66
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Development of Acidity in the Sodium-Y Zeolites EDUARDO A. LOMBARDO, G. A. SILL, and W. KEITH HALL 1
2
Mellon Institute, Carnegie-Mellon University, Pittsburgh, Pa. 15213
The isomerization of n-butenes was used as a test reaction to follow the development of catalytic activity in Na-Y zeo lite. The acidity was varied by the substitution of some of the Na (0.3 to 5.7%) with Ca and by creating a Na deficiency (up to 0.94%); both series of catalysts were stud ied with and without water added as cocatalyst. A pure Na-Y zeolite containing no decationated sites was found catalytically inactive for this reaction. In contrast with silica -alumina catalysts, carbonaceous residues did not appear to play a role in the formation of the catalytic sites as long as H O was used as cocatalyst. +
2+
+
2
A l t h o u g h there is g e n e r a l agreement r e g a r d i n g the v e r y l o w c a t a l y t i c a c t i v i t y of G r o u p Ι Α X o r Y zeolites f o r c a r b o n i u m i o n reactions, c o n s i d e r a b l e c o n t r o v e r s y exists c o n c e r n i n g the effects of vacancies, i m p u r i t i e s ( m a i n l y d i v a l e n t c a t i o n s ) , a n d cocatalysts o n this p r o p e r t y . O n e g r o u p of investigators r e p o r t e d n o c o r r e l a t i o n b e t w e e n c a t i o n d e f i c i e n c y and catalytic activity ( 7 ) .
S e v e r a l others
(1, 5, 6, 7, 13)
reported a
m a r k e d increase o n a d d i t i o n of p r o t o n donors to N a - a n d C a - X o r Y zeo lites. A n o t h e r (17)
r e p o r t e d o n l y a s m a l l increase f o r C a - Y zeolite, b u t
n o v a r i a t i o n w a s f o u n d (19)
f o r p u r e N a - Y zeolite.
T w o firmly estab
l i s h e d c o n c l u s i o n s d e r i v e d f r o m I R spectroscopy are that p u r e N a - X o r Y zeolites, either p a r t i a l l y o r t o t a l l y d e h y d r a t e d , s h o w n o e v i d e n c e of s t r u c t u r a l h y d r o x y l g r o u p s (4, 18, 19, 20, 21, 22),
a n d Bronsted acidity
Present address : F a c u l t a d de Ingenieria Q u i m i c a , U n i v e r s i d a d N a c i o n a l d e l L i t o r a l , Santa F e , A r g e n t i n a . * T o w h o m correspondence s h o u l d be addressed; G u l f Research a n d D e v e l o p m e n t C o . , P.O. B o x 2038, P i t t s b u r g h , P a . 15230. 1
346
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
66.
LOMBARDO E T
Acidity
AL.
in Sodium-Y
347
Zeolites
d e v e l o p s i n d i v a l e n t ( M e ) X a n d Y zeolites d u r i n g d e h y d r a t i o n (2, 4, 2 +
14, 15, 18, 20, 21, 22) t h r o u g h R e a c t i o n I .
Me
2 +
/
H
: Ο
\
O
+
Η
\ /
\ " /
/
Si
\
ΑΙ τ± M e + O H
/
\
Ο Ο
T h i s c h e m i s t r y suggests a role f o r H Downloaded by CHINESE UNIV OF HONG KONG on November 2, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch066
+
2
\ /
O H
/
Si
\
\
/
/
A l
(1)
\
0 0
0 as cocatalyst w i t h t h e m o n o v a l e n t
zeolites i f t h e e q u i l i b r i u m is m o v e d to the r i g h t i n t h e presence o f a base. I n t h e present w o r k , t h e effects o f s m a l l d e l i b e r a t e replacements o f N a b y C a , of cation deficiency, a n d of H 2 +
2
+
0 o n t h e c a t a l y t i c properties o f
N a - Y z e o l i t e w e r e s t u d i e d . A l s o i n v e s t i g a t e d w a s t h e p o s s i b i l i t y that carbonaceous residues f o r m t h e c a t a l y t i c sites, as w a s r e p o r t e d f o r t h e i s o m e r i z a t i o n o f n-butenes over s i l i c a - a l u m i n a catalysts
(3, 8, 9). T h e
i s o m e r i z a t i o n o f t h e n-butenes p r o v i d e d a u s e f u l t o o l f o r these studies b e cause i t f o l l o w s first-order k i n e t i c s (10) a n d proceeds over N a - Y zeolite via t h e s e c - b u t y l c a r b o n i u m i o n (11, 12). Experimental T h e static reactor, w h i c h w a s c o n n e c t e d t o a c o n v e n t i o n a l B E T system, a n d t h e p u r i f i c a t i o n o f t h e reactants h a v e b e e n d e s c r i b e d else where
(10).
Catalyst Preparation. N a - Y zeolite was s u p p l i e d b y L i n d e ( L o t N o . 1280-133). T h e chemical composition p r o v i d e d b y the supplier w a s : Component
A1 0 2
%
Si0
3
22.4
Na 0
2
2
63.2
12.6
CaO 0.7
A c c o r d i n g l y , the total cationic charge ( N a
+
M g O (Ti0 +Fe 0 ) 2
0.2
+ 2Mg
2 +
2
3
0.1
+ 2 C a ) w a s just 2 +
a b o u t b a l a n c e d b y t h e t o t a l negative charge o n t h e lattice; t h e ratio w a s 0.449/0.440 =
1.02. T h e i m p u r i t y a l k a l i n e earth ions h a d a p r o f o u n d
effect o n t h e c a t a l y t i c a c t i v i t y f o r b u t e n e i s o m e r i z a t i o n a n d , therefore, t h e c o n c e n t r a t i o n o f these w a s r e d u c e d g r e a t l y b y successive
exchanges
w i t h p u r i f i e d N a A c s o l u t i o n . T h e r e s u l t i n g catalyst w a s w a s h e d thor oughly w i t h slightly alkaline distilled water catenation. Ca
2 +
(pH=
1 0 ) , to avoid de
A l i q u o t s o f this " p a r e n t catalyst" ( I ) c o n t a i n i n g o n l y 0 . 0 2 %
u n d e r w e n t 2 k i n d s o f treatments: C a t a l y s t s I I t o V w e r e b a c k ex
c h a n g e d to increase t h e C a
2 +
content f r o m 0.02 t o 0 . 4 % ( T a b l e I ) , a n d
C a t a l y s t s V I t o X w e r e m a d e b y w a s h i n g a l i q u o t s of t h e p a r e n t m a t e r i a l w i t h i n c r e a s i n g amounts o f d i s t i l l e d d e i o n i z e d w a t e r . I n this w a y , some Na
+
w a s r e m o v e d , c r e a t i n g v a r y i n g degrees o f d e c a t i o n a t i o n ( T a b l e I I ).
T h e a m o u n t of N a extracted w a s d e t e r m i n e d i n t h e w a s h i n g w a t e r , a n d +
the degree o f d e c a t i o n a t i o n w £ s c a l c u l a t e d t h e r e f r o m . N o C a , M g , o r F e
American Chemical Society Library
1155Molecular 16th St., Flanigen and Sand; SieveN.W. Zeolites-II Advances in Chemistry; American ChemicalD.L Society: Washington, DC, 1971. Washington. 20036
348
M O L E C U L A R SIEVE ZEOLITES
II
w a s d e t e c t e d b y a t o m i c a b s o r p t i o n spectroscopy i n t h e w a s h i n g w a t e r . T h e r e w a s n o significant v a r i a t i o n i n t h e l e v e l of m i n o r i m p u r i t i e s ( B , B a , C r , C u , F e , M g , M n , T i ) b e t w e e n the p a r e n t m a t e r i a l a n d t h e
final
catalyst. P r o c e d u r e . A l l the catalysts w e r e p r e t r e a t e d w i t h 0
2
at 500 ° C a n d
e v a c u a t e d o v e r n i g h t at this t e m p e r a t u r e before e a c h r u n . T h e e x p e r i ments w e r e a l l m a d e u s i n g the same a m o u n t o f reactant ( 5 5 ce S T P ) a n d Downloaded by CHINESE UNIV OF HONG KONG on November 2, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch066
catalyst.
T h e r e q u i r e d a m o u n t of H
2
reactor before a d d i n g t h e reactant.
0 was v a c u u m transferred into the T h e carbonaceous m a t e r i a l w h i c h
w o u l d n o t desorb o n o v e r n i g h t e v a c u a t i o n at r o o m t e m p e r a t u r e w a s d e t e r m i n e d b y c o m b u s t i o n to C 0
[see also R e f . 12].
2
P r o d u c t analysis
was b y G L C . Results T h e effect of i n c r e a s i n g amounts of w a t e r , a d d e d as cocatalyst, is s h o w n i n F i g u r e 1 f o r t h e catalyst w i t h highest C a
2 +
content ( V ) . T h e
r e a c t i o n rate i n c r e a s e d s h a r p l y w i t h s m a l l w a t e r a d d i t i o n s a n d t h e n l e v e l e d off at a b o u t 10 H 0 / C a 2
(2H 0/cage).
2 +
Similar behavior was
2
o b s e r v e d w i t h t h e other 4 catalysts of this series. s h o w e d that a n i n c r e a s i n g f r a c t i o n of this H
2
Separate
experiments
0 w a s i n the gas phase w i t h
increasing addition under reaction conditions. T h e o v e r - a l l rate constants (k i
+
2
k )
f o r 1-butene d i s a p p e a r a n c e
31
f o r C a t a l y s t s I to V are g i v e n i n T a b l e I. T h e rate constants are d e f i n e d b y
1-butene
— ^
cis-2-butene
trans-2-butene When
t h e rate
against C a
constants
c o r r e s p o n d i n g to 2 H 0 / c a g e 2
were
plotted
c o n c e n t r a t i o n , a straight l i n e passing t h r o u g h t h e o r i g i n
2 +
( z e r o rate at zero C a ) r e s u l t e d . 2 +
I n e a c h case, t h e a d d i t i o n of this
a m o u n t of H 0 , w h i c h w a s sufficient to m a x i m i z e t h e rate, i n c r e a s e d t h e 2
rate b y a f a c t o r of a b o u t 40. T h e c a t a l y t i c a c t i v i t y is c o r r e l a t e d w i t h i n c r e a s i n g extent of d e c a t e n a t i o n i n T a b l e I I . W h e n the rates f o r the d r y catalyst w e r e p l o t t e d vs. c a t i o n d e f i c i e n c y , a straight l i n e p a s s i n g t h r o u g h the o r i g i n a g a i n r e s u l t e d . W h e n the rates f o r the w e t catalyst w e r e p l o t t e d , another straight l i n e w a s o b t a i n e d , b u t w i t h a n i n t e r c e p t c o r r e s p o n d i n g to t h e rate of C a t a l y s t I i n T a b l e I ( 6 Χ 10" m i n 2
- 1
gram" ). 1
W i t h a l l these catalysts, a s m a l l p o r t i o n of t h e reactant w a s r e t a i n e d b y t h e catalyst w h i c h c o u l d n o t b e r e m o v e d b y a n o v e r n i g h t e v a c u a t i o n
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
66.
LOMBARDO E T A L . Table I.
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Catalyst No. I II III IV V
Acidity
in Sodium-Y
Zeolites
349
Variation of Catalytic A c t i v i t y with Ca Content of N a - Y Zeolite"
Calcium Analysis,
% 0.02 0.07 0.1 0.2 0.4
Rate of Isomerization of 1-Butene (fc i + kz\) X 10 Min- G~
Ads. Gases + Residues, n-Butene/ Cage
2
Number of Na+ Replaced by C a + , %
2
2
1
l
Dry Catalyst
2H 0/ Cage
0.01 0.55
6.0 21.9 20.0 38.4 84.0
0.3 1.0 1.4 2.9 5.7
2
2.20
5
b
0.08 0.10 0.40
Static reactor, 55 ce ( S T P ) of reactant, 76 m g of catalyst (dry basis), reaction temperature 2 6 0 ° C . Residues determined after runs using water as cocatalyst w h e n the n-butene mixture was close to e q u i l i b r i u m . a
b
Table II. Variation of Catalytic A c t i v i t y with Decationation of N a - Y Zeolite" Extent of
*j
^NulTo? fei +
Catalyst No.
Na+Removed,
VI VII VIII IX X X
0.15 0.35 0.54 0.79 0.94 0.94
{ i{
somer
za
f
on
0
l-Butene
k ) Χ 10 Min,2
3Î
% Dry Catalyst 0.45 0.70 1.00 1.8 2.0
1
G~
l
2H 0/Cage 2
Adsorbed Gases + Residues, n-Butenes/ Cage b
0.15 0.60
6.7 8.9 10.4 10.4 11.9
0.40 0.15
Same as for T a b l e I. Residues were determined after using d r y catalyst when the n-butene m i x t u r e was close to e q u i l i b r i u m . a
6
at r o o m t e m p e r a t u r e .
U s i n g r a d i o a c t i v e tracers a n d C a t a l y s t I , i t w a s
s h o w n that this consisted of 2 fractions, 1 c o r r e s p o n d i n g to
exchangeable
a d s o r b e d b u t è n e s , a n d the other t o residues o r t i g h t l y h e l d ( p o l y m e r i z e d ? ) m o l e c u l e s (12). T h e t o t a l a m o u n t of this m a t e r i a l is r e p o r t e d i n t h e last c o l u m n s o f T a b l e s I a n d I I . solid increased w i t h increasing C a
2 +
T h e a m o u n t of gas r e t a i n e d b y the content ( T a b l e
II).
Discussion T h e results s h o w e d that d i v a l e n t cations, present a t i m p u r i t y levels ( as n o r m a l l y f o u n d i n the c o m m e r c i a l L i n d e zeolites ) m a r k e d l y i n c r e a s e d t h e c a t a l y t i c a c t i v i t y o f N a - Y zeolite.
I f these ions w e r e a l l i n t h e hex-
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
MOLECULAR
350
SIEVE Z E O L I T E S
II
a g o n a l p r i s m positions, as c o m m o n l y s u p p o s e d for these l o w r e p l a c e m e n t levels, this effect w o u l d not b e expected. per C a
2 +
R e l a t i v e l y m u c h larger increases
a d d e d w e r e o b s e r v e d after the S
7
sites w e r e
filled.
N o t e that
these effects a p p e a r e d w i t h the d r y catalyst; it is possible that the a d d e d H 0 p l a y e d a role i n d r a w i n g m o r e cations f r o m these positions. 2
Slight
d e c a t i o n a t i o n ( or c a t i o n d e f i c i e n c y ) p r o d u c e d a s i m i l a r effect. T h e i n t e r cepts of the rate plots s h o w e d that the a c t i v i t y f o r a c i d - c a t a l y z e d reac Downloaded by CHINESE UNIV OF HONG KONG on November 2, 2016 | http://pubs.acs.org Publication Date: June 1, 1971 | doi: 10.1021/ba-1971-0102.ch066
tions w o u l d b e n e g l i g i b l y l o w f o r a n i m p u r i t y - f r e e , n o n d e c a t i o n a t e d , N a - Y zeolite. T h e s e facts s u p p o r t t h e i d e a that the c a t a l y t i c a c t i v i t y is asso c i a t e d w i t h B r o n s t e d sites f o r m e d b y i n t e r a c t i o n of H 0 w i t h d i v a l e n t 2
cations or b y d e c a t i o n a t i o n t h r o u g h h y d r o l y s i s . If the in situ i n t e r a c t i o n of N a w i t h w a t e r contributes to the c a t a l y t i c a c t i v i t y , this c o n t r i b u t i o n +
is n e g l i b l e f o r a l l p r a c t i c a l purposes.
T h i s p o i n t is c l a r i f i e d b y the d a t a
s h o w n i n F i g u r e 1. T h e tangent to the e x p e r i m e n t a l c u r v e ( s o l i d l i n e ) corresponds to 1 H o O / C a ; the c a t a l y t i c a c t i v i t y w o u l d f o l l o w this c u r v e 2+
if every H 0 a d d e d c o u l d be adsorbed on C a . T h e dashed line, shown 2 +
2
f o r c o m p a r i s o n , corresponds to 2 H 0 / C a 2
2 +
. T h e rate does not
its m a x i m u m s a t u r a t i o n v a l u e , h o w e v e r , u n t i l 10 H 0 / C a 2
2 +
reach
have
been
a d d e d . T h i s is p r o b a b l y because w i t h larger a d d i t i o n s , a major f r a c t i o n of the H 0 remains i n the gas phase.
M o v e m e n t of d i v a l e n t ions f r o m
2
the S/ sites, effected b y i n c r e a s i n g s o l v a t i o n of the zeolite surface, c o u l d c o n t r i b u t e also.
T h i s analysis, together w i t h the fact that the r e a c t i o n
rate levels off m u c h before 1 H 0 / N a 2
+
is present i n the system, supports
the i d e a that the m e c h a n i s m represented i n E q u a t i o n 1 is responsible f o r the c a t a l y t i c a c t i v i t y , viz., that the B r o n s t e d sites are o n b r i d g i n g oxygens b e t w e e n s i l i c a a n d a l u m i n a tetrahedra a n d that these m a y be f o r m e d either b y h y d r o l y s i s of d i v a l e n t cations o r b y c r e a t i n g a c a t i o n deficiency. It is, of course, a m o o t q u e s t i o n w h e t h e r m o r e of these sites are f o r m e d adjacent to C a
2 +
i n the presence of H 0 or this m o l e c u l e p l a y e d a r e l a t e d
role as cocatalyst.
2
I n either case, the p i c t u r e agrees w e l l not o n l y w i t h
the a v a i l a b l e spectroscopic G o u r i s e t t i et al.
(6)
d a t a , b u t also w i t h the k i n e t i c results
for alcohol dehydration.
C a r e f u l analysis of
of the
present rate d a t a suggests that B r o n s t e d sites f o r m e d b y i n t r o d u c t i o n of d i v a l e n t ions are m o r e active t h a n those f o r m e d b y d e c a t i o n a t i o n .
This
m a y b e e x p l a i n e d b y the p o l a r i z i n g effect of the d i v a l e n t cations, as d i s cussed b y R i c h a r d s o n (16).
T h e r e is, h o w e v e r , one other p o s s i b i l i t y n o t
r u l e d out b y the present d a t a . T h e B r o n s t e d sites created b y d e c a t i o n a t i o n or b y E q u a t i o n 1 c o u l d h a v e b e e n p a r t i a l l y d e h y d r o x y l a t e d d u r i n g pretreatment.
T h e effect of H 0 o n the rate c o u l d t h e n c o r r e s p o n d to 2
the i n t e r a c t i o n of H 0 m o l e c u l e s w i t h these d e h y d r o x y l a t e d sites. 2
In
v i e w of the present state of k n o w l e d g e c o n c e r n i n g the t h e r m a l s t a b i l i t y of these materials, this e x p l a n a t i o n is d e e m e d b o t h u n l i k e l y a n d u n n e c essary.
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
66.
LOMBARDO E T A L .
351
Acidity in Sodium-Ύ Zeolites
u-
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•β——β
Figure 1.
Variation of catalytic activity with amount of cocatalyst
T h e results p r e s e n t e d h e r e i n afford a n e x p l a n a t i o n f o r some of t h e d i s c r e p a n c i e s f o u n d i n t h e l i t e r a t u r e (1, 5, 7, 13, 19, 23) w h e r e u s u a l l y the c h e m i c a l c o m p o s i t i o n of t h e zeolite has n o t b e e n specified c a r e f u l l y —e.g., H a b g o o d (7) n o t e d that the a c t i v i t y c h a n g e d f r o m o n e l o t of zeo lite to another a n d r e p o r t e d that t h e a c t i v i t y of t h e N a zeolites i n c r e a s e d o n a d d i t i o n of w a t e r ; W a r d (19),
o n t h e other h a n d , f o u n d that a p u r e
N a - Y zeolite w a s n o t a c t i v a t e d b y H 0 . 2
T h e r e f o r e , to define c l e a r l y a
G r o u p Ι Α X o r Y zeolite catalyst, i t is v e r y i m p o r t a n t to s p e c i f y t h e k i n d a n d a m o u n t of i m p u r i t i e s present. T h e carbonaceous m a t e r i a l w h i c h w a s r e t a i n e d b y the catalysts after e v a c u a t i o n w a s h e l d i n 2 f o r m s : 1 c o u l d b e r e c o v e r e d as b u t e n e m o l e cules (12)
b y exchange w i t h i s o t o p i c a l l y l a b e l l e d 1-butene; t h e other
c o u l d b e r e m o v e d o n l y b y c o m b u s t i o n to C 0 . W i t h s i l i c a - a l u m i n a cata 2
lysts, t h e latter ( r e s i d u e s )
is t h o u g h t to f o r m t h e a c t i v e sites f o r c a r -
b o n i u m i o n a c t i v i t y (3,8,9).
T h e present results s h o w e d that t h e a c t i v i t y
c o r r e l a t e d w i t h t h e degree of d e c a t i o n a t i o n o r t h e C a catalyst.
2 +
content of t h e
M o r e o v e r , t h e a m o u n t of r e s i d u e r e t a i n e d b y t h e catalyst ( n o n -
exchangeable ) w a s a b o u t 2 orders of m a g n i t u d e s m a l l e r t h a n t h e n u m b e r of d e c a t i o n a t e d sites of t h e s a m p l e (12).
It seems p r o b a b l e ,
therefore,
that residues d o not p l a y a n i m p o r t a n t role i n t h e d e v e l o p m e n t of c a t a l y t i c a c t i v i t y of these materials i n t h e presence of H 0 ; h o w e v e r , residues m a y 2
s u p p l y t h e necessary protons f o r c a t a l y t i c a c t i v i t y i n its absence.
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
352 MOLECULAR SIEVE ZEOLITES II
Acknowledgment This w o r k was sponsored b y the G u l f Research & Development C o . as p a r t of t h e r e s e a r c h p r o g r a m of t h e F e l l o w s h i p o n P e t r o l e u m . O n e o f us ( E A L ) is i n d e b t e d to t h e O r g a n i z a t i o n of A m e r i c a n States f o r t h e a w a r d of a F e l l o w s h i p .
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Literature Cited (1) Bartley, B. H., Habgood, H. W., George, Ζ. M.,J.Phys. Chem. 1968, 72, 1689. (2) Christner, L. G., Liengme, Β. V., Hall, W. K., Trans. Faraday Soc. 1968, 64, 1679. (3) Clark, Α., Proc. Intern. Congr. Catalysis, 4th, 1968, Paper No. 75. (4) Eberly, P. E.,J.Phys. Chem. 1968, 72, 1042. (5) Frilette, V. J., Munns, G. W.,J.Catalysis 1965, 4, 504. (6) Gourisetti, B., Cosyns, J., Leprince, P., Bull. Soc. Chim. France 1966, 3, 1085. (7) Habgood, H. W., George, Ζ. M., "London Conference on Molecular Sieves," 1968, 130. (8) Hightower, J. W., Hall, W. K., Chem. Eng. Progr. Symp. Ser. 1967, 63 (73), 122. (9) Hightower, J. W., Hall, W. K.,J.Am. Chem. Soc. 1967, 89, 778. (10) Lombardo, Ε. Α., Hall, W. K., A.I.Ch.E. J., in press. (11) Lombardo, Ε. Α., Hall, W. K., in preparation. (12) Lombardo, Ε. Α., Sill, G. Α., Hall, W. K., in preparation. (13) Matsumato, H., Yasul, K., Morita, Y.,J.Catalysis 1968, 12, 84. (14) Olson, D. H., J. Phys. Chem. 1968, 72, 1400. (15) Pickert, P. E„ Rabo, J. Α., Dempsey, E., Schomaker, V., Proc. Intern. Congr. Catalysis, 3rd, 1965, 1, 714. (16) Richardson, J. T.,J.Catalysis 1967, 9, 182. (17) Topchieva, K. F., Romanovski, Β. V., Piguzova, L. I., Thoang,H.,Bizreh, Y. W., Proc. Intern. Congr. Catalysis, 4th, 1968, Paper No. 57. (18) Uytterhoeven, J. B., Schoonheydt, R. S., Liengme, Β. V., Hall, W. K., J. Catalysis 1969, 13, 425. (19) Ward, J.,J.Catalysis 1968, 11, 238. (20) Ibid., 1968, 10, 34. (21) Ward, J.,J.Phys. Chem. 1968, 72, 1042. (22) Ibid., 1968, 72, 4211. (23) Watanake, I., Habgood, H. H.,J.Phys. Chem. 1968, 72, 3066. RECEIVED January 12, 1970.
Discussion Gourisetti Balamalliah ( I n d i a n Institute of P e t r o l e u m , D e h r a d u m , I n d i a ) : I w o u l d l i k e to d r a w t h e authors' attention to t h e f a c t t h a t t h e r e l a t i o n s h i p b e t w e e n t h e n u m b e r of w a t e r m o l e c u l e s a n d t h e n u m b e r of c a l c i u m ions f o r m a x i m u m c a t a l y t i c a c t i v i t y of C a X a n d C a Y m o l e c u l a r
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
66.
LOMBARDO E T A L .
Acidity
in Sodium-Ύ
sieves i n the d e h y d r a t i o n o f tert-butyl setti et al,
Compt.
Rend.
Zeolites
353
a l c o h o l w a s first r e p o r t e d b y G o u r i
1 9 6 4 , 258 ( 1 8 ) , 4 5 4 7 - 9 . I t w a s o b t a i n e d b y
d r a w i n g tangents to rate curves as s h o w n i n the present p a p e r . E . L o m b a r d o : W e r e p o r t e d i n o u r p a p e r u n d e r R e f . 6 a later w o r k of G o u r i s e t t i , B . , et ai. t h a t i n c l u d e s t h e d a t a g i v e n i n t h e short c o m m u
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n i c a t i o n r e f e r r e d to b y G o u r i s e t t i .
Flanigen and Sand; Molecular Sieve Zeolites-II Advances in Chemistry; American Chemical Society: Washington, DC, 1971.
