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Selective Ammoxidation of Propane on Vanadoaluminophosphate Catalysts
P.A. Jacobs and R.A. van Sanlen (Editors), Zeolites: Focts, Figrrres, Future 0 1989 Elsevier Science Publishers B.V.,Amsterdam - Printed in The Netherlands
1233
SELECTIVE AMMOXIDATION OF PROPANE ON VANADOALUYINOPHOSPHATE CATALYSTS
Akira MIYAMOTO, Yasumasa IWAMGTO, Yirokazu YATSUDA, and Tomoyuki I N U I Department of Hydrocarbon Chemistry, F a c u l t y of Engineering, Kyoto University, Sakyo-ku,
Kyoto 606, Japan
ABSTRACT Vanadoaluminophosphate(VAP0) c r y s t a l s h a v i n g t h e AlPO-5 s t r u c t u r e were synthesized by t h e r a p i d c r y s t a l l i z a t i o n method, and t h e i r p h y s i c a l p r o p e r t i e s and c a t a l y t i c performance i n t h e ammoxidation of propane were compared w i t h I t was t h o s e of vanadosilicate(V-silicate) h a v i n g t h e p e n t a s i l s t r u c t u r e . shown t h a t vanadium i o n s are incorpora ed more i n t h e AlPO-5 crystal t h a n i n ESR s i g n a l of V E t i n d i c a t e d t h a t t h e vanadium i o n was t h e s i l i c a t e crystal. a t o m i c a l l y d i s p e r s e d i n VAPO crystal and h a s t h e redox p o p e r t y t o change i t s o x i d a t i o n s t a t e b e t w e e n V4+ a n d V5+. A l t h o u g h t h e vanadium i o n i n t h e Vs i l i c a t e was a l s a t o m i c a l l y d i s p e r s e d , ESR and U V - v i s i b l e m e a s u r e m e n t s In s u g g e s t e d t h a t V2+ s t a t e i s more s t a b l e i n VAPO t h a n i n V-silicate. a c c o r d a n c e w i t h t h e d i f f e r e n c e b e t w e e n VAPO a n d V-silicate, VAPO was more a c t i v e and s e l e c t i v e t h a n V - s i l i c a t e f o r t h e a m m o x i d a t i o n o f p r o p a n e ; t h e s e l e c t i v i t y t o a c r y l o n i t r i l e a t t a i n e d 33% f o r VAPO.
INTRODUCTION Vanadium oxide c a t a l y s t s are i n d u s t r i a l l y very i q o r t a n t f o r a number of
catalytic processes including t h e s e l e c t i v e o x i d a t i o n s of hydrocarbons, p r o d u c t i o n of SOg, a m m o x i d a t i o n s o f h y d r o c a r b o n s , and r e d u c t i o n o f n i t r i c oxide w i t h ammonia(e.g.
refs.
1-7).
I n t e r e s t i n g methods have been groposed
f o r t h e p r e p a r a t i o n o f b o t h s u p p o r t e d and mixed o x i d e c a t a l y s t s t o i m p r o v e t h e i r catalytic performances.
Taking i n t o account of t h e long h i s t o r y of
t h e s e c o n v e n t i o n a l vanadium o x i d e c a t a l y s t s , however,
development of a
vanadium o x i d e w i t h n o v e l s t r u c t u r e would b e i m p o r t a n t f o r a s i g n i f i c a n t improvement of t h e catalytic performance.
By r e p l a c i n g t h e A 1 i n g e d i e n t of 'ZSM-5 w i t h v a r i o u s vanadium s a l t s a t t h e s t a g e o f g e l f o r m a t i o n i n t h e r a p i d c r y s t a l l i z a t i o n m e t h o d ( r e f s . 8-10). we have synthesized V-silicates having t h e p e n t a s i l s t r u c t u r e ( r e f s .
II,12).
It
has a l s o been shown t h a t t h e V-silicate e x h i b i t s c a t a l y t i c performances which have never been observed f o r p r e v i o u s vanadium oxide c a t a l y s t s ( r e f s . 13-18).
Namely, t h e a c t i v i t y of V-silicate has been 50 times higher t h a n t h a t of bulk V2O5 i n t h e H2 o x i d a t i o n , while considerably lower i n t h e NH3 oxidation. In t h e r e d u c t i o n of NO with NH3, t h e V-silicate e x h i b i t e d higher a c t i v i t y i n t h e
I234 a b s e n c e o f O2 t h a n i n t h e p r e s e n c e o f 02, a b e h a v i o r w h i c h had n e v e r b e e n observed f o r c o n v e n t i o n a l vanadium o x i d e s . The n o v e l a n d u n i q u e c a t a l y t i c p e r f o r m a n c e o f V-silicate h a s a l s o b e e n c o n f i r m e d i n t h e a m m o x i d a t i o n o f x y l e n e s ( r e f . 15). I n c o n t r a s t t o t h e b e h a v i o r o f t h e b u l k vanadium o x i d e , h i g h s e l e c t i v i t y t o t o l u n i t r i l e has been maintained f o r t h e V-silicate even a t h i g h temper a t ur e. Much a t t e n t i o n h a s a l s o b e e n g i v e n t o t h e s y n t h e s i s a n d c a t a l y t i c performances of aluminophosphates(AlPO), silicoaluminiphosphate(SAPO), a n d metal aluminophosphates(YeAPO)(e.g. r e f s . 19-21). Recent i n v e s t i g a t i o n s o f t h e s e AlPO-based
f a m i l i e s have suggested t h a t the s y n t h e s i s ,
p r o p e r t y , and c a t a l y t i c performance o f AlPO-based
physical
f a m i l i e s are s i g n i f i c a n t l y
d i f f e r e n t f r o m t h o s e o f t h e s i l i c a t e - b a s e d f a m i l i e s , s u c h a s ZSM-5 a n d metallosilicates(e.g.
r e f . 21).
For example,
c o n s i d e r e d t o b e w e a k e r t h a n t h a t o f H-ZSM-5(ref.
t h e a c i d s t r e n g t h of SAPO i s 22), a n d 18-membered r i n g
crystal has been s y n t h e s i z e d for A1W f a m i l y b u t n o t f o r s i l i c a t e f a m i l y ( r e f . 23).
We h a v e a l s o s y n t h e s i z e d by t h e r a p i d c r y s t a l l i z a t i o n method SAPO a n d
Fe-SAPO,
a n d h a v e shown t h a t t h e c a t a l y t i c p r o p e r t y i n t h e c o n v e r s i o n o f
m e t h a n o l t o h y d r o c a r b o n c h a n g e s c o n s i d e r a b l y f r o m H-ZSM-5(refs.
24-26),
Thus, i t would be i n t e r e s t i n g t o i n v e s t i g a t e c a t a l y t i c f u n c t i o n s o f vanadium i o n s i n c o r p o r a t e d i n t h e aluminophosphate crystal(VAP0).
The o b j e c t i v e s of
t h i s study were t h e n t o s y n t h e s i z e VAPO by t h e r a p i d c r y s t a l l i z a t i o n method, compare t h e catalytic performance of VAPO w i t h t h a t of V-silicate,
and r e v e a l
t h e e f f e c t of framework s t r u c t u r e o n t h e catalytic f u n c t i o n of vanadium ion. The ammoxidation of propane t o a c r y l o n i t r i l e was i n v e s t i g a t e d because of its s i g n i f i c a n c e i n t h e f u n c t i o n a l i z a t i o n of l i g h t p a r a f f i n s ( r e f s .
27-29).
METHOD VAPO c r y s t a l s were a l s o s y n t h e s i z e d by t h e r a p i d c r y s t a l l i z a t i o n method(refs.
8-12);
vanadium(II1) a c e t y l a c e t o n a t e , aluminium isopropoxide and
phosphoric a c i d were used as s t a r t i n g materials of V, A l , and P, r e s p e c t i v e l y , w h i l e tri-n-propylamine was employed as a t e m p l a t e molecule. Firstly, a gel m i x t u r e was p r e p a r e d by m i x i n g a l u m i n i u m i s o p r o p o x i d e , tri-n-propylamine, v a n a d i u m ( I I 1 ) a c e t y l a c e t o n a t e , water, a n d p h o s p h o r i c a c i d w i t h a n u l t r a disperser. The p r e c i p i t a t e was s e p a r a t e d from s o l u t i o n by c e n t r i f u g e , and t h e p r e c i p i t a t e d g e l m i x t u r e was m i l l e d by a g a t e m o r t a r . The m i l l e d p r e c i p i t a t e a n d s u p e r n a n t o f t h e d e c a n t s o l u t i o n were m i x e d t o g e t h e r a n d charged i n a n autoclave. w i t h 3 kg/cm2 gauge.
The atmosphere i n t h e a u t o c l a v e was r e p l a c e d by N2 T h i s was heated from room t e m p e r a t u r e t o 160°C w i t h a
c o n s t a n t h e a t i n g r a t e , l.6°C/min,
t h e n up t o 200°C w i t h a h e a t i n g r a t e , 0.2
"C/min, a n d f i n a l l y t h e t e m p e r a t u r e was m a i n t a i n e d a t 200°C f o r 4 h.
The
o b t a i n e d c r y s t a l was washed w i t h d i s t i l l e d water by u s i n g t h e c e n t r i f u g a l
1235
0
10
0
10
20 30 40 28 (degree)
20 30 28 (degree)
40
Fig. 2 X-ray d i f f r a c t i o n p a t t e r n s of VAPO (b) V/(AltP), 0.05 ( a ) AlPO-5; V/(AltP), 0 respectively.
A s shown i n Fig. 1, a l l of t h e XRD p a t t e r n s of V-silicates are
similar t o t h a t of H-ZSM-5 w i t h o u t vanadium incorporation.
This indicates
t h a t t h e V-silicate h a s t h e p e n t a s i l s t r u c t u r e . I n t h e XRD d i a d r a m of Vsilicate of V/Si 0.025, a peak i s seen a t 21.7 dedree of 20, which is a s s i g n e d t o a sodium silicate.
Thus, t h e V-silicate o f V/Si 0.025 was a m i x t u r e o f
t h e z e o l i t e having t h e G e n t a s i l structure and t h e sodium silicate.
I n other
words, vanadium i o n s are i n c o r p o r a t e d i n the silicate crystal t o t h e vanadium c o n t e n t of V/Si 0.011, b u t f u r t h e r i n c r e a s e i n vanadium l e a d s t o t h e f o r m a t i o n of sodium silicate.
A s shown i n F i g . 2, o n t h e o t h e r hand, XRD p a t t e r n of
VAPO w i t h V/(AltP) a t o m i c r a t i o 0.05 i s a l m o s t t h e same as t h a t o f AlPO-5 reported i n the literature(ref.
19).
YAP0 w i t h d i f f e r e n t V/(Al+P)
r a t i o b e l o w 0.05.
S i m i l a r r e s u l t s were also o b t a i n e d f o r T h i s means t h a t AlPO-5
f r a m e w o r k i s more e f f e c t i v e t h a n s i l i c a t e f r a m e w o r k t o i n c o r p o r a t e more vanadium ions. S t a t e of --
vanadium i o n i n V-silicate and VAPO F i g u r e s 3 and 4 show some examples of ESR s i g n a l s of V-silicates and VAPO,
1236 s e p a r a t o r ; d r i e d o v e r n i g h t a t 120°C, a n d t h e n c a l c i n e d a t 5OO0C i n a n a i r
stream f o r 1 h.
The c a t a l y s t was p r e s s e d , c r u s h e d , a n d s i e v e d i n t h e r a n g e
10-20 mesh t o p r o v i d e t h e r e a c t i o n .
Characterizations of t h e catalysts
were made w i t h Rigaku-Denki Geigerflex-2013 f o r X-ray w i t h Hitachi-Akashi
diffraction patterns,
scanning e l e c t r o n microscope MSM4C-102 f o r t h e shape and
s i z e o f t h e c r y s t a l , w i t h JEOL PE-2X s p e c t r o m e t e r f o r ESR, w i t h S h i m a d z u spectrophotometer MPS-2000 f o r W-Visible s p e c t r a , and w i t h N2 a d s o r p t i o n by t h e continuous f l o w method f o r t h e BET s u r f a c e area. The ammoxidation of propane was c a r r i e d o u t u s i n g a c o n v e n t i o n a l c o n t i n u o u s f l o w a p p a r a t u s under t h e f o l l o w i n g c o n d i t i o n s : c o n c e n t r a t i o n of propane, 10.2%; c o n c e n t r a t i o n o f 0 2 , 9.1-46.1%; balance gas, helium.
3.9-
c o n c e n t r a t i o n o f NH3, 15.8-43.72;
The p r o d u c t s were analyzed by gaschromatography.
RESULTS AND DISCUSSION Synthesis
of V-silicate
and VAPO
F i g u r e s l a n d 2 s h o w X-ray d i f f r a c t i o n p a t t e r n s of V - s i l i c a t e s a n d VAPO,
10
15
20
25
30
35
28 (degree\) Fig. 1 X-ray d i f f r a c t i o n p a t t e r n s of V-silicates w i t h d i f f e r e n t V/Si a t o m i c ratios. (a) H-ZSM-5; V/Si, 0 (b) V/Si, 0.005 (c) V/Si, 0.011 (d) V/Si, 0.025
1237 r e s p e c t i v e l y , under v a r i o u s c o n d i t i o n s .
The r e d u c t i o n o f t h e H-form V-
s i l i c a t e was made w i t h a f l o w i n s H2 a t 450°C for 3 h.
A s shown i n Fig. 3(c),
t h e o x i d i z e d V - s i l i c a t e d i d n o t e x h i b i t ESR s i g n a l o f V4+, i n d i c a t i n g t h a t The p e r m a n g a n a t e t i t r a t i o n o f s a m p l e vanadium i o n s a r e i n V5+ s t a t e . d i s s o l v e d w i t h H2S04 s o l u t i o n supported t h e v a l i d i t y o f t h e conclusion.
As
i s a l s o shown i n Fig. 3, ESR s i g n a l o f V4+ was c l e a r l y o b s e r v e d f o r t h e g e l , c r u d e crystal, and reduced V-silicate from VC13, V(acac)g, VOS04, and VOC204 salts. According t o Hecht and Johnstone(ref. 30), ESR p a r a m e t e r s f o r t h e V4+ i o n w i t h a n a x i a l symmetry c a n be determined by Eqs. 1 and 2.
HII = 2Ho/dll
- (41/gIl R)mI
( f o r 8 = 0)
(1)
HI = 2Ho/gL - ( A L / ~ ~ B ) ~ I (for 8 = a/2) (2) w h e r e HII and HI are p a r a l l e l a n d p e r p e n d i c u l a r p r i n c i p a l c o m p o n e n t s ,
r e s p e c t i v e l y , o f extremum p o i n t s o f ESR a b s o r p t i o n p e a k s ; 8 i s t h e Bohr
___c
Ho
--""i:J,vr 1xlf)O
5 x 1 00 (d 1
(b)
Fig. 3 ESR s i g n a l s of V4' i n V-silicates. (a) V - s i l i c a t e ( V / S i , 0.011) g e l p r e c i p i t a t e (b) V - s l i c a t e ( V / S i , 0.011) crude crystal. (c) oxidized V-silicate. (d) V-silicate reduced w i t h H2 a t 450'C f o r 3 h.
g,1
1 1 1 , 1 1 1 1 1
-712
Fig. 4 ESR s i g n a l of V4+ i n VAPO (a) VAFQ[V/(AltP), 0.051 c r u d e crystal.
h
( b ) o x i d i z e d VAFQ
712
1238 magneton; mI i s t h e nuclear magnetic quantum number of t h e V4+;
g,, and gL are
t h e p a r a l l e l and perpendicular p r i n c i p a l components, r e s p e c t i v e l y , of t h e hyperfine coupling tensor. S i m i l a r t o t h e method employed i n p r e v i o u s i n v e s t i g a t i o n s ( r e f s . 11,12), a l l of t h e ESR a b s o r p t i o n p e a k s i n Fig. 3 were assigned t o H and H components; a n example is shown i n Fig. 3(a) f o r t h e g e l from VOSO,, salt.
The complete assignment of t h e observed ESR s i g n a l s t o V4'
i o n s u p p o r t s t h e v a l i d i t y of t h e i d e a that t h e observed ESR s i g n a l s are due t o V4+ ions.
According t o Takahashi e t al.(ref.
31), t h e d i s p e r s e d vanadium i o n
e x h i b i t s t h e hyperfine s t r u c t u r e while agglomerated vanadium i o n s l e a d t o a s i n g l e t broad s i g n a l . Thus, t h e h y p e r f i n e s t r u c t u r e f o r t h e g e l , c r u d e c r y s t a l , and r e d u c e d H-form V - s i l i c a t e i n d i c a t e s t h a t t h e vanadium i o n i s a t o m i c a l l y d i s p e r s e d i n t h e s e phases.
A s i s a l s o shown i n Fig. 3, t h e
o x i d a t i o n i n a i r l e a d s t o d i a m a g n e t i c V5+ s t a t e , w h i l e t h e r e d u c t i o n i n H2 p r o d u c e s V4+,
and t h e b e h a v i o r was common t o a l l V - s i l i c a t e s f r o m VC13,
V ( a ~ a c ) ~VOS04, , and VOC204 s a l t s , i n d i c a t i n g t h a t vanadium i o n a t o m i c a l l y dispersed i n t h e crystal can proceed t h e redox cycle between V4+ and V5+. A s shown i n Fid. 4, t h e ESR s i g n a l of VAPO a l s o e x h i b i t s a clear hyperfine s t r u c t u r e due t o e l e c t r o n spin-nuclear s p i n coupling, i n d i c a t i n g t h a t vanadium
i o n i n VAPO i s a l s o a t o m i c a l l y d i s p e r s e d i n t h e AlPO-5 s t r u c t u r e .
The
o x i d a t i o n i n a i r a l s o l e a d s t o t h e d e c r e a s e i n t h e i n t e n s i t y o f V4+. However, t h e oxidation i n a i r a t 500 C does n o t completely convert V4+ t o V5+ f o r VAPO, suggesting t h a t t h e s t a b i l i t y of V4'
state was higher i n VAPO t h a n
Wave-length (m) Fig. 5 UV-Visible s p e c t r a of V - s i l i c a t e ( V / S i , 0.011) a t v a r i o u s s t a g e s of synthesis (a) g e l p r e c i p i t a t e (b) crude c r y s t a l (c) oxidized Na-V-silicate (d) oxidized H-V-silicate
1239
Fig. 6 W-Visible s p e c t r a of VAPO a t v a r i o u s s t a g e s of s y n t h e s i s (a) g e l p r e c i p i t a t e (b) c r u d e c r y s t a l (c) o x i d i z e d VAFQ i n V-silicate. I n accordance w i t h t h e r e s u l t of ESR measurements, t h e oxidized Na-form and H-form V-silicates were c o l o r l e s s and l i g h t yellow, r e s p e c t i v e l y , c o l o r of oxidized VAPO was l i g h t green.
while t h e
T h i s d i f f e r e n c e can be s e e n i n t h e
5) a n d VAPO(Fig. 6) a t v a r i o u s s t a g e s of synthesis. I n o t h e r words, a broad a b s o r p t i o n above 500 nm c a n b e s e e n i n t h e o x i d i z e d VAPO(Fig. 6), w h i l e t h i s c a n n o t b e o b s e r v e d f o r Na-form V-silicate(Fig. 5). I n t h e spectrum of H-form V-silicate, a band can b e o b s e r v e d a t a r o u n d 380 nm w h i c h i s a s s i g n e d t o t h e c h a r g e t r a n s f e r T h i s band c a n a l s o b e s e e n i n t h e o x i d i z e d a b s o r p t i o n band o f V=O s p e c i e s . I t i s g e n e r a l l y a c c e p t e d t h a t VpO s p e c i e s p l a y s t h e a c t i v e VAPO c r y s t a l . oxygen s p e c i e s f o r v a r i o u s catalytic r e a c t i o n s on vanadium o x i d e r e s u l t s of UV-visible s p e c t r a of V-silicate(Fig.
c a t a l y s t s ( r e f s . 1-7).
Thus, t h e p r e s e n c e o f V=O s p e c i e s i n V - s i l i c a t e a n d
VAPO s u g g e s t s t h a t t h e s e c a t a l y s t s are a c t i v e f o r v a r i o u s c a t a l y t i c r e a c t i o n s . Catalytic performance @ V-silicate and VAPO f o r t h e ammoxidation o f p r o p a n e
I n t h e ammoxidation of propane, a c r y l o n i t r i l e , a c e t o n i t r i l e , CO, and C02 were m a i n l y produced.
T a b l e 1 s h o w s some e x a m p l e s o f t h e r e s u l t s o n V-
s i l i c a t e and VAPO c a t a l y s t s .
It h a s b e e n shown t h a t V-silicate e x h i b i t s
n o v e l c a t a l y t i c p e r f o r m a n c e s i n t h e o x i d a t i o n s of H2 a n d NH3, t h e r e d u c t i o n of NO w i t h NH3,
and t h e ammoxidation of xylene t o t o l u n i t r i l e .
However, t h e
V-silicate was n o t very e f f e c t i v e f o r t h e ammoxidation of propane.
As shown i n T a b l e 1, VAPO c a t a l y s t e x h i b i t e d h i g h e r a c t i v i t y t h a n V-silicate.
1240
TABLE 1 R e s u l t s of t h e ammoxidation of propane on V-silicate and
VAW catalysts a t
500°C.a
v
Catalyst
contentb
(-1
'propane
Sacrylonitrile
'acetonitrile
2.5 5.5 15.3
(%I
H-V-silicate
0.01 1
0.51
1.2
Na-V-silicate
0.011
2.3
VAPO
0.050
5.6
5.9 13.0
'Concentrations
(%I
(XI
of propane, 02, and NH3 were 5.2, 14, and 16%, r e s p e c t i v e l y .
GHSV, 14000 h-*. bV/Si atomic r a t i o f o r V-silicate and V/(AltP) atomic r a t i o f o r VAPO.
0
A
I
20
I 1
I
25
Concentration of NH3
30 (%)
Fig. 7 E f f e c t of NH3 c o n c e n t r a t i o n on t h e ammoxidation of propane a t 500°C Concentration qf eropane, 5.2%. Concentration of 02, 12.0%. GHSV. 14000 h-
.
1241
F u r t h e r m o r e , t h e s e l e c t i v i t y t o a c r y l o n i t r i l e on VAPO was much h i g h e r t h a n The r e a c t i o n u n d e r v a r i o u s e x p e r i m e n t a l c o n d i t i o n s t h a t on V-silicate. showed t h a t t h e i n c r e a s e i n t h e NH3 c o n c e n t r a t i o n i s e f f e c t i v e f o r t h e i n c r e a s e i n t h e selectivity t o a c r y l o n i t r i l e , and t h e selectivity a s high as It can a l s o be noted t h a t 33% was observed f o r t h e VAPO catalyst(Fig. 7). t h e v a l u e i s h i g h e r t h a n t h e r e p o r t e d v a l u e f o r t h e c o n v e n t i o n a l V-P mixed oxide catalyst(ref.
27).
Although T a b l e 1 shows r e s u l t s f o r VAPO w i t h
V/(AltP) a t o m i c r a t i o 0.05, t h e h i g h s e l e c t i v i t y t o a c r y l o n i t r i l e was a l s o observed f o r VAPO with d i f f e r e n t compositions. I n conclusion, AlPO-5 framework was more e f f e c t i v e t h a n silicate p e n t a s i l framework t o incorporate more vanadium i o n s and t o provide vanadium s i t e s f o r t h e s e l e c t i v e ammoxidation of propane. REFERENCES 1 D J H uc k na 11,"Se 1e c t iv e 0x i d a t io n o f H y d r o c ar b on s I , Academic P r e s s , London (1979). 2 M.S. Wainwright and N.R. F o s t e r , Catal. Rev. 2, 211 (1979). 3 D.B. D a d y b u r j o i r , S.S. Jewur and E. R u c k e n s t e i n , C a t a l . Rev. 19, 293 (1979). 4 C.F. C u l l i s and D.J. H u c k n a l l , C a t a l y s i s ( T h e C h e m i c a l S o c i e t y ) Vol. 5, p. 273 (1982). 5 J. Haber, Proc. 8 t h I n t e r n . Congr. Catal., West B e r l i n , Vol. I, p.85 (1984). 6 P.J. Gellings, Catalysis(The Chemical Society) Vol. 7, p.105 (1985). 7 B.K. Hodnett, Catal. Rev. 27, 373 (1985), 8 T. I n u i , 0. Yamase, K. Fukuda, A. I t o h , J. Tarumoto, N. Morinaga, T. Hagiwara, a n d Y. Takegami, Proc. 8 t h I n t e r n . Cong. Catal., West B e r l i n , Vol. 3, p.569 (1984). 9 T. I n u i , A. Miyamoto, H. Matsuda, H. Nagata, Y. Makino, K. Fukuda, and F. Okazumi, Proc. 7th I n t e r n . Zeol. Conf., Tokyo, p.859 (1986). 10 T. I n u i , H. Matsuda, 0. Yamase, H. Nagata, K. Fukuda, T. Ukawa and A. Miyamoto, J. Catal. 98, 491 (1986). 11 T. I n u i , D. Medhanavyn, P. P r a s e r t h d a m , K. Fukuda, T. Ukawa, A. Sakamoto and A. Miyamoto, Appl. Catal. l8, 311 (1985). 12 A. Miyamoto, D. Medhanavyn and T. I n u i , Appl. C a t a l . 28, 89 (1986). 13 A. Miyamoto, D. Medhanavyn and T. I n u i , Chem. Express, 1,559 (1986). 14 A. Miyamoto, D. Medhanavyn and T. I n u i , Chem. Express, 1,559 (1986). 15 A. Miyamoto, D. Medhanavyn, T. I n u i , Proc. 9 t h I n t e r n . Congr. Catal. Vol. 1, p.437 (1988). 16 Z. Tvaruzkova, G. C e n t i , P. J i r u and F. T r i f i r o , Appl. C a t a l . 19,307 (1985). 17 G. C e n t i , K. H a b e r s b e r g e r , P. J i r u , F. T r i f i r o and Z. Tvaruzkova, Chem. Express I,717 (1986). 18 G . Centi, P. J i r u and F. T r i f i r o , Stud. Surf. Sci. C a t a l . i n p r e s s . 19 S.T. Wilson, B.M. Lok, C.A. Messina, T.R. Cannan a n d E.M. F l a n i g e n , J. Amer. Chem. SOC. 104, 1146 (1982); U.S. Pat 4,310,440 (1982). 20 l3.M. Lokv C.A. Messina, R.L. P a t t o n , R.T. Gajek, T.R. Cannan a n d E.M. Flanigen, J. Amer. Chem. SOC. 6092 (1984). 21 E.M. F l a n i d e n , R.M. Lok, R.L. P a t t o n and S.T. Wilson, Proc. 7 t h I n t e r n . Z e d . Conf., Tokyo, p.103 (1986). 22 R.J. P e l l e t , G.N. Long and J.A. Rabo, Proc. 7 t h I n t e r n . Zeal. Conf., Tokyo, 9.849 (1986). 23 M.E. D a v i s , c. S a l d a r r i a g e , c. Montes, J. Garces and C. Crowder, N a t u r e , 331, 698 (1988).
..
m,
-
1242 24 T. I n u i , H. Okaniwa, H. Matsuda, M. Yoshikawa a n d A. Miyamoto, Chern. Express 1, 379 (1986). 25 A. Miyamoto, H. Okaniwa, H. M a t s u d a and T. I n u i . Proc. 8 t h Japan-USSR C a t a l . Seminar, p. 271 (1986). 26 T. Inui, H. Matsuda, H. Okaniwa, S. T a n g s r i p o n d k u l and A. Miyamoto, Proc. Japan-France Seminar on C a t a l . Metal Compd., p. 83 (1987). 27 G. C e n t i , D. Pecheva, F. T r i f i r o , Appl. C a t a l . 33, 343 (1957). 28 G. Minow, K.-H. S c h n a b e l , a n d G. Ohlmann, React. K i n e t . Catal. L e t t . 22, 399 (1983). 29 7,. Osipova and V.D. S o k o l v s k i i , Kinet. Katal. 20, 510, 910 (1979). 30 H.G. Hecht and T.S. Johnstone, J. Chem. Phys. 46, 23 (1967). 31 H. T a k a h a s h i , M. S h i o t a n i , H. K o b a y a s h i a n d J. Sohma, J. Catal. l4, 134 (1969).
1233
SELECTIVE AMMOXIDATION OF PROPANE ON VANADOALUYINOPHOSPHATE CATALYSTS
Akira MIYAMOTO, Yasumasa IWAMGTO, Yirokazu YATSUDA, and Tomoyuki I N U I Department of Hydrocarbon Chemistry, F a c u l t y of Engineering, Kyoto University, Sakyo-ku,
Kyoto 606, Japan
ABSTRACT Vanadoaluminophosphate(VAP0) c r y s t a l s h a v i n g t h e AlPO-5 s t r u c t u r e were synthesized by t h e r a p i d c r y s t a l l i z a t i o n method, and t h e i r p h y s i c a l p r o p e r t i e s and c a t a l y t i c performance i n t h e ammoxidation of propane were compared w i t h I t was t h o s e of vanadosilicate(V-silicate) h a v i n g t h e p e n t a s i l s t r u c t u r e . shown t h a t vanadium i o n s are incorpora ed more i n t h e AlPO-5 crystal t h a n i n ESR s i g n a l of V E t i n d i c a t e d t h a t t h e vanadium i o n was t h e s i l i c a t e crystal. a t o m i c a l l y d i s p e r s e d i n VAPO crystal and h a s t h e redox p o p e r t y t o change i t s o x i d a t i o n s t a t e b e t w e e n V4+ a n d V5+. A l t h o u g h t h e vanadium i o n i n t h e Vs i l i c a t e was a l s a t o m i c a l l y d i s p e r s e d , ESR and U V - v i s i b l e m e a s u r e m e n t s In s u g g e s t e d t h a t V2+ s t a t e i s more s t a b l e i n VAPO t h a n i n V-silicate. a c c o r d a n c e w i t h t h e d i f f e r e n c e b e t w e e n VAPO a n d V-silicate, VAPO was more a c t i v e and s e l e c t i v e t h a n V - s i l i c a t e f o r t h e a m m o x i d a t i o n o f p r o p a n e ; t h e s e l e c t i v i t y t o a c r y l o n i t r i l e a t t a i n e d 33% f o r VAPO.
INTRODUCTION Vanadium oxide c a t a l y s t s are i n d u s t r i a l l y very i q o r t a n t f o r a number of
catalytic processes including t h e s e l e c t i v e o x i d a t i o n s of hydrocarbons, p r o d u c t i o n of SOg, a m m o x i d a t i o n s o f h y d r o c a r b o n s , and r e d u c t i o n o f n i t r i c oxide w i t h ammonia(e.g.
refs.
1-7).
I n t e r e s t i n g methods have been groposed
f o r t h e p r e p a r a t i o n o f b o t h s u p p o r t e d and mixed o x i d e c a t a l y s t s t o i m p r o v e t h e i r catalytic performances.
Taking i n t o account of t h e long h i s t o r y of
t h e s e c o n v e n t i o n a l vanadium o x i d e c a t a l y s t s , however,
development of a
vanadium o x i d e w i t h n o v e l s t r u c t u r e would b e i m p o r t a n t f o r a s i g n i f i c a n t improvement of t h e catalytic performance.
By r e p l a c i n g t h e A 1 i n g e d i e n t of 'ZSM-5 w i t h v a r i o u s vanadium s a l t s a t t h e s t a g e o f g e l f o r m a t i o n i n t h e r a p i d c r y s t a l l i z a t i o n m e t h o d ( r e f s . 8-10). we have synthesized V-silicates having t h e p e n t a s i l s t r u c t u r e ( r e f s .
II,12).
It
has a l s o been shown t h a t t h e V-silicate e x h i b i t s c a t a l y t i c performances which have never been observed f o r p r e v i o u s vanadium oxide c a t a l y s t s ( r e f s . 13-18).
Namely, t h e a c t i v i t y of V-silicate has been 50 times higher t h a n t h a t of bulk V2O5 i n t h e H2 o x i d a t i o n , while considerably lower i n t h e NH3 oxidation. In t h e r e d u c t i o n of NO with NH3, t h e V-silicate e x h i b i t e d higher a c t i v i t y i n t h e
I234 a b s e n c e o f O2 t h a n i n t h e p r e s e n c e o f 02, a b e h a v i o r w h i c h had n e v e r b e e n observed f o r c o n v e n t i o n a l vanadium o x i d e s . The n o v e l a n d u n i q u e c a t a l y t i c p e r f o r m a n c e o f V-silicate h a s a l s o b e e n c o n f i r m e d i n t h e a m m o x i d a t i o n o f x y l e n e s ( r e f . 15). I n c o n t r a s t t o t h e b e h a v i o r o f t h e b u l k vanadium o x i d e , h i g h s e l e c t i v i t y t o t o l u n i t r i l e has been maintained f o r t h e V-silicate even a t h i g h temper a t ur e. Much a t t e n t i o n h a s a l s o b e e n g i v e n t o t h e s y n t h e s i s a n d c a t a l y t i c performances of aluminophosphates(AlPO), silicoaluminiphosphate(SAPO), a n d metal aluminophosphates(YeAPO)(e.g. r e f s . 19-21). Recent i n v e s t i g a t i o n s o f t h e s e AlPO-based
f a m i l i e s have suggested t h a t the s y n t h e s i s ,
p r o p e r t y , and c a t a l y t i c performance o f AlPO-based
physical
f a m i l i e s are s i g n i f i c a n t l y
d i f f e r e n t f r o m t h o s e o f t h e s i l i c a t e - b a s e d f a m i l i e s , s u c h a s ZSM-5 a n d metallosilicates(e.g.
r e f . 21).
For example,
c o n s i d e r e d t o b e w e a k e r t h a n t h a t o f H-ZSM-5(ref.
t h e a c i d s t r e n g t h of SAPO i s 22), a n d 18-membered r i n g
crystal has been s y n t h e s i z e d for A1W f a m i l y b u t n o t f o r s i l i c a t e f a m i l y ( r e f . 23).
We h a v e a l s o s y n t h e s i z e d by t h e r a p i d c r y s t a l l i z a t i o n method SAPO a n d
Fe-SAPO,
a n d h a v e shown t h a t t h e c a t a l y t i c p r o p e r t y i n t h e c o n v e r s i o n o f
m e t h a n o l t o h y d r o c a r b o n c h a n g e s c o n s i d e r a b l y f r o m H-ZSM-5(refs.
24-26),
Thus, i t would be i n t e r e s t i n g t o i n v e s t i g a t e c a t a l y t i c f u n c t i o n s o f vanadium i o n s i n c o r p o r a t e d i n t h e aluminophosphate crystal(VAP0).
The o b j e c t i v e s of
t h i s study were t h e n t o s y n t h e s i z e VAPO by t h e r a p i d c r y s t a l l i z a t i o n method, compare t h e catalytic performance of VAPO w i t h t h a t of V-silicate,
and r e v e a l
t h e e f f e c t of framework s t r u c t u r e o n t h e catalytic f u n c t i o n of vanadium ion. The ammoxidation of propane t o a c r y l o n i t r i l e was i n v e s t i g a t e d because of its s i g n i f i c a n c e i n t h e f u n c t i o n a l i z a t i o n of l i g h t p a r a f f i n s ( r e f s .
27-29).
METHOD VAPO c r y s t a l s were a l s o s y n t h e s i z e d by t h e r a p i d c r y s t a l l i z a t i o n method(refs.
8-12);
vanadium(II1) a c e t y l a c e t o n a t e , aluminium isopropoxide and
phosphoric a c i d were used as s t a r t i n g materials of V, A l , and P, r e s p e c t i v e l y , w h i l e tri-n-propylamine was employed as a t e m p l a t e molecule. Firstly, a gel m i x t u r e was p r e p a r e d by m i x i n g a l u m i n i u m i s o p r o p o x i d e , tri-n-propylamine, v a n a d i u m ( I I 1 ) a c e t y l a c e t o n a t e , water, a n d p h o s p h o r i c a c i d w i t h a n u l t r a disperser. The p r e c i p i t a t e was s e p a r a t e d from s o l u t i o n by c e n t r i f u g e , and t h e p r e c i p i t a t e d g e l m i x t u r e was m i l l e d by a g a t e m o r t a r . The m i l l e d p r e c i p i t a t e a n d s u p e r n a n t o f t h e d e c a n t s o l u t i o n were m i x e d t o g e t h e r a n d charged i n a n autoclave. w i t h 3 kg/cm2 gauge.
The atmosphere i n t h e a u t o c l a v e was r e p l a c e d by N2 T h i s was heated from room t e m p e r a t u r e t o 160°C w i t h a
c o n s t a n t h e a t i n g r a t e , l.6°C/min,
t h e n up t o 200°C w i t h a h e a t i n g r a t e , 0.2
"C/min, a n d f i n a l l y t h e t e m p e r a t u r e was m a i n t a i n e d a t 200°C f o r 4 h.
The
o b t a i n e d c r y s t a l was washed w i t h d i s t i l l e d water by u s i n g t h e c e n t r i f u g a l
1235
0
10
0
10
20 30 40 28 (degree)
20 30 28 (degree)
40
Fig. 2 X-ray d i f f r a c t i o n p a t t e r n s of VAPO (b) V/(AltP), 0.05 ( a ) AlPO-5; V/(AltP), 0 respectively.
A s shown i n Fig. 1, a l l of t h e XRD p a t t e r n s of V-silicates are
similar t o t h a t of H-ZSM-5 w i t h o u t vanadium incorporation.
This indicates
t h a t t h e V-silicate h a s t h e p e n t a s i l s t r u c t u r e . I n t h e XRD d i a d r a m of Vsilicate of V/Si 0.025, a peak i s seen a t 21.7 dedree of 20, which is a s s i g n e d t o a sodium silicate.
Thus, t h e V-silicate o f V/Si 0.025 was a m i x t u r e o f
t h e z e o l i t e having t h e G e n t a s i l structure and t h e sodium silicate.
I n other
words, vanadium i o n s are i n c o r p o r a t e d i n the silicate crystal t o t h e vanadium c o n t e n t of V/Si 0.011, b u t f u r t h e r i n c r e a s e i n vanadium l e a d s t o t h e f o r m a t i o n of sodium silicate.
A s shown i n F i g . 2, o n t h e o t h e r hand, XRD p a t t e r n of
VAPO w i t h V/(AltP) a t o m i c r a t i o 0.05 i s a l m o s t t h e same as t h a t o f AlPO-5 reported i n the literature(ref.
19).
YAP0 w i t h d i f f e r e n t V/(Al+P)
r a t i o b e l o w 0.05.
S i m i l a r r e s u l t s were also o b t a i n e d f o r T h i s means t h a t AlPO-5
f r a m e w o r k i s more e f f e c t i v e t h a n s i l i c a t e f r a m e w o r k t o i n c o r p o r a t e more vanadium ions. S t a t e of --
vanadium i o n i n V-silicate and VAPO F i g u r e s 3 and 4 show some examples of ESR s i g n a l s of V-silicates and VAPO,
1236 s e p a r a t o r ; d r i e d o v e r n i g h t a t 120°C, a n d t h e n c a l c i n e d a t 5OO0C i n a n a i r
stream f o r 1 h.
The c a t a l y s t was p r e s s e d , c r u s h e d , a n d s i e v e d i n t h e r a n g e
10-20 mesh t o p r o v i d e t h e r e a c t i o n .
Characterizations of t h e catalysts
were made w i t h Rigaku-Denki Geigerflex-2013 f o r X-ray w i t h Hitachi-Akashi
diffraction patterns,
scanning e l e c t r o n microscope MSM4C-102 f o r t h e shape and
s i z e o f t h e c r y s t a l , w i t h JEOL PE-2X s p e c t r o m e t e r f o r ESR, w i t h S h i m a d z u spectrophotometer MPS-2000 f o r W-Visible s p e c t r a , and w i t h N2 a d s o r p t i o n by t h e continuous f l o w method f o r t h e BET s u r f a c e area. The ammoxidation of propane was c a r r i e d o u t u s i n g a c o n v e n t i o n a l c o n t i n u o u s f l o w a p p a r a t u s under t h e f o l l o w i n g c o n d i t i o n s : c o n c e n t r a t i o n of propane, 10.2%; c o n c e n t r a t i o n o f 0 2 , 9.1-46.1%; balance gas, helium.
3.9-
c o n c e n t r a t i o n o f NH3, 15.8-43.72;
The p r o d u c t s were analyzed by gaschromatography.
RESULTS AND DISCUSSION Synthesis
of V-silicate
and VAPO
F i g u r e s l a n d 2 s h o w X-ray d i f f r a c t i o n p a t t e r n s of V - s i l i c a t e s a n d VAPO,
10
15
20
25
30
35
28 (degree\) Fig. 1 X-ray d i f f r a c t i o n p a t t e r n s of V-silicates w i t h d i f f e r e n t V/Si a t o m i c ratios. (a) H-ZSM-5; V/Si, 0 (b) V/Si, 0.005 (c) V/Si, 0.011 (d) V/Si, 0.025
1237 r e s p e c t i v e l y , under v a r i o u s c o n d i t i o n s .
The r e d u c t i o n o f t h e H-form V-
s i l i c a t e was made w i t h a f l o w i n s H2 a t 450°C for 3 h.
A s shown i n Fig. 3(c),
t h e o x i d i z e d V - s i l i c a t e d i d n o t e x h i b i t ESR s i g n a l o f V4+, i n d i c a t i n g t h a t The p e r m a n g a n a t e t i t r a t i o n o f s a m p l e vanadium i o n s a r e i n V5+ s t a t e . d i s s o l v e d w i t h H2S04 s o l u t i o n supported t h e v a l i d i t y o f t h e conclusion.
As
i s a l s o shown i n Fig. 3, ESR s i g n a l o f V4+ was c l e a r l y o b s e r v e d f o r t h e g e l , c r u d e crystal, and reduced V-silicate from VC13, V(acac)g, VOS04, and VOC204 salts. According t o Hecht and Johnstone(ref. 30), ESR p a r a m e t e r s f o r t h e V4+ i o n w i t h a n a x i a l symmetry c a n be determined by Eqs. 1 and 2.
HII = 2Ho/dll
- (41/gIl R)mI
( f o r 8 = 0)
(1)
HI = 2Ho/gL - ( A L / ~ ~ B ) ~ I (for 8 = a/2) (2) w h e r e HII and HI are p a r a l l e l a n d p e r p e n d i c u l a r p r i n c i p a l c o m p o n e n t s ,
r e s p e c t i v e l y , o f extremum p o i n t s o f ESR a b s o r p t i o n p e a k s ; 8 i s t h e Bohr
___c
Ho
--""i:J,vr 1xlf)O
5 x 1 00 (d 1
(b)
Fig. 3 ESR s i g n a l s of V4' i n V-silicates. (a) V - s i l i c a t e ( V / S i , 0.011) g e l p r e c i p i t a t e (b) V - s l i c a t e ( V / S i , 0.011) crude crystal. (c) oxidized V-silicate. (d) V-silicate reduced w i t h H2 a t 450'C f o r 3 h.
g,1
1 1 1 , 1 1 1 1 1
-712
Fig. 4 ESR s i g n a l of V4+ i n VAPO (a) VAFQ[V/(AltP), 0.051 c r u d e crystal.
h
( b ) o x i d i z e d VAFQ
712
1238 magneton; mI i s t h e nuclear magnetic quantum number of t h e V4+;
g,, and gL are
t h e p a r a l l e l and perpendicular p r i n c i p a l components, r e s p e c t i v e l y , of t h e hyperfine coupling tensor. S i m i l a r t o t h e method employed i n p r e v i o u s i n v e s t i g a t i o n s ( r e f s . 11,12), a l l of t h e ESR a b s o r p t i o n p e a k s i n Fig. 3 were assigned t o H and H components; a n example is shown i n Fig. 3(a) f o r t h e g e l from VOSO,, salt.
The complete assignment of t h e observed ESR s i g n a l s t o V4'
i o n s u p p o r t s t h e v a l i d i t y of t h e i d e a that t h e observed ESR s i g n a l s are due t o V4+ ions.
According t o Takahashi e t al.(ref.
31), t h e d i s p e r s e d vanadium i o n
e x h i b i t s t h e hyperfine s t r u c t u r e while agglomerated vanadium i o n s l e a d t o a s i n g l e t broad s i g n a l . Thus, t h e h y p e r f i n e s t r u c t u r e f o r t h e g e l , c r u d e c r y s t a l , and r e d u c e d H-form V - s i l i c a t e i n d i c a t e s t h a t t h e vanadium i o n i s a t o m i c a l l y d i s p e r s e d i n t h e s e phases.
A s i s a l s o shown i n Fig. 3, t h e
o x i d a t i o n i n a i r l e a d s t o d i a m a g n e t i c V5+ s t a t e , w h i l e t h e r e d u c t i o n i n H2 p r o d u c e s V4+,
and t h e b e h a v i o r was common t o a l l V - s i l i c a t e s f r o m VC13,
V ( a ~ a c ) ~VOS04, , and VOC204 s a l t s , i n d i c a t i n g t h a t vanadium i o n a t o m i c a l l y dispersed i n t h e crystal can proceed t h e redox cycle between V4+ and V5+. A s shown i n Fid. 4, t h e ESR s i g n a l of VAPO a l s o e x h i b i t s a clear hyperfine s t r u c t u r e due t o e l e c t r o n spin-nuclear s p i n coupling, i n d i c a t i n g t h a t vanadium
i o n i n VAPO i s a l s o a t o m i c a l l y d i s p e r s e d i n t h e AlPO-5 s t r u c t u r e .
The
o x i d a t i o n i n a i r a l s o l e a d s t o t h e d e c r e a s e i n t h e i n t e n s i t y o f V4+. However, t h e oxidation i n a i r a t 500 C does n o t completely convert V4+ t o V5+ f o r VAPO, suggesting t h a t t h e s t a b i l i t y of V4'
state was higher i n VAPO t h a n
Wave-length (m) Fig. 5 UV-Visible s p e c t r a of V - s i l i c a t e ( V / S i , 0.011) a t v a r i o u s s t a g e s of synthesis (a) g e l p r e c i p i t a t e (b) crude c r y s t a l (c) oxidized Na-V-silicate (d) oxidized H-V-silicate
1239
Fig. 6 W-Visible s p e c t r a of VAPO a t v a r i o u s s t a g e s of s y n t h e s i s (a) g e l p r e c i p i t a t e (b) c r u d e c r y s t a l (c) o x i d i z e d VAFQ i n V-silicate. I n accordance w i t h t h e r e s u l t of ESR measurements, t h e oxidized Na-form and H-form V-silicates were c o l o r l e s s and l i g h t yellow, r e s p e c t i v e l y , c o l o r of oxidized VAPO was l i g h t green.
while t h e
T h i s d i f f e r e n c e can be s e e n i n t h e
5) a n d VAPO(Fig. 6) a t v a r i o u s s t a g e s of synthesis. I n o t h e r words, a broad a b s o r p t i o n above 500 nm c a n b e s e e n i n t h e o x i d i z e d VAPO(Fig. 6), w h i l e t h i s c a n n o t b e o b s e r v e d f o r Na-form V-silicate(Fig. 5). I n t h e spectrum of H-form V-silicate, a band can b e o b s e r v e d a t a r o u n d 380 nm w h i c h i s a s s i g n e d t o t h e c h a r g e t r a n s f e r T h i s band c a n a l s o b e s e e n i n t h e o x i d i z e d a b s o r p t i o n band o f V=O s p e c i e s . I t i s g e n e r a l l y a c c e p t e d t h a t VpO s p e c i e s p l a y s t h e a c t i v e VAPO c r y s t a l . oxygen s p e c i e s f o r v a r i o u s catalytic r e a c t i o n s on vanadium o x i d e r e s u l t s of UV-visible s p e c t r a of V-silicate(Fig.
c a t a l y s t s ( r e f s . 1-7).
Thus, t h e p r e s e n c e o f V=O s p e c i e s i n V - s i l i c a t e a n d
VAPO s u g g e s t s t h a t t h e s e c a t a l y s t s are a c t i v e f o r v a r i o u s c a t a l y t i c r e a c t i o n s . Catalytic performance @ V-silicate and VAPO f o r t h e ammoxidation o f p r o p a n e
I n t h e ammoxidation of propane, a c r y l o n i t r i l e , a c e t o n i t r i l e , CO, and C02 were m a i n l y produced.
T a b l e 1 s h o w s some e x a m p l e s o f t h e r e s u l t s o n V-
s i l i c a t e and VAPO c a t a l y s t s .
It h a s b e e n shown t h a t V-silicate e x h i b i t s
n o v e l c a t a l y t i c p e r f o r m a n c e s i n t h e o x i d a t i o n s of H2 a n d NH3, t h e r e d u c t i o n of NO w i t h NH3,
and t h e ammoxidation of xylene t o t o l u n i t r i l e .
However, t h e
V-silicate was n o t very e f f e c t i v e f o r t h e ammoxidation of propane.
As shown i n T a b l e 1, VAPO c a t a l y s t e x h i b i t e d h i g h e r a c t i v i t y t h a n V-silicate.
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TABLE 1 R e s u l t s of t h e ammoxidation of propane on V-silicate and
VAW catalysts a t
500°C.a
v
Catalyst
contentb
(-1
'propane
Sacrylonitrile
'acetonitrile
2.5 5.5 15.3
(%I
H-V-silicate
0.01 1
0.51
1.2
Na-V-silicate
0.011
2.3
VAPO
0.050
5.6
5.9 13.0
'Concentrations
(%I
(XI
of propane, 02, and NH3 were 5.2, 14, and 16%, r e s p e c t i v e l y .
GHSV, 14000 h-*. bV/Si atomic r a t i o f o r V-silicate and V/(AltP) atomic r a t i o f o r VAPO.
0
A
I
20
I 1
I
25
Concentration of NH3
30 (%)
Fig. 7 E f f e c t of NH3 c o n c e n t r a t i o n on t h e ammoxidation of propane a t 500°C Concentration qf eropane, 5.2%. Concentration of 02, 12.0%. GHSV. 14000 h-
.
1241
F u r t h e r m o r e , t h e s e l e c t i v i t y t o a c r y l o n i t r i l e on VAPO was much h i g h e r t h a n The r e a c t i o n u n d e r v a r i o u s e x p e r i m e n t a l c o n d i t i o n s t h a t on V-silicate. showed t h a t t h e i n c r e a s e i n t h e NH3 c o n c e n t r a t i o n i s e f f e c t i v e f o r t h e i n c r e a s e i n t h e selectivity t o a c r y l o n i t r i l e , and t h e selectivity a s high as It can a l s o be noted t h a t 33% was observed f o r t h e VAPO catalyst(Fig. 7). t h e v a l u e i s h i g h e r t h a n t h e r e p o r t e d v a l u e f o r t h e c o n v e n t i o n a l V-P mixed oxide catalyst(ref.
27).
Although T a b l e 1 shows r e s u l t s f o r VAPO w i t h
V/(AltP) a t o m i c r a t i o 0.05, t h e h i g h s e l e c t i v i t y t o a c r y l o n i t r i l e was a l s o observed f o r VAPO with d i f f e r e n t compositions. I n conclusion, AlPO-5 framework was more e f f e c t i v e t h a n silicate p e n t a s i l framework t o incorporate more vanadium i o n s and t o provide vanadium s i t e s f o r t h e s e l e c t i v e ammoxidation of propane. REFERENCES 1 D J H uc k na 11,"Se 1e c t iv e 0x i d a t io n o f H y d r o c ar b on s I , Academic P r e s s , London (1979). 2 M.S. Wainwright and N.R. F o s t e r , Catal. Rev. 2, 211 (1979). 3 D.B. D a d y b u r j o i r , S.S. Jewur and E. R u c k e n s t e i n , C a t a l . Rev. 19, 293 (1979). 4 C.F. C u l l i s and D.J. H u c k n a l l , C a t a l y s i s ( T h e C h e m i c a l S o c i e t y ) Vol. 5, p. 273 (1982). 5 J. Haber, Proc. 8 t h I n t e r n . Congr. Catal., West B e r l i n , Vol. I, p.85 (1984). 6 P.J. Gellings, Catalysis(The Chemical Society) Vol. 7, p.105 (1985). 7 B.K. Hodnett, Catal. Rev. 27, 373 (1985), 8 T. I n u i , 0. Yamase, K. Fukuda, A. I t o h , J. Tarumoto, N. Morinaga, T. Hagiwara, a n d Y. Takegami, Proc. 8 t h I n t e r n . Cong. Catal., West B e r l i n , Vol. 3, p.569 (1984). 9 T. I n u i , A. Miyamoto, H. Matsuda, H. Nagata, Y. Makino, K. Fukuda, and F. Okazumi, Proc. 7th I n t e r n . Zeol. Conf., Tokyo, p.859 (1986). 10 T. I n u i , H. Matsuda, 0. Yamase, H. Nagata, K. Fukuda, T. Ukawa and A. Miyamoto, J. Catal. 98, 491 (1986). 11 T. I n u i , D. Medhanavyn, P. P r a s e r t h d a m , K. Fukuda, T. Ukawa, A. Sakamoto and A. Miyamoto, Appl. Catal. l8, 311 (1985). 12 A. Miyamoto, D. Medhanavyn and T. I n u i , Appl. C a t a l . 28, 89 (1986). 13 A. Miyamoto, D. Medhanavyn and T. I n u i , Chem. Express, 1,559 (1986). 14 A. Miyamoto, D. Medhanavyn and T. I n u i , Chem. Express, 1,559 (1986). 15 A. Miyamoto, D. Medhanavyn, T. I n u i , Proc. 9 t h I n t e r n . Congr. Catal. Vol. 1, p.437 (1988). 16 Z. Tvaruzkova, G. C e n t i , P. J i r u and F. T r i f i r o , Appl. C a t a l . 19,307 (1985). 17 G. C e n t i , K. H a b e r s b e r g e r , P. J i r u , F. T r i f i r o and Z. Tvaruzkova, Chem. Express I,717 (1986). 18 G . Centi, P. J i r u and F. T r i f i r o , Stud. Surf. Sci. C a t a l . i n p r e s s . 19 S.T. Wilson, B.M. Lok, C.A. Messina, T.R. Cannan a n d E.M. F l a n i g e n , J. Amer. Chem. SOC. 104, 1146 (1982); U.S. Pat 4,310,440 (1982). 20 l3.M. Lokv C.A. Messina, R.L. P a t t o n , R.T. Gajek, T.R. Cannan a n d E.M. Flanigen, J. Amer. Chem. SOC. 6092 (1984). 21 E.M. F l a n i d e n , R.M. Lok, R.L. P a t t o n and S.T. Wilson, Proc. 7 t h I n t e r n . Z e d . Conf., Tokyo, p.103 (1986). 22 R.J. P e l l e t , G.N. Long and J.A. Rabo, Proc. 7 t h I n t e r n . Zeal. Conf., Tokyo, 9.849 (1986). 23 M.E. D a v i s , c. S a l d a r r i a g e , c. Montes, J. Garces and C. Crowder, N a t u r e , 331, 698 (1988).
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