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Evaluation of Non-Commercial Modified Large Pore Zeolites in FCC
H.G.Karge, J. Weitkamp (Editors),Zeolites (IS Catalysts, Sorbents and Detergent Builders 0 1989 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
EVALUATION OF NON-COMMERCIAL MODIFIED LARGE PORE ZEOLITES I N FCC E. JACQUINOT, F. RAATZ, A. MACEDO and Ch. MARCILLY
INSTITUT FRANCAIS DU PETROLE, 1-4 r u e du B o i s Preau BP311, 92506 Ruei 1 Malmai son, France ABSTRACT The c a t a l y t i c performances o f H-Y, H-Beta and H-Omega prepared by a steaming-acid l e a c h i n g procedure, have been e v a l u a t e d i n cyclohexene and i n Vacuum Gas O i l ( V G O ) t r a n s f o r m a t i o n . The l e a c h i n g i s a key s t e p , s i n c e depending on t h e o p e r a t i n g c o n d i t i o n s i t can decrease o r i n c r e a s e t h e c o n v e r s i o n l e v e l s . I n cyclohexene t r a n s f o r m a t i o n , t h e a c i d i t y o f t h e s o l i d s : controls the activity and the following ranking is obtained H-Beta)H-Y)H-Omega. I n c o n t r a s t , i n VGO c o n v e r s i o n a c c e s s i b i l i t y o f t h e a c i d c e n t e r s has t o be taken i n t o account which means t h a t H-Y l e a d s t o t h e b e s t r e s u l t s . Moreover, o p t i m i z a t i o n o f t h e a c i d i c p r o p e r t i e s o f H - Y t h r o u g h a s e l e c t i v e a c i d l e a c h i n g improves s i g n i f i c a n t l y t h e c o n v e r s i o n l e v e l s . INTRODUCTION
Y z e o l i t e s m o d i f i e d by two main techniques, (framework
and are
of
or
isomorphous
commercial
FCC
substitution
treatment
(framework
a c t i v e component
only)
hydrothermal
o v e r a l l dealumination), containing o r not containing r a r e earth cations, the
dealumination
i.e.
catalysts
(1,
2,
3).
Indeed,
a
tremendous amount o f d a t a i s a v a i l a b l e i n t h e l i t e r a t u r e on t h e b e h a v i o r o f t h e s e sol i d s . However, o t h e r l a r g e - p o r e z e o l i t e phases a r e p o t e n t i a l c a n d i d a t e s f o r t h i s a p p l i c a t i o n . Depending on whether o r n o t t h e aim i s t o f u l l y r e p l a c e t h e a c t u a l a c t i v e component, and e x c l u d i n g any p r i c e c o n s t r a i n t , two t y p e s o f s o l i d s c o u l d be a p r i o r i considered.
As an a l t e r n a t i v e t o t h e a c t u a l main
a c t i v e component, o n l y l a r g e - p o r e z e o l i t e s w i t h m u l t i d i m e n s i o n a l porous systems should be c o n s i d e r e d as p r o m i s i n g c a n d i d a t e s . zeolite
itself,
(hydrothermal structures
but
submitted
treatment
such
as
followed
ZSM-20
and
to by
a
I n t h i s c a t e g o r y we
conventional acid
zeolite
Beta
z e o l i t e s w i t h monodimensional porous systems,
overall
leaching),
(4).
and
find Y
dealumination other
Deal umi n a t e d
such as Omega and L,
modified
1 arge-pore a r e more
l i k e l y t o be o n l y u s e f u l as secondary a c t i v e components ( 5 ) . L i t t l e i s known about t h e c a t a l y t i c performances i n FCC o f t h e p o t e n t i a l c a n d i d a t e s mentioned above ( 4 , 51, and most o f t h e s t u d i e s a l r e a d y p u b l i s h e d have been devoted t o n o n - m o d i f i e d Beta z e o l i t e s . R e c e n t l y , A.
Corma e t a l .
( 6 - 9 ) have e v a l u a t e d t h e c r a c k i n g p r o p e r t i e s o f Beta z e o l i t e s w i t h v a r i o u s
Si/A1
ratios,
and o f c o n v e n t i o n a l l y dealuminated Y z e o l i t e s .
Two i m p o r t a n t
c o n c l u s i o n s emerge f r o m t h i s work : i ) a t l e a s t f o r n-heptane c r a c k i n g H-Beta i s superior t o H-Y,
and i i )a m i l d a c i d l e a c h i n g o f steamed H-Y g i v e s r i s e t o a
116
decrease o f t h e a c t i v i t y i n g a s - o i l c r a c k i n g . We aim h e r e t o e v a l u a t e t h e performances,
i n a model t e s t r e a c t i o n and i n
t h e c r a c k i n g o f a VGO o f z e o l i t i c phases, which a r e o f p o t e n t i a l i n t e r e s t i n FCC. Cyclohexene has been chosen as a t e s t molecule,
since i t allows a r a p i d
e v a l u a t i o n of t h e hydrogen t r a n s f e r tendency o f t h e c a t a l y s t s , i . e .
formation
o f benzene, cyclohexane and m e t h y l c y c l o p e n t a n e r a t h e r t h a n m e t h y l c y c l o p e n t e n e . I n a f i r s t approach, we w i l l
r e s t r i c t ourselves t o t h e study o f t h e f r e s h
c a t a l y s t s , which means t h a t h y d r o t h e r m a l a g i n g and p o i s o n i n g by metal w i l l n o t be c o n s i d e r e d h e r e .
EXPERIMENT SOL I D S S t a r t i n g f r o m low-sodium ( S i / A l = 14.0)
(NaC400 ppm)
and NH4-Omega ( S i / A l
= 2.91,
NH4-Y
(Si/Al
=
2.81,
dealuminated s o l i d s
NH4-Beta have been
prepared by a t w o - s t e p procedure, i.e. hydrothermal t r e a t m e n t (100% steam) a t v a r i o u s temperatures
(823 t o 1123 K )
s o l u t i o n a t 373 K ( 1 and 3N f o r H-Y,
f o l l o w e d by an a c i d l e a c h i n g i n HC1 1N f o r H-Beta,
0.5N f o r H-Omega). The
sol i d s were c h a r a c t e r i z e d a t each s t e p o f t h e p r e p a r a t i o n procedures by chemical a n a l y s i s , Further d e t a i l s
XRD,
29 S i
MASNMR,
I R spectroscopy
and
N2
adsorption.
on t h e d e a l u m i n a t i o n procedures and t h e c h a r a c t e r i z a t i o n
t e c h n i q u e s can be found i n r e f . ( 1 0 ) . The o r i g i n a l Y z e o l i t e was p r o v i d e d by Zeocat (Z-FlOO),
w h i l e Omega and Beta were s y n t h e s i z e d by J.L.
GUTH e t a1
( E c o l e N a t i o n a l e S u p c r i e u r e de Chimie, Mulhouse, F r a n c e ) . CATALYTIC TESTS MODEL MOLECULE. Cyclohexene t r a n s f o r m a t i o n was s t u d i e d u s i n g a Geomecanique m i c r o t e s t u n i t a l l o w i n g v e r y l o w c o n t a c t t i m e s and a n a l y s i s o f t h e p r o d u c t s a t v a r i o u s t i m e s on stream. The t e s t s were conducted a t atmospheric p r e s s u r e under 5 t h e f o l l o w i n g c o n d i t i o n s : cyclohexene p a r t i a l p r e s s u r e 0 . 2 0 ~ 1 0 Pa, c a r r i e r gas n i t r o g e n , c o n t a c t t i m e s i n t h e 0.25 t o 3.0 s range, t e m p e r a t u r e 643 K, sampling a t d i f f e r e n t t i m e s on s t r e a m ( 2 , 5, 8, 11 m i n ) . VACUUM GAS OIL. Aramco 150 c r a c k i n g was s t u d i e d u s i n g a MAT u n i t a t 755 K under
atmospheric p r e s s u r e . W h i l e k e e p i n g a c o n s t a n t i n j e c t i o n t i m e ( 7 5 s ) , d i f f e r e n t catalyst-to-oil
weight r a t i o s were used (1.2
t o 5.3)
i n order t o vary t h e
c o n v e r s i o n l e v e l s . P r i o r t o t h e MAT t e s t s , t h e z e o l i t e s (20 % i n w e i g h t ) were blended w i t h an aged s i l i c a - a l u m i n a m a t r i x . RESULTS The main physicochemical
characteristics
of
t h e modified zeolites
are
reported i n table 1 together with the operating conditions applied f o r the d e a l u m i n a t i o n procedures.
117 TABLE 1 a ) Chemical and t e x t u r a l c h a r a c t e r i s t i c s o f dealuminated Y z e o l i t e s . * C a l c u l a t e d f r o m t h e u n i t c e l l parameter, u s i n g t h e c o r r e l a t i o n g i v e n i n r e f . (19) ** XRD c r i s t a l l i n i t y , t h e o r i g i n a l NH4-Y i s t a k e n as a r e f e r e n c e . P r e p a r a t i o n procedure Steaming 823 K HCL 1 N HC1 3N Steaming 873 K HC1 1N HC1 3N
::: :::
57
37
Steaming 9 / 3 K HC1 1N HC1 3N
K
% DX**
(Si/Al
8I 4
% 69 % 0 %
9
00
1 0 80
%
72 %
11
>loo
69 %
42:;
T
85 % 79 % 93 %
::;
2 4
44
21 42
93 % 78 % 94 %
1:*8 74
> 50 > 50 > 50
91 % 87 % 91 %
43
Steaming 1043 K HC1 1N HC1 3N Steaming 1113 HC1 1N HC1 3N
( S i /A1 ) overall
16 41
b ) Chemical and t e x t u r a l c h a r a c t e r i s t i c s o f dealuminated B e t a z e o l i t e s I
I I I I I I
I I I I I I I
1
P r e p a r a t i o n procedure
( Si /A1
Steaming 873 K HC1 1N
1 8
Steaming 973 K HC1 1 N
1 4
Steaming 1073 K HC1 1 N Steaming 1123 K HC1 1 N
overall
62
53
14 29
7 4 19
118 c ) Chemical and t e x t u r a l c h a r a c t e r i s t i c s o f dealuminated Omega z e o l i t e s . * 29Si RMN s i m u l a t i o n a c c o r d i n g t o r e f ( 2 0 ) . 0 The c parameter i s n o t r e p o r t e d s i n c e i t o n l y v a r i e s between 7,51 and 7,55 A . ** XRD c r i s t a l l i n i t y , t h e o r i g i n a l NH4-0mega i s t a k e n as a r e f e r e n c e . ( S i / A l I V ) *% DX**
l p r e p a r a t i o n procedure
I I I I I I
I
I I I
I
I I I
a
(i)
Steaming 923 K HC1 0,5 N
T 2 - r l-Kl-31 1 10 94 % ia,io
Steaming 913 K HC1 0,5 N
1 8 85% ia 90 %
Steaming 1013 K HC1 0,5 N
3 068% 18;ar
Steaming 1123 K HC1 0,5 N
loo66% 77-38-
As
expected,
temperatures
70 %
30
100
whatever
leads
to
a
the
structure,
dealumination
18,Ol
18,OO
66 %
the
of
m 18,06
the
steaming framework.
at The
increasing resulting
extra-framework species cause a r e d u c t i o n of t h e N2 a d s o r p t i o n c a p a c i t y o f H-Y and H-Beta z e o l i t e s which do have a m u l t i d i m e n s i o n a l porous system (111, w h i l e a complete b l o c k i n g o f t h e monodimensional porous system o f H-Omega o c c u r s . Concerning t h e e f f e c t o f t h e p o s t - s t e a m i n g a c i d l e a c h i n g two s i t u a t i o n s have t o be c o n s i d e r e d : i ) s e l e c t i v e a c i d l e a c h i n g g i v i n g r i s e t o an e l i m i n a t i o n o f extra-framework species w i t h o u t any f u r t h e r framework d e a l u m i n a t i o n ( H - Y
and
H-Omega
ii)
treated
in
1N
and
0.5N
HC1
solutions,
respectively),
and
n o n - s e l e c t i v e a c i d l e a c h i n g r e s u l t i n g i n a s e v e r e framework d e a l u m i n a t i o n (H-Y and H-Beta t r e a t e d i n 3N and 1N HC1 s o l u t i o n s , r e s p e c t i v e l y ) . I n c o n t r a s t t o t h e steamed H - Y and H-Omega,
steamed H-Beta appeared t o be
very s e n s i t i v e t o a c i d l e a c h i n g , s i n c e even a m i l d l e a c h i n g l e a d s t o v e r y h i g h o v e r a l l S i / A 1 r a t i o s . T h i s i s l i k e l y t o be due t o t h e s i g n i f i c a n t amount o f s t r u c t u r a l defects present i n t h i s z e o l i t e a f t e r t h e synthesis. Without going i n t o t o o much d e t a i l , i t s h o u l d be n o t e d t h a t most of t h e s o l i d s have a h i g h degree o f c r y s t a l l i n i t y , and t h a t f o r each s t r u c t u r e a wide range o f framework and o v e r a l l S i / A 1
r a t i o s a r e covered.
performances o f t h r e e v e r y framework and o v e r a l l S i / A l
important
Thus,
t h e i n f l u e n c e on t h e c a t a l y t i c
parameters namely
the
structure,
the
r a t i o s o f t h e s o l i d s can be s t u d i e d . Since i t i s
n o t always p o s s i b l e t o d e t e r m i n e w i t h good accuracy t h e framework S i / A l r a t i o
o f a l l t h e s o l i d s (H-Beta and a c i d leached s o l i d s c o u l d c o n t a i n many s t r u c t u r a l d e f e c t s ) , we have chosen t o r e p o r t t h e c o n v e r s i o n l e v e l s versus t h e steaming temperature o f t h e o r i g i n a l NH4-form, acid leaching.
even f o r s o l i d s s u b m i t t e d t o a subsequent
119
HY-ZEOLITES
A f t e r steaming, t h e cyclohexene c o n v e r s i o n p r e s e n t s a f l a t optimum versus t h e temperature employed f o r t h e steaming t r e a t m e n t Si/Al
(i.e.
versus t h e framework
r a t i o o f t h e s o l i d s , see t a b l e 1 ) and s e r i o u s l y decreases f o r steaming
temperatures h i g h e r t h a n about 900 K ( f i g u r e 1 ) . The most i m p o r t a n t p o i n t which i s evidenced on f i g u r e 1 concerns t h e e f f e c t o f t h e a c i d l e a c h i n g . Depending on whether o r n o t t h e l e a c h i n g i s s e l e c t i v e ( e x t r a - f r a m e w o r k A1 e x t r a c t i o n w i t h o u t any f u r t h e r framework d e a l u m i n a t i o n , t a b l e 11, an i n c r e a s e o r a decrease o f t h e cyclohexene c o n v e r s i o n l e v e l s i s observed. The same e f f e c t s a r e o b t a i n e d i n VGO transformation ( f i g u r e 2 ) . H-BETA ZEOLITES
Steaming a t i n c r e a s i n g temperatures l e a d s t o a monotonic decrease o f t h e cyclohexene steaming,
conversion
levels
(figure
1).
I t should
be n o t e d t h a t
after
t h e cyclohexene c o n v e r s i o n l e v e l s o f H-Beta a r e h i g h e r t h a n t h o s e
o b t a i n e d f o r H-Y.
The m i l d p o s t - s t e a m i n g a c i d l e a c h i n g r e s u l t s i n a severe
r e d u c t i o n o f t h e s e c o n v e r s i o n l e v e l s , whereas t h e same t r e a t m e n t has a p o s i t i v e e f f e c t f o r H-Y ( f i g u r e 1 ) . As i n t h e case of cyclohexene,
t h e VGO c o n v e r s i o n i s s t r o n g l y a f f e c t e d by
steaming ( f i g u r e 2 ) b u t shows a d i f f e r e n t b e h a v i o r a f t e r a c i d l e a c h i n g . The l a t t e r t r e a t m e n t g i v e s r i s e t o a small i n c r e a s e o f t h e VGO c o n v e r s i o n l e v e l s ( f i g u r e 21, which should be compared w i t h t h e n e g a t i v e e f f e c t evidenced f o r t h e cyclohexene t r a n s f o r m a t i o n ( f i g u r e 1 ) . Moreover, i n VGO c o n v e r s i o n whatever t h e p r e p a r a t i o n procedures
we
used,
H-Beta
gives
lower
performances
t h a n H-Y
(figure 2 ) .
H-OMEGA ZEOLITES
C o n t r a r y t o H-Y and H-Beta,
v e r y low cyclohexene c o n v e r s i o n l e v e l s a r e
o b t a i n e d f o r steamed H-Omega whatever t h e steaming t e m p e r a t u r e ( f i g u r e 1 ) . For t h e s e s o l i d s even a v e r y m i l d and non-optimized a c i d l e a c h i n g l e a d s t o a severe increase o f the conversion l e v e l s . Similarly,
t h e VGO c o n v e r s i o n
level
after
steaming
is
very
low
and
i n c r e a s e s v e r y s i g n i f i c a n t l y a f t e r t h e a c i d l e a c h i n g ( T a b l e 2). However, w h i l e for
the
acid-leached
H-Omega
the
conversion
levels
in
cyclohexene
i t i s no l o n g e r t h e case f o r t h e VGO t r a n s f o r m a t i o n f o r which H-Y appears t o be s u p e r i o r t o H-Omega ( f i g u r e s 1, Table 2 ) .
t r a n s f o r m a t i o n a r e v e r y c l o s e t o t h o s e o f H-Y,
120
75
H-Y
923
STEAMING TEMPERATURE IKI
-7
01
823
1w
1023
873
1123
1
I
261
823
973
1073
I 973
1073
STEAMING TEMPERATURE IK
ti-BETA
I
I
1 on
923
STEAMING TEMPERATURE (Kl H-OMEGA
I
873
1123
I
1
STEAMING TEMPERATURE ( K 1
F i g u r e 2 : Conversion o f VGO versus t h e steaming t e m p e r a t u r e (,steamed + ; steamed and a c i d leached + HC1 1N ; + HC1 3N) R e a c t i o n t e m p e r a t u r e = 755 K ; i n j e c t i o n t i m e = 75 s ; C/O = 3 ; WHSV = 16 h-1 TABLE 2 MAT c o n v e r s i o n and y i e l d s of d i f f e r e n t products o f gas-oil cracking f o r H -Omeg a. Preparation procedure
MAT conv. (wt.%)
Sti;!,"g
25.7
HC1 0.5N
41.2
STEAMING TEMPERATURE (Kl
Fi ure 1 Conversion l e v e l o f c y c l o b e i s u s t h e steaming t e m p e r a t u r e (steamed + ; steamed and a c i d leached +HC1 0,5N ; + HC1 1N ; +HC1 3N) Reaction t e m p e r a t u r e = 643K ; c o n t a c t t i m e = 0,5 s ; t i m e on stream = 2 min.
Gasoline yield (wt.%)
19,8
Gas
;% ! (wt.%) 5.1 14.0
Coke yield (wt.")
1.4 6.0
121
DISCUSSION
CONVERSION. Obviously, t h e framework d e a l u m i n a t i o n o c u r r i n g i n t h e c o u r s e o f t h e steaming procedure i s r e s p o n s i b l e f o r t h e decrease o f t h e cyclohexene and VGO c o n v e r s i o n l e v e l s .
However,
s e v e r a l i m p o r t a n t remarks have t o be made.
F i r s t , a t l e a s t i n t h e case o f H-Y t h e decrease i s non-monotonic,
i.e a f l a t
optimum i s observed near 900 K . Since i t has been shown t h a t t h e s t r e n g t h o f t h e framework a c i d s i t e s i n H - Y i n c r e a s e s w i t h t h e d e a l u m i n a t i o n l e v e l (12,131, t h i s optimum i s l i k e l y t o r e s u l t f r o m two c o m p e t i t i v e e f f e c t s , i . e r e d u c t i o n o f t h e number o f s i t e s and i n c r e a s e o f t h e i r a c i d s t r e n g t h . According t o t h e model advanced by Barthomeuf (141,
such an optimum i s n o t observed f o r z e o l i t e s ,
which a r e s y n t h e s i z e d w i t h t o o h i g h an i n i t i a l
Si/A1
ratio.
This
i s for
example, t h e case w i t h H-Beta. Framework d e a l u m i n a t i o n c o n t r i b u t e s a l s o t o t h e r e d u c t i o n o f t h e c o n v e r s i o n l e v e l s f o r H-Omega, b u t f o r t h i s s t r u c t u r e b l o c k i n g o f t h e channels by extra-framework species p l a y s t h e m a j o r r o l e ( T a b l e 1 ) . T h i s b e h a v i o r i s l i k e l y t o be t y p i c a l o f z e o l i t e s s y n t h e s i z e d w i t h low S i / A l r a t i o s and possessing an u n i d i m e n s i o n a l porous system. The most i m p o r t a n t p o i n t evidenced i n t h i s work i s l i k e l y t o concern t h e e f f e c t o f t h e post-steaming a c i d l e a c h i n g , which c o u l d have a n e g a t i v e b u t a l s o a s t r o n g l y p o s i t i v e i n f l u e n c e on t h e c o n v e r s i o n l e v e l s . Focussing on t h e d a t a p r e s e n t e d here, i t appears t h a t s e l e c t i v e a c i d l e a c h i n g , which o n l y e x t r a c t s extra-framework aluminium species, w i l l l e a d t o an i n c r e a s e o f t h e c o n v e r s i o n levels. giving
The r e v e r s e i s t r u e f o r n o n - s e l e c t i v e rise to
a further
framework
r a t i o n a l i z e d ? Since t h e a c i d accessibility
acid treatments,
dealumination.
How can
leaching could a f f e c t
o f the a c t i v e acid centers,
two
types
c o n s i d e r e d : i ) those possessing a m u l t i d i m e n s i o n a l
the of
i.e.
those
such
behavior
acidity
and t h e
solids
s h o u l d be
porous system,
and ii)
those h a v i n g a monodimensional porous s t r u c t u r e . For s o l i d s w i t h a m u l t i d i m e n s i o n a l porous system ( Y , b e t a ) , o n l y a l i m i t e d r e d u c t i o n o f t h e m i c r o p o r e volume occurs upon steaming, volume i s n o t i n c r e a s e d v e r y s i g n i f i c a n t l y
and t h e m i c r o p o r e
by l e a c h i n g .
Thus,
the positive
e f f e c t on t h e c o n v e r s i o n l e v e l s o f s e l e c t i v e a c i d l e a c h i n g (H-Y t r e a t e d i n 1N HC1 s o l u t i o n ) i s more l i k e l y t o be due t o an i n c r e a s e i n t h e a c i d i c p r o p e r t i e s
o f the s o l i d s r a t h e r than t o a b e t t e r a c c e s s i b i l i t y o f t h e a c i d s i t e s . statement i s s t r o n g l y supported by p r e v i o u s work which has shown, complementary p h y s i c a l techniques,
This
by v a r i o u s
t h a t an i n c r e a s e i n t h e number o f s t r o n g
framework s i t e s occurs t h r o u g h t h e e l i m i n a t i o n , by s e l e c t i v e a c i d l e a c h i n g , o f poisoning
extra-framework
aluminium c a t i o n s
formed
in
the
course
of
the
steaming procedure ( 1 2 ) . Extra-framework aluminium s p e c i e s which e x h i b i t a c i d i c p r o p e r t i e s a r e a l s o e l i m i n a t e d by m i l d l e a c h i n g .
However,
these s i t e s o n l y
possess a moderate Bronsted a c i d i t y ( 1 2 ) and t h u s a r e n o t l i k e l y t o p l a y t h e
122 m a j o r r o l e i n t h e c a t a l y t i c performances o f t h e s o l i d s under t h e c o n d i t i o n s we It s h o u l d be s t r e s s e d t h a t t o b e t t e r r e v e a l t h e b e n e f i t o f a
have employed.
s e l e c t i v e l e a c h i n g o f H-Y i n VGO c o n v e r s i o n , t h e s o l i d has t o be t e s t e d w i t h an a c t i v e m a t r i x so t h a t molecules which a r e t o o l a r g e t o e a s i l y e n t e r t h e z e o l i t e crystals
c o u l d r e a c t more
rapidly.
Otherwise t h e
extra-framework
material
l o c a t e d a t t h e e x t e r n a l s u r f a c e o f t h e z e o l i t e s c r y s t a l would h e l p i n t h e t r a n s f o r m a t i o n o f such heavy molecules,
and t h e s e l e c t i v e a c i d l e a c h i n g would
p o s s i b l y have a n e g a t i v e e f f e c t (8, 9). T h i s p o i n t remains t o be c o n f i r m e d . On t h e
contrary
i n the
case
of
Omega
for
which
the
unidimensional
microporous system i s n e a r l y c o m p l e t e l y b l o c k e d a f t e r t h e steaming s t e p ,
the
p o s i t i v e e f f e c t o f a s e l e c t i v e post-steaming a c i d leaching c l e a r l y r e s u l t s from t h e e l i m i n a t i o n o f t h e extra-framework m a t e r i a l s located i n t h e pores. This does n o t mean t h a t t h e a c i d i c p r o p e r t i e s of t h e framework a r e n o t
m o d i f i e d by
l e a c h i n g , b u t t h e s e changes i n a c c e s s i b i l i t y a r e h e r e predominant. C o n s i d e r i n g now n o n - s e l e c t i v e a c i d l e a c h i n g (H-Y and H-Beta t r e a t e d i n 3N and 1N HC1 s o l u t i o n s r e s p e c t i v e l y ) , i t i s c l e a r t h a t framework d e a l u m i n a t i o n o c c u r r i n g as a r e s u l t o f t h i s t r e a t m e n t i s r e s p o n s i b l e f o r t h e r e d u c t i o n o f t h e conversion
levels.
Indeed,
as
shown
by
physical
techniques,
the
acidic
p r o p e r t i e s o f s o l i d s s u b m i t t e d t o a n o n - s e l e c t i v e l e a c h i n g a r e v e r y low ( 1 2 ) . However,
H-Beta d i f f e r s f r o m H-Y,
since non-selective
leaching leads t o a
s t r o n g decrease o f t h e cyclohexene c o n v e r s i o n , w h i l e a small
increase o f t h e
VGO c o n v e r s i o n occurs. To e x p l a i n such b e h a v i o r t h e r o l e o f a c c e s s i b i l i t y has t o be t a k e n i n t o account. Cyclohexene i s a s m a l l m o l e c u l e f o r which s t e r i c c o n s t r a i n t s a r e n o t v e r y i m p o r t a n t , t h u s i t m a i n l y probes t h e a c i d i c p r o p e r t i e s o f t h e s o l i d s . From t h a t p o i n t of
view,
t h e f o l l o w i n g r a n k i n g i s o b t a i n e d : steamed H-Beta > steamed
H-Yxteamed + a c i d leached H-Omega. T h i s r a n k i n g i s i n q u a l i t a t i v e agreement w i t h t h e a c i d i c p r o p e r t i e s o f t h e s o l i d s as d e t e r m i n e d by p h y s i c a l t e c h n i q u e s , and indeed s t r o n g a c i d s i t e s a r e p r e s e n t i n steamed H-Beta ( 1 5 ) . On t h e o t h e r hand i n VGO c o n v e r s i o n s t e r i c c o n s t r a i n t s cannot
be n e g l e c t e d .
T h i s would
suggest t h a t t h e m u l t i d i m e n s i o n a l channel system o f H-Beta i s n o t as a c c e s s i b l e f o r l a r g e molecules as t h e microporous system o f H - Y .
I n o t h e r words, i n a v e r y
f i r s t approximation, t h e a c c e s s i b i l i t y of t h e a c i d s i t e s r a t h e r t h a n t h e i r a c i d s t r e n g t h c o n t r o l s t h e VGO c o n v e r s i o n
l e v e l s o v e r H-Beta.
This
proposal
is
s u p p o r t e d by a r e c e n t work ( 7 1 , a c c o r d i n g t o which t h e gas o i l c o n v e r s i o n o v e r n o n - m o d i f i e d H-Beta does n o t depend much on i t s Si/A1 r a t i o ,
and by t h e n i c e
s t r u c t u r a l s t u d y o f TREACY e t a l . ( 1 1 ) which s t r o n g l y suggests t h a t t h e open s t r u c t u r e of
z e o l i t e Beta i s
accessibility
considerations
likely would
to
contain
structural
also
explain
why
defects.
acid-leached
These H-Omega
p r e s e n t r a t h e r low VGO c o n v e r s i o n l e v e l s , w h i l e t h e i r cyclohexene c o n v e r s i o n
123
-MAT CONVERSION (wt.%)
CVCLOHEXENE CONVERSION lmol.%l
15 COKE
10 s . c
I
-9 3
Y
>
5
0 CVCLOHEXENE CONVERSION lmol.%J
25
35
45
55
MAT CONVERSION Iw1.X)
STEAMED (923 I0 AND ACID LEACHED ( 0.5 N) H-OMEGA 0
CVCLOHEXENE CONVERSION (mol.%)
F i g u r e 3 : Comparison o f s e l e c t i v i t y curves f o r cyclohexene t r a n s f o r m a t i o n over H-Y, H-Beta and H-Omeaa z e o l i t e s ( I s o m e r i s a t i o n + ; Hydrogen t r a n s f e r + )
F i g u r e 4 : Comparison o f s e l e c t i v i t y curves f o r VGO c r a c k i n g on t h r e e z e o l i t e s = (steamed H - Y (873K) -c : steamed (97310 and a c i d leached (1Nj H-Beta +; steamed (92310 and a c i d leached (0.5N) H-Omega c 1.
124 l e v e l s a r e n o t t o o f a r f r o m t h o s e o f H-Y. SELECTIVITY CYCLOHEXENE. As
described
i n detail
cyclohexene t r a n s f o r m a t i o n o f
elsewhere
(161,
are
m o d i f i e d H-Y
framework Si/A1 r a t i o . H - Y w i t h a u n i t c e l l parameter f a v o r s hydrogen t r a n s f e r r e a c t i o n s (cyclohexane,
the
mainly
selectivities
determined
by
in its
h i g h e r t h a n 24.27
benzene,
methylcyclopentane
formation) r a t h e r than isomerisation (methylcyclopentene..),
while H-Y w i t h a
0
u n i t c e l l parameter l o w e r t h a n 24.27 A i s c h a r a c t e r i z e d by v e r y l o w hydrogen t r a n s f e r s e l e c t i v i t i e s (17, 1 8 ) ( f i g u r e 3 ) . T h i s b e h a v i o r c o u l d be r a t i o n a l i z e d as f o l l o w s . Depending on whether o r n o t t h e s o l i d s c o n t a i n more t h a n about one 0
A1 per supercage ( u n i t c e l l parameter lower o r h i g h e r t h a n about 24.27 A), t h e y
w i l l o r w i l l n o t promote b i m o l e c u l a r r e a c t i o n s such as hydrogen t r a n s f e r . It i s now i m p o r t a n t t o determine how t h e s e l e c t i v i t i e s o f m o d i f i e d H-Beta and H-Omega towards hydrogen t r a n s f e r compare w i t h t h o s e o f m o d i f i e d H-Y.
Considering t h e
s e l e c t i v i t y diagrams r e p o r t e d i n f i g u r e 3, i t appears t h a t t h e s e l e c t i v i t i e s o f H-Beta and H-Omega w i t h r a t h e r low-framework S i / A l t h o s e o f h i g h l y dealuminated H-Y.
r a t i o s are very s i m i l a r t o
T h i s would mean t h a t H-Beta and H-Omega do
n o t much promote b i m o l e c u l a r r e a c t i o n s . I t i s n o t c l e a r a t t h e moment whether such b e h a v i o r d e r i v e s f r o m s t e r i c c o n s t r a i n t s (no cages a r e p r e s e n t i n Omega and i n B e t a ) , o r f r o m a s p e c i f i c A1 s i t i n g . Since non dealuminated H-Mordenite i s a l s o c h a r a c t e r i z e d by a l o w hydrogen t r a n s f e r s e l e c t i v i t y i n cyclohexene c o n v e r s i o n (101, i t i s l i k e l y t h a t s t e r i c c o n s t r a i n t s a r e r e s p o n s i b l e f o r t h e low hydrogen t r a n s f e r
s e l e c t i v i t y o f H-Beta and H-Omega.
The
intermediate
s p e c i e s would be i n t h a t s p e c i f i c case t o o l a r g e t o e a s i l y f o r m i n 12-membered r i n g z e o l i t e s which do n o t possess l a r g e cages. VGO. As shown on f i g u r e 4, t h e s e l e c t i v i t i e s i n VGO c o n v e r s i o n o f H-Beta and
H-Omega v e r y s i g n i f i c a n t l y d i f f e r f r o m t h o s e H-Omega produce v e r y h i g h y i e l d s o f
light
of
gases,
modified H-Y. the
H-Beta
and
s e l e c t i v i t y towards
g a s o l i n e b e i n g r a t n e r l o w . However, H-Beta l e a d s t o a l o w coke l e v e l w h i l e t h e r e v e r s e i s t r u e f o r H-Omega.
From t h e
l o w hydrogen
transfer
tendency
of
H-Omega, one would have p r e d i c t e d a reduced coke f o r m a t i o n , which i s o b v i o u s l y not t r u e .
I n fact,
previously stressed,
i n VGO c o n v e r s i o n over
these
solids,
as
it
has been
a c c e s s i b i l i t y c o n s i d e r a t i o n s a r e o f p r i m a r y importance
which means t h a t performances
o b t a i n e d w i t h model
molecules could not
be
d i r e c t l y t r a n s f e d t o r e a l f e e d . The h i g h s e l e c t i v i t y f o r gases, f o r i n s t a n c e ,
i s l i k e l y t o be due t o an easy o v e r c r a c k i n g o f t h e g a s o l i n e f r a c t i o n i n s i d e t h e n o t s u f f i c i e n t l y open channel system o f H-Beta and H-Omega. CONCLUSION The post-steaming a c i d l e a c h i n g has been shown t o p l a y a major r o l e i n t h e c a t a l y t i c performances o f H-Y,
H-Beta and H-Omega s i n c e i t can i n c r e a s e o r
125
decrease t h e c o n v e r s i o n l e v e l s i n cyclohexene as w e l l as i n VGO t r a n s f o r m a t i o n . I n t h e case o f v e r y open s t r u c t u r e s such as H-Y,
the positive effect o f a
s e l e c t i v e l e a c h i n g m a i n l y r e s u l t s f r o m an i n c r e a s e o f t h e number o f s t r o n g a c i d s i t e s ( e l i m i n a t i o n o f p o i s o n i n g aluminium s p e c i e s ) , w h i l e f o r s t r u c t u r e s w i t h a monodimensional porous system such as H-Omega t h e a c c e s s i b i l i t y o f s i t e s i s o f predominant importance ( i n c r e a s e i n t h e microporous volume). When a model t e s t r e a c t i o n i s employed, a q u a l i t a t i v e r a n k i n g o f t h e s o l i d s a c c o r d i n g t o t h e i r a c i d i c p r o p e r t i e s i s o b t a i n e d . I n t h a t r e g a r d , t h e c a t a l y t i c performances o f H-Beta a r e b e t t e r t h a n t h o s e o f H-Y and H-Omega. However, t h i s r a n k i n g i s no l o n g e r t r u e f o r VGO conversion.
For such a t r a n s f o r m a t i o n o f heavy molecules
a c c e s s i b i l i t y c o n s i d e r a t i o n s have t o be t a k e n i n t o account, which means t h a n t h e most open s t r u c t u r e ,
namely H-Y,
leads t o t h e best
performances.
The
performances o f H-Y can be s i g n i f i c a n t l y improved when t h e a c i d i c p r o p e r t i e s o f steamed H-Y a r e o p t i m i z e d t h r o u g h a s e l e c t i v e a c i d l e a c h i n g . B I BLI OGRAPHY 1 . J . Scherzer, ACS Symposium S e r i e s 248, (19831, 157-200. 2. J.S. Magee, W.E. Cormier and G.M. m t e r m a n , K a t a l i s t i k s ' 6 t h Annual F l u i d Cat. Cracking Symposium, Munich, Germany (19851, May 22-23. 3. Grupo Especializado de Catalisis, Madrid, Spain (19871, September 28-October 1. Winthrop, European P a t e n t A p p l i c a t i o n , (19871, 4. E.G. Campbell and P.A. n"243629. 5. F. Raatz and Ch. M a r c i l l y , European P a t e n t A p p l i c a t i o n , (19861, n o 206871. 6. A. Corma, V . Fornes, J.B. Monton and A.V. O r c h i l l e s , J o u r n a l o f C a t a l y s i s 107, (1987) 288-295. 7. E C o r m a , V. Fornes, F. Melo and J . Perez-Pariente, Symposium on advances i n FCC, American Chemical S o c i e t y , New Orleans meeting, (19871, August 30 September 4. 8. A. Corma, E. H e r r e r o , A. M a r t i n e z and J. P r i e t o , Symposium on advances i n FCC, American Chemical S o c i e t y , New Orleans meeting, (19871, August 30 September 4. 9. A. Corma, V. Fornes, A. M a r t i n e z , F. Melo and 0. P a l l o t a , Symposium on " I n n o v a t i o n i n Z e o l i t e M a t e r i a l s Science", Stud. S u r f . S c i . Cat., Vol 37, (19881, 495. 10. E. J a c q u i n o t , PhD, ENSPM, R u e i l Malmaison, France, i n p r e p a r a t i o n . 11. M.M. J . Treacy and J.M. Newsam, Nature, 332, (19881, March 17. 12. A. Macedo, PhD, ENSPM, R u e i l M a l m a i s o r France, (19881 and r e f e r e n c e s there in. 13. R. Beaumont and D. Barthomeuf, J o u r n a l o f C a t a l y s i s , 26, (19721, 218-225. 14. D. Barthomeuf, M a t e r i a l s Chemistry and P h y s i c s , ( l 3 8 7 1 , 49. 15. M. Maache and J.C. L a v a l l e y , i n p r e p a r a t i o n . 16. E. J a c q u i n o t , A . Mendes, F. Raatz, Ch. M a r c i l l y , F.R. R i b e i r o and J. Caiero, a r t i c l e s u b m i t t e d f o r p u b l i c a t i o n . 17. L.A. Pine, P.J. Maher and W.A. Wachter, J o u r n a l o f C a t a l y s i s , (19841, 466-476. 18. R.E. R i t t e r , J.E. C r e i g h t o n , T.G. Roberie, D.S. Chin, C.C. Wear, p r e s e n t e d a t NPRA Annual Meeting, Los Angeles, paper AM 86-45, (19861, March 23. Lohse, G. E n g e l h a r d t and V. Patzelova, 19. H. F i c h t n e r - S c h m i t t l e r , U. Cryst-Res-Tech. 1 1 , (19841, ( 1 1 . 20. A. Macedo, F. RaTtz, R. B o u l e t , J.C. L a v a l l e y and A. Janin, Symposium on " I n n o v a t i o n i n Z e o l i t e M a t e r i a l s Science", Stud. S u r f . S c i . Cat, Vol 37, (19881, 375.
11,
g,
EVALUATION OF NON-COMMERCIAL MODIFIED LARGE PORE ZEOLITES I N FCC E. JACQUINOT, F. RAATZ, A. MACEDO and Ch. MARCILLY
INSTITUT FRANCAIS DU PETROLE, 1-4 r u e du B o i s Preau BP311, 92506 Ruei 1 Malmai son, France ABSTRACT The c a t a l y t i c performances o f H-Y, H-Beta and H-Omega prepared by a steaming-acid l e a c h i n g procedure, have been e v a l u a t e d i n cyclohexene and i n Vacuum Gas O i l ( V G O ) t r a n s f o r m a t i o n . The l e a c h i n g i s a key s t e p , s i n c e depending on t h e o p e r a t i n g c o n d i t i o n s i t can decrease o r i n c r e a s e t h e c o n v e r s i o n l e v e l s . I n cyclohexene t r a n s f o r m a t i o n , t h e a c i d i t y o f t h e s o l i d s : controls the activity and the following ranking is obtained H-Beta)H-Y)H-Omega. I n c o n t r a s t , i n VGO c o n v e r s i o n a c c e s s i b i l i t y o f t h e a c i d c e n t e r s has t o be taken i n t o account which means t h a t H-Y l e a d s t o t h e b e s t r e s u l t s . Moreover, o p t i m i z a t i o n o f t h e a c i d i c p r o p e r t i e s o f H - Y t h r o u g h a s e l e c t i v e a c i d l e a c h i n g improves s i g n i f i c a n t l y t h e c o n v e r s i o n l e v e l s . INTRODUCTION
Y z e o l i t e s m o d i f i e d by two main techniques, (framework
and are
of
or
isomorphous
commercial
FCC
substitution
treatment
(framework
a c t i v e component
only)
hydrothermal
o v e r a l l dealumination), containing o r not containing r a r e earth cations, the
dealumination
i.e.
catalysts
(1,
2,
3).
Indeed,
a
tremendous amount o f d a t a i s a v a i l a b l e i n t h e l i t e r a t u r e on t h e b e h a v i o r o f t h e s e sol i d s . However, o t h e r l a r g e - p o r e z e o l i t e phases a r e p o t e n t i a l c a n d i d a t e s f o r t h i s a p p l i c a t i o n . Depending on whether o r n o t t h e aim i s t o f u l l y r e p l a c e t h e a c t u a l a c t i v e component, and e x c l u d i n g any p r i c e c o n s t r a i n t , two t y p e s o f s o l i d s c o u l d be a p r i o r i considered.
As an a l t e r n a t i v e t o t h e a c t u a l main
a c t i v e component, o n l y l a r g e - p o r e z e o l i t e s w i t h m u l t i d i m e n s i o n a l porous systems should be c o n s i d e r e d as p r o m i s i n g c a n d i d a t e s . zeolite
itself,
(hydrothermal structures
but
submitted
treatment
such
as
followed
ZSM-20
and
to by
a
I n t h i s c a t e g o r y we
conventional acid
zeolite
Beta
z e o l i t e s w i t h monodimensional porous systems,
overall
leaching),
(4).
and
find Y
dealumination other
Deal umi n a t e d
such as Omega and L,
modified
1 arge-pore a r e more
l i k e l y t o be o n l y u s e f u l as secondary a c t i v e components ( 5 ) . L i t t l e i s known about t h e c a t a l y t i c performances i n FCC o f t h e p o t e n t i a l c a n d i d a t e s mentioned above ( 4 , 51, and most o f t h e s t u d i e s a l r e a d y p u b l i s h e d have been devoted t o n o n - m o d i f i e d Beta z e o l i t e s . R e c e n t l y , A.
Corma e t a l .
( 6 - 9 ) have e v a l u a t e d t h e c r a c k i n g p r o p e r t i e s o f Beta z e o l i t e s w i t h v a r i o u s
Si/A1
ratios,
and o f c o n v e n t i o n a l l y dealuminated Y z e o l i t e s .
Two i m p o r t a n t
c o n c l u s i o n s emerge f r o m t h i s work : i ) a t l e a s t f o r n-heptane c r a c k i n g H-Beta i s superior t o H-Y,
and i i )a m i l d a c i d l e a c h i n g o f steamed H-Y g i v e s r i s e t o a
116
decrease o f t h e a c t i v i t y i n g a s - o i l c r a c k i n g . We aim h e r e t o e v a l u a t e t h e performances,
i n a model t e s t r e a c t i o n and i n
t h e c r a c k i n g o f a VGO o f z e o l i t i c phases, which a r e o f p o t e n t i a l i n t e r e s t i n FCC. Cyclohexene has been chosen as a t e s t molecule,
since i t allows a r a p i d
e v a l u a t i o n of t h e hydrogen t r a n s f e r tendency o f t h e c a t a l y s t s , i . e .
formation
o f benzene, cyclohexane and m e t h y l c y c l o p e n t a n e r a t h e r t h a n m e t h y l c y c l o p e n t e n e . I n a f i r s t approach, we w i l l
r e s t r i c t ourselves t o t h e study o f t h e f r e s h
c a t a l y s t s , which means t h a t h y d r o t h e r m a l a g i n g and p o i s o n i n g by metal w i l l n o t be c o n s i d e r e d h e r e .
EXPERIMENT SOL I D S S t a r t i n g f r o m low-sodium ( S i / A l = 14.0)
(NaC400 ppm)
and NH4-Omega ( S i / A l
= 2.91,
NH4-Y
(Si/Al
=
2.81,
dealuminated s o l i d s
NH4-Beta have been
prepared by a t w o - s t e p procedure, i.e. hydrothermal t r e a t m e n t (100% steam) a t v a r i o u s temperatures
(823 t o 1123 K )
s o l u t i o n a t 373 K ( 1 and 3N f o r H-Y,
f o l l o w e d by an a c i d l e a c h i n g i n HC1 1N f o r H-Beta,
0.5N f o r H-Omega). The
sol i d s were c h a r a c t e r i z e d a t each s t e p o f t h e p r e p a r a t i o n procedures by chemical a n a l y s i s , Further d e t a i l s
XRD,
29 S i
MASNMR,
I R spectroscopy
and
N2
adsorption.
on t h e d e a l u m i n a t i o n procedures and t h e c h a r a c t e r i z a t i o n
t e c h n i q u e s can be found i n r e f . ( 1 0 ) . The o r i g i n a l Y z e o l i t e was p r o v i d e d by Zeocat (Z-FlOO),
w h i l e Omega and Beta were s y n t h e s i z e d by J.L.
GUTH e t a1
( E c o l e N a t i o n a l e S u p c r i e u r e de Chimie, Mulhouse, F r a n c e ) . CATALYTIC TESTS MODEL MOLECULE. Cyclohexene t r a n s f o r m a t i o n was s t u d i e d u s i n g a Geomecanique m i c r o t e s t u n i t a l l o w i n g v e r y l o w c o n t a c t t i m e s and a n a l y s i s o f t h e p r o d u c t s a t v a r i o u s t i m e s on stream. The t e s t s were conducted a t atmospheric p r e s s u r e under 5 t h e f o l l o w i n g c o n d i t i o n s : cyclohexene p a r t i a l p r e s s u r e 0 . 2 0 ~ 1 0 Pa, c a r r i e r gas n i t r o g e n , c o n t a c t t i m e s i n t h e 0.25 t o 3.0 s range, t e m p e r a t u r e 643 K, sampling a t d i f f e r e n t t i m e s on s t r e a m ( 2 , 5, 8, 11 m i n ) . VACUUM GAS OIL. Aramco 150 c r a c k i n g was s t u d i e d u s i n g a MAT u n i t a t 755 K under
atmospheric p r e s s u r e . W h i l e k e e p i n g a c o n s t a n t i n j e c t i o n t i m e ( 7 5 s ) , d i f f e r e n t catalyst-to-oil
weight r a t i o s were used (1.2
t o 5.3)
i n order t o vary t h e
c o n v e r s i o n l e v e l s . P r i o r t o t h e MAT t e s t s , t h e z e o l i t e s (20 % i n w e i g h t ) were blended w i t h an aged s i l i c a - a l u m i n a m a t r i x . RESULTS The main physicochemical
characteristics
of
t h e modified zeolites
are
reported i n table 1 together with the operating conditions applied f o r the d e a l u m i n a t i o n procedures.
117 TABLE 1 a ) Chemical and t e x t u r a l c h a r a c t e r i s t i c s o f dealuminated Y z e o l i t e s . * C a l c u l a t e d f r o m t h e u n i t c e l l parameter, u s i n g t h e c o r r e l a t i o n g i v e n i n r e f . (19) ** XRD c r i s t a l l i n i t y , t h e o r i g i n a l NH4-Y i s t a k e n as a r e f e r e n c e . P r e p a r a t i o n procedure Steaming 823 K HCL 1 N HC1 3N Steaming 873 K HC1 1N HC1 3N
::: :::
57
37
Steaming 9 / 3 K HC1 1N HC1 3N
K
% DX**
(Si/Al
8I 4
% 69 % 0 %
9
00
1 0 80
%
72 %
11
>loo
69 %
42:;
T
85 % 79 % 93 %
::;
2 4
44
21 42
93 % 78 % 94 %
1:*8 74
> 50 > 50 > 50
91 % 87 % 91 %
43
Steaming 1043 K HC1 1N HC1 3N Steaming 1113 HC1 1N HC1 3N
( S i /A1 ) overall
16 41
b ) Chemical and t e x t u r a l c h a r a c t e r i s t i c s o f dealuminated B e t a z e o l i t e s I
I I I I I I
I I I I I I I
1
P r e p a r a t i o n procedure
( Si /A1
Steaming 873 K HC1 1N
1 8
Steaming 973 K HC1 1 N
1 4
Steaming 1073 K HC1 1 N Steaming 1123 K HC1 1 N
overall
62
53
14 29
7 4 19
118 c ) Chemical and t e x t u r a l c h a r a c t e r i s t i c s o f dealuminated Omega z e o l i t e s . * 29Si RMN s i m u l a t i o n a c c o r d i n g t o r e f ( 2 0 ) . 0 The c parameter i s n o t r e p o r t e d s i n c e i t o n l y v a r i e s between 7,51 and 7,55 A . ** XRD c r i s t a l l i n i t y , t h e o r i g i n a l NH4-0mega i s t a k e n as a r e f e r e n c e . ( S i / A l I V ) *% DX**
l p r e p a r a t i o n procedure
I I I I I I
I
I I I
I
I I I
a
(i)
Steaming 923 K HC1 0,5 N
T 2 - r l-Kl-31 1 10 94 % ia,io
Steaming 913 K HC1 0,5 N
1 8 85% ia 90 %
Steaming 1013 K HC1 0,5 N
3 068% 18;ar
Steaming 1123 K HC1 0,5 N
loo66% 77-38-
As
expected,
temperatures
70 %
30
100
whatever
leads
to
a
the
structure,
dealumination
18,Ol
18,OO
66 %
the
of
m 18,06
the
steaming framework.
at The
increasing resulting
extra-framework species cause a r e d u c t i o n of t h e N2 a d s o r p t i o n c a p a c i t y o f H-Y and H-Beta z e o l i t e s which do have a m u l t i d i m e n s i o n a l porous system (111, w h i l e a complete b l o c k i n g o f t h e monodimensional porous system o f H-Omega o c c u r s . Concerning t h e e f f e c t o f t h e p o s t - s t e a m i n g a c i d l e a c h i n g two s i t u a t i o n s have t o be c o n s i d e r e d : i ) s e l e c t i v e a c i d l e a c h i n g g i v i n g r i s e t o an e l i m i n a t i o n o f extra-framework species w i t h o u t any f u r t h e r framework d e a l u m i n a t i o n ( H - Y
and
H-Omega
ii)
treated
in
1N
and
0.5N
HC1
solutions,
respectively),
and
n o n - s e l e c t i v e a c i d l e a c h i n g r e s u l t i n g i n a s e v e r e framework d e a l u m i n a t i o n (H-Y and H-Beta t r e a t e d i n 3N and 1N HC1 s o l u t i o n s , r e s p e c t i v e l y ) . I n c o n t r a s t t o t h e steamed H - Y and H-Omega,
steamed H-Beta appeared t o be
very s e n s i t i v e t o a c i d l e a c h i n g , s i n c e even a m i l d l e a c h i n g l e a d s t o v e r y h i g h o v e r a l l S i / A 1 r a t i o s . T h i s i s l i k e l y t o be due t o t h e s i g n i f i c a n t amount o f s t r u c t u r a l defects present i n t h i s z e o l i t e a f t e r t h e synthesis. Without going i n t o t o o much d e t a i l , i t s h o u l d be n o t e d t h a t most of t h e s o l i d s have a h i g h degree o f c r y s t a l l i n i t y , and t h a t f o r each s t r u c t u r e a wide range o f framework and o v e r a l l S i / A 1
r a t i o s a r e covered.
performances o f t h r e e v e r y framework and o v e r a l l S i / A l
important
Thus,
t h e i n f l u e n c e on t h e c a t a l y t i c
parameters namely
the
structure,
the
r a t i o s o f t h e s o l i d s can be s t u d i e d . Since i t i s
n o t always p o s s i b l e t o d e t e r m i n e w i t h good accuracy t h e framework S i / A l r a t i o
o f a l l t h e s o l i d s (H-Beta and a c i d leached s o l i d s c o u l d c o n t a i n many s t r u c t u r a l d e f e c t s ) , we have chosen t o r e p o r t t h e c o n v e r s i o n l e v e l s versus t h e steaming temperature o f t h e o r i g i n a l NH4-form, acid leaching.
even f o r s o l i d s s u b m i t t e d t o a subsequent
119
HY-ZEOLITES
A f t e r steaming, t h e cyclohexene c o n v e r s i o n p r e s e n t s a f l a t optimum versus t h e temperature employed f o r t h e steaming t r e a t m e n t Si/Al
(i.e.
versus t h e framework
r a t i o o f t h e s o l i d s , see t a b l e 1 ) and s e r i o u s l y decreases f o r steaming
temperatures h i g h e r t h a n about 900 K ( f i g u r e 1 ) . The most i m p o r t a n t p o i n t which i s evidenced on f i g u r e 1 concerns t h e e f f e c t o f t h e a c i d l e a c h i n g . Depending on whether o r n o t t h e l e a c h i n g i s s e l e c t i v e ( e x t r a - f r a m e w o r k A1 e x t r a c t i o n w i t h o u t any f u r t h e r framework d e a l u m i n a t i o n , t a b l e 11, an i n c r e a s e o r a decrease o f t h e cyclohexene c o n v e r s i o n l e v e l s i s observed. The same e f f e c t s a r e o b t a i n e d i n VGO transformation ( f i g u r e 2 ) . H-BETA ZEOLITES
Steaming a t i n c r e a s i n g temperatures l e a d s t o a monotonic decrease o f t h e cyclohexene steaming,
conversion
levels
(figure
1).
I t should
be n o t e d t h a t
after
t h e cyclohexene c o n v e r s i o n l e v e l s o f H-Beta a r e h i g h e r t h a n t h o s e
o b t a i n e d f o r H-Y.
The m i l d p o s t - s t e a m i n g a c i d l e a c h i n g r e s u l t s i n a severe
r e d u c t i o n o f t h e s e c o n v e r s i o n l e v e l s , whereas t h e same t r e a t m e n t has a p o s i t i v e e f f e c t f o r H-Y ( f i g u r e 1 ) . As i n t h e case of cyclohexene,
t h e VGO c o n v e r s i o n i s s t r o n g l y a f f e c t e d by
steaming ( f i g u r e 2 ) b u t shows a d i f f e r e n t b e h a v i o r a f t e r a c i d l e a c h i n g . The l a t t e r t r e a t m e n t g i v e s r i s e t o a small i n c r e a s e o f t h e VGO c o n v e r s i o n l e v e l s ( f i g u r e 21, which should be compared w i t h t h e n e g a t i v e e f f e c t evidenced f o r t h e cyclohexene t r a n s f o r m a t i o n ( f i g u r e 1 ) . Moreover, i n VGO c o n v e r s i o n whatever t h e p r e p a r a t i o n procedures
we
used,
H-Beta
gives
lower
performances
t h a n H-Y
(figure 2 ) .
H-OMEGA ZEOLITES
C o n t r a r y t o H-Y and H-Beta,
v e r y low cyclohexene c o n v e r s i o n l e v e l s a r e
o b t a i n e d f o r steamed H-Omega whatever t h e steaming t e m p e r a t u r e ( f i g u r e 1 ) . For t h e s e s o l i d s even a v e r y m i l d and non-optimized a c i d l e a c h i n g l e a d s t o a severe increase o f the conversion l e v e l s . Similarly,
t h e VGO c o n v e r s i o n
level
after
steaming
is
very
low
and
i n c r e a s e s v e r y s i g n i f i c a n t l y a f t e r t h e a c i d l e a c h i n g ( T a b l e 2). However, w h i l e for
the
acid-leached
H-Omega
the
conversion
levels
in
cyclohexene
i t i s no l o n g e r t h e case f o r t h e VGO t r a n s f o r m a t i o n f o r which H-Y appears t o be s u p e r i o r t o H-Omega ( f i g u r e s 1, Table 2 ) .
t r a n s f o r m a t i o n a r e v e r y c l o s e t o t h o s e o f H-Y,
120
75
H-Y
923
STEAMING TEMPERATURE IKI
-7
01
823
1w
1023
873
1123
1
I
261
823
973
1073
I 973
1073
STEAMING TEMPERATURE IK
ti-BETA
I
I
1 on
923
STEAMING TEMPERATURE (Kl H-OMEGA
I
873
1123
I
1
STEAMING TEMPERATURE ( K 1
F i g u r e 2 : Conversion o f VGO versus t h e steaming t e m p e r a t u r e (,steamed + ; steamed and a c i d leached + HC1 1N ; + HC1 3N) R e a c t i o n t e m p e r a t u r e = 755 K ; i n j e c t i o n t i m e = 75 s ; C/O = 3 ; WHSV = 16 h-1 TABLE 2 MAT c o n v e r s i o n and y i e l d s of d i f f e r e n t products o f gas-oil cracking f o r H -Omeg a. Preparation procedure
MAT conv. (wt.%)
Sti;!,"g
25.7
HC1 0.5N
41.2
STEAMING TEMPERATURE (Kl
Fi ure 1 Conversion l e v e l o f c y c l o b e i s u s t h e steaming t e m p e r a t u r e (steamed + ; steamed and a c i d leached +HC1 0,5N ; + HC1 1N ; +HC1 3N) Reaction t e m p e r a t u r e = 643K ; c o n t a c t t i m e = 0,5 s ; t i m e on stream = 2 min.
Gasoline yield (wt.%)
19,8
Gas
;% ! (wt.%) 5.1 14.0
Coke yield (wt.")
1.4 6.0
121
DISCUSSION
CONVERSION. Obviously, t h e framework d e a l u m i n a t i o n o c u r r i n g i n t h e c o u r s e o f t h e steaming procedure i s r e s p o n s i b l e f o r t h e decrease o f t h e cyclohexene and VGO c o n v e r s i o n l e v e l s .
However,
s e v e r a l i m p o r t a n t remarks have t o be made.
F i r s t , a t l e a s t i n t h e case o f H-Y t h e decrease i s non-monotonic,
i.e a f l a t
optimum i s observed near 900 K . Since i t has been shown t h a t t h e s t r e n g t h o f t h e framework a c i d s i t e s i n H - Y i n c r e a s e s w i t h t h e d e a l u m i n a t i o n l e v e l (12,131, t h i s optimum i s l i k e l y t o r e s u l t f r o m two c o m p e t i t i v e e f f e c t s , i . e r e d u c t i o n o f t h e number o f s i t e s and i n c r e a s e o f t h e i r a c i d s t r e n g t h . According t o t h e model advanced by Barthomeuf (141,
such an optimum i s n o t observed f o r z e o l i t e s ,
which a r e s y n t h e s i z e d w i t h t o o h i g h an i n i t i a l
Si/A1
ratio.
This
i s for
example, t h e case w i t h H-Beta. Framework d e a l u m i n a t i o n c o n t r i b u t e s a l s o t o t h e r e d u c t i o n o f t h e c o n v e r s i o n l e v e l s f o r H-Omega, b u t f o r t h i s s t r u c t u r e b l o c k i n g o f t h e channels by extra-framework species p l a y s t h e m a j o r r o l e ( T a b l e 1 ) . T h i s b e h a v i o r i s l i k e l y t o be t y p i c a l o f z e o l i t e s s y n t h e s i z e d w i t h low S i / A l r a t i o s and possessing an u n i d i m e n s i o n a l porous system. The most i m p o r t a n t p o i n t evidenced i n t h i s work i s l i k e l y t o concern t h e e f f e c t o f t h e post-steaming a c i d l e a c h i n g , which c o u l d have a n e g a t i v e b u t a l s o a s t r o n g l y p o s i t i v e i n f l u e n c e on t h e c o n v e r s i o n l e v e l s . Focussing on t h e d a t a p r e s e n t e d here, i t appears t h a t s e l e c t i v e a c i d l e a c h i n g , which o n l y e x t r a c t s extra-framework aluminium species, w i l l l e a d t o an i n c r e a s e o f t h e c o n v e r s i o n levels. giving
The r e v e r s e i s t r u e f o r n o n - s e l e c t i v e rise to
a further
framework
r a t i o n a l i z e d ? Since t h e a c i d accessibility
acid treatments,
dealumination.
How can
leaching could a f f e c t
o f the a c t i v e acid centers,
two
types
c o n s i d e r e d : i ) those possessing a m u l t i d i m e n s i o n a l
the of
i.e.
those
such
behavior
acidity
and t h e
solids
s h o u l d be
porous system,
and ii)
those h a v i n g a monodimensional porous s t r u c t u r e . For s o l i d s w i t h a m u l t i d i m e n s i o n a l porous system ( Y , b e t a ) , o n l y a l i m i t e d r e d u c t i o n o f t h e m i c r o p o r e volume occurs upon steaming, volume i s n o t i n c r e a s e d v e r y s i g n i f i c a n t l y
and t h e m i c r o p o r e
by l e a c h i n g .
Thus,
the positive
e f f e c t on t h e c o n v e r s i o n l e v e l s o f s e l e c t i v e a c i d l e a c h i n g (H-Y t r e a t e d i n 1N HC1 s o l u t i o n ) i s more l i k e l y t o be due t o an i n c r e a s e i n t h e a c i d i c p r o p e r t i e s
o f the s o l i d s r a t h e r than t o a b e t t e r a c c e s s i b i l i t y o f t h e a c i d s i t e s . statement i s s t r o n g l y supported by p r e v i o u s work which has shown, complementary p h y s i c a l techniques,
This
by v a r i o u s
t h a t an i n c r e a s e i n t h e number o f s t r o n g
framework s i t e s occurs t h r o u g h t h e e l i m i n a t i o n , by s e l e c t i v e a c i d l e a c h i n g , o f poisoning
extra-framework
aluminium c a t i o n s
formed
in
the
course
of
the
steaming procedure ( 1 2 ) . Extra-framework aluminium s p e c i e s which e x h i b i t a c i d i c p r o p e r t i e s a r e a l s o e l i m i n a t e d by m i l d l e a c h i n g .
However,
these s i t e s o n l y
possess a moderate Bronsted a c i d i t y ( 1 2 ) and t h u s a r e n o t l i k e l y t o p l a y t h e
122 m a j o r r o l e i n t h e c a t a l y t i c performances o f t h e s o l i d s under t h e c o n d i t i o n s we It s h o u l d be s t r e s s e d t h a t t o b e t t e r r e v e a l t h e b e n e f i t o f a
have employed.
s e l e c t i v e l e a c h i n g o f H-Y i n VGO c o n v e r s i o n , t h e s o l i d has t o be t e s t e d w i t h an a c t i v e m a t r i x so t h a t molecules which a r e t o o l a r g e t o e a s i l y e n t e r t h e z e o l i t e crystals
c o u l d r e a c t more
rapidly.
Otherwise t h e
extra-framework
material
l o c a t e d a t t h e e x t e r n a l s u r f a c e o f t h e z e o l i t e s c r y s t a l would h e l p i n t h e t r a n s f o r m a t i o n o f such heavy molecules,
and t h e s e l e c t i v e a c i d l e a c h i n g would
p o s s i b l y have a n e g a t i v e e f f e c t (8, 9). T h i s p o i n t remains t o be c o n f i r m e d . On t h e
contrary
i n the
case
of
Omega
for
which
the
unidimensional
microporous system i s n e a r l y c o m p l e t e l y b l o c k e d a f t e r t h e steaming s t e p ,
the
p o s i t i v e e f f e c t o f a s e l e c t i v e post-steaming a c i d leaching c l e a r l y r e s u l t s from t h e e l i m i n a t i o n o f t h e extra-framework m a t e r i a l s located i n t h e pores. This does n o t mean t h a t t h e a c i d i c p r o p e r t i e s of t h e framework a r e n o t
m o d i f i e d by
l e a c h i n g , b u t t h e s e changes i n a c c e s s i b i l i t y a r e h e r e predominant. C o n s i d e r i n g now n o n - s e l e c t i v e a c i d l e a c h i n g (H-Y and H-Beta t r e a t e d i n 3N and 1N HC1 s o l u t i o n s r e s p e c t i v e l y ) , i t i s c l e a r t h a t framework d e a l u m i n a t i o n o c c u r r i n g as a r e s u l t o f t h i s t r e a t m e n t i s r e s p o n s i b l e f o r t h e r e d u c t i o n o f t h e conversion
levels.
Indeed,
as
shown
by
physical
techniques,
the
acidic
p r o p e r t i e s o f s o l i d s s u b m i t t e d t o a n o n - s e l e c t i v e l e a c h i n g a r e v e r y low ( 1 2 ) . However,
H-Beta d i f f e r s f r o m H-Y,
since non-selective
leaching leads t o a
s t r o n g decrease o f t h e cyclohexene c o n v e r s i o n , w h i l e a small
increase o f t h e
VGO c o n v e r s i o n occurs. To e x p l a i n such b e h a v i o r t h e r o l e o f a c c e s s i b i l i t y has t o be t a k e n i n t o account. Cyclohexene i s a s m a l l m o l e c u l e f o r which s t e r i c c o n s t r a i n t s a r e n o t v e r y i m p o r t a n t , t h u s i t m a i n l y probes t h e a c i d i c p r o p e r t i e s o f t h e s o l i d s . From t h a t p o i n t of
view,
t h e f o l l o w i n g r a n k i n g i s o b t a i n e d : steamed H-Beta > steamed
H-Yxteamed + a c i d leached H-Omega. T h i s r a n k i n g i s i n q u a l i t a t i v e agreement w i t h t h e a c i d i c p r o p e r t i e s o f t h e s o l i d s as d e t e r m i n e d by p h y s i c a l t e c h n i q u e s , and indeed s t r o n g a c i d s i t e s a r e p r e s e n t i n steamed H-Beta ( 1 5 ) . On t h e o t h e r hand i n VGO c o n v e r s i o n s t e r i c c o n s t r a i n t s cannot
be n e g l e c t e d .
T h i s would
suggest t h a t t h e m u l t i d i m e n s i o n a l channel system o f H-Beta i s n o t as a c c e s s i b l e f o r l a r g e molecules as t h e microporous system o f H - Y .
I n o t h e r words, i n a v e r y
f i r s t approximation, t h e a c c e s s i b i l i t y of t h e a c i d s i t e s r a t h e r t h a n t h e i r a c i d s t r e n g t h c o n t r o l s t h e VGO c o n v e r s i o n
l e v e l s o v e r H-Beta.
This
proposal
is
s u p p o r t e d by a r e c e n t work ( 7 1 , a c c o r d i n g t o which t h e gas o i l c o n v e r s i o n o v e r n o n - m o d i f i e d H-Beta does n o t depend much on i t s Si/A1 r a t i o ,
and by t h e n i c e
s t r u c t u r a l s t u d y o f TREACY e t a l . ( 1 1 ) which s t r o n g l y suggests t h a t t h e open s t r u c t u r e of
z e o l i t e Beta i s
accessibility
considerations
likely would
to
contain
structural
also
explain
why
defects.
acid-leached
These H-Omega
p r e s e n t r a t h e r low VGO c o n v e r s i o n l e v e l s , w h i l e t h e i r cyclohexene c o n v e r s i o n
123
-MAT CONVERSION (wt.%)
CVCLOHEXENE CONVERSION lmol.%l
15 COKE
10 s . c
I
-9 3
Y
>
5
0 CVCLOHEXENE CONVERSION lmol.%J
25
35
45
55
MAT CONVERSION Iw1.X)
STEAMED (923 I0 AND ACID LEACHED ( 0.5 N) H-OMEGA 0
CVCLOHEXENE CONVERSION (mol.%)
F i g u r e 3 : Comparison o f s e l e c t i v i t y curves f o r cyclohexene t r a n s f o r m a t i o n over H-Y, H-Beta and H-Omeaa z e o l i t e s ( I s o m e r i s a t i o n + ; Hydrogen t r a n s f e r + )
F i g u r e 4 : Comparison o f s e l e c t i v i t y curves f o r VGO c r a c k i n g on t h r e e z e o l i t e s = (steamed H - Y (873K) -c : steamed (97310 and a c i d leached (1Nj H-Beta +; steamed (92310 and a c i d leached (0.5N) H-Omega c 1.
124 l e v e l s a r e n o t t o o f a r f r o m t h o s e o f H-Y. SELECTIVITY CYCLOHEXENE. As
described
i n detail
cyclohexene t r a n s f o r m a t i o n o f
elsewhere
(161,
are
m o d i f i e d H-Y
framework Si/A1 r a t i o . H - Y w i t h a u n i t c e l l parameter f a v o r s hydrogen t r a n s f e r r e a c t i o n s (cyclohexane,
the
mainly
selectivities
determined
by
in its
h i g h e r t h a n 24.27
benzene,
methylcyclopentane
formation) r a t h e r than isomerisation (methylcyclopentene..),
while H-Y w i t h a
0
u n i t c e l l parameter l o w e r t h a n 24.27 A i s c h a r a c t e r i z e d by v e r y l o w hydrogen t r a n s f e r s e l e c t i v i t i e s (17, 1 8 ) ( f i g u r e 3 ) . T h i s b e h a v i o r c o u l d be r a t i o n a l i z e d as f o l l o w s . Depending on whether o r n o t t h e s o l i d s c o n t a i n more t h a n about one 0
A1 per supercage ( u n i t c e l l parameter lower o r h i g h e r t h a n about 24.27 A), t h e y
w i l l o r w i l l n o t promote b i m o l e c u l a r r e a c t i o n s such as hydrogen t r a n s f e r . It i s now i m p o r t a n t t o determine how t h e s e l e c t i v i t i e s o f m o d i f i e d H-Beta and H-Omega towards hydrogen t r a n s f e r compare w i t h t h o s e o f m o d i f i e d H-Y.
Considering t h e
s e l e c t i v i t y diagrams r e p o r t e d i n f i g u r e 3, i t appears t h a t t h e s e l e c t i v i t i e s o f H-Beta and H-Omega w i t h r a t h e r low-framework S i / A l t h o s e o f h i g h l y dealuminated H-Y.
r a t i o s are very s i m i l a r t o
T h i s would mean t h a t H-Beta and H-Omega do
n o t much promote b i m o l e c u l a r r e a c t i o n s . I t i s n o t c l e a r a t t h e moment whether such b e h a v i o r d e r i v e s f r o m s t e r i c c o n s t r a i n t s (no cages a r e p r e s e n t i n Omega and i n B e t a ) , o r f r o m a s p e c i f i c A1 s i t i n g . Since non dealuminated H-Mordenite i s a l s o c h a r a c t e r i z e d by a l o w hydrogen t r a n s f e r s e l e c t i v i t y i n cyclohexene c o n v e r s i o n (101, i t i s l i k e l y t h a t s t e r i c c o n s t r a i n t s a r e r e s p o n s i b l e f o r t h e low hydrogen t r a n s f e r
s e l e c t i v i t y o f H-Beta and H-Omega.
The
intermediate
s p e c i e s would be i n t h a t s p e c i f i c case t o o l a r g e t o e a s i l y f o r m i n 12-membered r i n g z e o l i t e s which do n o t possess l a r g e cages. VGO. As shown on f i g u r e 4, t h e s e l e c t i v i t i e s i n VGO c o n v e r s i o n o f H-Beta and
H-Omega v e r y s i g n i f i c a n t l y d i f f e r f r o m t h o s e H-Omega produce v e r y h i g h y i e l d s o f
light
of
gases,
modified H-Y. the
H-Beta
and
s e l e c t i v i t y towards
g a s o l i n e b e i n g r a t n e r l o w . However, H-Beta l e a d s t o a l o w coke l e v e l w h i l e t h e r e v e r s e i s t r u e f o r H-Omega.
From t h e
l o w hydrogen
transfer
tendency
of
H-Omega, one would have p r e d i c t e d a reduced coke f o r m a t i o n , which i s o b v i o u s l y not t r u e .
I n fact,
previously stressed,
i n VGO c o n v e r s i o n over
these
solids,
as
it
has been
a c c e s s i b i l i t y c o n s i d e r a t i o n s a r e o f p r i m a r y importance
which means t h a t performances
o b t a i n e d w i t h model
molecules could not
be
d i r e c t l y t r a n s f e d t o r e a l f e e d . The h i g h s e l e c t i v i t y f o r gases, f o r i n s t a n c e ,
i s l i k e l y t o be due t o an easy o v e r c r a c k i n g o f t h e g a s o l i n e f r a c t i o n i n s i d e t h e n o t s u f f i c i e n t l y open channel system o f H-Beta and H-Omega. CONCLUSION The post-steaming a c i d l e a c h i n g has been shown t o p l a y a major r o l e i n t h e c a t a l y t i c performances o f H-Y,
H-Beta and H-Omega s i n c e i t can i n c r e a s e o r
125
decrease t h e c o n v e r s i o n l e v e l s i n cyclohexene as w e l l as i n VGO t r a n s f o r m a t i o n . I n t h e case o f v e r y open s t r u c t u r e s such as H-Y,
the positive effect o f a
s e l e c t i v e l e a c h i n g m a i n l y r e s u l t s f r o m an i n c r e a s e o f t h e number o f s t r o n g a c i d s i t e s ( e l i m i n a t i o n o f p o i s o n i n g aluminium s p e c i e s ) , w h i l e f o r s t r u c t u r e s w i t h a monodimensional porous system such as H-Omega t h e a c c e s s i b i l i t y o f s i t e s i s o f predominant importance ( i n c r e a s e i n t h e microporous volume). When a model t e s t r e a c t i o n i s employed, a q u a l i t a t i v e r a n k i n g o f t h e s o l i d s a c c o r d i n g t o t h e i r a c i d i c p r o p e r t i e s i s o b t a i n e d . I n t h a t r e g a r d , t h e c a t a l y t i c performances o f H-Beta a r e b e t t e r t h a n t h o s e o f H-Y and H-Omega. However, t h i s r a n k i n g i s no l o n g e r t r u e f o r VGO conversion.
For such a t r a n s f o r m a t i o n o f heavy molecules
a c c e s s i b i l i t y c o n s i d e r a t i o n s have t o be t a k e n i n t o account, which means t h a n t h e most open s t r u c t u r e ,
namely H-Y,
leads t o t h e best
performances.
The
performances o f H-Y can be s i g n i f i c a n t l y improved when t h e a c i d i c p r o p e r t i e s o f steamed H-Y a r e o p t i m i z e d t h r o u g h a s e l e c t i v e a c i d l e a c h i n g . B I BLI OGRAPHY 1 . J . Scherzer, ACS Symposium S e r i e s 248, (19831, 157-200. 2. J.S. Magee, W.E. Cormier and G.M. m t e r m a n , K a t a l i s t i k s ' 6 t h Annual F l u i d Cat. Cracking Symposium, Munich, Germany (19851, May 22-23. 3. Grupo Especializado de Catalisis, Madrid, Spain (19871, September 28-October 1. Winthrop, European P a t e n t A p p l i c a t i o n , (19871, 4. E.G. Campbell and P.A. n"243629. 5. F. Raatz and Ch. M a r c i l l y , European P a t e n t A p p l i c a t i o n , (19861, n o 206871. 6. A. Corma, V . Fornes, J.B. Monton and A.V. O r c h i l l e s , J o u r n a l o f C a t a l y s i s 107, (1987) 288-295. 7. E C o r m a , V. Fornes, F. Melo and J . Perez-Pariente, Symposium on advances i n FCC, American Chemical S o c i e t y , New Orleans meeting, (19871, August 30 September 4. 8. A. Corma, E. H e r r e r o , A. M a r t i n e z and J. P r i e t o , Symposium on advances i n FCC, American Chemical S o c i e t y , New Orleans meeting, (19871, August 30 September 4. 9. A. Corma, V. Fornes, A. M a r t i n e z , F. Melo and 0. P a l l o t a , Symposium on " I n n o v a t i o n i n Z e o l i t e M a t e r i a l s Science", Stud. S u r f . S c i . Cat., Vol 37, (19881, 495. 10. E. J a c q u i n o t , PhD, ENSPM, R u e i l Malmaison, France, i n p r e p a r a t i o n . 11. M.M. J . Treacy and J.M. Newsam, Nature, 332, (19881, March 17. 12. A. Macedo, PhD, ENSPM, R u e i l M a l m a i s o r France, (19881 and r e f e r e n c e s there in. 13. R. Beaumont and D. Barthomeuf, J o u r n a l o f C a t a l y s i s , 26, (19721, 218-225. 14. D. Barthomeuf, M a t e r i a l s Chemistry and P h y s i c s , ( l 3 8 7 1 , 49. 15. M. Maache and J.C. L a v a l l e y , i n p r e p a r a t i o n . 16. E. J a c q u i n o t , A . Mendes, F. Raatz, Ch. M a r c i l l y , F.R. R i b e i r o and J. Caiero, a r t i c l e s u b m i t t e d f o r p u b l i c a t i o n . 17. L.A. Pine, P.J. Maher and W.A. Wachter, J o u r n a l o f C a t a l y s i s , (19841, 466-476. 18. R.E. R i t t e r , J.E. C r e i g h t o n , T.G. Roberie, D.S. Chin, C.C. Wear, p r e s e n t e d a t NPRA Annual Meeting, Los Angeles, paper AM 86-45, (19861, March 23. Lohse, G. E n g e l h a r d t and V. Patzelova, 19. H. F i c h t n e r - S c h m i t t l e r , U. Cryst-Res-Tech. 1 1 , (19841, ( 1 1 . 20. A. Macedo, F. RaTtz, R. B o u l e t , J.C. L a v a l l e y and A. Janin, Symposium on " I n n o v a t i o n i n Z e o l i t e M a t e r i a l s Science", Stud. S u r f . S c i . Cat, Vol 37, (19881, 375.
11,
g,