A Review and New Perspectives in Zeolite Crystallization - American

10 A Review and New Perspectives in Zeolite Crystallization EDITH M. FLANIGEN

Downloaded by UNIV OF ARIZONA on November 13, 2012 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0121.ch010

Union Carbide Corp., Linde Division Laboratory, Tarrytown Technical Center, Tarrytown, Ν. Y. 10591

The synthesis of a variety of zeolite species which represent compositional variants of known structures and possible new framework topologies has been reported in the interim of this review. Extensive use has been made of mixed bases of the alkali, alkaline earth, and organic cations. A correlation of zeolite structures with the cations used in synthesis shows a strong speci ficity for the formation of framework type and polyhedral build ing unit by one or, at the most, two cations. The cation "tem plating" concept is supported for the formation of several poly hedral cages. The organic cation plays a limited role in direct ing structure but more generally provides a source of hydroxyl ions and stabilizes the formation of sol-like aluminosilicate species.

'Tphe scope and objectives of zeolite crystallization investigations cover A

three areas :

synthesis of new structure types and known structure types

with different chemical compositions, kinetic and mechanistic studies on zeolite crystallization, and growth of large single crystals of zeolites. on a Chemical

Abstracts

Based

count, about 200 papers and patents have been

published on zeolite synthesis since 1969.

This paper reviews a selected

portion of the literature and progress in zeolite crystallization in each of the above three areas since the Second Molecular Sieve Conference at Worcester in 1970 and presents different perspectives and new data on zeolite nucleation and crystallization phenomena and suggestions for future directions in zeolite synthesis investigations.

The literature on the formation and

phase relations of the more thermodynamically stable zeolites is not covered. Review of Literature Zhdanov (1) gave a detailed review of zeolite crystallization at Wor cester which covered the literature until about 1969 with special emphasis 119 In Molecular Sieves; Meier, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1973.


120

MOLECULAR SIEVES

o n t h e m e c h a n i s m a n d k i n e t i c s of zeolite c r y s t a l l i z a t i o n f r o m gels. Barrer (2) p r e s e n t e d a p r e v i o u s review at the L o n d o n M o l e c u l a r Sieve Conference i n 1967. S i n c e 1969, S e n d e r o v a n d K h i t a r o v (3) h a v e p u b 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 i n b o o k f o r m . I t c o n t a i n s a c o m p l e t e , u p - t o - d a t e r e v i e w of a l l s y n t h e t i c a n d m i n e r a l zeolites i n c l u d i n g t h e i r synthesis c o n d i t i o n s , compositions, x-ray diffraction data, and other properties. A useful list of x - r a y d v a l u e s a n d i n t e n s i t i e s for 79 s y n t h e t i c a n d m i n e r a l zeolite species is a p p e n d e d . I t is especially v a l u a b l e for i t s extensive i n c l u s i o n of the R u s s i a n w o r k . I n t h e i r d i s c u s s i o n of the m e c h a n i s m of zeolite c r y s t a l l i z a t i o n , t h e t h e r m o d y n a m i c aspects of c r y s t a l l i z a t i o n , b o t h i n t e r m s of s t r u c t u r e a n d c h e m i c a l c o m p o s i t i o n , are d e v e l o p e d i n d e t a i l . T h e b o o k is a v a i l able o n l y i n R u s s i a n . Zeolite Compositions. I n the first area of p r e v i o u s l y u n r e p o r t e d c o m p o s i t i o n s , t h e m a i n focus i n recent zeolite s y n t h e s i s w o r k has been i n t h e m i x e d a l k a l i - o r g a n i c c a t i o n base systems. T o a v o i d t h e c u m b e r s o m e n o m e n c l a t u r e of t h e organic cations, a s h o r t h a n d d e s i g n a t i o n is used, w hich is defined i n t h e A p p e n d i x . T h e o n l y s y n t h e s i s of p u r e organic c a t i o n zeolites i n a l k a l i - f r e e systems has been r e p o r t e d b y B a e r l o c h e r a n d M e i e r w h o d e scribe the s y n t h e s i s of T M A - g i s m o n d i n e (4) a n d T M A - s o d a l i t e (5). B o t h are m o r e h i g h l y siliceous t h a n t h e i r s t r u c t u r a l analogs f o r m e d i n a l k a l i s y s t e m s . B a r r e r et al. (6) showed t h a t the synthesis of N - A , a siliceous a n a l o g of zeolite A , c o u l d n o t be c a r r i e d out i n the p u r e T M A s y s t e m s y s t e m b u t r e q u i r e d the presence of N a i o n , a l b e i t i n t r a c e a m o u n t s , for i t s f o r m a t i o n . T h e o r g a n i c - a l k a l i base systems u p t o 1969 h a d r e s u l t e d i n the s y n t h e s i s of s e v e r a l zeolite species as r e v i e w e d b y B r e c k (7). A l l were s y n t h e s i z e d i n N a - a l k y l a m m o n i u m c a t i o n systems a n d i n c l u d e d siliceous c o m p o s i t i o n s of k n o w n s t r u c t u r e types, s u c h as N - A , a n d t h e new s t r u c t u r e t y p e s : Z K - 5 , w i t h N a - D D O ; Ω a n d zeolite N , w i t h N a - T M A ; a l e v y n i t e t y p e , w i t h N a M D O ; a n d zeolite β, w i t h N a - T E A . T h e e x t e n s i o n of zeolite synthesis t o o t h e r a l k a l i - o r g a n i c s y s t e m s has p r e d i c t a b l y o c c u r r e d since t h a t t i m e . r

A series of zeolites c a l l e d Z S M - 5 , 8, a n d 11 has been r e p o r t e d b y scientists at M o b i l O i l C o r p . T h e y are s y n t h e s i z e d i n b i n a r y c a t i o n s y s t e m s c o n t a i n i n g b o t h N a a n d a n organic c a t i o n , w i t h t h e organic c a t i o n T E A i n Z S M - 8 (8), T P A i n Z S M - 5 (9,10), a n d T B A , T B P , a n d B T P P i n Z S M - 1 1 (11). T h i s is t h e first r e p o r t e d synthesis of zeolites i n t h e presence of q u a t e r n a r y p h o s p h o n i u m cations. T h e r e a c t a n t a n d zeolite c o m p o s i t i o n s r e p o r t e d are h i g h l y siliceous ( S i / A l u p t o 100). A d s o r p t i o n p o r e v o l u m e s of t h e order of 0.10-0.12 c m / g r a m a n d pore sizes near 7 A are i n d i c a t e d . B a s e d o n t y p i c a l x - r a y p o w d e r d i f f r a c t i o n d a t a g i v e n , these zeolites show s t r o n g resemblances t o each other. N o a n a l o g y t o a n y p r e v i o u s l y k n o w n s t r u c t u r e t y p e is g i v e n . 2

3

Z S M - 1 0 (12), described as a f a m i l y of zeolites b y C i r i c , is s y n t h e s i z e d i n t h e K - D D O s y s t e m a n d has a n S i / A l of 5-7, a n H 0 pore v o l u m e of a b o u t 0.14 c m / g r a m , a n d a n effective pore d i a m e t e r of 7-8 A . A c h a r a c t e r i s t i c 2

2

3

In Molecular Sieves; Meier, W., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1973.

10.

FLANiGEN

121

Zeolite Crystallization

x - r a y p o w d e r d i f f r a c t i o n p a t t e r n is g i v e n w h i c h is s a i d t o be u n r e l a t e d t o p r e v i o u s l y k n o w n zeolite structures b u t bears a s t r o n g resemblance t o t h a t of zeolite L w i t h w h i c h i t c o m m o n l y c o c r y s t a l l i z e s . A n u n n a m e d zeolite described b y R u b i n a n d R o s i n s k i (13) is c r y s t a l l i z e d i n t h e N a - K - B T M A s y s t e m w i t h a n S i / A l of 7-10, a n H 0 pore v o l u m e u p t o 0.21 c m / g r a m , a n d a pore size near 5 A . I t seems t o be a n e r i o n i t e - t y p e s t r u c t u r e . R u b i n (14) a n d J e n k i n s (15) r e p o r t e d t h e synthesis of a p u r e offretite-type zeolite from the ternary cation system, K - N a - T M A .


2

2

3

A i e l l o a n d B a r r e r (16) p u b l i s h e d t h e first b r o a d s t u d y of zeolite c r y s t a l l i z a t i o n fields i n a l u m i n o s i l i c a t e gels i n t h e presence of t h e m i x e d a l k a l i - o r g a n i c bases, N a O H , K O H , a n d T M A O H , i n c l u d i n g t h e i r t e r n a r y m i x t u r e s . A v a r i e t y of s t r u c t u r e t y p e s s y n t h e s i z e d p r e v i o u s l y i n t h e m o n o a n d b i n a r y a l k a l i c a t i o n systems ( K , N a ) was s y n t h e s i z e d i n the m i x e d T M A - a l k a l i bases. T h e s e i n c l u d e zeolites w i t h t h e s t r u c t u r e t y p e s of erionite, sodalite, c h a b a z i t e , g i s m o n d i n e ( P ) , p h i l l i p s i t e , a n d g m e l i n i t e . O n l y t w o s t r u c t u r e t y p e s are f o u n d e x c l u s i v e l y i n the presence of T M A , zeolites Ω a n d Ο (offretite). T h e a u t h o r s e x p l a i n the s t r u c t u r e specificity of t h e m i x e d cations i n t e r m s of t h e t e m p l a t i n g of different cage s t r u c t u r e s b y t h e larger organic a n d s m a l l e r a l k a l i cations. T h e a s s o c i a t i o n of t h e T M A i o n w i t h the 14-hedron g m e l i n i t e cage i n offretite a n d Ω is suggested to p l a y a n i m p o r t a n t role i n t h e i r synthesis b y a t e m p l a t i n g a c t i o n of t h e T M A i o n i n f o r m i n g t h e a l u m i n o s i l i c a t e p r e c u r s o r of t h e larger g m e l i n i t e cage. T h e s m a l l e r a l k a l i ions p l a y a role i n charge c o m p e n s a t i o n of t h e a l u m i n a t e t r a h e d r a a n d i n t e m p l a t i n g s m a l l e r cage s t r u c t u r e s s u c h as t h e c a n c r i n i t e u n i t a n d h e x a g o n a l p r i s m s . C o c r y s t a l l i z a t i o n i n these m i x e d systems is extensive, a n d the incidence of c o m m o n s t r u c t u r a l u n i t s a m o n g the c o c r y s t a l l i z e d phases is e m p h a s i z e d i n c l u d i n g p o l y h e d r a l cages a n d t h e sequence of chains of f o u r r i n g s . T h e s t r o n g effect of T M A i n p r o m o t i n g the f o r m a t i o n of s i l i c a - r i c h zeolites is c o n f i r m e d for m a n y s t r u c t u r e - t y p e s : Ω, offretite ( 0 ) , erionite ( E ) , a n d sodalite ( T ) . S y n t h e s i s of zeolites i n m i x e d a l k a l i - T M A systems is extended t o q u a t e r n a r y c a t i o n systems i n zeolites described i n a p a t e n t b y K o u w e n h o v e n a n d C o l e (17). T h e s e zeolites, designed " K S O - 2 - 6 , " are s y n t h e s i z e d f r o m t e r n a r y a n d q u a t e r n a r y systems of T M A a n d N a , a n d a t h i r d or f o u r t h c a t i o n c o n s i s t i n g of Κ or L i , or b o t h . T h e y h a v e pore v o l u m e s i n t h e r e g i o n of 0.12-0.15 c m / g r a m a n d s t a t e d pore sizes f r o m 5 t o 7 A . A l l appear t o be related to previously k n o w n structure types. 3

A n e w zeolite, designated " L o s o d , " has been s y n t h e s i z e d i n the a l k a l i o r g a n i c c a t i o n s y s t e m , N a - B P , b y Sieber (18). I t was also f o r m e d i n t h e presence of the r e l a t e d base P P - O H a n d f r o m N T M A - O H . T h e gels c o n t a i n e d v e r y h i g h organic base contents a n d a l o w N a content ( N a / A l < 1), a n d t h e organic c a t i o n was n o t i n c o r p o r a t e d i n t o the zeolite phase. Based o n s t r u c t u r e studies b y W . T h e o n i , a n e w f r a m e w o r k s t r u c t u r e is p r o p o s e d for " L o s o d " c o n s i s t i n g of a n A B A C s t a c k i n g of p a r a l l e l six r i n g s (19) a n d


122

MOLECULAR SIEVES


l e a d i n g t o t w o p o l y h e d r a l cages, c a n c r i n i t e cages a n d a " L o s o d " cage. T h e l a t t e r is a n e w t y p e of 30-hedra cage c o n t a i n i n g 11 s i x - m e m b e r e d a n d 6 f o u r m e m b e r e d r i n g s . A l t h o u g h t h e size a n d fit of t h e c a t i o n i n t h e " L o s o d " cage are a n a p p e a l i n g concept for a " t e m p l a t i n g " effect i n p r e c u r s o r f o r m a t i o n , t h e fact t h a t the zeolite c o n t a i n s n o organic c a t i o n d i s p u t e s t h i s m e c h a n i s m . Sieber proposes t h a t t h e b u l k y q u a t e r n a r y a m m o n i u m ions u s e d h a v e t o o s m a l l a surface charge d e n s i t y a n d , therefore, do n o t exert significant c o o r d i n a t i v e a n d p o l a r i z i n g force o n t o t h e a l u m i n o s i l i c a t e anions. A l k a l i i o n s are necessary for p o l y m e r i z a t i o n t o a s o l i d . H e concludes t h a t t h e organic base o n l y serves as a source of h y d r o x y l ions a n d has n o c r i t i c a l influence o n t h e s t r u c t u r e f o r m e d . B a r r e r a n d M a i n w a r i n g (20) r e p o r t the use of m e t a k a o l i n as t h e a l u m i n o s i l i c a t e r a w m a t e r i a l for r e a c t i o n w i t h t h e h y d r o x i d e s of Κ a n d B a as w e l l as the b i n a r y base systems B a - K a n d B a - T M A t o f o r m zeolites. Z e o l i t e phases p r e v i o u s l y s y n t h e s i z e d i n t h e analogous h y d r o u s a l u m i n o silicate gel systems were c r y s t a l l i z e d w i t h K O H , i n c l u d i n g p h i l l i p s i t e - , chabazite-, K - F - , a n d L - t y p e structures. T h e b a r i u m system yielded two u n i d e n t i f i e d zeolite phases ( B a - T a n d B a - N ) a n d a species B a - G , L w i t h a s t r u c t u r a l resemblance t o L i n d e zeolite L . B a - G , L was r e p o r t e d p r e v i o u s l y b y B a r r e r a n d M a r s h a l l (21) as B a - G . S i m i l a r phases were f o r m e d i n the B a - K s y s t e m a n d i n t h e T M A - B a s y s t e m where, i n a d d i t i o n , e r i o n i t e - t y p e phases were f o r m e d . T h e L - t y p e s t r u c t u r e s are s a i d t o represent a l u m i n o u s analogs of t h e zeolite L p r e v i o u s l y r e p o r t e d (22). O t h e r examples of synthesis of k n o w n s t r u c t u r e t y p e s i n n e w c a t i o n systems h a v e been r e p o r t e d . R o b s o n (28) reports a process for t h e s y n thesis of a n R b - N a zeolite w i t h a n e r i o n i t e - t y p e s t r u c t u r e . B o r e r a n d M e i e r (24), S a n d , C o b l e n z , a n d S a n d (25), a n d P e r e y r o n , G u t h , a n d W e y (26) h a v e i n v e s t i g a t e d synthesis i n t h e b i n a r y a l k a l i L i - N a s y s t e m . Many zeolite s t r u c t u r e t y p e s p r e v i o u s l y c r y s t a l l i z e d i n t h e i n d i v i d u a l c a t i o n s y s t e m s were f o u n d b y B o r e r a n d M e i e r , as w e l l as a n e w L i , N a - 0 species (not a t y p i c a l zeolite) a n d a L i , N a a n a l o g of K - F zeolite. P u r e L i analogs of m o r d e n i t e , a n a l c i m e , a n d p h i l l i p s i t e are r e p o r t e d b y S a n d et al. P e r e y r o n , G u t h , a n d W e y r e p o r t e d t w o N a - L i p o l y t y p e s of faujasite. K o k o t a i l o a n d C i r i c (27) describe t h e s t r u c t u r e a n d properties of Z S M - 3 zeolite also s y n t h e s i z e d i n the N a - L i s y s t e m (27, 28). T h e i r proposed s t r u c t u r e for Z S M - 3 is based o n a h e x a g o n a l s t a c k i n g of the sodalite-hexa g o n a l p r i s m s present i n t h e faujasite s t r u c t u r e a n d c o n t a i n i n g a v a r i e t y of m i x e d s t a c k i n g sequences. T w o zeolite species, Z-21 a n d N a - V , h a v e been s y n t h e s i z e d i n t h e N a s y s t e m . C o l l e l a a n d A i e l l o (29) r e p o r t t h e c r y s t a l l i z a t i o n of zeolite N a - V f r o m the r e a c t i o n of a r h y o l i t i c glass i n s t r o n g caustic s o l u t i o n . I t is f o r m e d i n t h e c r y s t a l l i z a t i o n fields of X a n d I ( h y d r o x y sodalite), the phase c r y s t a l l i z i n g b e i n g a f u n c t i o n of a g i t a t i o n c o n d i t i o n s a n d t e m p e r a t u r e . C o l l e l a a n d A i e l l a suggest t h a t N a - V is s t r u c t u r a l l y r e l a t e d t o zeolite Ν


PLANIGEN

10.


123

p r e p a r e d i n t h e T M A - N a s y s t e m b y A c a r a (30) a n d t o t h e zeolite N a , T M A - V species of M a i n w a r i n g (31).

Z-21 is described b y D u e c k e r , W e i s s ,

a n d G u e r r a (32) as a large-pore adsorbent w i t h a cubic u n i t c e l l of a ~ 37 A , 0

b a s e d o n a n unspecified t e t r a h e d r a l a r r a n g e m e n t of s o d a l i t e u n i t s g e n e r a t i n g pores of 17 A .

N o a d s o r p t i o n c h a r a c t e r i z a t i o n is g i v e n , b u t b a s e d o n t h e

w a t e r content of t h e c o m p o s i t i o n s h o w n ( ~ 1 2 w t % ) , a n " o p e n " s t r u c t u r e w i t h t h e p o s t u l a t e d pore size of 17 A is n o t i n d i c a t e d .

Z-21 is s y n t h e s i z e d

u n d e r a v e r y specific set of r e a c t i o n c o n d i t i o n s w h i c h i n c l u d e s v i o l e n t a g i t a t i o n d u r i n g m i x i n g , v e r y h i g h caustic c o n c e n t r a t i o n s , a n d r a p i d c r y s t a l lization.

I t appears t h a t zeolites N , N a - V , T M A , N a - V , a n d Z-21 h a v e


related framework structures.

A d s o r p t i o n c h a r a c t e r i z a t i o n of zeolite

Ν

(30) s h o w e d i t t o be a s m a l l - p o r e a d s o r b e n t s l o w l y a d s o r b i n g w a t e r u p t o 0.16 g r a m per g r a m near s a t u r a t i o n .

T h e c o m m o n element of a g i t a t i o n

a n d o t h e r n a r r o w p a r a m e t e r s of f o r m a t i o n observed for a l l of these zeolites i n d i c a t e t h a t these systems m a y represent t h e extremes of m e t a s t a b i l i t y of formation.

T h e i r c o m m o n coexistence w i t h zeolites X a n d A a n d w i t h

h y d r o x y sodalite, m a k e t h e presence of s o d a l i t e u n i t s i n t h e i r f r a m e w o r k structures a p l a u s i b l e h y p o t h e s i s . B a r r e r a n d C o l e (33) s t u d i e d t h e i m b i b i t i o n of salts b y sodalite a n d cancrinite during their hydrothermal formation.

T h e i r results are i n t e r

p r e t e d i n t e r m s of a D o n n a n e q u i l i b r i u m b e t w e e n s a l t i n s o l u t i o n a n d c r y s t a l l i n e i n t e r c a l a t e d salt a n d i n c l u d e a c a l c u l a t i o n of a c t i v i t i e s of t h e i n c l u d e d salts.

T h e y r e p o r t a s t a b i l i z i n g effect of i n c l u d e d salts o n t h e

a l u m i n o s i l i c a t e f r a m e w o r k of sodalite r e s u l t i n g i n v a r i a t i o n i n t h e r m a l s t a b i l i t y as a f u n c t i o n of different i n c l u d e d salt species a n d suggest t h a t salt i n c l u s i o n i n t o t h e sodalite or c a n c r i n i t e u n i t s i n zeolites c o n t a i n i n g these cages, s u c h as A , X , Y , a n d L zeolites, s h o u l d also enhance t h e i r t h e r m a l stability.

R a b o , P o u t s m a , a n d Skeels (34) h a v e r e c e n t l y r e p o r t e d t h e i n

c l u s i o n of h a l i d e a n d n i t r a t e salts i n t o t h e sodalite cages i n Y zeolite a n d their resulting enhanced t h e r m a l stability.

B a r r e r , C o l e , a n d V i l l i g e r (35)

describe the synthesis of s a l t - f i l l e d c a n c r i n i t e s i n sodalite c r y s t a l l i z a t i o n fields.

T h e y suggest t h a t s a l t a n i o n s as w e l l as c a t i o n s m a y p l a y a t e m p l a t

i n g role i n n u c l e a t i o n .

S y n t h e s i s of s a l t - b e a r i n g a l u m i n o s i l i c a t e s has also

been r e p o r t e d b y B a r r e r a n d M a r c i l l y (36).

T h e species Ρ a n d Q c o n t a i n

i n g i n t e r c a l a t e d B a C l a n d B a B r are s a i d t o be based o n t h e same a l u m i n o 2

2

silicate f r a m e w o r k as zeolite Z K - 5 a n d species Ν a n d O , c o n t a i n i n g K C 1 a n d K B r , based o n the f r a m e w o r k of the zeolite K - F .

A q u e o u s e x t r a c t i o n of t h e

i n c l u d e d s a l t was r e p o r t e d t o c o n v e r t t h e s a l t - b e a r i n g species, P , t o a zeolite of t h e Z K - 5 t y p e . zeolites is discussed.

T h e close r e l a t i o n s h i p of t h e felspathoids a n d

W i t h t h e same a l u m i n o s i l i c a t e f r a m e w o r k , s a l t - f i l l e d

species s u c h as sodalite or c a n c r i n i t e are classified as felspathoids a n d t h e same filled w i t h w a t e r as zeolites.

T h e phases described here e x e m p l i f y t h e

c o n t i n u o u s c o n v e r s i o n of one t o t h e other b y s a l t ±=> H 0 s u b s t i t u t i o n . 2


124

MOLECULAR SIEVES

K i i h l (37) has extended t h e a l u m i n o p h o s p h a t e c o m p l e x i n g t e c h n i q u e t o t h e m i x e d N a - T M A c a t i o n s y s t e m a n d reports t h e synthesis of siliceous zeolites of T y p e A s t r u c t u r e c o n t a i n i n g i n t e r c a l a t e d phosphate. H e dis tinguishes t w o species, Z K - 2 1 c o n t a i n i n g N a c a t i o n a n d Z K - 2 2 c o n t a i n i n g N a a n d T M A cations i n the zeolite. T h e w o r k exemplifies the three c o m b i n e d effects of T M A c a t i o n , p h o s p h a t e c o m p l e x i n g , a n d salt i n c l u s i o n w i t h i n t h e A - t y p e f r a m e w o r k . T h e presence of T M A i o n a n d t h e p h o s p h a t e c o m p l e x i n g of a l u m i n a t e i o n b o t h result i n a n increase i n the S i / A l i n t h e zeolite f r a m e w o r k . T h e i n t e r c a l a t i o n of u p t o one phosphate i o n per u n i t cell, assigned t o one per sodalite u n i t , is consistent w i t h the salt i n clusion characteristics i n sodalite-containing structures. Downloaded by UNIV OF ARIZONA on November 13, 2012 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0121.ch010

2

U s e of t h e m i n e r a l zeolites m o r d e n i t e a n d c l i n o p t i l o l i t e as r a w m a t e r i a l s for synthesis of f a u j a s i t e - t y p e zeolites was r e p o r t e d b y M i y a t a a n d S u s u m u (38) a n d N e g i s h a a n d N a k a n u r a (39) b y r e a c t i o n w i t h N a O H / N a C l near 100°C. d e n i t e -> a m o r p h o u s

aqueous

T h e c o n v e r s i o n sequence c l i n o p t i l o l i t e / m o r X

sodalite was observed

(39).

U t a d a and

M i n a t o (40) r e p o r t the synthesis of species Ρ a n d a n a l c i m e f r o m t h e r e a c t i o n of n a t u r a l l y o c c u r r i n g c l i n o p t i l o l i t e w i t h N a O H a n d find t h e t r a n s formation

through

Pi (cubic)

and

P (tetragonal) 2

to

analcime.

They

suggest t h a t t h i s is analogous t o t h e reactions t h a t t a k e place i n s e d i m e n t a r y r o c k s d u r i n g diagenesis. Kinetics and Mechanism.

S o m e dozen or m o r e papers c o n t a i n i n g

i n f o r m a t i o n r e l e v a n t to k i n e t i c s a n d m e c h a n i s m h a v e a p p e a r e d Z h d a n o v ' s r e v i e w (1).

since

A i e l l o , B a r r e r , a n d K e r r (41) showed t h a t c r y s t a l

l i z a t i o n of zeolites f r o m s o l u t i o n proceeds t h r o u g h f o r m a t i o n of a m o r p h o u s s o l i d l a m e l l a e w h i c h e v o l v e i n t o larger p a r t i c l e s after w h i c h x - r a y c r y s t a l Unity

appears.

N u c l e a t i o n is heterogeneous.

The

transition through

a m o r p h o u s gel s o l i d is consistent w i t h O s t w a l d ' s l a w of successive t r a n s formations

and Goldsmith's simplexity principle. Aiello,

Collela,

and

Sersale (42), i n studies o n t h e t r a n s f o r m a t i o n of n a t u r a l a n d s y n t h e t i c s o d i u m a l u m i n o s i l i c a t e glasses to zeolites b y r e a c t i o n w i t h N a O H , r e p o r t t h e existence of a s o l i d gel phase as a n i n t e r m e d i a t e i n t h e glass -> zeolite transformation.

T h e r e a c t i o n k i n e t i c s presented for X c r y s t a l l i z a t i o n show

t w o different, n e a r l y l i n e a r r a t e s — a slower r a t e u p to 3 0 % c r y s t a l l i z a t i o n a n d a faster r a t e f r o m a b o u t 30 t o 7 0 % . S c h w o c h o w a n d H e i n z e (43), i n s t u d y i n g the l i q u i d - p h a s e compositions i n s o d i u m a l u m i n o s i l i c a t e gels d u r i n g t h e c r y s t a l l i z a t i o n r e a c t i o n , s h o w t h a t t h e zeolite species c r y s t a l l i z e d f r o m separated l i q u i d phases depends

not

o n l y o n t h e c o m p o s i t i o n of t h e l i q u i d phase b u t also, at constant c o m p o s i t i o n , o n t h e size of the p o l y m e r i c a n i o n .

T h e higher m o l e c u l a r w e i g h t

anions p r o m o t e t h e f o r m a t i o n of a " p h i l l i p s i t e - t y p e " phase (presumed to be P) over a f a u j a s i t e - t y p e phase.

A t t h e t i m e of n u c l e a t i o n , t h e c o m p o s i t i o n

of the l i q u i d phase m u s t correspond to v e r y h i g h S i 0 / A l 0 2

2

3

ratios (>20),


10.

FLANiGEN


125


a n d the dissolved silica m u s t be present p r e d o m i n a n t l y i n a m o n o m e r i c state t o c r y s t a l l i z e f a u j a s i t e - t y p e s t r u c t u r e s . P o l a k (44) concludes t h a t p o l y c o n d e n s a t i o n reactions t a k e place i n t h e s o l i d phase a n d between t h e s o l i d a n d l i q u i d phases i n t h e a l u m i n o silicate h y d r o g e l d u r i n g the " r i p e n i n g " step w h i c h precedes zeolite c r y s t a l l i z a t i o n . M i g a l a n d N e l y u b o v (45) r e p o r t o n t h e effect of r a t e a n d order of m i x i n g d u r i n g g e l a t i o n o n c r y s t a l size; larger c r y s t a l s ( 3 5 - 4 0 Mmeters) result f r o m silicate to a l u m i n a t e m i x i n g t h a n f r o m the reverse order. T h e y conclude t h a t c r y s t a l l i z a t i o n of zeolites proceeds i n t h e s o l i d phase of t h e gel. M i r s k i i a n d P i r o z h k o v (46) emphasize t h e role of t h e c r y s t a l surface i n the m e c h a n i s m a n d k i n e t i c s of zeolite c r y s t a l l i z a t i o n . B y seeding of X gels, t h e y f i n d a decrease i n b o t h the i n d u c t i o n p e r i o d a n d t i m e for t o t a l c r y s t a l l i z a t i o n a n d conclude t h a t the r a t e of c r y s t a l l i z a t i o n is a f u n c t i o n of the e x t e r n a l surface area of the seed c r y s t a l a d d e d to the gel. T h e i r r a t e curves for increased a m o u n t s of seed show a n i n t e r e s t i n g e v o l u t i o n of t h e t y p i c a l s i g m o i d shape i n t o curves w i t h t w o d i s t i n c t l i n e a r p o r tions, a n i n i t i a l slower r a t e p r e s u m a b l y r e l a t e d t o seeded g r o w t h a n d a l a t e r faster p o r t i o n r e l a t e d t o unseeded g r o w t h . S e v e r a l chapters i n t h i s v o l u m e offer a d d i t i o n a l i n s i g h t i n t o the k i n e t i c s a n d m e c h a n i s m of zeolite c r y s t a l l i z a t i o n . S c h w o c h o w a n d M e i s e (47) r e p o r t a k i n e t i c s t u d y of zeolite A f o r m a t i o n where the steps of n u c l e a t i o n a n d c r y s t a l l i z a t i o n are t r e a t e d as separate k i n e t i c entities. T h e c r y s t a l l i z a t i o n is first order, a n d the n u c l e a t i o n step is of higher order. Alkalinity p r e f e r e n t i a l l y affects the n u c l e a t i o n r a t e a n d o n l y s l i g h t l y t h e c r y s t a l l i z a t i o n r a t e . Çulfaz a n d S a n d (48) s t u d i e d q u a n t i t a t i v e l y t h e energetic parameters a n d k i n e t i c s of n u c l e a t i o n a n d c r y s t a l g r o w t h for m o r d e n i t e a n d f o u n d a c t i v a t i o n energies for n u c l e a t i o n of 23 k c a l / m o l e a n d for c r y s t a l g r o w t h of 14 k c a l / m o l e , t h e l a t t e r i n agreement w i t h p r e v i o u s v a l u e s r e p o r t e d b y Z h d a n o v (1). A surface n u c l e a t i o n g r o w t h m e c h a n i s m is p o s t u l a t e d for t h e seeded systems w i t h n u c l e a t i o n a t the gel-seed interface a n d is e x t r a p o l a t e d t o t h e unseeded systems. M c N i c o l et al. (49) used luminescence a n d R a m a n spectroscopy t o s t u d y s t r u c t u r a l a n d c h e m i c a l aspects of gel g r o w t h of A a n d f a u j a s i t e - t y p e c r y s t a l s . T h e i r results are consistent w i t h a solid-phase t r a n s f o r m a t i o n of t h e s o l i d a m o r p h o u s n e t w o r k i n t o zeolite c r y s t a l s . B e a r d (50) used i n f r a r e d s p e c t r o s c o p y t o d e t e r m i n e t h e size a n d s t r u c t u r e of silicate species i n s o l u t i o n i n r e l a t i o n s h i p t o zeolite c r y s t a l l i z a t i o n . r

A n a l o g o u s m e c h a n i s t i c studies of t h e f o r m a t i o n of zeolite m i n e r a l s h a v e been r e p o r t e d . K o s s o w s k a y a (51), i n t h i s v o l u m e , considers t h e genetic associations of s e d i m e n t a r y zeolites a n d t h e d o m i n a n t factors c o n t r o l l i n g t h e i r process of f o r m a t i o n . A n especially l u c i d a n d concise present a t i o n of t h e m e c h a n i s m of f o r m a t i o n of s e d i m e n t a r y zeolites u n d e r l o w t e m p e r a t u r e c o n d i t i o n s is g i v e n b y M a r i n e r a n d S u r d a m (52). I n studies o n the f o r m a t i o n of zeolites i n saline a l k a l i n e lakes, t h e y show differential


126

MOLECULAR SIEVES

s o l u b i l i t y of s i l i c a a n d a l u m i n a w i t h change i n p H . I n the r e a c t i o n of silicic glass a n d a l k a l i n e s o l u t i o n , a gel forms, whose S i / A l r a t i o is c o n t r o l l e d b y t h e S i / A l r a t i o of t h e s o l u t i o n , a n d a zeolite forms f r o m the gel whose S i / A l is, i n t u r n , c o n t r o l l e d b y t h e c o m p o s i t i o n of t h e gel. T h e y propose t h a t t h e i m p o r t a n t s i l i c a species i n gel f o r m a t i o n is the u n c h a r g e d S i ( O H ) a n d t h a t t h e charged A l ( O H ) ~ species catalyzes t h e f o r m a t i o n of t h e h y d r o u s a l u m i n o s i l i c a t e gel. I f the charged a l u m i n a species were absent, as the a l k a l i n i t y increases, silica w o u l d c o n t i n u e t o dissolve, a n d no gel w o u l d f o r m . T h e m e c h a n i s m is a p p l i e d t o the f o r m a t i o n of the n a t u r a l s o d i u m a l u m i n o s i l i c a t e gels described b y E u g s t e r a n d Jones (53) f r o m the i n t e r a c t i o n of a l k a l i n e s p r i n g waters w i t h a l k a l i t r a c h y t e r o c k s . T h e gel f o r m a t i o n is suggested t o be i n the i n t e r s t i t i a l brines associated w i t h t h e a s h b e d or a t t h e i n t e r f a c e between t h e glass s h a r d a n d s o l u t i o n . T h e m e c h a n i s m appears t o be analogous t o t h a t o c c u r r i n g i n zeolite synthesis f r o m gels. M a n y of the elements of M a r i n e r a n d S u r d a m ' s m e c h a n i s m are s i m i l a r t o those p r e v i o u s l y proposed b y C o o m b s et al. (54), H a y (55), a n d other a u t h o r s , a n d r e v i e w e d b y S h e p p a r d (56). 4


4

S i n g l e - C r y s t a l G r o w t h . A s i n g u l a r p a p e r i n t h i s area b y C h a r n e l l (57) describes a m e t h o d for p r e p a r i n g l a r g e r q u a n t i t i e s of single c r y s t a l s (100-140 μπιβΐβΓβ) of A a n d X zeolite, s u i t a b l e for x - r a y d i f f r a c t i o n , d i f f u s i o n , a n d other studies, w h e r e t h e l a c k of large c r y s t a l s has h a m p e r e d m a n y scientific i n v e s t i g a t i o n s . T h e m e t h o d represents a significant a d v a n c e over t h e gel g r o w t h one of C i r i c (58) where l o w y i e l d s a n d a d m i x t u r e s are t y p i c a l . C h a r n e l P s m e t h o d i n v o l v e s c r y s t a l l i z a t i o n of gels i n a m i x e d a q u e o u s - t r i e t h a n o l a m i n e s o l v e n t s y s t e m a n d c a r e f u l filtration of i n i t i a l a l u m i n a t e a n d s i l i c a t e s o l u t i o n s t h r o u g h microfilters (0.2 /zmeter) before g e l a t i o n . R i l e y , Seff, a n d S h o e m a k e r (59) h a v e r e p o r t e d successful use of C h a r n e l P s m e t h o d t o g r o w u p to 70 μπιβΐβΓ A c r y s t a l s w h e n m o d i f i e d t o i n c l u d e a second c r y s t a l l i z a t i o n u s i n g seed c r y s t a l s f r o m t h e first p r e p a r a tion. Discussion Z e o l i t e c r y s t a l l i z a t i o n represents one of the most c o m p l e x s t r u c t u r a l chemical problems i n crystallization phenomena. F o r m a t i o n under condi t i o n s of h i g h m e t a s t a b i l i t y leads to a dependence of t h e specific zeolite phase c r y s t a l l i z i n g o n a large n u m b e r of v a r i a b l e s i n a d d i t i o n t o t h e classical ones of r e a c t a n t c o m p o s i t i o n , t e m p e r a t u r e , a n d pressure f o u n d u n d e r e q u i l i b r i u m phase c o n d i t i o n s . T h e s e v a r i a b l e s (e.g., p H , n a t u r e of r e a c t a n t m a t e r i a l s , a g i t a t i o n d u r i n g r e a c t i o n , t i m e of r e a c t i o n , etc.) h a v e been e n u m e r a t e d b y p r e v i o u s reviewers (1, 2, 22). C r y s t a l l i z a t i o n of a d m i x t u r e s of several zeolite phases is c o m m o n . R e a c t i o n s i n v o l v e d i n zeolite c r y s tallization include polymerization-depolymerization, solution-precipita t i o n , n u c l e a t i o n - c r y s t a l l i z a t i o n , a n d c o m p l e x p h e n o m e n a encountered i n aqueous c o l l o i d a l dispersions. T h e large n u m b e r of k n o w n a n d h y p o -


10.

FLANiGEN


127


t h e t i c a l zeolite f r a m e w o r k s a n d t h e occurrence of m i x e d s t a c k i n g sequences a d d t o the c o m p l e x i t y . I n the i n t e r i m of the r e v i e w , a p r o l i f e r a t i o n of zeolite species has a p p e a r e d as a r e s u l t of t h e increase i n t h e v o l u m e of e x p e r i m e n t a l w o r k c a r r i e d o u t a n d the n u m b e r of a d d i t i o n s a n d p e r m u t a t i o n s of k n o w n a n d n e w v a r i a b l e s s t u d i e d i n the synthesis systems. The s i t u a t i o n is s u c c i n c t l y s u m m a r i z e d b y B a r r e r a n d C o l e (33): " T h e a r t of s y n t h e s i z i n g m o l e c u l a r sieve zeolites has developed more q u i c k l y t h a n the c h e m i c a l science w h i c h w o u l d p r o p e r l y account for t h e i r f o r m a t i o n i n n a t u r e a n d i n the l a b o r a t o r y f r o m a p p a r e n t l y s i m p l e a l u m i n o s i l i c a t e c o m p o s i t i o n s . " I n d e e d , t h e f a c i l i t y of synthesis appears t o be p r o p o r t i o n a l t o t h e d i f f i c u l t y of the science. N u m e r o u s p r o b l e m s h a v e a c c o m p a n i e d the a c c r u a l of i n c r e a s i n g n u m bers of zeolite species i n a d d i t i o n t o the w e l l - r e c o g n i z e d one of n o m e n c l a t u r e . O f t e n , the r e p o r t e d synthesis of a species does n o t i n c l u d e sufficient c h a r a c t e r i z a t i o n of properties t o c o m p l e t e l y describe i t as a zeolite. A l t h o u g h c h e m i c a l c o m p o s i t i o n a n d d e t a i l e d x - r a y p o w d e r d i f f r a c t i o n d a t a are g i v e n i n m o s t (but n o t all) cases, other i m p o r t a n t s t r u c t u r e - r e l a t e d p r o p erties s u c h as a d s o r p t i o n , i o n exchange, a n d s t a b i l i t y are n o t r e p o r t e d . T h e assignment of a specific f r a m e w o r k t y p e to a zeolite species based o n s i m i l a r i t y i n the x - r a y p o w d e r d i f f r a c t i o n p a t t e r n t o a p r e v i o u s l y k n o w n f r a m e w o r k t o p o l o g y is n o t j u s t i f i e d w i t h o u t d e t a i l e d s t r u c t u r a l d e t e r m i n a t i o n . T h e s i m i l a r i t y i n x - r a y p o w d e r d i f f r a c t i o n d a t a for r e l a t e d b u t different f r a m e w o r k topologies has been p o i n t e d o u t b y several a u t h o r s (22, 60, 61). O f t e n , l i t t l e proof is g i v e n of the species b e i n g a single h o mogeneous phase, free of other c r y s t a l l i n e or a m o r p h o u s i m p u r i t i e s . B e cause of the large sizes of zeolite u n i t cells (up t o ^ 3 5 A ) , t h e i r x - r a y p o w der d i f f r a c t i o n p a t t e r n s c o n t a i n a large n u m b e r of reflections i n t h e r e g i o n 2 5 - 1 . 5 A n o r m a l l y used for c h a r a c t e r i z a t i o n . T h i s , c o u p l e d w i t h t h e large n u m b e r of k n o w n zeolites, results i n the coincidence of some i n t e r p l a n a r spacings a m o n g several zeolites. T h u s , i d e n t i f i c a t i o n of t h e zeolite phases present i n a synthesis p r o d u c t is difficult a n d often a m b i g u o u s . The p r o b l e m s of s t r u c t u r a l d e t e r m i n a t i o n f r o m x - r a y p o w d e r d a t a o b t a i n e d o n c r y s t a l s w i t h the large u n i t cells t y p i c a l of zeolites w i l l c o n t i n u e t o l i m i t t h e n u m b e r of n e w c o m p o s i t i o n s w i t h a d e q u a t e l y c h a r a c t e r i z e d f r a m e w o r k structure. O f t h e zeolites r e p o r t e d since 1969, most represent

compositional

v a r i a n t s of p r e v i o u s l y k n o w n f r a m e w o r k s t r u c t u r e t y p e s w i t h respect t o c a t i o n , f r a m e w o r k , a n d i n t e r c a l a t e d salt compositions.

Zeolite

t h a t m a y represent n e w t y p e s of f r a m e w o r k topologies i n c l u d e : (18);

Z S M - 5 , 8, a n d 11 (8, 10, 11);

a n d L i , N a - 0 (24).

Z S M - 1 0 (12);

species "Losod"

B a - N and B a - T

(20);

Zeolites Z-21 (32) a n d N a - V (29) are n o t i n c l u d e d

because of t h e i r a p p a r e n t s t r u c t u r a l r e l a t i o n s h i p t o zeolite N .

E x c e p t for

" L o s o d , " n o s t r u c t u r a l studies h a v e been r e p o r t e d .


128

MOLECULAR SIEVES

T w o synthesis v a r i a b l e s seemed t o h a v e received m o s t a t t e n t i o n i n t h e w o r k r e v i e w e d here, the c a t i o n c o m p o s i t i o n a n d the n a t u r e a n d source of t h e a l u m i n o s i l i c a t e r e a c t a n t . E x t e n s i v e use of m i x e d bases of t h e a l k a l i , a l k a l i n e e a r t h , a n d organic cations h a v e b e e n r e p o r t e d as w e l l as a w i d e v a r i e t y of r e a c t a n t a l u m i n o s i l i c a t e s i n c l u d i n g solutions, hydrogels, glasses, k a o l i n (raw a n d c a l c i n e d ) , a n d n a t u r a l l y o c c u r r i n g zeolites.

Mono


a

Li Na Κ Rb Cs

Table I. Cation Systems for Zeolite Synthesis Ternary Quaternary Binary Na-Li-TMA Na-K-TMA Na-K-BTMA

Na-Li |Na-K>| Na-Rb

Na-K-Li-TMA

K-Ba |Ca-TMA-] Ba-TMA

Ca Sr Ba TMA

Na-RiN+ |Na-TMA 1 Na-TEA° Na-TPA Na-TBA Na-NTMA Na-MDO-| Na-DDO Na-BP Na-PP K-TMA K-DDO Na-R4P Na-TBP Na-BTPP +

α

Reported before 1969.

T h e c a t i o n p l a y s a p r o m i n e n t s t r u c t u r e - d i r e c t i n g role i n zeolite c r y s t a l l i z a t i o n . T h e u n i q u e s t r u c t u r a l characteristics of zeolite f r a m e w o r k s c o n t a i n i n g p o l y h e d r a l cages (62, 63) h a v e l e d t o t h e p o s t u l a t e t h a t t h e c a t i o n stabilizes t h e f o r m a t i o n of s t r u c t u r a l s u b u n i t s w h i c h are t h e p r e cursors or n u c l e a t i n g species i n c r y s t a l l i z a t i o n . T h e m a n y zeolite c o m p o s i tions a n d complex c a t i o n base systems s t u d i e d a l l o w a test of the s t r u c t u r e d i r e c t i n g role of the c a t i o n a n d t h e c a t i o n " t e m p l a t i n g " concept. T a b l e I s u m m a r i z e s t h e c a t i o n base systems f r o m w h i c h zeolites h a v e b e e n s y n thesized. T h e systems used before 1969 are i n d i c a t e d t o i l l u s t r a t e t h e n u m b e r a n d complexities of n e w c a t i o n systems i n v e s t i g a t e d since t h a t t i m e . T a b l e I I presents a s u m m a r y of zeolite f r a m e w o r k s t r u c t u r e t y p e s , t h e c a t i o n systems i n w h i c h t h e y h a v e been f o r m e d , a n d a p r o p o s a l for a c a t i o n specificity for the f o r m a t i o n of each f r a m e w o r k t y p e . A s i m i l a r


10.

FLANiGEN Table Π.

Synthesis Cation/Framework Structure Relationships

Building Units Zeolite Structure Double Type Rings Polyhedra

a


129


A X , Y , faujasite ZK-5 ZSM-3 Gmelinite Ω

D-4 D-6 D-6 D-6 D-6 —

Offretite Erionite (with offretite)

D-6 D-6

L

D-6

Chabazite

D-6

Synthesis Cation

0

Cation Specificity for Framework Structure

Na, N a - T M A , N a - K , N a - L i N a Na Na, N a - T M A , N a - K Na-DDO N a - D D O , (Ba salts?) a Na-Li Na-Li Sodal Na N a , N a - T M A , (Ca-N?) Gmel Na-TMA Na-TMA, Na-K-TMA, Gmel Na-Li-TMA K-TMA Gmel, cane K - T M A , K - N a - T M A Na-K, Na-Rb, Cane (gmel) N a - K , B a - T M A , N a - R b , Na-TMA, Na-TMA, Na-K-TMA, Ba-TMA Na-Li-TMA, N a - K BTMA K , K - N a , K - D D O , K - N a - Κ or B a Cane T M A , Ba, B a - T M A N a , K , or Sr N a , K , N a - K , B a - K , Sr, (K-TMA?), (K-Na-TMA?)

Sodal, a Sodal

The structure types and building units and their nomenclature in Tables II, III, and IV are the same as in ref. 85. Sodal = sodalite cage, gmel = gmelinite cage, cane = cancrinite cage, a = the truncated cuboctahedron (48 tetrahedra). β

c o r r e l a t i o n is developed for t h e p o l y h e d r a l b u i l d i n g u n i t s i n T a b l e I I I . O n l y those zeolite f r a m e w o r k t y p e s w h i c h are w e l l c h a r a c t e r i z e d a n d c o n t a i n p o l y h e d r a l u n i t s are i n c l u d e d . I t is clear f r o m t h e large n u m b e r of c a t i o n systems r e p o r t e d for t h e synthesis of zeolites c o n t a i n i n g o n l y single r i n g s of four, five, s i x , a n d eight t e t r a h e d r a t h a t there is l i t t l e i n d i c a t i o n of a s t r u c t u r a l c a t i o n specificity. T h u s , m o r d e n i t e w i t h p r e d o m i n a n t l y 5-rings has been s y n t h e s i z e d f r o m N a , L i , N a - L i , S r , a n d C a c a t i o n base systems. S i m i l a r l y , a n a l c i m e w i t h 4a n d 6-rings a n d h a r m o t o m e / p h i l l i p s i t e f r a m e w o r k s w i t h 4- a n d 8-rings h a v e been s y n t h e s i z e d i n a large n u m b e r of a l k a l i a n d a l k a l i n e e a r t h c a t i o n base systems. T a b l e s I I a n d I I I are presented as a n i n i t i a l a t t e m p t t o e s t a b l i s h a b r o a d c o r r e l a t i o n between c r y s t a l l i z a t i o n a n d s t r u c t u r e i n t e r m s of c a t i o n composition. T h e extensive a s s u m p t i o n s a n d u n c e r t a i n t i e s i n v o l v e d are w e l l recognized i n c l u d i n g acceptance of assignment of f r a m e w o r k t y p e based o n s i m i l a r i t y of x - r a y p o w d e r d i f f r a c t i o n p a t t e r n s , e x c l u s i o n of some p o l y h e d r a l cages f o u n d i n zeolite s t r u c t u r e s (62) t h e r e l a t i v e c o n c e n t r a t i o n s of cations i n m i x t u r e s , v a r i a b l e s other t h a n c a t i o n , a n d t h e possible presence of i m p u r i t y cations n o t r e p o r t e d b u t d e r i v e d f r o m reagents or r e a c t i o n vessels. y

T h e a b o v e a p p r o a c h shows t h a t t h e f o r m a t i o n of a specific f r a m e w o r k t y p e a n d a p o l y h e d r a l b u i l d i n g u n i t depends o n one or a t t h e most t w o


130

MOLECULAR SIEVES

Table III. Building Unit


Sodalite

Gmelinite

Cancrinite

D-4

D-6

Synthesis Cation-Building Unit Relationship

Synthesis Cation Systems Na Na-TMA Na-DDO Na-K Na-Li Na; (TMA) Na-TMA Na-K Na-Li Na Na-TMA K-TMA K-Na-TMA Na-Li-TMA K ; Ba K-Na; Ba-TMA K - T M A ; Na-Rb K-DDO; Na-TMA K-Na-TMA K-Na-BTMA Na Na-TMA Na-K Na-Li Na; Ba K ; Sr K-Na; Ba-K Na-Li; Ba-TMA Na-TMA K-Na-TMA Na-Ii-TMA Na-K-BTMA Na-DDO K-DDO

Zeolite Framework Types Containing Building Units

Cation Specificity for Building Unit

A, ZK-5

Na

A, X , Y , ZSM-3, (TMA-sodalite)

N a or T M A

Gmelinite, offretite,

N a or T M A

Erionite/offretite, L

K , B a , or R b (or T M A ? )

Na

X , Y , ZK-5, ZSM-3, chabazite, gmelinite, erionite/offretite, L

N a , K , Sr, or B a

c a t i o n species. S t r o n g c a t i o n specificity is f o u n d for the p o l y h e d r a l u n i t s D - 4 , c a n c r i n i t e , g m e l i n i t e , sodalite, a n d t h e a cage a n d zeolite f r a m e w o r k s c o n t a i n i n g these u n i t s i n t h e i r s t r u c t u r e s . T h e c a t i o n specificity is l o w for t h e f o r m a t i o n of D - 6 r i n g s a l t h o u g h no D - 6 r i n g s t r u c t u r e s h a v e been rep o r t e d i n t h e L i a n d C a systems. T h e r e l a t i v e sizes of t h e p o l y h e d r a l cages a n d the r e l a t e d specific cations are s h o w n i n T a b l e I V . A good fit for t h e a n h y d r o u s d i a m e t e r is o b s e r v e d for the T M A i o n i n the g m e l i n i t e a n d sodalite cages, t h e K , B a , a n d R b ions i n t h e c a n c r i n i t e cage, a n d for the d i a m e t e r of the h y d r a t e d N a i o n i n t h e g m e l i n i t e a n d sodalite cages. T a b l e I V shows t h a t the B a a n d R b ions c a n s u b s t i t u t e for K , a n d T M A c a n s u b -


FLANiGEN

10.

131



stitute for the hydrated N a ion in their structure-forming roles. This analysis tends to support the cation-templating concept for most of the the polyhedral cages considered. T h e cation specificities agree with the correlations reported previously b y Aiello and Barrer (16) for T M A with the gmelinite cage and Κ with the cancrinite cage as well as with zeolite structure studies showing the occupancy of the sodalite cage b y T M A (6), the gmelinite cage b y T M A (16, 64), and the cancrinite cage b y Κ (16). T h e absence of a sodium ion near the center of the sodalite cage in hydrated N a A as reported b y Gramlich and Meier (66) is inconsistent with the con cept of templating of the sodalite cage b y the hydrated N a ion as initially proposed by Breck (66) and as developed here. T h e thermodynamic stabilization of open aluminosilicate structures b y the intracrystalline guest species, water or salts, has been developed ex tensively by Barrer (2, 62) and must be considered in their formation. The role of water structure in templating open zeolite frameworks was suggested b y Belov (67). H e proposed that the dodecahedral clathraterelated molecule, H 0 · 20H O, is the nucleus for formation of A and X zeo lite. The presence of the dodecahedral water structure [ N a - H O ] - 2 0 H O in the large α cage of hydrated N a A has been confirmed b y Gramlich and Meier (65). 2

2

2

2

The templating theory is based on a stereospecificity which cannot be separated from the chemistry of the cation. Zeolites are crystallized i n alkaline solutions, most readily at a p H greater than 11, limiting the cations used in zeolite synthesis to alkali, some alkaline earths, and organic cations Table IV.

Cation Specific Building Units i n Zeolite Structures Specific Cation

Building Unit

Diameter, A

a

Anhydrous

Free Dimensions, A

(Crystal)

Hydrated

7.2 2.0 7.2 2.0 7.2 (Na), 7.3 2.0 (Na), 6.9 (TMA) (TMA) 7.2 (Na), 7.3 2.0 (Na), 6.9 Gmelinite 6 . 0 X 7 . 4 Na or T M A (TMA) (TMA) 2.8 (K), 2.7 6.6 (K), 8.1 Cancrinite 3.5-5.0 K, Ba, or Rb (Ba), 6.6 (Ba), 3.0 (Rb) (Rb) 7.2-8.2 D-6 3.6 Na, K, Sr, or Ba 2.0-2.8 Hydrated diameters and crystal diameter of T M A are from ref. 86. Other crys tal diameters are those of Shannon-Prewitt for sixfold coordination as listed in ref. 87; higher coordination numbers as observed in many zeolite structures (e.g., 12-fold for Κ in the cancrinite unit in L and offretite) increase the diameter by up to 0.5 A. Range of free diameter of maximum included sphere observed in the structures of L and offretite (3.5 A) and in the structure of cancrinite (5.0 A). Variation reflects the degree of distortion of the ideal unit (60, 88). D-4 a Sodalite

2.3 11.4 6.6

Na Na Na or T M A

6

a

6


132

MOLECULAR SIEVES

s u c h as q u a t e r n a r y a m m o n i u m . I n a l m o s t a l l cases, t h e c a t i o n ( M ) is a d d e d as a base, M O H , r e s u l t i n g i n t h e c o n c e n t r a t i o n of O H " b e i n g c o n t r o l l e d s i m u l t a n e o u s l y w i t h t h e c o n c e n t r a t i o n of c a t i o n . T h e h y d r o x y l i o n affects d i s s o l u t i o n a n d p o l y m e r i z a t i o n - d e p o l y m e r i z a t i o n reactions of silicates a n d a l u m i n o s i l i c a t e s . C o n s i d e r e d separate f r o m i t s p r o v i d i n g h y d r o x y l ions, t h e extent of i n t e r a c t i o n of t h e c a t i o n w i t h a n a n i o n i c a l u m i n o s i l i c a t e species s h o u l d be a f u n c t i o n of i t s charge d e n s i t y , Z /r (where Ζ = i o n i c charge a n d r = i o n i c r a d i u s ) . F o r t h e a l k a l i a n d a l k a l i n e e a r t h ions w i t h a p X b r a n g e of —1.7 t o 1.5, t h e order of decreasing pK or i n c r e a s i n g Z /r i s : C s > R b > Κ > N a > L i > B a > S r > C a (68). T h e u n i q u e c h a r a c t e r i s t i c s of N a a n d Κ i n p r o m o t i n g t h e facile f o r m a t i o n of v e r y open zeolite n e t w o r k s c l e a r l y i n v o l v e m o r e t h a n t h e i r a c i d - b a s e c h e m i s t r y a n d m u s t also r e l a t e t o t h e c o n t r o l of t h e f o r m a t i o n of specific a l u m i n o s i l i c a t e species i n t h e gel systems. T h e organic cations of t h e q u a t e r n a r y a m m o n i u m t y p e u s e d i n zeolite synthesis are s t r o n g bases (puT ~ 1 ) a n d e x h i b i t h i g h s o l u b i l i t i e s for s i l i c a a n d a l u m i n a analogous t o t h e a l k a l i ions (69). S o l u b i l i t i e s of S1O2 a n d AI2O3 are l o w e r i n aqueous a l k a l i n e e a r t h h y d r o x i d e s a n d i n L i O H t h a n i n t h e bases of N a , K , a n d T M A . L i t t l e has been p u b l i s h e d o n t h e s o l u b i l i t y of m e t a l - a l u m i n o s i l i c a t e p r e c i p i t a t e s , b u t d i f f e r e n t i a l s o l u b i l i t y of a l u m i n a a n d s i l i c a as a f u n c t i o n of c a t i o n p r o b a b l y occurs. A m o n g t h e soluble silicates, t h e m o l e c u l a r w e i g h t a n d size of s i l i c a t e species increase i n order N a < Κ < L i < T M A (70). Similarly, the molecular weight and s t r u c t u r e of a l u m i n o s i l i c a t e species s h o u l d d e p e n d o n c a t i o n t y p e . 2


h

2

b

Sieber (18) suggests t h a t l a r g e r organic bases are p r i n c i p a l l y a source of h y d r o x y l ions a n d do n o t p e r f o r m a s t r u c t u r e - d i r e c t i n g role. E x c e p t for t h e T M A i o n , t h i s m a y be a general c h a r a c t e r i s t i c of organic bases i n zeolite c r y s t a l l i z a t i o n . H o w e v e r , t h e c o l l o i d c h e m i s t r y of organic cations m u s t be considered as w e l l as t h e i r s t r o n g base properties. Q u a t e r n a r y a m m o n i u m bases h a v e been r e p o r t e d t o f o r m stable a l u m i n o s i l i c a t e sols (18, 71). The a d d i t i o n of a l k a l i is necessary for p r e c i p i t a t i o n a n d c r y s t a l l i z a t i o n t o occur. A n elegant e x a m p l e of t h e p r e c i p i t a t i n g a n d c r y s t a l l i z i n g p r o p e r t y of t h e N a i o n is i l l u s t r a t e d i n w o r k f r o m t h i s l a b o r a t o r y b y A c a r a a n d H o w e l l (72) w h e r e a T M A - a l u m i n o s i l i c a t e s o l w h i c h d i d n o t p r e c i p i t a t e solids after h e a t i n g a t 1 0 0 ° C was " t i t r a t e d " w i t h aqueous N a C l . T h e r e s u l t i n g f o r m a t i o n of gel a n d of A c r y s t a l s w a s p r o p o r t i o n a l i n r a t e , y i e l d , a n d size of c r y s t a l t o t h e a m o u n t of N a C l a d d e d . T h e n e a r c u b i c A c r y s t a l s f o r m e d w i t h sizes f r o m 250 A t o 0.3 Mmeter are s h o w n i n t h e sequence of e l e c t r o n m i c r o g r a p h s i n F i g u r e 1. I t is proposed t h a t i n m i x e d organic b a s e - a l k a l i systems, t h e presence of t h e organic base changes t h e s o l i d - l i q u i d e q u i l i b r i u m a n d stabilizes l a r g e r s o l - l i k e a l u m i n o s i l i c a t e species ( ~ 2 5 ταμ). T h e a l k a l i i o n affects a g g l o m e r a t i o n of t h e sol p a r t i c l e s t o larger a m o r p h o u s p r e c i p i t a t e p a r t i c l e s f r o m 100 t o 500 πΐμ i n size w h i c h s u b s e q u e n t l y c r y s t a l l i z e t o zeolite.



10.

FLANiGEN

133


Figure 1. Addition of NaCl to α ΤM A-Aluminosilicate sol. Elec tron photomicrographs of zeolite A crystals recovered after 24 hours at 100°C: (a) 0.1 NaCl/AWz, (&) 0.2 NaCl/AWz, (C) 0.5 NaCl/AWz, (d) 1.0NaCl/AW*; magnification 14,170X. T h e precipitation and solution phenomena depend on the relative concen t r a t i o n s of t h e organic a n d a l k a l i c a t i o n a n d o n p H . T h i s w o u l d p r e d i c t t h a t zeolites w i l l n o t c r y s t a l l i z e f r o m p u r e organic c a t i o n s y s t e m s i n t h e absence of a l k a l i . T h e t w o exceptions t o t h i s appear t o be M e i e r a n d B a e r l o c h e r ' s c r y s t a l l i z a t i o n of T M A - g i s m o n d i n e zeolite (4) a n d t h e felsp a t h o i d T M A - s o d a l i t e (5). T h e r e is considerable evidence t h a t t h e a l k a l i c a t i o n is s t r o n g l y a n d s t o i c h i o m e t r i c a l l y associated w i t h a n a l u m i n a t e species. T h e a l k a l i - A l r a t i o i n t h e s o l i d phase of t h e gel reaches a v a l u e near one e a r l y i n t h e c r y s t a l l i z a t i o n r e a c t i o n (1). T h i s suggests t h a t a n i o n p a i r i n g or a n asso c i a t e d species of [ N a ] [ A 1 0 H - ] or N a A 1 0 is t h e r e a c t i n g or diffusing species a n d is also t h e p r e c i p i t a t i n g agent. +

4

2

Z h d a n o v (1 ) describes t h e m e c h a n i s m of zeolite c r y s t a l l i z a t i o n i n t e r m s of a q u a s i e q u i l i b r i u m b e t w e e n t h e s o l i d a n d l i q u i d phase i n gels a n d e m phasizes t h a t the f o r m a t i o n a n d g r o w t h of n u c l e i occurs i n t h e l i q u i d phase.


134

MOLECULAR SIEVES


T h e gel solids serve as n u t r i e n t a n d dissolve c o n t i n u o u s l y d u r i n g c r y s t a l l i z a t i o n w i t h b u l k t r a n s p o r t of t h e d i s s o l v e d species t o t h e g r o w i n g n u c l e i or c r y s t a l s i n t h e l i q u i d phase. T h e r e s u l t i n g m e c h a n i s m is analogous t o homogeneous n u c l e a t i o n a n d g r o w t h f r o m s o l u t i o n as i n i t i a l l y proposed b y K e r r (73) a n d l a t e r s u p p o r t e d b y C i r i c (74) · T h e i m p o r t a n c e of t h e s o l i d phase of the gel as t h e locus of zeolite n u c l e a t i o n - c r y s t a l l i z a t i o n a n d h e t e r o geneous n u c l e a t i o n p h e n o m e n a h a d been e m p h a s i z e d b y F l a n i g e n a n d B r e c k i n t h e i r i n i t i a l p r o p o s a l of m e c h a n i s m (76). S e v e r a l references c i t e d s u p p o r t (1) t h e f o r m a t i o n of a s o l i d a m o r p h o u s " p r e c u r s o r " w h i c h precedes zeolite c r y s t a l l i z a t i o n f r o m s o l u t i o n , (2) heterogeneous n u c l e a t i o n p h e n o m e n a , a n d (3) t h e v i e w t h a t c r y s t a l l i z a t i o n occurs p r e d o m i n a n t l y i n t h e s o l i d phase of t h e gel b y a n o r d e r i n g of the a l u m i n o s i l i c a t e n e t w o r k . Khat a m i a n d F l a n i g e n (76) observed c r y s t a l l i z a t i o n of gel solids i n the absence of l i q u i d phase. S o l i d s r e m o v e d f r o m a t y p i c a l zeolite X gel near t h e e n d of t h e i n d u c t i o n p e r i o d were w a s h e d free of l i q u i d phase a n d d r i e d a t a m b i e n t t e m p e r a t u r e t o a n a m o r p h o u s p h y s i c a l l y " d r y " free-flowing p o w d e r of c o m p o s i t i o n l . l N a O A l 0 - 2 . 7 S i 0 - 4 . 6 H 0 (about 20 w t % a d s o r b e d H 0 ) . X - R a y d i f f r a c t i o n a n a l y s i s of t h e solids after 10 d a y s a t a m b i e n t s h o w e d a t r a c e (2%) of c r y s t a l l i n e X , a n d 2 0 % X after 47 d a y s a t a m b i e n t . The p h e n o m e n o n was c o n f i r m e d w i t h s e v e r a l o t h e r s i m i l a r gel solids. 2

2

3

2

2

2

C o n s i d e r a b l e emphasis has been p l a c e d o n a solid-phase vs. a l i q u i d phase m e c h a n i s m . Z h d a n o v has n o t e d t h e m a n y c o m m o n elements of b o t h approaches (1). I t is suggested here t h a t f u r t h e r progress i n u n d e r s t a n d i n g c r y s t a l l i z a t i o n m a y r e s u l t f r o m s t u d y i n g zeolite c r y s t a l l i z i n g s y s t e m s as u n s t a b l e aqueous c o l l o i d a l dispersions where the i m p o r t a n c e of t h e roles of t h e s o l i d - l i q u i d interface a n d t h e d i f f u s i o n a l or m e t h o r i c a l l a y e r is w e l l recognized. S u c h emphasis places more focus o n t h e c h e m i s t r y of c o l l o i d a l p a r t i c l e s a n d the m e c h a n i s m s of p a r t i c l e g r o w t h i n s u c h systems. T e z a k suggested i n t h e discussion of C i r i c ' s p a p e r (74) t h a t his a p p r o a c h t o c o m p l e x p r e c i p i t a t i n g bodies (77, 78) be a p p l i e d t o zeolite c r y s t a l l i z a t i o n . H e proposes at least four subsystems i n s t e a d of t h e t w o of n u c l e a t i o n a n d c r y s t a l l i z a t i o n : (1) f o r m a t i o n of s i m p l e a n d p o l y n u c l e a r complexes, (2) e m b r y o n a t i o n as a state of aggregation of complexes, (3) n u c l e a t i o n as aggregate f o r m a t i o n w i t h a c r y s t a l l i n e core a n d f o r m a t i o n of micelles ( p r i m a r y p a r t i c l e s ) , a n d (4) aggregation of p r i m a r y p a r t i c l e s i n t o larger secondary s t r u c t u r e s t h r o u g h c r y s t a l l i n e (oriented) aggregation. S u c h a n a p p r o a c h seems a p p l i c a b l e t o zeolite c r y s t a l l i z i n g systems. A c a r a a n d H o w e l l ' s results s h o w n i n F i g u r e 1 are consistent w i t h a m e c h a n i s m of o r i e n t e d or c r y s t a l l i n e aggregation for zeolite A f o r m a t i o n . I n u n s t a b l e aqueous c o l l o i d a l dispersions, the large i n t e r f a c i a l free energy associated w i t h s m a l l p a r t i c l e s is a d r i v i n g force t o reduce t h e t o t a l p r e c i p i t a t e surface area b y a secondary g r o w t h process c a l l e d r i p e n i n g (79, 80). R i p e n i n g c a n occur b y d i s s o l u t i o n of smaller p a r t i c l e s a n d g r o w t h of larger ones ( O s t w a l d r i p e n i n g ) or b y c o a g u l a t i o n or aggregation c o m b i n e d


10.

FLANIGEN

135


w i t h c r y s t a l l i z a t i o n (81). E a n e s a n d P o s n e r (82) h a v e a p p l i e d s u c h m e c h a n i s m s t o t h e c r y s t a l l i z a t i o n of h y d r o x y a p a t i t e w h i c h proceeds t h r o u g h t h e f o r m a t i o n of a n i n t e r m e d i a t e a m o r p h o u s s o l i d ( " g e l " ) phase w h i c h subseq u e n t l y c r y s t a l l i z e s b y a secondary O s t w a l d r i p e n i n g m e c h a n i s m . Z e o l i t e c r y s t a l l i z a t i o n c a n be i n t e r p r e t e d i n t e r m s of a r i p e n i n g m e c h a n i s m . T h e i n i t i a l l y f o r m e d gel consists of a m o r p h o u s dispersed p a r t i c l e s of the order of 100-300 A i n size. G r o w t h of these p a r t i c l e s t o a p p r o x i m a t e l y 1000 A occurs d u r i n g t h e i n d u c t i o n p e r i o d after w h i c h zeolite c r y s t a l s a p p e a r i m b e d d e d i n the a m o r p h o u s gel m a t r i x . T h i s is especially e v i d e n t i n electron microscopic studies of gel solids (66 83). Ciric comments on the o b s e r v a t i o n of g r o w i n g c r y s t a l s " i m b e d d e d i n gel particles w h i c h , as t h e c r y s t a l s grow, t e n d t o s h r i n k together, r e s u l t i n g i n coalescence" (74)·


y

B e c a u s e of the h i g h surface free energy a t t h e l i q u i d - s o l i d interface, i t is suggested t h a t t h e stages of n u c l e a t i o n , t r a n s p o r t of species b y surface diffusion, a n d c r y s t a l l i z a t i o n o c c u r a t the interface i n t h e b o u n d a r y l a y e r . Çulfaz a n d S a n d i n t h i s v o l u m e (48) propose a m e c h a n i s m w i t h n u c l e a t i o n at t h e s o l i d - l i q u i d interface. T h i s m e c h a n i s m s h o u l d be m o s t e v i d e n t i n m o r e c o n c e n t r a t e d gel systems where i n t e r p a r t i c l e c o n t a c t is m a x i m i z e d for aggregation, coalescence, or r i p e n i n g processes. T h e e p i t a x y observed b y K e r r et al. (84) i n c o c r y s t a l l i z a t i o n of zeolites L , offretite, a n d erionite f u r t h e r s u p p o r t s a surface n u c l e a t i o n m e c h a n i s m . T h e c o n s t a n c y of t h e c h e m i c a l c o m p o s i t i o n a n d a m o u n t of t h e b u l k s o l i d a n d b u l k l i q u i d phase t h r o u g h o u t n u c l e a t i o n a n d c r y s t a l l i z a t i o n are also consistent w i t h t h i s m e c h a n i s m . T r a n s p o r t of n u t r i e n t f r o m a m o r phous gel solids t o g r o w i n g n u c l e i w o u l d occur b y surface diffusion, a n d therefore l i t t l e change w o u l d be expected i n t h e b u l k s o l i d or l i q u i d . The m e c h a n i s m is consistent w i t h t h a t of Z h d a n o v except t h a t n u c l e a t i o n a n d t r a n s p o r t of n u t r i e n t t o g r o w i n g n u c l e i a n d c r y s t a l s t a k e place i n t h e s u r face diffusion l a y e r r a t h e r t h a n i n the b u l k l i q u i d . I t is also consistent w i t h o r d e r i n g i n t h e s o l i d phase since a r i p e n i n g g r o w t h process c a n o c c u r w i t h or w i t h o u t o r d e r i n g . Conclusion Progress i n zeolite c r y s t a l l i z a t i o n i n t h e l a s t several years has b e e n m o s t l y i n the e x p e r i m e n t a l r e a l m a n d has r e s u l t e d i n several n e w s y n t h e t i c zeolites a n d c o m p o s i t i o n a l v a r i a n t s of p r e v i o u s l y k n o w n s t r u c t u r e s . T h e o r e t i c a l advances h a v e come m o r e s l o w l y b u t are significant. Until t h e e l u c i d a t i o n of zeolite s t r u c t u r e s i n t h e last decade or so, s t r u c t u r a l i n t e r p r e t a t i o n of c r y s t a l l i z a t i o n p h e n o m e n a was n o t possible. A s a d d i t i o n a l p h y s i c a l a n d c h e m i c a l techniques are a p p l i e d t o t h e c o m p l e x s t r u c t u r a l c h e m i s t r y of zeolite c r y s t a l l i z a t i o n , our u n d e r s t a n d i n g of the m e c h a n i s m increases, a n d t h e extent of e m p i r i c i s m i n synthesis decreases. A r e a s of i n v e s t i g a t i o n s t i l l u n e x p l o r e d t h a t s h o u l d a d d considerable u n d e r s t a n d i n g


136

MOLECULAR SIEVES


t o zeolite c r y s t a l l i z a t i o n a r e : t h e t h e r m o d y n a m i c properties of zeolites as d e t e r m i n e d , for example, b y s o l u b i l i t y s t u d i e s ; definitive studies of t h e s o l u b i l i t y characteristics of a l u m i n o s i l i c a t e precipitates i n bases; t h e t h e r m o c h e m i s t r y of t h e c r y s t a l l i z a t i o n r e a c t i o n s ; a p p l i c a t i o n of techniques used c o m m o n l y i n c o l l o i d c h e m i s t r y w i t h respect t o r h e o l o g y a n d surface e l e c t r o k i n e t i c p h e n o m e n a ; d e t e r m i n a t i o n of t h e size a n d n u m b e r of n u c l e a t i n g species b y i n d i r e c t k i n e t i c m e t h o d s (81); a n d a m o r e rigorous a p p l i c a t i o n of t h e f u n d a m e n t a l s of s o l u t i o n a n d p o l y m e r c h e m i s t r y t o zeolite c r y s t a l l i z a t i o n . T h e scientific goals of c o n c e i v i n g a n d b u i l d i n g n e w zeolite structures a n d k n o w i n g h o w t o p r e d i c t a b l y synthesize t h e m i n t h e l a b o r a t o r y are n o t o u t of r e a c h b u t are f a r f r o m a c h i e v e d .

Acknowledgment T h e a u t h o r t h a n k s D . W . B r e c k for his i n v a l u a b l e assistance d u r i n g t h e p r e p a r a t i o n of t h e m a n u s c r i p t a n d U n i o n C a r b i d e C o r p . for p e r m i s s i o n t o publish it. Appendix.

Organic Base Nomenclature

R N+ TMA TEA TPA TBA BTMA NTMA

( C H ) N , tetramethylammonium ( C H ) 4 N , tetraethylammonium (C3H )4N , tetrapropylammonium ( C 4 H ) 4 N , tetrabutylammonium C6H CH (CH3)3N , benzyltrimethylammonium C H n (CH )aN , neopentyltrimethylammonium

R P TBP BTPP

( C H ) 4 P , tetrabutylphosphonium CeHeCHjj (CeH )3P , benzyltriphenylphosphonium

4

4

3

2

+

4

+

5

+

7

+

9

6

+

2

5

3

+

+

4

9

+

5

+

Complex MDO

DDO

BP

PP

C H i s N +, 6-azonia-spiro [4.5 ]decane 9

(PP from piperidinium and pyrrolidinium)


10.

FLANiGEN


137

Literature Cited 1.

Zhdanov, S. P., ADVAN. CHEM. SER. (1971) 101, 20.

2. Barrer, R. M., "Molecular Sieves," p. 39, Society of the Chemical Industry, London, 1968. 3. Senderov, Ε. E., Khitarov, Ν. E., "Zeolites, Their Synthesis and Conditions of Formation in Nature," Nauka Publishing House, Moscow, 1970. 4. Baerlocher, Ch., Meier, W. M., Helv. Chim. Acta (1970) 53, 1285. 5. Baerlocher, Ch., Meier, W. M., Helv. Chim. Acta(1969) 52, 1853. 6. Barrer, R. M., Denny, P. J., Flanigen, E. M., U. S. Patent 3,306,922 (1967).


7.

Breck, D. W., ADVAN. CHEM. SER. (1971) 101, 1.

8. Mobil Oil Corp., Netherlands Patent 7,014,807 (1971). 9. Argauer, R. J., Olson, D. H., Landolt, G. R., South African Patent 68/1973 (1968). 10. Argauer, R. J., Landolt, G. R., U. S. Patent 3,702,886 (1972). 11. Mobil Oil Corp., Netherlands Patent 7,015,416 (1971). 12. Ciric, J., U. S. Patent 3,692,470 (1972). 13. Rubin, M. K., Rosinski, E. J., U. S. Patent 3,699,139 (1972). 14. Rubin, M. K., German Patent Appl. OFS 1,806,154 (1969). 15. Jenkins, E. E., U. S. Patent 3,578,398 (1971). 16. Aiello, R., Barrer, R. M., J. Chem. Soc. (1970) 1470. 17. Kouwenhoven, H. W., Cole, J. F., South African Patent 71/1172 (1971). 18. Sieber, W., PhD. Thesis, Eidgenossischen Technischen Hochschule, Zurich, 1972. 19. Smith, J. V., Amer. Mineral. Soc., Spec. Paper (1963) 1, 281. 20. Barrer, R. M., Mainwaring, D. E., JCS Dalton Trans. (1972) 1254, 1259. 21. Barrer, R. M., Marshall, D. J., J. Chem. Soc. (1964) 2296. 22. Breck, D. W., Flanigen, Ε. M., "Molecular Sieves," p. 47, Society of the Chemi cal Industry, London, 1968. 23. Robson, H. E., U. S. Patent 3,674,425 (1972). 24. Borer, H., Meier, W. M., ADVAN. CHEM. SER. (1971) 101, 122. 25. Sand, M . L., Coblenz, W. S., Sand, L. B., ADVAN. CHEM. SER. (1971) 101, 127. 26. Pereyron, Α., Guth, H. L., Wey, R., C. R. Acad.Sci.,Ser. D (1971) 272, 181. 27. Kokotailo, G. T., Ciric, J., ADVAN. CHEM. SER. (1971) 101, 109. 28. Ciric, J., U. S. Patent 3,415,736 (1968). 29. Collela, C., Aiello, R., Ann. Chim. (Rome) (1971) 61, 721. 30. Acara, Ν. Α., U. S. Patent 3,414,602 (1968). 31. Mainwaring, D. E., PhD. thesis, University of London, 1970. 32. Duecker, H. C., Weiss, Α., Guerra, C. R., U. S. Patent 3,567,372 (1971). 33. Barrer, R. M., Cole, J. F., J. Chem. Soc. A (1970) 1516. 34. Rabo, J. Α., Poutsma, M . L., Skeels, G. W., Prepr. Int. Congr. Catal. (1972) 5. 35. Barrer, R. M., Cole, J. F., Villiger, H., J. Chem. Soc. A (1970) 1523. 36. Barrer, R. M., Marcilly, C., J. Chem. Soc. A (1970) 2735. 37. Kühl, G. H., Inorg. Chem. (1971) 10, 2489. 38. Miyata, Y., Susumu, O., Kogyo Kagaku Zasshi (1970) 73, 1940. 39. Negisha, T., Nakanura, H., Kobutsugaku Zasshi (1970) 10, 72. 40. Utada, M., Minato, H., Mineral. J. (1969) 6, 57. 41. Aiello, R., Barrer, R. M., Kerr, I. S., ADVAN. CHEM. SER. (1971) 101, 44. 42. Aiello, R., Collela, C., Sersale, R., ADVAN. CHEM. SER. (1971) 101, 51. 43. Schwochow, F. E., Heinze, G. W., ADVAN. CHEM. SER. (1971) 101, 102.


138

MOLECULAR SIEVES

44. 45.

Polak, F., Przem. Chem. (1971) 50, 83. Migal, P. K., Nelyubov, S. V., Sb. Nauch. Statei, Kishinev. Gos. Univ., Estestv. Mat. Nauk (1969) 105. 46. Mirskii, Y. V., Pirozhkov, V. V., Zh. Fiz. Khim (1970) 44, 2646; Russ. J. Phys. Chem. (1970) 44, 1508. 47. Schwochow, F. E., Meise, F., ADVAN. CHEM. SER. (1973) 121, 169. 48. Culfaz, Α., Sand, L. B., ADVAN. CHEM. SER. (1973) 121, 152. 49. McNicol, B. D., Pott, G. T., Loos, K. R., Mulder, N., ADVAN. CHEM. SER. (1973) 121, 169; McNicol, B. D., Pott, G. T., Loos, K. R., J. Phys. Chem. (1972) 76, 3388.


50. 51.

Beard, W. C., ADVAN. CHEM. SER. (1973) 121, 162. Kossowskaya, A . G., ADVAN. CHEM. SER. (1973) 121, 200.

52. 53. 54.

Mariner, R. H., Surdam, E. C., Science (1970) 110, 977. Eugster, H. P., Jones, B. F., Science (1968) 161, 160. Coombs, D. S., Ellis, A. J., Fyfe, W. S., Taylor, A. M., Geochim. Cosmochim. Acta (1959) 17, 53. 55. Hay, R. L., Geol. Soc. Amer. Spec. Papers (1966) 85, 1. 56.

Sheppard, R. Α., ADVAN. CHEM. SER. (1971) 101, 279.

57. 58. 59. 60.

Charnell, J. F., J. Cryst. Growth (1971) 8, 291. Ciric, J., Science (1967) 155, 373. Riley, P. E., Seff, K., Shoemaker, D. P., J. Phys. Chem. (1972) 76, 2593. Barrer, R. M., Villiger, H., Z. Kristallogr. (1969) 128, 352.

61.

Beard, W. C., ADVAN. CHEM. SER. (1971) 101, 237.

62. 63.

Barrer, R. M., Chem. Ind. (London) (1968) 1203. Meier, W. M., "Molecular Sieves," pp. 10-27, Society of the Chemical In dustry, London, 1968. 64. Barrer, R. M., Villiger, H., Chem. Commun. (1969) 659. 65. Gramlich, V., Meier, W. M., Z. Kristallogr. (1971) 133, 134. 66. Breck, D. W., J. Chem. Educ. (1964) 48, 678. 67. Belov, Ν. V., "Crystal Chemistry of Large-Cation Silicates," pp. 34-36, Consultants Bureau, Ν. Y., Academy of Science Press, Moscow, 1961. 68. Douglas, B. E., McDaniel, D. H., "Concepts and Models of Inorganic Chem istry," pp. 198-202, Blaisdell, Waltham, Mass., 1965. 69. Merrill, R. C., Spencer, R. W., J. Phys. Chem. (1951), 55, 187. 70. Weldes, H. H., Lange, K. R., Ind. Eng. Chem. (1969) 61, 29. 71. Barrer, R. M., Denny, P. J., J. Chem. Soc. (1961) 971. 72. Acara, Ν. Α., Howell, P. Α., unpublished work. 73. Kerr, G. T., J. Phys. Chem. (1966) 70, 1947. 74. Ciric, J., J. Colloid Interfac. Sci. (1968) 28, 315. 75. Flanigen, Ε. M., Breck, D. W., Abstracts, 137th National Meeting of the American Chemical Society, p. 33M, Cleveland, Ohio, 1960. 76. Khatami, H., Flanigen, Ε. M., unpublished work. 77. Tezak, B., "Colloid Stability in Aqueous and Nonaqueous Media," Discuss. Faraday Soc. (1966) 42, 175. 78. Füredi, H., in Walton, A. G., "The Formation and Properties of Precipitates," Chapter 6, p. 188, Interscience, Ν. Y., 1967. 79. Parfitt, G. D., "Dispersion of Powders in Liquids," p. 88, Elsevier, Ν. Y., 1969. 80. Walton, A. G., "The Formation and Properties of Precipitates," pp. 71-72, Interscience, Ν. Y., 1967. 81. Nielson, Α. Ε., "Kinetics of Precipitation," pp. 40-65 and 108-119, Pergamon Press, Ν. Y., 1964. 82. Eanes, E. D., Posner, A. S., Mat. Res. Bull. (1970) 5, 377.


10.

FLANIGEN


139

83. Breck, D. W., Smith, J. V., Sci. Amer. (1959) 200, 85. 84. Kerr, I. S., Gard, J. Α., Barrer, R. M., Galabova, I. M., Amer. Mineral. (1970) 55, 441. 85. Flanigen, E. M., Khatami, H., Szymanski, H. Α., ADVAN. CHEM. SER. (1971) 101, 201. 86. Nightingale, E. R., Jr., J. Phys. Chem. (1959) 63, 1381. 87. Bloss, F. D., "Crystallography and Crystal Chemistry," pp. 208-218, Holt Rinehart and Winston, N. Y., 1971. 88. Gard, J. Α., Tait, J. M., Acta Crystallogr. Β (1972) 28, 825.


RECEIVED December 9, 1972.


A Review and New Perspectives in Zeolite Crystallization - American

Recommend Documents