Physicochemical Properties of High Silica L and Clinoptilolite Zeolites

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Physicochemical Properties of High Silica L and Clinoptilolite Zeolites G.

V.

TSITSISHVILI

Institute of Physical and Organic Chemistry, Academy of Sciences of the Georgian SSR, Tbilisi, U.S.S.R.

Physicochemical properties of L zeolites and of clinoptilolite were studied by adsorption, chromatographic, spectral, and thermogravimetric methods. The sodium form of L zeolite is characterized by better adsorption with respect to water and benzene vapor and by higher retention volumes ofC -C hydrocarbons and CO than potassium and cesium forms. The activation energy of dehydration determined by the thermogravimetric method decreases on going from the sodium to cesium form of L zeolite. When calcium is replaced by potassium ions in clinoptilolite, the latter shows a decreased adsorption with respect to water vapor. The infrared spectra of the L zeolite at different levels of hydration show the existence of several types of water with different bond characters and arrangements in the lattice. 1

4

T T i g h silica zeolites a t t r a c t great a t t e n t i o n since t h e y are c h a r a c t e r i z e d b y r e l a t i v e l y h i g h t h e r m a l s t a b i l i t y a n d considerable a c i d resistance. P h y s i c o c h e m i c a l properties of h i g h silica zeolites, despite a n u m b e r of i n v e s t i g a t i o n s , h a v e n o t been sufficiently s t u d i e d . T h e same is t r u e for L - a n d c l i n o p t i l o l i t e zeolite. T h e d a t a o n synthesis, s t r u c t u r e , a d s o r p t i o n properties, d e c a t i o n i z a t i o n , d e a l u m i n i z a t i o n , a d s o r p t i o n heats, a n d other properties of t h e a b o v e - m e n t i o n e d zeolites h a v e been g i v e n (1-15). R e sults of studies of p h y s i c o c h e m i c a l properties of L zeolites a n d of n a t u r a l a n d m o d i f i e d c l i n o p t i l o l i t e are g i v e n here. Experimental A d s o r p t i o n properties were s t u d i e d w i t h a m i c r o b a l a n c e at 20° ± 0.05°C. Zeolites were d e h y d r a t e d a t 3 0 0 ° - 4 0 0 ° C u n t i l a r e s i d u a l p r e s sure of 1 0 ~ t o r r a n d a c o n s t a n t s a m p l e w e i g h t were reached. C h r o m a t o g r a p h i c s e p a r a t i o n was s t u d i e d o n 0.5-1.0 m m grains, w h i c h , after p r e l i m i n a r y t h e r m a l a c t i v a t i o n at 5 0 0 ° C , were l o a d e d i n t o a c h r o 6

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

MOLECULAR SIEVES

292

m a t o g r a p h i c c o l u m n 100 c m l o n g w i t h a d i a m e t e r of 0.4 c m . T h e c a r r i e r gas was h e l i u m , v e l o c i t y was 50 m l / m i n , a n d t h e d e t e c t o r was a k a t h a r o m eter ( t h e r m a l c o n d u c t i v i t y t y p e ) . I n f r a r e d a b s o r p t i o n s p e c t r a were s t u d i e d o n samples o f 15 m g / c m . P u m p i n g was done for 2 h o u r s in vacuo a t 1 0 ~ t o r r . S p e c t r a were recorded w h e n t h e s a m p l e was cooled a t 0.53 c m ' V s e c (16). T h e r m o g r a v i m e t r i c studies were done w i t h d e r i v a t o g r a p h (17). T h e r m a l curves were r e c o r d e d a t 1 0 ° / m i n . T h e s t a n d a r d was A 1 0 h e a t treated at 1600°C. 2

5

- 1


2

3

Results and Discussion W e h a v e s t u d i e d t h e p o t a s s i u m f o r m of zeolite L ( b a t c h 385-386), t h e same zeolite e n r i c h e d w i t h s o d i u m a n d c e s i u m ions ( N a L a n d C s L ) , a n d a s a m p l e of p o t a s s i u m L - z e o l i t e (sample A ) . m e n t a l batches.

B o t h zeolites were e x p e r i -

T h e c h e m i c a l c o m p o s i t i o n of d e h y d r a t e d zeolites is g i v e n

in Table I. Table I.

C h e m i c a l C o m p o s i t i o n of D e h y d r a t e d Z e o l i t e s Oxide Components, wt %

Sample

K0

Na*0

Cs 0 + Na^O

AWz

Si0

K L (385-386) NaL CsL I0L(A)

18.08 8.12 6.10 17.16

2.40 6.96 — 2.22

— — 29.05 —

20.17 23.31 17.00 20.09

60.07 61.07 48.38 61.08

2

2

2

T h e zeolite f r o m D z e g v i (the G e o r g i a n S S R ) w a s used f o r s t u d y (18). N a t u r a l zeolite w a s e n r i c h e d w i t h p o t a s s i u m ions a n d d e a l u m i n i z e d . E n r i c h m e n t of exchangeable ions of L zeolites a n d of c l i n o p t i l o l i t e w a s d o n e b y m u l t i p l e t r e a t m e n t w i t h 0.5N solutions of t h e c o r r e s p o n d i n g n i t r a t e s . D e c a t i o n i z a t i o n a n d d e a l u m i n i z a t i o n were done b y t r e a t i n g t h e n a t u r a l zeolite w i t h solutions of h y d r o c h l o r i c a c i d 0.25-12.0iV. The Si0 /Al 0 r a t i o increased f r o m 8.0 t o 69.5, a n d t h e C a O content decreased f r o m 6.30 t o l . 0 0 w t % (Table I I ) . P o t a s s i u m i o n content increased f r o m 1.18 w t % for K 0 ( n a t u r a l c l i n o p t i l o l i t e ) t o 6.17 w t % . T h e C a O content decreased f r o m 6.30 t o 2.29 w t % , t h a t of N a 0 f r o m 2.00 t o 0.54 w t % a n d of M g O f r o m 1.81 t o 1.40 w t % . W e s t u d i e d a d s o r p t i o n properties of L - z e o l i t e s w i t h respect t o w a t e r a n d benzene v a p o r s . T h e e x p e r i m e n t a l d a t a are g i v e n as i s o t h e r m s for 2

2

2

2

Table I I .

C h e m i c a l C o m p o s i t i o n of D e h y d r a t e d Natural Clinoptilolite

Oxide Components Wt%

Si0

AWz

Fe 0

CaO

MgO

K0

NoW

68.04

14.40

3.99

6.99

2.00

1.30

2.22

2

2

3

2

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

3

26.

293

High Silica L and Clinoptilolite

TsrrsiSHViLi

benzene v a p o r ( F i g u r e 1 a n d T a b l e I I I ) f o r different p o i n t s of a d s o r p t i o n i n t e r p o l a t e d b y the isotherms.

T h e adsorption volume, corresponding t o

t h e p r i m a r y porous s t r u c t u r e , is filled at a r e l a t i v e pressure of P/P = 0.2. s

T h e d a t a i n T a b l e I I I s h o w t h a t benzene a n d w a t e r are a d s o r b e d m o s t strongly o n N a L and most weakly o n C s L .

Thus, the amount

adsorbed

increases w i t h t h e electric field o f t h e cation—i.e., i n v e r s e l y w i t h i o n i c


r a d i u s (19,20).

Figure 1. Isotherms of adsorption of benzene vapor on L-zeolites: (1) NaL, (2) KL, (3) CsL, U) KL(A) Table ΠΙ.

A d s o r p t i o n V a l u e s (a, m m o l e / g r a m ) a t 2 0 ° C H2O

CQHQ

P/P. 0.005 0.010 0.020 0.050 0.100 0.005 0.010 0.020 0.050 0.100 KL (38&386) NaL CsL K L (A)

4.75 5.12 5.58 6.25 5.50 5.75 6.05 6.57 3.20 3.45 3.80 4.43 5.25 5.57 5.85 6.25

7.15 1.14 1.18 1.24 7.45 1.16 1.20 1.26 5.20 0.95 0.99 1.05 6.75 1.09 1.11 1.14

1.34 1.46 1.37 1.49 1.17 1.25 1.18 1.22


294

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1+2+3

I


6

5

Min. 20 Figure 2.

16

5 5

10

8

6

4

0

Separation of air mixture (1), CH*(2), CO(3), ftffeOi), ^Η^(δ), CzH (6), CzH*(7), CiH (8). Chromatographic column temperature, lIfi°C %

w

C h r o m a t o g r a p h i c properties of L zeolites h a v e been s t u d i e d l i t t l e (7). A s a r e s u l t of t h i s w o r k we h a v e established w h e n the p o t a s s i u m (original) f o r m of zeolite L is u s e d w i t h the m o d e l m i x t u r e of C i - C h y d r o c a r b o n s a n d C O , m e t h a n e is e l u t e d after c a r b o n m o n o x i d e a t a l l c o l u m n t e m p e r a t u r e s ; t h e same is t r u e for p o t a s s i u m X - z e o l i t e s (21). I n b o t h the p o t a s s i u m a n d exchanged forms of L - z e o l i t e s a n d i n h y d r o g e n X - z e o l i t e s (22), a t a n y t e m p e r a t u r e of the c h r o m a t o g r a p h i c c o l u m n , each s a t u r a t e d h y d r o c a r b o n e l u t i o n is f o l l o w e d b y a n u n s a t u r a t e d c o m p o u n d w i t h t h e same n u m b e r of a t o m s i n t h e m o l e c u l e — i.e., c a r b o n m o n o x i d e , m e t h a n e , ethane, ethylene, propane, p r o p y l e n e a n d b u t a n e ( F i g u r e 2 ) . T h i s m i x t u r e of gases is sepa r a t e d a t a l o w e r c o l u m n t e m p e r a t u r e t h a n for X - z e o l i t e s , a p p a r e n t l y as a result of a l o w e r c a t i o n c o n c e n t r a t i o n i n t h e L - z e o l i t e u n i t cell. F o r c e s i u m c o n t a i n i n g samples, t h e r e t e n t i o n v o l u m e s decrease, especially w i t h u n saturated compounds. 4

I n f r a r e d spectra of zeolite L i n t h e range of frequencies of valence a n d d e f o r m a t i o n v i b r a t i o n s of w a t e r h a v e n o t b e e n s t u d i e d m u c h (8). A l t h o u g h we elucidate t h e bonds of w a t e r molecules w i t h t h e frame, the n a t u r e of the r e s i d u a l w a t e r is of interest (23). O u r studies of zeolite L (sample A ) s h o w t h a t i t s s p e c t r u m i n t h e r a n g e of f r a m e v i b r a t i o n f r e quencies coincides w i t h t h e d a t a of R e f . 9. T h e s p e c t r u m of t h e zeolite K L , o b t a i n e d after e v a c u a t i o n a t 6 0 0 ° C was t a k e n as t h e c u r v e of c o m p l e t e t r a n s m i s s i o n . I n f r a r e d s p e c t r a of t h e zeolite K L after e v a c u a t i o n at different t e m p e r a t u r e s are g i v e n i n F i g u r e 3.



26.

TSiTSiSHViLi

295


1550 1650 1750 FREQUENCY,Cm H

3100

330 0 3500 3700 FREQUENCY, C f l H

Figure 3. Infrared spectra of KL zeolite in the range of deformation (A) and valence (B) vibrational frequencies of water molecule after evaluation at different temperatures (°C): (1)40; (2)100; (3)820; (4)410; (5)500 E v a c u a t i o n of a i r - d r y zeolite K L a t r o o m t e m p e r a t u r e leads t o d e s o r p t i o n of most of t h e o r i g i n a l w a t e r . T h i s w a t e r i s n o t as s t r o n g l y b o u n d w i t h t h e sorbent a n d is a p p a r e n t l y l o c a l i z e d i n t h e m a i n channels of t h e zeolites (3). T h e s p e c t r u m has t w o m a x i m a a t 1640 a n d 3450 c m , s h o w i n g p a r t i c i p a t i o n of w a t e r molecules w i t h a s t r o n g h y d r o g e n b o n d . I n t h e s p e c t r u m of zeolite K L , a t t h e t e m p e r a t u r e of e v a c u a t i o n ( 1 0 0 ° 5 0 0 ° C ) , stronger w a t e r - b o u n d b a n d s (3665, 3685, 3700 c m " a n d 1602, 1630, a n d 1650-1660 c m ) are f o u n d . A b s o r b a n c e of these b a n d s d e creases a b o v e 4 0 0 ° C . A p a r a l l e l i s m i n t h e absorbance decrease i s s h o w n for t h e 1602 a n d 3700 c m bands (preserved t o 6 0 0 ° C ) a t i n c r e a s e d d e h y d r a t i o n temperature. These bands are n o t recovered o n r e h y d r a t i o n , a t either l o w o r a t h i g h temperatures. W a t e r molecules a r e , e v i d e n t l y , l o c a l i z e d i n t h e secondary s y s t e m of channels (3). P e r h a p s w a t e r is l o c a l i z e d i n c a n c r i n i t e cells. T h e i n f r a r e d spectra of zeolite K L s h o w single molecules of r e s i d u a l w a t e r , p r o b a b l y b o u n d w i t h p o t a s s i u m ions as a r e s u l t of a n u n s h a r e d elect r o n p a i r f r o m a n o x y g e n a t o m (24). P o t a s s i u m , s o d i u m , a n d c e s i u m forms of t h e L zeolite were s t u d i e d b y t h e t h e r m o g r a v i m e t r i c m e t h o d . T h e r e is a n e n d o t h e r m a l effect o n t h e i n i t i a l p o t a s s i u m zeolite K L - D T A c u r v e w i t h i n 5 0 ° - 3 0 0 ° C caused b y t h e loss of a d s o r b e d w a t e r . M o s t of t h e w a t e r (15.1%) is lost i n t h i s n a r r o w - 1

1

- 1

-

1


296

MOLECULAR SIEVES


t e m p e r a t u r e range. is 1 6 . 6 % .

T h e t o t a l a m o u n t of w a t e r lost o n h e a t i n g t o 1000° C

T h e n a t u r e of t h e exchanged i o n i n a zeolite determines t h e a m o u n t of e q u i l i b r a t e d adsorbed w a t e r , decreasing f r o m 1 6 . 3 % f o r N a L t o 1 2 . 5 % f o r CsL. A c t i v a t i o n energies of t h e d e h y d r a t i o n process were c a l c u l a t e d f o r these zeolites b y t h e m e t h o d g i v e n i n R e f . 25. T h e i r values for s o d i u m , p o t a s s i u m , a n d c e s i u m forms are 4.52, 2.31, a n d 1.85 k c a l / m o l e . T h e results show t h a t t h e s m a l l e r t h e c a t i o n r a d i u s is (i.e., t h e stronger i t s field), t h e higher t h e a c t i v a t i o n energy i s . W e h a v e s t u d i e d t h e effect of c h e m i c a l m o d i f i c a t i o n o n a d s o r p t i o n properties of n a t u r a l c l i n o p t i l o l i t e (18). Studies of w a t e r v a p o r a d s o r p t i o n s h o w a decrease i n a d s o r p t i o n for D z e g v i c l i n o p t i l o l i t e , d e c a t i o n i z e d a n d d e a l u m i n i z e d o n t h e w a t e r b a t h , w i t h increased a c i d c o n c e n t r a t i o n , c o m p a r e d w i t h t h e a d s o r p t i o n of t h e n a t u r a l c l i n o p t i l o l i t e . T h e m a i n c o n t r i b u t i o n t o a d s o r p t i o n is f r o m p r i m a r y p o r o s i t y . Benzene vapor adsorption o n natural a n d acid-treated clinoptilolite occurs o n t h e surface of secondary pores. A c i d m o d i f i c a t i o n leads t o secondary p o r o s i t y — l a r g e r micropores f o r m . P o t a s s i u m ions i n t h e n a t u r a l c l i n o p t i l o l i t e ( 3 . 5 - 5 . 2 % ) affect a d s o r p t i o n o n l y s l i g h t l y w i t h respect t o w a t e r v a p o r . n - H e x a n e as w e l l as b e n zene v a p o r s are adsorbed o n t h e secondary porous s t r u c t u r e of t h e zeolite OW). W e used a r g o n - o x y g e n - n i t r o g e n as a m o d e l t o s t u d y c h r o m a t o g r a p h i c properties of n a t u r a l c l i n o p t i l o l i t e a n d of i t s p o t a s s i u m forms. T h e c o l u m n

300° Figure

4-

clinoptilolites

Thermogram [wt % K 0 2

4(3.96);

of the natural in parenthesis]: 5(5.22);

(1) and 2(3.46);

potassium 3(3.72);

6(6.17)


26. TSiTSiSHViLi


temperature varied from 0° to 70°C. Taking clinoptilolite with relatively low replacement of C a by K (potassium ions to 3.72%) the following sequence of elution was observed: argon, nitrogen, oxygen, and for sam ples with potassium ions to 6.17%, there was another sequence of elution: argon, oxygen, nitrogen. This is probably the result of a smaller oxygen molecule diameter relative to a nitrogen molecule (2.8 and 3 A). When a few calcium ions are substituted by potassium ions in clinoptilolite, a small broadening of the window probably takes place; this permits an oxygen molecule to penetrate into zeolite pores, and nitrogen molecules are ad sorbed only on the "external surface" (27). On further substitution of C a by K window broadening results from an increase of their diameter and this permits adsorption in the zeolite cavities. Dzegvi clinoptilolite and its potassium substituted forms were studied thermogravimetrically (28). The differential gravimetric analysis and the differential thermal analysis gave curves of similar shape for the samples studied. Water loss occurred in stages in a wide temperature range (see Figure 4). Increasing substitution of C a by Κ + in clinoptilolite causes these curves to smooth out because of energy homogenization of adsorption centers. The main endothermal effect is shifted toward higher tempera tures, and the water content in a zeolite decreases with increasing potassium content. Thus, our results show that chemical modification of L-zeolites and of clinoptilolite (despite high silicon:aluminum ratio) affects their physicochemical properties considerably. 2 +


297

2 +

+

+

2 +

Literature Cited 1. Breck, D. W., Flanigen, Ε. M., "Molecular Sieves," p. 47, Society of Chemical Industry, London, 1968. 2. Barrer, R. M., Lee, I. Α., Surface Sci. (1968) 12, 341, 354. 3. Barrer, R. M., Villiger, H., Z. Kristallog. (1969) 128, 352. 4. Nikolina, V. Ya., Krasniy, E. B., Musin, T. G., Kirnakh, L. I., Kolloid. Z. (1971) 33, 693. 5. Khvoschev, S. S., Zhdanov, S. P., Shubaeva, Μ. Α., Dokl. Akad. Nauk SSSR (1971) 196, 1391. 6. Shirinskiy, L. P., Ermolenko, N. F., Kulikovskaya, N. P., Nikolina, V. Ya., Pryakhina, N. P., Zh. Fiz. Khim. (1972) 41, 142. 7. Tsitsishvili, G. V., Nikolina, V. Ya., Osipova, Ν. Α., Sabelashvili, Sh. D., Andro nikashvili, T. G., Kvantaliani, Ε. K., Dokl. Akad. Nauk SSSR, in press. 8.

Ward, I. W., ADVAN. CHEM. SER. (1971) 101, 380.

9. Flanigen, Ε. M., Szymanski, Η. Α., Khatami, H., ADVAN. CHEM. SER. (1971) 101, 201. 10. Mason, B., Sand, L. B., Am. Mineral. (1960) 45, 91. 11. Mumpton, F. Α., Am. Mineral. (1960) 45, 351. 12. Barrer, R. M., Makki, M . B., Can. J. Chem. (1964) 42, 1481; Barrer R. M., Murphy, Ε. V. P., J. Chem. Soc. A (1970) 2506. 13. Barrer, R. M., Coughlan, B., "Molecular Sieves," p. 141, "Society of Chemical Industry, London, 1968. 14. Piguzova, L. I., "Natural Sorbents," p. 166, Nauka, 1967.



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MOLECULAR SIEVES

15. Mirsalimov, A. M., Muminov, S. Z., Aripov Ε. Α., Akhmedov K. S., Uzbeckskiy khim. Zh. (1970) 44. 16. Tsitsishvili, G. V., Charkviani, M . K., Dokl. Akad. Nauk SSSR (1972) 202, 143. 17. Paulik, F., Paulik, S., Erdey, L., Z. Anal. Chem. (1958) 160, 4. 18. Gvakharia, G. V., Skhirtladze, N. N., Batiashvili, T. V., Akhvlediani, R . Α., Mikadze, G. Α., Dokl. Akad. Nauk SSSR, Ser. Geol. (1972) 205, 179. 19. Tsitsishvili, G. V., Andronikashvili, T. G., ADVAN. CHEM. SER. (1971) 102, 217. 20. Tsitsishvili, G. V., Barnabishvili, D. N., Nikolina, VYa., Bull. Acad. Sci. Geor gian SSR, in press. 21. Tsitsishvili, G. V., Andronikashvili, T. G., Sabelashvili, Sh. D., Chkheidze, S. S., Neftekhimia (1967) 7, 305. 22. Tsitsishvili, G. V., Andronikashvili, T. G., Sabelashvili, Sh. D., Bezhashvili, Κ. Α., "Adsorption, Chromatographic, and Catalytic Properties of Zeolites," p. 122, Metsnierebra, Tbilisi, 1972. 23. Charkviani, M . K., Tsitsishvili, G. V., Dokl. Akad. Nauk SSSR, in press. 24. Bertsch, J., Habgood, H. W., J. Phys. Chem. (1963) 67, 1621. 25. Piloyan, G. O., "Introduction to the Theory of Thermal Analysis," Nauka, Moscow, 1964. 26. Tsitsishvili, G. V., Barnabishvili, D. N., Gogodze, N. L., Koridze, Ζ. I., Kru pennikova, A. Yu., Bull. Acad.Sci.,GeorgianSSR,in press. 27. Tsitsishvili, G. V., Andronikashvili, T. G., Sabelashvili, Sh. D., Koridze, Ζ. I., Dokl. Akad. Nauk SSSR (1970) 194, 1346. 28. Tsitsishvili, G. V., Sabelashvili, Sh. D., Koridze, Z. I., Kvantaliani, Ε. K., Andronikashvili, T. G., Izv. AN SSSR, Z. Anorg. Mater., in press. RECEIVED November 27, 1972.


Physicochemical Properties of High Silica L and Clinoptilolite Zeolites

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