Crystal Chemical Relationships in the Analcite ... - ACS Publications

12 Crystal Chemical Relationships

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in the Analcite Family I.

Synthesis and Cation Exchange Behavior

WILLIAM D. BALGORD and RUSTUM ROY 1

Materials Research Laboratory, The Pennsylvania State University, University Park, Pa. Systematic investigation of analyzed analcites (NaAlSi O · H O, ideal formula) of normal, high, and low Al/Si ratios prepared by hydrothermal synthesis and cation exchange showed that the anionic framework common to all members of the family—analcite, leucite, wairakite, pollucite, viseite, and certain other artificially prepared cation derivatives not yet found in nature—possesses a distinct robustness with respect to resisting major reconstructive transformations over broad ranges of composition, temperature, and p . How ever, detectable second-order structural changes and devia tions from cubic symmetry were brought about by variation of Al/Si ratio and cation population. 2

6

2

H2O

'Tphe unit cell of stoichiometric analcite contains 16 NaAlSi 0 • H 0 formulas. The structure of analcite has been described in some detail, first by Taylor (14) and later by Coombs (7). Of direct concern here are the cavities within the structure which lie collinear with 3 sets of nonintersecting channels. The cavities are of 2 types: a set of 16 sites (1/8, 1/8, 1/8) occupied by H 0 , as in analcite, or by Κ or Cs, as in leucite or pollucite, coordinated by 12 framework oxygens, and a set of 24 smaller sites (1/8, 0, 1/4) occupied statistically by 16 Na in normal analcite. Since 1950, Barrer and coworkers (3, 4, 5, 6) have reported on the properties of various cation exchanged forms of analcite having the ideal 2

6

2

A

2

Present address: Division of Laboratories and Research, New York State Department of Health, Albany, Ν. Y. 1

140 In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

12.

BALGORD

A N D

Crystal

ROY

Chemical

141

Rehtionships

A l / S i r a t i o — v i z , 1 / 2 . H o w e v e r , there h a v e b e e n n o i o n e x c h a n g e i n v e s t i gations of t h e systems, N a - K , N a - C a , o r K - C a i n analcites of h i g h e r o r l o w e r t h a n n o r m a l A l / S i ratios. W h e r e a s e a r l i e r attempts to effect c a t i o n exchange of n o r m a l a n a l c i t e b y L i , C s , M g , C a , a n d B a w e r e m e t w i t h o n l y l i m i t e d success, i n d i r e c t m e t h o d s

of e x c h a n g e o r d i r e c t synthesis

f r o m gels p r o v i d e d means w h e r e b y L i , K , C a , C s , a n d P b

2 +

forms

were

s a i d t o h a v e b e e n o b t a i n e d (1, 3, 4, 5 ) . I n t h e present s t u d y , s y n t h e t i c analcites h a v i n g fixed A l / S i ratios of 2 / 3 , 1 / 2 , a n d 1 / 3 w e r e s u b j e c t e d to i o n e x c h a n g e w i t h a series of cations


of v a r i o u s size, charge, a n d p o l a r i z a b i l i t y to fix l i m i t s of c r y s t a l l i n e s o l u b i l i t y a n d to d e t e r m i n e t h e effects of c o m p o s i t i o n a l c h a n g e o n structure. S t r u c t u r e d a t a as a f u n c t i o n of t e m p e r a t u r e a n d p

H 2

o (to be presented

i n a f u t u r e p u b l i c a t i o n ) a r e a v a i l a b l e i n a d o c t o r a l thesis b y B a l g o r d ( 2 ) . Experimental Parent

materials were

synthesized

hydrothermally i n multigram

q u a n t i t i e s f r o m gels a c c o r d i n g t o m e t h o d s d e s c r i b e d b y - R o y ( 1 0 ) , S a h a a n d L u t h a n d Ingamells ( 9 ) . D e t a i l e d procedures used i n prepar-

(11),

i n g b o t h p a r e n t analcites a n d c a t i o n - e x c h a n g e d d e r i v a t i v e s a r e o b t a i n a b l e also f r o m t h e d o c t o r a l thesis b y B a l g o r d ( 2 ) . A l l samples w e r e

examined b y optical microscopy,

powder

x-ray

d i f f r a c t i o n , a n d c h e m i c a l analysis to d e t e r m i n e phase c o m p o s i t i o n , h o m o geneity, m o r p h o l o g y , changes of s y m m e t r y , A l / S i r a t i o , c a t i o n p o p u l a t i o n , and H PH O 2

2

0 content.

P r e c i s e l a t t i c e parameters w e r e o b t a i n e d a t c o n t r o l l e d

u s i n g i n t e r n a l standards a n d c o m p u t e r

least squares

refinement.

C h e m i c a l analyses w e r e p e r f o r m e d b y flame p h o t o m e t r y , x - r a y

fluores-

cence, e m i s s i o n s p e c t r o g r a p h y , d i r e c t - r e a d i n g e m i s s i o n s p e c t r o m e t r y , a n d thermogravimetry. Results M o d i f i c a t i o n s i n t h e m e t h o d s u s e d b y S a h a (11) to p r e p a r e m i l l i g r a m q u a n t i t i e s of analcites of several A l / S i ratios l e d t o successful p r e p a r a t i o n of m u l t i g r a m q u a n t i t i e s of o p t i c a l l y h o m o g e n e o u s m a t e r i a l s h a v i n g t h e following characteristics: A l / S i = 2/3

Na .4 (Ali9.6Si .4) 0 1 9

a

Q

A l / S i = 1/2

= 13.74

2 8

8

I V

1 5

Q

V I

= 13.72

I V

9 6

a

0

= 13.65

25

2

25

I V

9 6

X I 1

= 1.494 ±

· 16.4H O D

3

9

2

=fc 0.017 A , n

Nai2.4 (A]i2.2Si 5.8) 0 V I

· 14.2H O D

3

4

9 6

± 0.017 A , n

Na .6 (Ali5.9Si 2.i) 0 a

A l / S i = 1/3

V I

X I 1

= 1.486 ±

. 18.4H O 2

0.002

0.002

x n

± 0.017 A , n ™ = 1.470 =Jb 0.002 D

In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

142

MOLECULAR SIEVE ZEOLITES

1

S y m m e t r y , as d e t e r m i n e d f r o m x - r a y p o w d e r p a t t e r n s , is consistent w i t h the

space g r o u p Ia3d.

B i r e f r i n g e n c e w a s absent o r at m o s t e x t r e m e l y

weak. I o n exchange runs w e r e c a r r i e d o u t u n d e r v a r i o u s c o n d i t i o n s u s i n g salts of s e v e r a l m o n o v a l e n t a n d d i v a l e n t cations w i t h t h e d u a l objectives of p r e p a r i n g materials for d e h y d r a t i o n a n d s t a b i l i t y studies ( t o b e d e s c r i b e d i n a subsequent p a p e r ) a n d d e f i n i n g the l i m i t s of t r u e c r y s t a l l i n e s o l u b i l i t y i n the a n a l c i t e structure. A s m a y be i n f e r r e d f r o m T a b l e I , o n l y c e r t a i n ions are a c c o m m o d a t e d r e a d i l y b y t h e a n a l c i t e structure. F o u n d a m o n g this g r o u p are L i , A g , Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch012

+

K , NH +

4

+

+

, a n d R b . B u t not so r e a d i l y a p p a r e n t f r o m T a b l e I is that +

extensive s u b s t i t u t i o n i n v o l v i n g K , N H +

4

+

, R b , or T l +

+

i n v a r i a b l y gives

rise to the e x s o l u t i o n of a t e t r a g o n a l phase seen b o t h b y x - r a y d i f f r a c t i o n a n d b y m i c r o s c o p y as c o n c e n t r i c r e a c t i o n zones of c o n t r a s t i n g relief. I o n e x c h a n g e of h i g h a n d l o w A l / S i a n a l c i t e w i t h K , o n t h e other h a n d , y i e l d s p r o d u c t s c o n t a i n i n g a p p r e c i a b l e e x c h a n g e d Κ w i t h i n a single c u b i c p h a s e : 62 a n d 3 5 % , r e s p e c t i v e l y . M u c h m o r e difficult is the e x c h a n g e of d i v a l e n t ions for N a

+

in

analcite. O n l y w i t h some effort w e r e the w r i t e r s a b l e to a c h i e v e exchange Table I.

Results of Cation Exchange of Analcite Conditions

Al/Si

Cation

1/2

Li(81) Ag(100) K(93) NH +(100)

100 100 22 100

Rb(100)

100

Tl(92)

250

e

c

4

rf

Mg(32) Ca(82) Sr(55) Co(3) Ni(ll) 2/3

K(62) Ca(100)

1/3

K(35) Ca(81)

a 6 c d

PSI

225 250 225 100 100 8

4000 5000 4000 b b b

250

5000

8 250

b 5000

Cell Edges, A

Refractive Indices

13.53 13.68 13.79 13.12, 13.70 13.2, 13.6 13.5,

1.501 1.560 1.490 1.524 1.520 1.640

14.6 13.7 13.64 13.64 13.7 13.7

1.491 1.492 1.502-1.512 1.486 1.486

13.80 13.62

1.500 1.514

13.62 13.64

1.472-1.478 1.474-1.481

Numbers in parentheses indicate percentage exchange. Autogenous pressure. Metastable species, exsolution gives rise to leucite + K-saturated analcite. Taylor {IS).


12.

Crystal

BALGORD A N D ROY

/ / / / V

Να

Chemical

/ / / / / / /

Relationships

f / / //

Metastable

ftttft


Li

** Κ I4,/a

/////// T3 fO Ο

143

la 3d

M

9

/ / / / / / / / / / / / / / / / / / / / / / Ca //////////// Sr Co

T n I

a

f

r

t

°

r

Ni

Να X

0

20 40 60 80 100 % REPLACEMENT OF Na

Figure 1.

Extent of cation exchange in 1 /2 analcite

with C a , M g , and Sr . 2 +

2 +

i n saturated C a C l

2+

2

T w o successive 4-day treatments of a n a l c i t e

at 250 ° C a n d 5000 p s i p r o d u c e d 8 2 % exchange w h i l e

maintaining cubic symmetry.

B u t r e p e a t e d treatments w i t h salts of S r ,

M g , N i , a n d C o p r o d u c e d c u b i c analcites c o n t a i n i n g lesser p o p u l a t i o n s o f altervalent ions d e c r e a s i n g i n t h e stated order. B o t h h i g h a n d l o w A l / S i analcites r e a d i l y u n d e r g o exchange w i t h C a at 250 ° C , 5000 p s i d u r i n g successive 4-day treatments. Analcite partially exchanged w i t h A g underwent a photosensitized +

r e d o x r e a c t i o n b e l i e v e d to i n v o l v e A g w i t h H +

2

0 w i t h i n t h e cavities, a n d

g i v i n g rise to A g ° . T h e p h e n o m e n o n w a s m a n i f e s t e d first b y t h e a p p e a r ance of a y e l l o w d i s c o l o r a t i o n of the b u l k m a t e r i a l , suggesting t h e p r e s ence of c o l o r centers, a n d later b y o p a q u e m e t a l l i c s i l v e r d i s s e m i n a t e d a l o n g g r a i n b o u n d a r i e s w i t h i n a n a l c i t e crystallites. Discussion F o r m e r l y , a l l zeolites w e r e p r e s u m e d t o possess t h e a b i l i t y t o ex change

their "exchangeable"

change.

A s t u d y b y T a y l o r a n d R o y (12)

cations

readily a n d without

structural

o n the P-type zeolite demon

strated e m p h a t i c a l l y t h a t this a s s u m p t i o n is a gross o v e r s i m p l i f i c a t i o n . I n the present s t u d y , despite a greater degree of "openness" of t h e interstices of a n a l c i t e r e l a t i v e to t h e P-zeolites, the extent of exchange w i t h m a n y cations is v e r y m u c h l i m i t e d .

I n F i g u r e 1, d a t a are p r e s e n t e d o n t h e

extent to w h i c h a g i v e n c a t i o n c a n substitute f o r s o d i u m i n t h e p a r e n t " a n a l c i t e " structure. I n t h e case o f K exchange, n o m o r e t h a n 2 5 % K +

+

( a n d p r o b a b l y as l i t t l e as 1 0 % ) is t o l e r a t e d i n t h e c r y s t a l l i n e s o l u t i o n o f the N a phase at e q u i l i b r i u m .

S u b s e q u e n t exchange r e s u l t i n g i n f u r t h e r


144

MOLECULAR SIEVE ZEOLITES—I

r e p l a c e m e n t of N a b y Κ o n l y succeeds i n b r i n g i n g a b o u t a d o u b l e

decom

p o s i t i o n r e a c t i o n g i v i n g rise to t h e e x s o l u t i o n of a K - r i c h s e c o n d

phase,

leucite. I n c l u d e d also i n F i g u r e 1 is i n f o r m a t i o n r e g a r d i n g s y m m e t r y changes i n d u c e d b y c a t i o n exchange.

I n v i e w of these d a t a , d e r i v e d f r o m p o w d e r

d i f f r a c t i o n d a t a , t h e analcites, i n m a r k e d c o n t r a d i s t i n c t i o n to t h e P - z e o l i t e f a m i l y , s h o w r a t h e r strong a n d easily r e c o g n i z a b l e

(by powder

x-ray

p a t t e r n ) f a m i l i a l affinities despite a n y c a t i o n changes. T h e d i f f i c u l t y of r e p l a c e m e n t of N a b y d i v a l e n t ions is d e m o n s t r a t e d +


a m p l y i n t h e o b s e r v a t i o n t h a t a l l p r e v i o u s w o r k e r s f a i l e d to a c h i e v e s u b s t i t u t i o n of C a

2 +

exchange m e t h o d s .

f o r N a t o a n y significant extent b y s t r a i g h t f o r w a r d +

A l t h o u g h C a s u b s t i t u t i o n w a s a c h i e v e d i n this s t u d y

u n d e r h y d r o t h e r m a l c o n d i t i o n s , i t is n o t c e r t a i n w h e t h e r t h e p a r t i a l r e p l a c e m e n t of N a b y M g , N i , o r C o is l i m i t e d k i n e t i c a l l y o r represents equilibrium.

T h e relative facility w i t h w h i c h C a

2 +

replaces 2 N a

+

i n the

h i g h - A l a n a l c i t e m a y p r o v i d e e v i d e n c e t h a t A l / S i o r d e r i n g exercises some d e g r e e of c o n t r o l over t h e extent of exchange. Na

+

sites a c t u a l l y o c c u p i e d b y C a

2 +

A h i g h p r o p o r t i o n of t h e

p r e s u m a b l y a r e c o o r d i n a t e d b y at

least 2 of 4 f r a m e w o r k oxygens w h i c h themselves a r e p a r t of A l - c o n t a i n i n g tetrahedra. T h e r e l a t i o n of t h e n u m b e r of w a t e r m o l e c u l e s p e r u n i t c e l l to t h e size of t h e exchangeable c a t i o n a n d free v o l u m e ( h e r e defined as u n i t c e l l v o l u m e less t h e v o l u m e o c c u p i e d

b y t h e f r a m e w o r k a n d c a t i o n s ) , is

p r e s e n t e d i n F i g u r e 2. T w o groups of phases emerge,

fully hydrated

Ο

ANALCITE GR Ag

z 30 or UJ

û-20

LEUCITE GR

CO UJ

ο 10 UJ

NH4

i Ο

CVJ X

*

>

Να

Ca

+

κ

Rb,| 1200

Li#

4

1400 1600 FREE VOLUME,A 3

Figure 2. Relationship between free volume and H 0 con tent of 1 /2 analcite unit cell exchangeable cation population 2


12.

Crystal

BALGORD A N D ROY

Chemical

145

Rehtionships

structures h a v i n g a n e x p a n d e d c e l l , d e s i g n a t e d " a n a l c i t e , " a n d c o n t r a c t e d structures c o n t a i n i n g l i t t l e or n o w a t e r , d e s i g n a t e d " l e u c i t e . " T h e s i t u a t i o n m a y b e r a t i o n a l i z e d i n terms of F i g u r e 3, a d a p t e d f r o m D e e r et al.


( 8 ) , w h i c h shows s c h e m a t i c a l l y a v i e w of t h e sites i n t h e a n a l c i t e s t r u c -

WAIRAK IT Ε Figure 3. Schematic representation of H 0 and cation sites in the analcite structure 2

8

ι

kmm

W

Temp, of exchange ? 8°C 4 25° "50° • 100°

:

Ο

CM

h-

5

2

UJ

20 40 60 80 % EXCHANGE, Na BY Κ Figure

4.

Dependence

of H 0 analcite 2

100

content on Κ in 1 /2


146


1

ture normally occupied by N a and H 0 , respectively. Depicted in Figures 1 and 3 are the relationships on the limits of solubility and the location of the cations and the H 0 molecules. In principle, the divalent cationic species should admit more water. That the extra "space" in the channels is not occupied to any appreciable extent by water (at given p o and T) implies an exclusion of the H 0 molecules from the Na site. In a K -saturated cubic analcite, the water content is constant (Figure 4); here a random (Na , K ) distribution over the Na sites per tains. In leucite, however, the K (Figure 3) occupies the H 0 sites, thus excluding the H 0 molecule. H 0 in turn cannot occupy the vacated Na sites because part of the occupied channel volume of leucite is taken up by a contraction of the unit cell. Finally, a decrease of A l / S i ratio from 2/3 to 1/3 occasions a marked increase in water content. This fact, however, is consistent with the lower cation density in the Na sites of the low-Al analcite. +

2

2

H2

2

+

+

+


2

+

+

2

2

+

+

Literature Cited (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)

Ames, L. L., Sand, L. B., Am. Mineralogist 1958, 43, 477. Balgord, W. D., Ph.D. Thesis, Pennsylvania State University, 1966. Barrer, R. M.,J.Chem. Soc. (London) 1950, 2344. Barrer, R. M., Baynham, J. M.,J.Chem. Soc. (London) 1956, 2888. Barrer, R. M., Hinds, L.,J.Chem. Soc. (London) 1953, 1883. Barrer, R. M., McCallum, N.,J.Chem. Soc. (London) 1953, 4029-4031. Coombs, D. S., Mineral. Mag. 1955, 30, 699-708. Deer, W. Α., Howie, R. Α., Zussman, J., "Rock-forming Minerals," Vol. 4, p. 350, Wiley, New York, 1964. Luth, W. C., Ingamells, C. O., Am. Mineralogist 1965, 50, 255-258. Roy, Rustum, J. Am. Ceram. Soc. 1956, 39, 145-146. Saha, Prasenjit, Am. Mineralogist 1959, 44, 300-313. Taylor, A. M., Roy, Rustum, Am. Mineralogist 1964, 49, 656-682. Taylor, H. F. W.,J.Chem. Soc. (London) 1949, 1256. Taylor, W. H., Z. Krist. 1930, 74, 1-19.

RECEIVED January 21, 1970.

Discussion Brian D. McNicol ( Koninklijke/Shell Laboratorium, Amsterdam, Netherlands): With respect to your comment on the formation of Ag° within the cavities by a photosensitized redox reaction, if the Ag° atoms are monatomically dispersed, then they could be identified by electron spin resonance. Ag°, of course, is paramagnetic. W. D. Balgord: Yes, if they stay that way (monatomic) long enough to measure them.


+

12.

BALGORD

Crystal

A N D ROY

Chemical

147

Refotionships

J . A . Rabo ( U n i o n C a r b i d e R e s e a r c h I n s t i t u t e , T a r r y t o w n , Ν. Y . 1 0 5 9 1 ) : T h e existence of A g ° a t o m s — u p o n r e d u c t i o n of A g — i n zeolites +

has b e e n extensively i n v e s t i g a t e d w i t h X a n d Y zeolites u s i n g E S R w i t h out success.

T h e smallest r e d u c e d species f o u n d so f a r are A g

2

+

ions,

w h i c h exist u p to — — 8 0 ° C i n Y zeolite. W . D . Balgord: S e v e r a l questioners seem to h a v e i n t e r p r e t e d o u r c o m m e n t s o n p . 143 to m e a n A g i n t h e analcite.

that w e a c t u a l l y o b s e r v e d

monatomic

N o effort w a s m a d e to detect A g atoms.

the p a r a g r a p h does n o t m e n t i o n t h e m as such.

I n fact,

It does seem reason

able, h o w e v e r , that silver, i f i n i t i a l l y present as i n d i v i d u a l A g ions i n Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch012

+

t h e r e s t r i c t e d a n a l c i t e cavities, m a y h a v e existed as discrete A g ° atoms, i f o n l y m o m e n t a r i l y , at one step i n t h e m e c h a n i s m b y w h i c h t h e m e t a l l i c silver aggregated. Douglas S. Coombs ( U n i v e r s i t y of O t a g o , D u n e d i n , N e w Z e a l a n d ) : In

connection

w i t h t h e discussion o n n o n l i n e a r i t y o f c e l l

dimensions

p l o t t e d against A l atoms p e r f o r m u l a u n i t , i t m a y b e c o m m e n t e d

that

Sana's p l o t w a s f o r c e l l edge against A l / S i r a t i o . I f this latter gives a s t r a i g h t - l i n e r e l a t i o n s h i p , a p l o t o f c e l l e d g e against n u m b e r o f A l atoms must be curvilinear. When H

0 exceeds 16 p e r u n i t c e l l , w h e r e is this extra w a t e r a c

2

c o m m o d a t e d ? I f i t is d i s t r i b u t e d t h r o u g h t w o l a t t i c e sites, is this reflected in dehydration phenomena? W . D . Balgord: A r e p l o t of c e l l edge a n d I R d a t a us. A l / S i r a t i o does n o t r e v e a l t h e l i n e a r r e l a t i o n s h i p i m p l i e d i n t h e first of D r . C o o m b s ' questions.

F r o m t h e u n i t c e l l c o m p o s i t i o n d a t a presented, i t m a y b e o b

s e r v e d that a decrease o f 4 N a ions, associated w i t h a +

corresponding

1.490

13.800

π

13.700

-ο--

1.480

f /

/

r

/ 13.600 0.300

—[ J /

/ —

0.400

0.500

0.600

A l / S i Ratio

American Chemical Society Library 1155 16th St., N.W. Washington D.& 20036


1.470 0.700

148


decrease of 4 A l

3 +

1

ions f r o m A l / S i r a t i o of 1 / 2 to 1 / 3 , is a c c o m p a n i e d b y

a n increase of 2 H 0 m o l e c u l e s . T h e inverse r e l a t i o n s h i p b e t w e e n 2 N a 2

a n d H 0 suggests t h a t the c o n c u r r e n c e

of v a c a n t a d j o i n i n g N a

p r o v i d e s sufficient space to a c c o m m o d a t e

the a d d i t i o n a l H 0 2

+

sites

molecule.


2

+


Crystal Chemical Relationships in the Analcite ... - ACS Publications

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