l l e d b y c h e m i c a l
l ys t i n c o u n t e r - i o n e q u i v a l e n t s ) i s t h e s a m e r e a c t i o n a t t h e s u rf a c e . I n t r a p a r t i c l e d if f u-
i n b o t h c a s e s . A s i g n i f i c a n t d i f f e r e n c e b e - s i o n c a n a f f e c t t h e o v e r a l l r a t e o f r e a c t i o n ,
t w e e n h o m o g e n e o u s c at al ys is a n d h e t e r o g e - b u t i t c a n n e v e r b e t h e s o le r a t e - d e t e r m i n i n g
n i z e d h o m o g e n e o u s c a t al y si s is t h e p r e s e n c e s t e p a s d i f f u s io n a n d c h e m i c a l r e a c t i o n
o f d i f f u si o n a l p r o c e s s e s i n t h e l a t e r c a s e. a r e p a r a l l e l s t ep s , o c c u r r i n g s i m u l t a n e o u s l y
M o s t o f t h e i o n e x c h a n g e r e s i n c a t a l y z e d w i t h i n t h e r e s i n b e a d .
r e a c t i o n s r e p o r t e d i n t h e l i t e r a t u r e h a v e b e e n T h e s e c o n s i d e r a t i o n s s u g g e s t t h a t , i n t h e
c a r r i e d o u t i n t h e li q u i d p h a s e ; t h e r e f o r e , l i m i t in g c a s es , t h e o v e ra l l r a t e o f a n y i o n
o u r d i s c u s si o n w i l l b e l i m i t e d t o t h e l iq u i d - e x c h a n g e r e s i n c a t a l y z e d r e a c t i o n i s co n -
p h a s e r e a c t io n s . H o w e v e r , t h e s a m e t r e a t - t r o l l e d b y : i ) f i lm d i ff u s io n ; i i ) c h e m i c a l
m e n t c a n b e a d a p t e d , w i t h a f e w o b v i o u s r e a c t i o n t h r o u g h o u t t h e p a r t ic l e ; a n d
i i i )
c h a n g e s , t o g a s - p h a s e r e a c t io n s . I n o r d e r f o r c h e m i c a l r e a c t i o n a t t h e s u r fa c e . O b v i o u s l y
t h e r e a c t i o n t o o c c u r , r e a c t a n t m o l e c u l e s i n t e r m e d i a t e c a s e s a r i s e i f t h e r a t e s o f i n d i-
m u s t f ir s t m i g r a t e f r o m t h e b u l k s o l u t io n i n t o v i d u a l st e p s a r e c o m p a r a b l e . H o w e v e r , i t i s
t h e i o n e x c h a n g e r ; a n d m u s t r e a c t ; t h e r e a c - f o u n d g e n e r a l l y t h a t fi lm d i f fu s i o n d o e s n o t
t i o n p r o d u c t s m u s t t h e n m i g r a t e b a c k i n t o c o n t r o l t h e o v e r a l l r a t e i n i o n e x c h a n g e r e s i n
t h e s o lu t i o n . T h u s , t h r e e p h e n o m e n a c a n c a t a l y z e d p r o c e s s e s. I f t h e v i sc o s it y o f t h e
a f f ec t t h e r a t e o f o v e r a l l p r o c e ss : i ) d i ff u - r e a c t a n t m i x t u r e i s t o o h i g h o r t h e s p e e d o f
s i o n o f t h e r e a c t a n t s a n d p r o d u c t s a cr o s s t h e a g i t a t io n i s t o o lo w , t h e n f il m d i f fu s i o n m a y
f i lm N e r n s t d i f f u s i o n l a y e r ) s u r r o u n d i n g t h e c o n t r o l [ 16 ]. B u t t h e s e a r e e x c e p t i o n a l c a s e s .
ca ta lys t pa r t i c le ;
i i )
d i f fu s i o n o f t h e r e a c - O f t e n t h e o v e r a ll r a t e is c o n t r o l l e d b y a
t a n t s a n d p r o d u c t s i n t h e i n t e r i o r o f t h e c o m b i n a t i o n o f i n t r a p a r t i c l e r e a c t i o n a n d i n -
c a t a l y s t p a r t i c l e ; a n d
i i i )
c h e m i c a l r e a c t i o n t r a p a r t i c le d i f fu s i on .
a t t h e a c t iv e s it e s. I f f il m d i f fu s i o n i s m u c h T h e p r o c e d u r e f o r d i s c e r n i n g t h e c o n t r o l -
s l o w e r t h a n th e c h e m i c a l r e a c t i o n , i t m u s t l in g m e c h a n i s m in i o n e x c h a n g e re s i n c a t -
-
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a l y z e d l i q u i d / s o l i d r e a c t i o n h a s b e e n d i s - a c c e s si b il it y = f ( d i v i n y l b e n z e n e c o n t e n t , p a r -
c u s s e d i n d e t a i l b y D o r a i s w a m y a n d S h a r m a t ic l e s iz e , p o r o si t y, r e a c t i o n m e d i u m , d i ff u -
[46 ]. T h ey h av e a l so d i scu sse d th e p ro ced u re s s iv ity) .
f o r d i s c e r n i n g t h e c o n t r o l l i n g m e c h a n i s m i n F o r a g i v e n t y p e o f a c i d r e s i n c a ta l ys t ,
g a s / l i q u i d / s o l i d ( w h e r e t h e so l id a c ts as t h e h i g h e r d i v i n yl b e n z e n e c o n t e n t w i ll r e d u c e t h e
ca ta ly s t) r eac t io n s ca r r i ed o u t in s lu r ry o r sw e l l in g ab i l it y o f th e r e s in , t h u s r ed u c in g
f ix ed b ed re ac to r s [4 7 ] . C ar ra [4 8 ] h as d is - access ib il i ty to th e cata ly s t . In th e p re sen ce
c u s s e d t h e t y p e o f r e a c to r s u s e d , r o le o f o f m o r e p o l a r r e a c t i o n m e d i u m , t h e
h y d r o d y n a m i c f a ct o rs , m a s s t r a n sf e r i n a gi - p o l y m e r - b o u n d - S O 3 H g r o u p s a r e m o r e d is -
t a t e d s y st e m s , r o l e o f i n t r a p a r t i c l e d i f fu s i on , s o c i a t e d l e a d i n g t o a d e c r e a s e i n t h e a c id i ty
etc . ,
f o r i o n e x c h a n g e r e s i n c a t a l y z e d r e a c - o f t h e s u l fo n i c a c i d r e s in . W i t h m o r e p o l a r
t io n s , c o m p o n e n t s , t h e s w e l li n g o f t h e r e s i n i s
h ig h er an d , h en c e , t h e access ib i li t y i s im-
8 . 2 . K i n e t i c m o d e l
p ro v ed . B u t t e r sack [4 9 ] h as fu r th e r c l a ss i f i ed
t h e a c c e s si b il it y i n t o n o n - i n t e r a c t i o n a n d i n -
T h e sco p e o f ca t a ly t ic ap p l i ca t io n o f t e rac t io n access ib i li t y. T h e fo rm er i s ak in to
s t r on g l y a c i d ic i o n e x c h a n g e r e s i n s i n t h e t h e t e r m d i s p e r s i o n u s e d i n t h e c o n v e n -
l i q u id p h a s e e x t e n d s f r o m e s s e n t i a ll y h o m o - t i o n a l h e t e r o g e n e o u s c a ta l ys is fo r d e f i n i n g
g e n e o u s m e c h a n i s m s t o c l as s ic a l h e t e r o g e - t h e f r a c t io n o f c a t al y ti c a ll y a c t iv e g r o u p s a t
n e o u s c a t al ys is . D e p e n d i n g o n t h e i n t e r a c - t h e s u r f ac e a n d is r e l a t e d t o t h e m o r p h o l o g y
t i o n o f t h e s o lv e n t w i t h t h e a c i d g r o u p s a n d o f t h e r e s i n i n t h e d r y s t at e . T h e l a t t e r r e -
t h e p o l y m e r b a c k b o n e , d i f f e r e n t d e g r e e s a n d f l ec t s t h e i n f l u e n c e o f t h e s o l v e n t a n d a d -
p o s s ib l y t y p e s o f s w e l l in g o c c u r. T h e i d e a l - s o r b e d m o l e c u l e s ( t h e s t e a d y s t a t e r e a c t i o n
i z e d h o m o g e n e o u s s t a te r e q u i re s c o m p l e t e m e d i u m ) o n t h e i o n e x c h a n g e r e s in c a ta ly st .
sw e l l in g an d to t a l d i s so c ia t io n o f th e po ly - T h e access ib i li t y i s a l so a fu n c t io n o f th e
m e t - b o u n d - S O 3 H g r o u p ( s p e c if i c c a ta ly s is ), e f f e c t iv e d i ff u si v it y o f t h e r e a c t a n t s w i t h i n
W h e r e a s , t h e h e t e r o g e n e o u s s t a t e i s c h a r a c - t h e p o r e s , w h i c h is r e l a t e d t o t h e T h i e l e
t e r i z e d b y a d i r e c t i n t e r a c t i o n o f t h e s u b - m o d u l u s t h r o u g h t h e e q u a t i o n
s t ra t e w i th t h e p o ly m e r - b o u n d - S O 3 H g r o u p
= R f k / D
(g en era l ca t a ly s i s) . Mo s t r e s in -ca ta ly ze d reac -
t io n s can b e c la ss i f i ed e i th e r a s q u as i -h o m o - w h e re R is th e r ad iu s o f th e ca ta ly s t p a r t i c l e ,
g e n e o u s
( e . g . ,
h y d ro ly s i s o f su c ro se , ca r - k i s t h e r eac t io n r a t e co n s tan t , an d D i s th e
b o x y l i c e s t e r s ) o r q u a s i - h e t e r o g e n e o u s
( e . g . ,
e f fec t iv e d i f fu s iv ity o f th e r eac ta n t .
b e n z e n e p r o p y l a t io n , i s o b u t y l e n e o l i g o m e r - A p a r t f r o m t h e a d s o r p t i o n i s o t h e r m a n d
i z a ti o n ). C o m p l i c a t e d s i t u a ti o n s a r i se w h e r e d i s t r ib u t i o n c o e f f i c i e n t o f t h e re a c t a n t , t h e
t h e s o l v e n t c a u s e s o n l y p a r t i a l d i s s o c i a ti o n o f T h i e l e m o d u l u s a l so a ff e c ts t h e a c t u a l n u m -
- S O 3 H g r o u p s , d u e t o a l o w d e g r e e o f s o lv a - b e r o f s i te s , o u t o f t h e t o t a l a c c e s s ib l e s it e s,
t i o n
( e . g . ,
M T B E sy n th es i s ) [49 ]. o ccu p ied b y th e r eac tan t . T h e e f fec t o f in t r a -
T h e r a t e o f a r e s i n - c a t a ly z e d r e a c t i o n w i ll p a r t i c le d i f fu s i o n c a n b e i n c o r p o r a t e d in t h e
b e a fu n c t io n o f (1 ) th e ac id ity an d (2 ) th e r a t e ex p re ss io n b y w ay o f th e e f fec t iv en e ss
access ib i li t y o f th e ac t iv e s i t e s [1 3 ] ,
i . e . ,
f a c t o r ~ w h i c h c a n b e c o r r e l a t e d t o t h e
r = f ( ac id i ty , access ib il i ty ) T h ie l e mo d u lu s . A tw o -p h ase m o d e l h as b e en
w h e r e s u g g e s t e d f o r t h e e f f e c t i v e n e s s f a c t o r o f a
ac id i ty = f ( ty p e an d n u m b e r o f ac id g ro u p s , ma cro re t i cu la r r e s in [5 0 ] , s in ce i t i s e s sen t i a l
d i v i n y lb e n z e n e c o n t e n t , r e a c t io n m e d i u m ) t o t a k e a c c o u n t o f b o t h m a c r o p o r e a n d m i -
an d c ro -p h ase d i f fu s io n .
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I n t h e a b s e n c e o f a n y i n t r a p a r t i c l e d if f u - s a t i s fa c t o r i ly a p p l i e d in t h e c a s e o f i s o b u t y l-
s i on l i m i t at i o n , t h e r a t e o f r e a c t i o n c a n b e e n e o l i g o m e r i z a t i o n [ 55 ], d i m e r i z a t i o n o f
e x p r es s e d u s in g a s i m p le p s e u d o h o m o g e - i s o a m y l e n e [ 5 6 ] , a n d b e n z e n e p r o p y l a ti o n
n e o u s m o d e l o r a m o r e c o m p l e x m o d e l b a s e d [3 4]. A m o r e c o m p l e x s i t u a t io n a ri s e s f o r t h e
o n t h e L a n g m u i r - H i n s h e l w o o d m e c h a n i s m , e t h e r if i c a ti o n r e a c ti o n s o f o l ef in s w i t h a lc o -
T h e p s e u d o h o m o g e n e o u s m o d e l is b a s e d o n h o ls M T B E / E T B E / T A M E s yn th es is ): d e -
t h e H e l f f er i c h a p p r o a c h w h i c h t r e a t s t h e p e n d i n g u p o n t h e c o n c e n t r a t i o n o f t h e a lc o -
c a ta l ys i s b y i o n e x c h a n g e r es i n s a s h o m o g e - h o l , t h e r e c an b e a t r a n s i t io n f r o m g e n e r a l t o
n e o u s c a t a l y si s c o n f i n e d w i t h i n t h e i n t e r n a l s p e c i f i c c a t al y s is . F o r M T B E s y n t h e s i s , a t
c a t a l y s t ma s s
i . e . ,
r e s i n v o l u m e ) , w h e r e i n l o w e r c o n c e n t r a t i o n o f m e t h a n o l t h e c a ta l y si s
t h e r e a c t a n t s , p r o d u c t s a n d s o l ve n t s a r e i n i s b y t h e p o l y m e r - b o u n d - S O 3 H g r o u p s
d i s t r ib u t i o n e q u i l i b r i u m w i t h t h e b u l k s o lu - w h i c h a r e v e r y a c t iv e b u t i f t h e c o n c e n t r a t i o n
t io n . H e r e , t h e r e a c t i o n m e c h a n i s m is s i m i l ar o f m e t h a n o l i s i n c r e a s e d , m e t h a n o l d i ss o c i-
t o t h e o n e o b s e r v e d w i t h t h e d i s so l v e d e l e c - a t e s t h e a c i d g r o u p s a n d s o l v a te d p r o t o n s
t ro l y te s . T h e d i ff e r e n c e i n t h e p e r f o r m a n c e b e c o m e t h e c a t a ly t ic a g e n t s w h i c h a r e r e l a -
o f t h e tw o is a t t r i b u t e d t o t h e s e l e c t iv e s o r p - t iv e l y l e s s a c t iv e . A t v e r y h i g h m e t h a n o l c o n -
t i o n o f o n e o f t h e r e a c t a n t s b y t h e r e s in c e n t r a t i o n s , t h e m e t h a n o l is n o l o n g e r a b l e
d e p e n d i n g u p o n t h e n a t u r e e . g . , p o l a r i t y ) o f t o a f f e c t t h e r a t e e i t h e r a s r e a c t a n t o r a s
t h e r e a c t a n t s / s o l v e n t m e d i u m . I n t h is m o d e l , s o l ve n t , h a v i n g c o m p l e t e l y l e v e l le d t h e c a t a -
l i n e a r r e l a t io n s h i p s a r e a s s u m e d b e t w e e n t h e l ys t a c ti vi ty . S o m e r e s e a r c h e r s V o l o c h et a l .
r e a c t a n t c o n c e n t r a t i o n a t t h e a c t iv e s it e s [5 7], S u b r a m a n i a m a n d B h a t i a [5 8]) h a v e u s e d
w i t h in t h e r e s in a n d t h a t i n t h e b u lk . B u t t e r- a p s e u d o h o m o g e n e o u s m o d e l i n t h e c as e o f
s a c k [4 9] h a s d e f i n e d a c a t a ly t i c e f f ic i e n c y q ) M T B E s y n t h e s is a n d h a v e b e e n a b l e to co r -
a s t h e r at i o o f t h e o v e ra l l r e a c t i o n r a t e p e r r e l a t e t h e e x p e r i m e n t a l k i n e t i c d a t a s a ti sf a c-
a c i d s it e, o b t a i n e d w i t h a r e s i n c a t a ly s t t o t o ri ly ; n o n e t h e l e s s L a n g m u i r - H i n s h e l w o o d
t h a t o b t a i n e d w i t h a m i n e r a l a c id . T h e q o r R i d e a l - E l e y m o d e l s h av e b e e n m o r e
v a lu e s f o r m a n y r e a c ti o n s h a v e b e e n f o u n d t o w i d e l y u s e d H o f f m a n n
e t a l .
[ 5 9 - 6 2 ] , A n c i l -
b e i d e n t i c a l t o t h e d i s t r i b u t i o n c o e f f i c i e n t s , l o t ti e t a l . [ 5 ] , G i c q u e l a n d T o r c k [ 6 3] , G a t e s
T h e p s e u d o h o m o g e n e o u s a p p r o a c h is p a r t ic - a n d J o h n s o n [ 64 ], C u n i l l e t a l . [65]), and
u l a r l y a p p l i c a b l e i n c a s e s w h e r e o n e o f t h e t h e s e c a n b e a p p l i e d a n d e x t r a p o l a t e d o v e r a
r e a c t a n t s o r s o l v e n t is h i g h ly p o l a r . I n t h e w i d e r r a n g e o f c o n c e n t r a t i o n s . W h e n t h e
p r e s e n c e o f p o l a r c o m p o n e n t s , s o l v a ti o n o f r a t e - li m i t i n g s t e p i n vo l ve s a r e a c t a n t f r o m a
t h e p o l y m e r - b o u n d - S O 3 H g r o u p t a k e s f lu i d p h a s e w i t h o n e t h a t is a d s o r b e d , t h e
p l a c e , a n d th e c a ta l ys i s is b y t h e s o l v a te d m e c h a n i s m is c a l l e d a R i d e a l - E l e y m e c h a -
p r o t o n . F o r e x a m p l e , t h is m o d e l h a s b e e n n i sm . If a ll t h e r e a c t a n t s in v o l v e d i n t h e
s u c c es s fu l ly u s e d f o r t h e h y d r o l y si s o f s u - r a t e - d e t e r m i n i n g s t e p a r e a d s o r b e d , t h e c o r -
c r o s e [5 1], t h e h y d r o ly s is o f c a r b o xy l ic e s t e r s r e s p o n d i n g k i n e t i c b e h a v i o u r i s t e r m e d
[5 1], t h e h y d r a t i o n o f o l e f in s [5 2,5 3], a n d t h e L a n g m u i r - H i n s h e l w o o d . A fe w r e a c t i o n s e x -
d e h y d r a t i o n o f a l c o h o l s [5 4] . h i b i t m a x i m u m o f r e a c t i v i t y a t c e r t a i n s u b -
W h e r e , d u e t o t h e n o n - p o l a r n a t u r e o f t h e s t ra t e c o n c e n t r a t i o n e . g . , v a p o u r - p h a s e d e -
r e a c t a n t o r s o l ve n t, t h e p o l y m e r - b o u n d h y d r a t i o n o f a l c o h o l s , v a p o u r - p h a s e s y n t h e s i s
u n d i s s o c ia t e d - S O 3 H g r o u p is t h e p r o t o n o f M T B E / E T B E [6 6]). S u c h a m a x i m u m c a n
d o n o r , a s i m p l e h o m o g e n e o u s m o d e l m a y b e e x p l a in e d b y a L a n g m u i r - H i n s h e l w o o d
n o t f it t h e d a t a . A m o r e s u i t a b le a p p r o a c h i s m e c h a n i s m , b a s e d o n t w o - s it e a d s o r p t i o n o f
o n e b a s e d o n t h e L a n g m u i r - H i n s h e l w o o d o r i s o b u t e n e a n d th e e th e r , a n d a s i m p le a d -
R i d e a l - E l e y m e c h a n i s m . T h e s e h a v e b e e n s o r p ti o n o f m e t h a n o l . B u t t e r s a ck [ 4 9 ] h a s
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11
s u g g e s t e d a m o r e g e n e r a l c o n c e p t o f v a r ia b l e
8 .3 . D i s t r ibu t ion coe f f i c i en t
a c t i v e c e n t r e s , i n w h i c h , a t l o w d e g r e e o f
a d s o r p t i o n , e a c h s u b s t r a t e m o l e c u l e r e q u i r e s A s d i s c u s s e d e a r li e r , w h e n c a ta l ys i s b y t h e
a c e r t a i n n u m b e r o f a c i d s it e s t o f o r m a n c a t i o n e x c h a n g e r i s s i m i l a r t o h o m o g e n e o u s
a c t i v e c e n t r e . A s i s k n o w n f o r a u s u a l L a n g - c a t al y s is , t h e a c t u a l c o n c e n t r a t i o n o f t h e d i f-
m u i r i s o t h e r m , a f r a c t i o n o f s i te s p a r t i c i p a t e f e r e n t c o m p o n e n t s o f t h e r e a c t i o n m i x t u r e i n
i n t h e a d s o r p t i o n a n d a n o t h e r f r a c t i o n o f t h e r e s i n p h a s e m a y n o t b e t h e s a m e a s t h a t
s i te s r e m a i n u n o c c u p i e d . W h e n al l s i te s p a r - i n t h e b u l k s o l u t io n , s i n c e t h e m i c r o e n v i r o n -
t i c ip a t e i n t h e a d s o r p t i o n , t h e m a x i m u m r e - m e n t o f t h e r e s i n m a y d i f f e r s u b s t a n ti a l ly
a c t i o n r a t e is a c h i e v e d . A f t e r a t t a i n m e n t o f f r o m t h e b u l k . T h e r e m a y b e p r e f e r e n t i a l
s a t u r a t i o n , f u r t h e r a d s o r p t i o n o f t h e s u b - d i s t r i b u t io n o f s o m e o f t h e c o m p o n e n t s d e -
s t r a t e m o l e c u l e s is p o s s ib l e b y l o w e r i n g t h e p e n d i n g o n t h e i r r e l at i v e c o m p a t i b i l it y w i t h
s iz e o f t h e a c ti v e c e n t r e s d o w n t o o n e a c i d t h e r e s i n p h a s e . T h e r e f o r e , k n o w l e d g e o f t h e
g r o u p p e r s u b s t r a t e m o l e c u l e . T h i s s i z e -r e - d i s t r i b u t i o n c o e f f i c i e n t s i s n e c e s s a r y t o f i n d
d u c t i o n o f t h e a c t iv e c e n t r e s c a u s e s a d e - o u t t h e a c t u a l c o n c e n t r a t i o n o f t h e d i f f e r e n t
c r e a s e o f t h e a c id i ty a n d t h e re a c t i o n r a te . c o m p o n e n t s i n t h e r e s i n p h a s e . D i s t r i b u t i o n
T h u s th e m a x i m u m o f r e ac t iv i ty d e p e n d s o n c o e ff i ci e n t o f a p a r t ic u l a r c o m p o n e n t is d e -
t h e p r o t o n a c c e p t o r a b il it y o f t h e s u b s t r a t e ; f i n e d a s t h e r a t io o f t h e c o n c e n t r a t i o n o f t h a t
t h e h i g h e r t h e a b il it y t h e s h a r p e r is t h e m a x i - c o m p o n e n t i n t h e r e s in p h a s e t o t h a t in t h e
m u m a n d t h e l o w e r i s t h e s u b s t r a t e c o n c e n - b u l k p h a s e . D i s t r i b u t i o n c o e ff i c i en t c a n b e
t r a t i o n a t m a x i m u m r e a c ti v it y . I n t h e e x - f o u n d o u t b y t h e m e t h o d d e s c r i b e d b y H e l f -
t r e m e c a s e w h e n t h e p r o t o n a c c e p t o r a b il it y f e r ic h [6 9,7 0]. T w o m e t h o d s h av e b e e n s u g -
o f t h e s u b s t r a t e i s v e r y l ow , th e m a x i m u m g e s t e d f o r t h is p u r p o s e . I n t h e f ir s t o n e , t h e
d i s a p p e a r s a t i n f in i t e s u b s t r a t e c o n c e n t r a - r e a c t a n t s a r e e q u i l i b r a t e d w i t h t h e c a ta l ys t
t i o n s , a n d t h e g e n e r a l k i n e t i c s r e d u c e s t o t h e f r o m w h i c h t h e c a ta l y t ic a l ly a c t iv e s p e c i e s i s
R i d e a l - E l e y k i n e t ic s . W h e n o p e r a t i n g i n a r e p l a c e d w i t h s o m e i n a c ti v e i o ns . I t m a y n o t
s o l v e n t w i t h h i g h e r p r o t o n a c c e p t o r ab i li ty p r e s e n t t h e a c t u a l p i c t u r e ; t h e r e p l a c e m e n t
t h a n t h a t o f t h e s u b s t r a t e , t h e a d d i t i o n a l o f c a t a ly t i c al l y a c t i v e s p e c i e s b y s o m e i n a c -
i n f l u e n c e o f t h e s u b s t r a t e c a n b e n e g l e c t e d , t iv e i o n s m u s t c h a n g e t h e e n v i r o n m e n t w i t h i n
a n d t h e s t a t u s o f t h e a c i d si t e s i s n e a r l y t h e r e s i n p h a s e , l e a d i n g t o a c h a n g e i n t h e
e x c lu s iv e ly d e t e r m i n e d b y s o l v at i on , s o t h a t d i s t r i b u t io n o f t h e c o m p o n e n t s . T h e o t h e r
a n a ct i ve c e n t r e s h o u l d b e i d e n t i c a l w i t h a m e t h o d , w h i c h i s m o r e a c c u ra t e , c o n s is t s o f
s i n g l e s o l v a t e d a c i d s i te . T h u s , t h e d e a c t i v a - e q u i l i b r a t i n g s m a l l p a r t i c l e s o f t h e c a t a l y s t
t i o n o f t h e r e s i n c a t al y s t b y t h e s u b s t r a t e h a s w i t h t h e r e a c t a n t s t o e n s u r e t h e a t t a i n m e n t
b e e n e x p l a i n e d s a t is f a ct o r il y b y t h e c o n c e p t o f s o r p t i o n e q u i l i b r i u m b e f o r e a n y a p p r e c i a -
o f v a r i a b le a c ti v e c e n t r e s f o r t h e p r o p y l a t i o n b l e c o n v e r s i o n o c c u r s . T h e n t h e c o n t e n t s o f
o f b e n z e n e B u t t e r s a ck
et al .
[6 7]). t h e r e s i n a r e e l u t e d b y s o m e s o l v e n t , a n d t h e
r e a c t i o n i s c o m p l e t e d i n t h e e l u a t e b y s o m e
s o l u b l e c a ta l ys t. T h e a m o u n t o f th e p r o d u c t s
R e a c t i o n s u n d e r s u p e r c r i t i c a l c o n d i t i o n s
i n t h e e l u a t e w h i c h i s s t o i c h i o m e t r i c a l l y
T h e m a n u f a c t u r e o f i s o p r o p a n o l b y h y d r a - e q u i v a l e n t t o t h e a m o u n t o f r e a c t a n t i n it ia l ly
t io n o f p r o p y l e n e a n d s e c - b u t a n o l b y h y d r a - t a k e n u p b y t h e r e s i n ) i s t h e n a n a l y t ic a l l y
t i o n o f b u t e n e s m a y i n vo l v e s u p e r c r it i c a l c o n - d e t e r m i n e d . I n t h is m e t h o d , t h e r e i s n o p ro -
d i t io n s . H e r e f ix e d b e d r e a c t o r s a r e e m - v i s io n f o r e s t i m a t i n g t h e d i s t r i b u t i o n c o e ff i-
p l o y e d . T h e r e is h a r d l y a n y l i t e r a t u r e o n t h e c i e n t o f t h e p r o d u c t w h i c h n e e d s t o b e c on -
k i n e t i c s i n s u c h r e a c t i o n s y s t e m s [6 8]. s i d e r e d i n t h e c a s e o f a r e v e r s i b l e r e a c t i o n .
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TABLE 1
Physical properties of some cation exchange resins
Catalyst Properties
Crosslinking density Surface rea Pore volume Ca paci ty Maximum perating
( DVB) (m2/g) (ml/g) (meq/g) temperature (C)
Amberlyst-15 20 45 0.35 4.8 120
Amberlyst-35 20 44 0.41 5.2 140
Amberlyst XN-1010 > 50 540 0.47 5.3 150
Nation NR 50 _ a 0 .003 no n-po ro us 0.8 200
Lewatit SPC 118 18 40 0.46 5.0 120
a Not applicable.
Anothe r method (adopted in our laboratory) 9. Reactions catalyzed by cation exchange
which may be more useful is as follows. The
resins Reactions of industrial importance
reaction is carried out for some time. The
resin phase is then carefully filtered off from All the reactions generally catalyzed by
the bulk solution. The co ntents of the resin mineral acids, can be carried out in the pres-
phase are th en elute d by some suitable sol- ence of cation exchange resin as catalyst with
vent and analyzed by the usual method . The some of the advantages which have been
bulk phase is then analyzed as usual. Thus by discussed earlier. The physical properties of
knowing the composition of the resin phase relevant cation exchange resins are listed in
and the bulk phase, the distribution coeffi- Table 1. A num ber of cation exchange resin
cient of the reactant s and the products can catalyzed processes have been commercial-
be fo und out. ized, a list is given in Tab le 2. Tab le 3 lists
TABLE 2
Some important commercial processes catalyzed by cation exchange resins
Name of the product Key reactants Ref.
Methyl
tert-butyl
ether (MTBE) Methanol + Isobutylene 77,133
Ethyl
tert-butyl
ether (ETBE) Ethanol + Isobutylene 77
tert-Amyl methyl ether (TAME) Methanol + Isoamylene 77
Isobutylene tert-Butanol 134-137
tert-Butanol
Isobutylene + Water 137
Isopropanol Propylene + Water 138-140
sec-Butanol
n-Butenes + Water 141, 142
Isopropyl esters Propylene + Carboxylic acids up to C20 143
sec-Butyl
acetate Butene + Acetic acid 144
sec-Butyl acrylate 1/2-Butene + Acrylic acid 145
Acrylates and Methacrylates Acrylic acid or Methacrylic acid + Alcohols 146-148
Alkylphenols Phenols + Olefins 149
Bisphenol A Phenol + Acetone 149
Methyl glucoside Dextrose + Methanol 150
Methyl isopropenyl ketone Methyl ethyl ketone + Formalin 151
Methyl isobutyl ketone Acetone + H 2 152
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TABLE 3
Examples of the reactions catalyzed by cation exchange resins
Reaction System Catalyst Ref.
Aceta l format ion
Glyoxal + 3-Hydroxypropene Sulfonic acid resin 153
Formaldehyde + Methanol Lewatit SPC 118 104
Furfural + Ethylene glycol D61, D72 154
Benzophenone + Trimethyl orthoformate Nafion-H 155
Acetone
Butanone ~ + Methanol Dowex 50 3
Cyclohexanone]
[Ethylene glycol
Cyciohexanone + ~ 1,3-Propanediol Amberlyst-15 156
Alkylation of benzene / substituted benzene
Benzene + Ethylene Nation-H 157
Benzene + Propylene Amberlyst-15,
Dowex 50W-X2,
Dowex 50W-X4,
Dowex 50W-X12 34
Benzene + 1-Dodecene Amberlyst- 15,
Amberlyst XN-1010 158
m-Xylene + Isoprene Nafion-H 159
Benzene + Styrene Nation-H,
Amberlyst-15 42
Toluene + Styrene
idem.
42
p-Xylene + Styrene
idem.
42
o-Xylene + Styrene
idem.
42
m-Xylene + Styrene
idem.
42
1,2,4-Trimethylbenzene + Styrene idem. 42
1,3,5-Trimethylbenzene + Styrene
idem.
42
Toluene + p-Methylstyrene Nafion-H 42
m-Xylene + p-Methylstyrene
idem.
42
Alkylat ion of naphthalene
Naphthalene + Propylene Amberlyst-15 160
Alky lation o f phe nol / substituted phenols
Phenol + Ethylene Nafion-H 161
Phenol + Propylene Nation-H,
Amberlyst-15 161
Phenol + Isobutylene IB)
idem.
161
Phenol + Propylene Amberlyst-15, 43
Phenol + Butenes Amberlyst XN-010, 43
Phenol + IB Nation NR-50 43
Phenol + Isoamylene IA)
idem.
43
Phenol + 1-Octene
idem.
43
Phenol + Diisobutylene DIB)
idem.
43
Phenol + a-Methylstyrene
idem.
43
Phenol + a-Methylstyrene Amberlyst-15 163
Phenol + IB Sulfonic acid resin 162
Phenol + DIB Strongly acidic ion
exchanger 164
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A. Chakrabart i, M.M . Sharma / React . Polym. 20 1993) 1-4 5
T A B L E 3 ( c o n t in u e d )
Reac t ion Sys tem Ca ta lys t Ref .
Alkylation o f phenol / substituted phenols
Phenol + DIB Am ber lys t -15 ,
Am ber lys t XN-1010 165
Phenol + 1-Dodecene
idem.
165
Phenol + 1-Decene KU -2 166
Phen ol + C8_18 n-ole tins Sulfo-ba sed cation excha ngers 167
Phenol + P ropylen e t r imer Am ber lys t XN-1010 168
Phenol + Cyc lohexene Am ber lys t-15 ,
Amber l i te IR-120,
Na t ion NR-50 124
Phen ol + Styren e Na tion 117 169
Pyroga l lo l + S tyrene
idem.
170
Phenol + 1-Pentanol Wo fa t i t KPS 171
o-Cresol + 4-M ethyl - l -pe ntene Am ber lys t-15 172
m- C r e so l + I B N a t io n - H ,
Amberlyst-15 173
p-Creso l + IB Am ber lys t - 15 174
m- C r e so l /
p -Creso l /
2,5-Xylenol~ + AM S
idem.
100
2,4-Xylenol /
2,6-Xylenol}
m- C r e so l
p - C r e so l ~ + D I B
idem.
100
2,6-Xylenol )
Phenol /
o - C h lo r o p h e n o l
+ IB
idem.
7a
o - E th y lp h e n o l
G u a ia c o l
P h e n o l
o - C h l o r o p h e n o l | _ .
+ I A
idem.
7a
o - E th y lp h e n o l
Gua iacol )
P h e n o l + M T B E
idem.
44, 175
m- C r e so l + M T B E W o f a t i t O K - 8 0 1 76
Hyd roquino nes + IB Am ber lys t -15 177
Alkylation o f naphthols
a - N a p h th o l ~
t -Naphthol~ + IB
idem.
7a
a - N a p h th o l~ _ .
/3-Naphthol~ + IA
idem.
7a
Alkylation o f poly p-vinylphenol)
Poly(p-v inylphenol) +
tert-Butanol idem.
178
Alkylation o f phenylalkoxy- and hydroxy-benzoates
Phenylsa l icy la te + IB Wo fa t i t OK-80 179
Carbonylation
Form aldehy de ace ta l + Unspec i f ied comm erc ia l
Carbo n mon oxide ion exchanger 180
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15
TABLE 3 (continued)
Reaction System Catalyst Ref.
Condensation
Methyl N-phenylcarbamate + Formaldehyde Cation exchange resin 181
Anethole + Acetaldehyde
idem.
182
Phenol + Acetone Revachit SPC-118 BG
(20 neutralized
with
H 2 N C H 2 C H z S H )
183
Phenol + Acetone Cation exchange resin 184-189
o-Benzoylbenzoic acid Sulfonic acid resin 190
1,4-Bis 2-propanol)benzene
+ Aniline Perfluorinated
sulfonic acid resin 191
Cyclohexanone Amberlite IR-120,
Dowex 50 192
to-Undecylenic acid Amberlyst- 15 193
Cross-dimerization
ot-p-Dimethylstyrene + IA
idem.
194
Cyanoethylation
Aniline + Acrylonitrile Strongly acidic resin 195
Decomp osition / cracking
MTBE Lewatit SPC 118, 65,
Amberlyst-15 196
TAME SiO2-modified
Lewatit SPC 118 197
Cumene hydroperoxide Amberlyst XN-1010,
Amberlite IR-118 127
p-tert-Butyl cum ene-hydroperoxide)
Vionit CS-1 198
Dim eriza ion / oligomeriza ion
IB Indion-130 199-201
IB Wofatit OK-80 202
IA Amberlyst-15, Polystyrene
sulfonic acid 203
1-Butene, 2-Butene Sulfonated polystyrene resin 204
DIB Macroporous cation
exchanger 205
Styrene Nafion-H,
Amberlyst-15 206-208
AMS Nafion NR-50,
Amberlyst-15, K2661,
Lewasorb AC 10 FT 209
Formaldehyde Ion exchange resin 210
Epoxidation
Ricebran oil + Hydrogen peroxide Strongly acidic
ion exchange resin 211
Cottonseed oil + Hydrogen peroxide Ion exchange resin 212
Esterification o f olefins
Propene +Acetic acid Lewatit SPC 213, 214
n-Butenes + Acetic acid KU-23 215
1-Butene
Isobutylene
1-Octene ] +Aceti c acid Amberlyst-15 95
1 - D o d e c e n e ]
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T AB L E 3 ( c on tinue d)
Rea ction System Catalyst Ref .
Esterification o f olefins
Cyclohexene + Acetic acid 001 x 7 (Cation exchanger) 216
Cyclohexene + Acetic acid Amberlyst-15 217
Cyclohexene + Acetic acid + water Lew atit SPC 118 218
/Fo rm ic acid Cation exchange resin 219
Cam phen e + ~Acetic ac id
Dihydrom yrcene + A cet ic ac id idem. 219
Styrene + Acetic acid Ostion KS 220
Styrene +A ceti c acid Amberlyst-15, Am berlyst
XN-1010, Nation NR -50,
Mon odisperse K2661,
K2631 221
Propy lene + Ch loroacetic acid Amberlyst-15 95
1-Butene + Acrylic acid Lew atit SPC 118 145, 222
Ca mp hen e + Methacrylic acid D001-ML 223
Dicy lopentad iene + Acetic acid Lew atit SPC 108 224
2_Methyl_l_butene Lew atit SPC
Isopren e ) + Acetic acid 118 (45
Cyclopentadiene ] neut ra l ized 225
with K + )
Pro py lene + My ristic acid Am berlyst-15 226
Esterification o f alcohols
I sopropanol + Acet ic ac id Dia ion HP K 55
(Modif ied to ge t
cor responding
f luor ina ted ion
exchange resin) 227
Hexyl alcohol + Acetic anh ydrid e Ion Exch anger 228
Glycerol +A cet ic anhydr ide EX 146H 229
fAce t ic ac id
Glycerol + ~Propionic acid D61, D7 2, Am berlyst-15 230
Eth ano l + Oxalic acid Am berli te IR-120 123, 231
C 6-12 Alc hls + Maleic anh ydrid e Vion it 232
M ethan ol + Methacrylic acid Cation exchange resin 233
2-Ethylhexanol + Methacrylic acid idem. 234
2-Ethylhexanol + Acrylic acid Dia ion PK 208 235
Ethy lene glycol )
Di-e thy lene glycol ~ Strongly acidic 236
Tri-ethylene glycol [ + Acrylic acid ion exchanger
Tetra-eth ylene glycol]
Me thanol + Fa t ty ac id Lewat i t 237
4-Oxo-pentanoic acid r)
c/s-Pinanoic acid
trans-Aconitic acid + M etha nol Amberlyst-15 238
( S) - M a nde l i c a c id
Oleic acid
Malonic ac id m onoethyl es te
Phe nol + Methacrylic acid idem. 239
Ring o pened adduct of cyanoethyl a lcohol
and e-Cap rolactone + Acrylic acid idem. 240
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T A BL E 3 c o n t in u e d )
Re act io n System Catalyst Ref.
Esterification of alcohols
Lip ids + Acet i c anhydr ide Cat ion exchange res in 241
Pyr role diacids + m ethan ol Am berl i te IR-120 242
Ethy lene g lycol H-fo rm ca t ion
mo noethy l e ther + Acet i c ac id exchanger 243
D i me t h y l p h o s p h o r a mi d o t h i o a t e
+ Ac et ic anhy dride Amberlyst -15 244
Tr ioxane + Carbon monox ide St rong ly ac id ic
+ me thano l ion exchanger 245
Etherification
IB + M ethano l Cat ion exchange res in 5 , 77 ,
246-261
IB + Eth ano l Am berlyst - 15, 77,
Amberlyst-35, 262,
Fluorocarbo n su l fon ic
acid 263
IA + M ethan ol Amberlyst -15 77, 264-2 66
2-M ethy l - l -bu tene + M ethano l Vion i t CS-34 267
IA + Eth ano l Amberlyst -15,
Amberlyst-35 267
IB + Eth ylen e glycol Acidic ion
exchange res in ,
Amberlyst -15 268-270
IB + Pro pylen e glycol Amberlyst -15 6, 271
E t h y l e n e
/ G l y c o l
1 -Butene + ~Propy lene idem. 270
| G l y c o l
I,Di -e thy lene g lycol e the r
E t h y l e n e
| G l y c o l
P r o p e n e + ~Pr o p y l e n e idem. 270
| G l y c o l
~Di -e thy lene g lyco l e ther
Dicy lopen tad iene + E thy lene g lycol idem. 272
[ E t h a n o l
Cam phene + ~Isopropano l Cat ion exchange res in 273
D i h y d r o my r c e n e + Me t h a n o l idem. 273
D I B
M ethy lpen tene + M ethano l Amber lys t-15 274
P i n e n e
a - P i n e n e ~
~ - P i n e n e ] + M e t h a n o l idem. 275
Cyc lohexen e + 2-Methyl-2-phenyl ethan ol idem. 276
Cyclohexene + Phene thy l a l coho l idem. 277
f Isoamyl alcohol
Sty rene + ~Cyclohexano l idem. 278
A M S + Me t h a n o l idem. 91
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A. Chakrabart i, M.M. Sharma React. Polym. 20 (1993) 1-4 5
TABLE 3 continued)
Reaction System Catalyst Ref.
E theri ic a tion
Phenol
IB + {a-Naphthol idem. 7a
~/3-Naphthol
Phenol
IA + {a-Naphthol
idem.
7a
~/3-Naphthol
Glucose + Methanol Nation 511, 150,
Amberlyst-15 279, 280
Methylolurea +
2-Methylpropanol Wofati t OK 80 281
Hydration
Propylene + Water Cation exchange resin 282
Propylene + Water Imac C8P 52
n-Butenes + Water XE-307 53
IB + Water Amberlyst-15,
Amberlyst XN-1010 84, 87, 283
Isopentenes + Water Amberlyst- 15,
Amberlyst XN-1010,
Lewatit SPC 118,
Lewatit SC 102 284-287
Camphene
a-Pinene
Dihydromyrcene + Water Cation exchange resin 288
Dipentene
Carene
Camphene + Water D001-ML, Strongly 289,
acidic ion exchange resin 290
Citronellol + Water Amberlyst-15 291
Cyclohexene + Water Lewatit SPC 118, 88-90,
Amberlite XE-307 218
AMS + Water Amberlyst-15,
Amberlite IR-120 91
Acrolein + Water Duolite C467, 292,
Amberlite ICR-718 293
Cyclohexene
oxide + Water Diaion-PK228 294b
2-Cyclohexenone + Water Ion exchanger
containing SO H
or NH4OH 294b
Acrylonitrile + Water Strongly acidic
ion exchanger
containing Cu ions 295
Hydrolysis
Methyl Acetate + Water Ion exchange resin 296
sec-Butyl-trifluoro
acetate + Water Nation NR 501 297
Ethylene glycol
mono-tert-butyl
ether + Water Amberlyst-15 298
Ethylene glycol
di-tert-butyl
ether + Water
idem.
299
Benzophe none
dimethyl acetal + Water Nation-H 155
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T A B L E 3 ( c o n t in u e d )
Reac t ion Sys tem Ca ta lys t Ref .
Hydrolysis
2,2-Dim ethyl- 1,3-dioxolane + W ater Am berlys t- 15 300
D i - me th y lp h o sp h o e n o lp y r u v a t e + W a te r D o w e x 5 0 H 3 01
Isomerization
endo-Dicyc lopentadiene Strong ac id ion exchanger 302
2-M ethy l- l-bu tene Sulfonic acid resin 303
1-Butene Ca t ion exchange re s in 304
2,5-Dimethylhexadienes Duo l i te C26H 305
Styrene oxide Na t ion 501 ,
Amberlyst-15 306
Epoxides Am ber l i te IR-120 307
2,4 -Dihydroxy -2 ,2 -d iphenylpropan e Dow ex MSC - 1 308
2,4 -Dihydroxy -2 ,2 -d iphenylpropan e Dow ex MSC - 1
conta in ing
(HSC H 2CH 2)2 N H 309
Mixture of 3-me thyl te t rahydroph