- Email: [email protected]
Vapor-Phase Oxidation of Alpha-Methylstyrene to Phenylacrolein
G . Centi and F. Trifiro’ (Editors), New Developments in Selective Oxidation 0 1990 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
257
VAPOR-PHASE OXIDATION OF ALPHA-METHYLSTYRENE TO PHENYLACROLEIN
M. A1 Research L a b o r a t o r y o f Resources U t i l i z a t i o n , Tokyo I n s t i t u t e o f Technology, Yokohama 227 (Japan)
4259 Nagatsuta, Midori-ku, ABSTRACT
V a r i o u s Mo-Te-based t e r n a r y o x i d e s were t e s t e d as c a t a l y s t s f o r t h e vaporphase a i r o x i d a t i o n o f P t - m e t h y l s t y r e n e t o f o r m p h e n y l a c r o l e i n (atropoaldehyde). The b e s t c a t a l y s t performances were found w i t h Mo/Te/Ti, Mo/Te/W, and Mo/Te/Fe oxides: t h e one-pass y i e l d o f p h e n y l a c r o l e i n a t t a i n e d 63 mol% a t t h e ol-methyls t y r e n e c o n v e r s i o n o f 96.5 %. The c a t a l y t i c f u n c t i o n s o b t a i n e d w i t h t h e s e c o m b i n a t i o n s o f o x i d e s were a l s o i n v e s t i g a t e d i n t h e l i g h t o f b o t h acid-base and o x i d i z i n g f u n c t i o n s o b t a i n e d f r o m t h e c a t a l y t i c a c t i v i t y f o r d e h y d r a t i o n dehydrogenation o f 2-propanol and o x i d a t i o n o f 1-butene. INTRODUCTION Propylene i s o x i d i z e d t o a c r o l e i n w i t h a v e r y h i g h s e l e c t i v i t y o v e r Bi-Moand Sb-based mixed-oxide c a t a l y s t s . i.e.,
F u r t h e r , m e t h y l - s u b s t i t u t e d propylene,
n-butene and isobutene, a r e o x i d i z e d t o b u t a d i e n e and m e t h a c r o l e i n ,
r e s p e c t i v e l y , o v e r s i m i l a r t y p e o f mixed-oxide c a t a l y s t s .
However, i n t h e
o x i d a t i o n o f a r o m a t i c compounds, t h e s e c a t a l y s t s cannot u s u a l l y e x h i b i t an e x c e l l e n t performance.
Indeed, i n t h e o x i d a t i o n o f ethylbenzene t o s t y r e n e ,
t h e c a t a l y s t s proposed t o be e f f e c t i v e a r e d i f f e r e n t f r o m t h o s e used i n t h e o x i d a t i o n o f p r o p y l e n e and butenes ( r e f . 1 ) . benzaldehyde, V-P o x i d e s ( r e f . 2),
I n the o x i d a t i o n o f toluene t o
Mo-P o x i d e s ( r e f . 3 ) . Mo-P-based
o x i d e s ( r e f . 4), Mo-based o x i d e s ( r e f .
5).
and V-Ti o x i d e s ( r e f .
ternary
6) have been
proposed t o be e f f e c t i v e . As f o r t h e o x i d a t i o n o f p h e n y l - s u b s t i t u t e d propylene, i.e., [2-phenylpropene]
t o f o r m d - p h e n y l a c r o l e i n [ atropoaldehyde,
d-methylstyrene
2-phenylpropenal ]
( a b b r e v i a t e d h e r e a f t e r as PhA), t h e r e have been v e r y few s t u d i e s .
Adams ( r e f .
7 ) r e p o r t e d t h a t Bi-Mo o x i d e i s n o t e f f e c t i v e : t h e y i e l d o f PhA i s about 3 mol% a t t h e d - m e t h y l s t y r e n e c o n v e r s i o n o f 45 %. Recently, G r a s s e l l i e t a l . ( r e f . 8) r e p o r t e d a 30 mol% y i e l d o f PhA a t t h e c o n v e r s i o n o f 50 % o v e r Nb-promoted Sb-U oxides. I n t h e p r e c e d i n g s t u d y ( r e f . 9).
i t was found t h a t t h e b e s t performance f o r
t h e p r o d u c t i o n o f PhA i s o b t a i n e d w i t h Moo3 among t h e v a r i o u s s i n g l e - o x i d e s t e s t e d and t h a t Mo/Te atomic r a t i o = 10/4 o x i d e e x h i b i t s t h e b e s t performance among t h e v a r i o u s Mo-based b i n a r y o x i d e s t e s t e d .
The y i e l d o f PhA a t t a i n e d
258 48.5 mol% a t t h e c o n v e r s i o n o f 96.3 %. I t was a l s o found t h a t d - m e t h y l s t y r e n e i s much more r e a c t i v e t h a n p r o p y l e n e and butenes. I n t h i s study, f o r purpose o f e x p l o r i n g more e f f e c t i v e c a t a l y s t s f o r t h i s p a r t i a l o x i d a t i o n , v a r i o u s o x i d e s were combined w i t h t h e Mo/Te atomic r a t i o = 10/4 o x i d e and t h e i r c a t a l y t i c p r o p e r t i e s were t e s t e d .
Then, t h e f u n c t i o n s o f
o x i d e r e q u i r e d f o r c a t a l y z i n g t h i s o x i d a t i o n r e a c t i o n were i n v e s t i g a t e d . EXPERIMENTAL Catalysts The c a t a l y s t s used i n t h i s s t u d y were Mo/Te/X ( X i s t h e t h i r d component) a t o m i c r a t i o = 10/4/x ( x = 0 t o 16) t e r n a r y oxides.
They were supported on 8-
t o 20-mesh s i z e pumice o r i g i n a t i n g from v o l c a n i c stone c o n s i s t i n g o f macropores
2
( p a c k i n g d e n s i t y = ca. 0.4 g/ml and s p e c i f i c s u r f a c e area = 0.3 t o 0.6 m /g). F o r example, t h e Mo/Te/W = 10/4/8 c a t a l y s t was prepared as f o l l o w s . (NH ) 4 6
Mo7024.4H20 (35.3 g ) was d i s s o l v e d i n h o t w a t e r and 41.8 g o f (NH4)10W,2041'
5H20 was a l s o d i s s o l v e d i n a n o t h e r h o t w a t e r u s i n g o x a l i c acid.
The two s o l u -
t i o n s were mixed and 18.0 g o f H6Te06 was d i s s o l v e d t o t h e s o l u t i o n .
Excess
w a t e r was evaporated o f f w i t h s t i r r i n g w i t h t h e a i d o f h o t a i r c u r r e n t , y i e l d i n g a s t i c k y syrup.
T h e r e a f t e r , 100 m l o f t h e pumice was added t o t h e s t i c k y
s y r u p and t h e m i x t u r e was evaporated t o dryness w i t h s t i r r i n g w i t h t h e a i d o f h o t a i r current.
The o b t a i n e d s o l i d was evaporated a g a i n i n an oven a t 200°C
f o r 4 h and t h e n i t was c a l c i n e d a t 450°C f o r 6 h i n a stream o f a i r . R e a c t i o n procedures The vapor-phase c o n t a c t o x i d a t i o n o f d - m e t h y l s t y r e n e was conducted w i t h 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 system. cm l o n g and 1.8 cm i.d.,
The r e a c t o r was made o f a s t e e l tube, 50
mounted v e r t i c a l l y and immersed i n a l e a d bath.
Air
was i n t r o d u c e d f r o m t h e t o p o f t h e r e a c t o r . w i t h d - m e t h y l s t y r e n e b e i n g i n j e c t e d i n t o t h e p r e h e a t i n g s e c t i o n o f t h e r e a c t o r by means o f a s y r i n g e pump. Unless o t h e r w i s e i n d i c a t e d , t h e f e e d r a t e s were f i x e d as f o l l o w s : a i r , 400 m l ( a t 20°C)/min (ca.
i n air).
1.0 mol/h);
d - m e t h y l s t y r e n e . 11.9 mmol/h (ca. 1.19 mol%
The e f f l u e n t gas f r o m t h e ' r e a c t o r was l e d s u c c e s s i v e l y i n t o f o u r
c h i l l e d scrubbers c o n t a i n i n g 2-propanol pounds. (120 m l ) .
A f e t r 1 h time-on-stream,
t o r e c o v e r t h e 2-propanol-soluble
com-
t h e c o n t e n t o f t h e scrubbers was c o l l e c t e d
The r e a c t i o n p r o d u c t s and unreactedd-methylstyrene were analysed by
gas chromatograph: a 1-m column o f M o l e c u l a r s i e v e 13X f o r CO; a 6-m column o f p r o p y l e n e carbonate f o r C02; a 2-m column o f PEG 20M a t 160°C f o r d - m e t h y l s t y rene, benzaldehyde, and 2-propanol;
a 1-m column o f AT-1200 t H3P04 a t 160°C
f o r PhA, benzaldehyde. m a l e i c anhydride,
and benzoic acid.
The amount o f t o t a l
a c i d was a l s o checked by t i t r a t i o n w i t h 0.1 N NaOH u s i n g a pH meter.
The
259 amount was u s u a l l y i n accord w i t h t h e sum o f maleic anhydride and benzoic a c i d measured by gas chromatograph. Since PhA i s n o t a v a i l a b l e as a chemical agent, t h e i d e n t i f i c a t i o n was performed by means o f GC-MS ( H i t a c h i H-80) and t h e q u a n t i t y was determined on t h e b a s i s o f t h e approximation t h a t t h e peak area o f PhA recorded i n gas chromatograph ( F I D ) i s equal t o t h a t o f cinnamaldehyde [p-phenylacrolein,
3-phenyl-
propenal 1. The y i e l d and s e l e c t i v i t y o f a p a r t i c u l a r product were defined as mole percentage y i e l d and s e l e c t i v i t y on a carbon-account-fo; o f carbon oxides [COX].
basis.
As f o r t h e y i e l d
t h e COX accompanied w i t h t h e formation o f benzoic acid,
benzaldehyde, and maleic anhydride was excluded.
RESULTS AND DISCUSSION Performances o f t h e Mo-Te-based
t e r n a r y oxide c a t a l y s t s
The r e s u l t s obtained over 10 g-portions o f Mo-Te-based t e r n a r y oxide catal y s t s a t t h e o p t i m a l r e a c t i o n temperatures are l i s t e d i n Table 1, according t o t h e c l a s s i f i c a t i o n o f oxide i n view o f both acid-base and o x i d i z i n g f u n c t i o n s ( r e f . 9,lO).
The r e s u l t s may be summarized as follows.
( 1 ) The a d d i t i o n o f W03, Ti02, and Fep03 t o t h e Mo/Te = 10/4 oxide enhances markedly b o t h t h e o x i d a t i o n a c t i v i t y and s e l e c t i v i t y t o PhA.
The presence
o f an optimum amount was observed f o r each t h i r d component. ( 2 ) The b e s t r e s u l t s are obtained w i t h t h e Mo/Te/Ti = 10/4/4 oxide: t h e onepass y i e l d of PhA a t t a i n s 63.0 mol% a t t h e d - m e t h y l s t y r e n e conversion o f 96.5 %.
(3) The second best r e s u l t s a r e obtained w i t h t h e Mo/Te/W = 10/4/8 oxide: t h e PhA y i e l d a t t a i n s 59.5 mol% a t t h e conversion o f 98.4
4.
(4) The t h i r d b e s t r e s u l t s are obtained w i t h t h e Mo/Te/Fe = 10/4/4 oxide: t h e PhA y i e l d a t t a i n s 58.0 mol% a t t h e conversion o f 96.7 %.
(5) The a d d i t i o n o f Zr02,
Bi20g, and Co304 enhances t h e o x i d a t i o n a c t i v i t y , b u t
i t enhances t h e s e l e c t i v i t y o n l y a l i t t l e . (6) The e f f e c t o f V205 i s small.
( 7 ) The a d d i t i o n of U308. SnO2. ZnO. NiO, and Mn02 enhances t h e o x i d a t i o n a c t i v i t y , b u t i t decreases t h e s e l e c t i v i t y .
(8) The a d d i t i o n o f an a c i d i c oxide such as P205, B203, and Sb205 decreases markedly t h e o x i d a t i o n a c t i v i t y and i t does n o t improve t h e s e l e c t i v i t y . Performances o f t h e b i n a r y oxide c a t a l y s t s For understanding t h e f u n c t i o n o f each component i n t h e Mo/Te/W, Mo/Te/Ti. and Mo/Te/Fe t e r n a r y oxides, t h e c a t a l y s t performance f o r t h e o x i d a t i o n o f d-methylstyrene obtained over each b i n a r y oxide c o n s i s t i n g o f t h e t e r n a r y
260
TABLE 1 Performances o f Mo-Te-based t e r n a r y o x i d e c a t a l y s t s * Catalyst atomic r a t i o Mo
T ("C)
Conv
(2)
PhA
Baci
Y i e l d (mol%) Bald MA COX
450 460
81.5 90.0
18.5 20.5
12.5 13.8
15.9 17.1
5.6 7.0
4.1 6.4
24.9 15.2
23.0 23.0
other
'PhA (mol%)
Mo/Te
1014
430 440
92.5 96.3
45.0 48.5
11.3 13.7
2.5 2.0
2.1 2.0
4.4 5.0
27.2 25.1
48.5 50.5
Mo/Te/P Mo/Te/B Mo/Te/Sb Mo/Te/Zr
101414 101414 101414 101414
468 500 490 415
95.7 58.5 78.0 91.4
44.0 26.5 42.0 51.5
12.4 3.9 8.2 11.5
4.3 2.5 7.7 5.0
4.5 2.0 3.0 4.5
8.1 3.3 4.8 7.0
22.4 20.3 12.7 11.9
46.0 45.0 54.0 56.0
Mo/Te/W
101412
395 400
88.8 95.9
52.5 55.5
11.9 14.6
3.0 5.2
3.4 3.3
4.7 3.7
13.3 13.6
59.1 57.9
101414
390 410
54.0 93.5
37.0 53.5
6.0 11.3
2.4 4.5
1.5 1.6
1.8 5.0
5.3 17.6
69.0 57.0
101418
385 390 395
89.0 96.2 98.4
58.5 58.5 59.5
12.3 13.2 16.9
3.0 3.6 4.2
2.6 2.5 2.9
3.8 4.4 4.9
8.8 14.0 10.0
66.0 61 .O 60.5
1014116
375 38 5
51 .O 85.5
21.8 28.2
8.7 16.3
3.6 8.4
2.9 5.0
3.0 7.8
11.0 19.8
43.0 33.0
Mo/Te/V
101414
435 440
88.5 95.0
46.5 45.5
15.8 14.1
6.7 7.1
2.5 2.5
2.9 6.0
14.1 19.8
52.5 48.0
Mo/Te/U
101414
400
94.7
44.1
14.1
4.8
4.7
4.8
22.2
46.5
Mo/Te/Ti 101412
440 4 50
83.7 88.3
47.8 49.3
8.1 9.3
3.6 4.8
3.2 2.8
2.6 4.1
18.4 18.0
57.0 56.0
101414
390 400
83.5 96.5
59.3 63.0
13.7 15.0
2.4 3.6
3.5 3.2
2.3 3.8
2.3 7.4
71 .O 65.0
101418
400 41 0
90.6 96.7
50.5 56.8
12.8 15.7
2.4 4.8
3.2 3.2
5.5 5.6
16.2 10.6
56.0 59.0
Mo/Te/Sn 101414
390
90.0
27.0
12.3
3.6
7.2
24.7
14.7
30.3
Mo/Te/Fe 101414
420 430 375 385
89.0 96.7 86.5 90.0
56.8 58.0 40.7 44.1
11.4 13.3 22.0 18.5
4.0 3.6 9.6 8.4
3.4 3.5 4.5 3.0
0.6 0.6 1.4 3.7
12.8 17.2 8.3 12.3
64.0 60.0 47.0 49.0
Mo/Te/Bi 101414 Mo/TelZn 101414 Mo/Te/Ni 101414
395 41 0 390
83.2 96.2 96.4
47.6 47.2 40.5
9.6 16.0 15.8
3.0 4.8 4.2
2.1 5.0 4.6
7.5 4.7 10.5
13.3 18.5 20.8
57.2 49.0 41.8
Mo/Te/Co 101414
390 400
82.0 94.8
46.1 49.3
14.7 14.7
2.4 3.6
0.7 3.6
6.0 7.7
12.1 15.9
56.2 52.0
Mo/Te/Cr 10/4/4 Mo/Te/Mn 101414
405 41 0
89.6 92.7
40.2 36.3
17.4 15.3
4.8 5.4
5.0 4.1
7.0 10.7
15.0 20.9
44.6 39.1
101418
*
T = temperature, PhA = phenylacrolein, Baci = benzoic hyde, MA = maleic anhydride, COX = carbon oxides, o t h e r of d-methylstyrene) - ( sum o f t h e y i e l d s of PhA t Baci SphA = s e l e c t i v i t y t o PhA, amount o f c a t a l y s t used = 10
acid, Bald = benzalde= [ ( o v e r a l l conversion
t Bald t COX)], g.
261 TABLE 2 Comparison o f t h e performances of t h e t e r n a r y oxides w i t h those of b i n a r y oxides Cata 1y s t
T
Conv
atomic r a t i o
("C)
(X)
PhA
Baci
Bald
MA
1014 1014 1014 101418
440 400 410 395
96.3 88.0 95.8 98.4
48.5 32.5 46.2 59.5
13.7 11.5 18.6 16.9
2.0 4.8 9.6 4.2
2.0 4.1 4.0 2.9
5.0 12.9 4.0 4.9
25.1 22.2 13.4 10.0
50.5 37.0 48.3 60.5
Mo/Te Ti/Te Mo/Ti Mo/Te/Ti
1014 1014 1014 101414
440 410 350 400
96.3 52.0 89.0 96.5
48.5 23.3 6.4 63.0
13.7 4.9 9.4 15.0
2.0 2.4 5,4 3.6
2.0 2.1 15.3 3.2
5.0 14.7 31.4 3.8
25.1 4.6 21.1 7.4
50.5 45.0 7.2 65.0
Mo/Te Fe/Te Mo/Fe Mo/Te/Fe
1014 1014 1014 10/4/4
440 345 370 430
96.3 33.0 79.4 96.7
48.5 1.7 18.1 58.0
13.7 0. 14.7 13.3
2.0 4.8 7.8 3.6
2.0 0. 6.5 3.5
5.0 17.5 4.9 0.6
25.1 9.0 27.4 17.2
50.5 5.1 22.8 60.0
Mo/Te W/Te Mo/W Mo/Te/W
Y i e l d (mol%)
COX
other
'PhA (molX)
~
~~
Abbreviations a r e t h e same as f o r Table 1. The amount o f c a t a l y s t used i s 10 g. oxides were compared w i t h those obtained over t h e t e r n a r y oxides. The t e s t s The r e s u l t s a r e shown i n
were performed u s i n g 10 g-portion o f t h e c a t a l y s t s . Table 2. The r e s u l t s may be summarized as follows.
W03 by i t s e l f i s n o t e f f e c t i v e as a c a t a l y s t f o r t h i s o x i d a t i o n ( r e f . 9) and Te02 has no o x i d a t i o n a c t i v i t y .
However, t h e combination o f t h e two
oxides generates a h i g h o x i d a t i o n a c t i v i t y , b u t t h e s e l e c t i v i t y t o PhA i s lower and t h e formation of COX i s much g r e a t e r than those obtained w i t h t h e MoITe oxide.
On t h e o t h e r hand, t h e a d d i t i o n o f W03 t o Moog enhances
markedly both t h e o x i d a t i o n a c t i v i t y and s e l e c t i v i t y :
t h e performance o f
t h e Mo/W = 1014 oxide i s comparable w i t h t h a t o f t h e Mo/Te = 1014 oxide. Therefore. i t i s considered t h a t t h e a d d i t i o n o f Te02 improves t h e Mo/W oxide much as i t improves t h e Moo3 alone c a t a l y s t . The performances o f t h e T i I T e and Fe/Te oxides are much lower than t h a t o f t h e W/Te oxide.
Further. t h e a d d i t i o n o f Ti02 and Fe203 t o Moo3
increases t h e o x i d a t i o n a c t i v i t y , b u t i t decreases t h e s e l e c t i v i t y t o PhA. However, an e x c e l l e n t c a t a l y t i c performance i s obtained by t h e a d d i t i o n o f Te02 t o t h e MoITi and Mo/Fe oxides, suggesting t h a t t h e presence o f Moo3 and Te02 i s e s s e n t i a l f o r a c a t a l y s t t o be e f f e c t i v e f o r t h i s o x i d a t i o n . Acid-base p r o p e r t i e s of t h e c a t a l y s t s The acid-base p r o p e r t i e s of t h e t e r n a r y and b i n a r y oxide c a t a l y s t s were studied.
Simce t h e c a t a l y s t s are colored, t h e i n d i c a t e r / t i t r a t i o n method i s
262 TABLE 3 C a t a l y t i c a c t i v i t y f o r d e h y d r a t i o n and dehydrogenation o f 2-propanolQ
S
Catalyst
( X 10
mol/h
2
m )
(m2/g)
r P
ra
ralr P
0.61 2.4 1.1 1.05
7.0 2.3 15.4 8.6
15.7 2.0 26.5 20.0
2.3 0.9 1.7 2.4
Ti/Te 1014 Mo/Ti 1014 Mo/Te/Ti 10/4/4
3.7 8.6 0.9
0.18 28.7 13.3
1 .o 7.6 18.6
5.7 0.26 1.4
1014 Fe/Te MoIFe 1014 Mo/Te/Fe 101414
24.6 1.6 0.45
0.11 15.7 4.6
0.96 15.6 8.7
8.6 1.0 1.9
atomic r a t i o Mo/Te W/Te Mo/W MoITelW
*
1014 1014 1014 101414
S, s u r f a c e area:
n o t applicable.
r
P'
r a t e o f dehydration:
Therefore,
ra, r a t e o f dehydrogenation.
t h e p r o p e r t i e s were e s t i m a t e d i n d i r e c t l y from t h e
c a t a l y t i c a c t i v i t i e s f o r a c i d - and base-catalyzed t e s t - r e a c t i o n s .
As a measure
of t h e a c i d i c p r o p e r t y , t h e a c t i v i t y f o r d e h y d r a t i o n o f 2-propanol
t o propylene,
and as a measure o f t h e b a s i c p r o p e r t y , t h e ( a c t i v i t y f o r o x i d a t i v e dehydrog e n a t i o n o f 2-propanol t o a c e t o n e ) / ( a c t i v i t y r a t i o , were employed (refs.11-14).
f o r d e h y d r a t i o n o f 2-propanol)
The a c t i v i t i e s were measured under t h e
f o l l o w i n g c o n d i t i o n s : temperature, 220°C; 2-propanol c o n c e n t r a t i o n ,
1.3 mol%
i n a i r : f e e d r a t e o f a i r , 400 ml/min. The r e s u l t s a r e l i s t e d t o g e t h e r w i t h t h e s p e c i f i c s u r f a c e area i n T a b l e 3. They may be summarized as f o l l o w s . ( 1 ) The o x i d e s which a r e poor i n t h e a c i d i c p r o p e r t y a r e n o t e f f e c t i v e as c a t a l y s t s f o r t h e f o r m a t i o n o f PhA; f o r example, t h e T i / T e and Fe/Te o x i d e s . ( 2 ) The o x i d e s which a r e poor i n t h e b a s i c p r o p e r t y a r e n o t e f f e c t i v e i n t h e o x i d a t i o n : f o r example, t h e Mo/Ti.
W/Te.
and Mo/Fe oxides.
( 3 ) The a d d i t i o n o f Te02 suppresses t h e a c i d i c p r o p e r t y and enhances t h e b a s i c property, t o a c e r t a i n extent. ( 4 ) The possession o f a c e r t a i n l e v e l i n b o t h t h e a c i d i c and b a s i c p r o p e r t i e s seems t o be r e q u i r e d t o achieve a good performance i n t h e o x i d a t i o n . Performances i n t h e o x i d a t i o n o f 1-butene. To know t h e c h a r a c t e r i s t i c f e a t u r e s o f t h e t e r n a r y o x i d e s which show a good performance i n t h e o x i d a t i o n o f & - m e t h y l s t y r e n e . t h e performances o f t h e s e o x i d e s i n t h e o x i d a t i o n o f 1-butene were s t u d i e d .
The r e a c t i o n was conducted
under t h e f o l l o w i n g c o n d i t i o n s ; 1-butene c o n c e n t r a t i o n , 2.03 molz i n a i r : f e e d
263
TABLE 4 Performances i n t h e o x i d a t i o n o f 1-butene" Cata 1ys t Atomic r a t i o
T
Conv
("C)
Y i e l d (mol%) 'qH6
'C H
(moWj
Acid
Mo/W
1014
440 460
27.7 39.0
20.2 22.6
74 58
Mo/Te/W
10/4/4
440 460 480
66.3 79.4 88.8
60.3 65.9 64.7
14.4
91. 83 73.
72.0
5.4
38.0
60.0 75.4 92.1 94.5
55.0 65.5 66.5 55.0
Mo/Ti
1014
360
Mo/Te/Ti
101414
420 440 460 480
~~
',
~
7.5 92. 87. 72. 58.
25.5
~
Mo/Fe
1014
440 460
47.5 57.0
11.3 12.0
24. 21.
Mo/Te/Fe
10/4/4
460 480
34.0 41 .O
33.0 39.5
97. 96.5
*ScqH6,
s e l e c t i v i t y t o butadiene;
amount o f c a t a l y s t used, 20 g.
Acid was measured by t h e t i t r a t i o n and t h e amount was c a l c u l a t e d as a c e t i c a c i d o r maleic anhydride. r a t e o f a i r , 280 ml/min:
amount o f c a t a l y s t used, 20 g.
The y i e l d s o f
butadiene and a c i d (mainly a c e t i c a c i d and maleic anhydride) and t h e select i v i t y t o butadiene are l i s t e d i n Table 4. The r e s u l t s may be summarized as follows.
(1) The t e r n a r y oxides which show a h i g h s e l e c t i v i t y i n t h e o x i d a t i o n o f pr-methylstyrene t o PhA, show a very h i g h s e l e c t i v i t y i n t h e o x i d a t i o n o f 1-butene t o butadiene, too.
A t a h i g h conversion, a f a i r amount o f
a c e t i c a c i d and maleic anhydride i s formed.
Possibly, they may be formed
by t h e consecutive o x i d a t i o n o f butadiene. (2) The Mo/Ti and Mo/Fe oxides are n o t e f f e c t i v e i n t h e o x i d a t i o n o f 1-butene t o butadiene much as i n t h e o x i d a t i o n o f ac-methylstyrene t o PhA. s e l e c t i v i t y t o butadiene decreases i n t h e o r d e r o f Mo/W)
Mo/Fe)
The Mo/Ti.
This order i s i n c o n f o r m i t y w i t h t h a t o f t h e s e l e c t i v i t y t o PhA. (3) The a d d i t i o n o f Te02 t o t h e Mo/W oxide enhances t h e c a t a l y t i c a c t i v i t y i n o x i d a t i o n o f both d-methylstyrene and 1-butene.
Whereas, t h e a d d i t i o n o f
Te02 t o t h e Mo/Ti and Mo/Fe oxides s t r o n g l y decreases t h e a c t i v i t y i n t h e both o x i d a t i o n reactions.
The Te02 enhances t h e basic p r o p e r t y o f t h e
Mo/W oxide, whereas i t suppresses t h e a c i d i c p r o p e r t y o f t h e Mo/Ti and Mo/Fe oxides (Table 3).
264
Discussion The a d d i t i o n o f Te02 t o t h e Mo/Ti and Mo/Fe o x i d e s decreases markedly t h e o x i d a t i o n a c t i v i t y . T h i s may be a s c r i b e d t o t h e decrease i n t h e s u r f a c e area. Since b o t h a-methylstyrene and PhA a r e b a s i c compounds, t h e o x i d a t i o n o f d - m e t h y l s t y r e n e t o PhA i s a "base
+ base
t y p e r e a c t i o n " ( r e f . 10).
Therefore,
t h e possession o f b o t h a c i d i c and b a s i c p r o p e r t i e s i n a p r o p e r l e v e l i s r e q u i r e d as a c a t a l y s t f o r t h i s t y p e o f p a r t i a l o x i d a t i o n ( r e f s . 10.11.13). The Mo/Te/Ti,
Mo/Te/W,
and Mo/Te/Fe t e r n a r y o x i d e s may b e s t f i t t h e r e q u i r e d
balance and/or l e v e l o f t h e two o p p o s i t e p r o p e r t i e s . The presence of Moo3 i n t h e c a t a l y s t may be e s s e n t i a l t o have a c i d i c and redox p r o p e r t i e s .
The W03. Ti02, and Fe203 p l a y a r o l e i n enhancing t h e a c i d i c
p r o p e r t y , b u t t h e p r o p e r t y may be t o o s t r o n g t o suppress t h e s i d e - r e a c t i o n s ; f o r example, c o n s e c u t i v e o x i d a t i o n o f b a s i c p r o d u c t s and C-C bond f i s s i o n . The a d d i t i o n o f Te02 t o t h e Mo-based b i n a r y o x i d e s suppresses t h e a c i d i c p r o p e r t y t o a p r o p e r l e v e l and a l s o enhances t h e b a s i c p r o p e r t y . I t s h o u l d be noted t h a t t h e o x i d e s which show a good performance i n t h e
o x i d a t i o n o f 1-butene t o butadiene.
do n o t always show a good performance a l s o
i n t h e o x i d a t i o n o f d - m e t h y l s t y r e n e t o PhA.
F o r example, 8i-Mo-
and Sb-based
o x i d e s a r e e f f e c t i v e f o r o x i d a t i o n t o butadiene, b u t a r e n o t e f f e c t i v e f o r t h e o x i d a t i o n o f +methylstyrene
A t present.
t o PhA.
i t i s s t i l l hard t o e x p l a i n t h e reason.
We f e e l t h a t a more
s t r i c t l e v e l o f acid-base p r o p e r t i e s , which we c a n n o t measure now, i s r e q u i r e d t o a c h i e v e a good performance i n t h e o x i d a t i o n o f d - m e t h y l s t y r e n e . REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14
G. Emig and H. Hofman. J. Catal.. 84 (1983) 15-26. M. A i , Kogyo Kagaku Zasshi. 73 (1970) 946-950: Chem. Abst., 73 (1970) 76790k. M. A i , Kogyo Kagaku Zasshi. 74 (1971) 1636-1639: Chem. Abst. 75 (1971) 109992~. M. A i , Nippon Kagaku K a i s h i , (1972) 1151-1156: Chem. Abst., 77 (1972) 66559k. N.K. Nag, T. Frasen and P. Mars, J. Catal., 68 (1981) 77-85. A.J. Van Hengstum, J.E. Ommen. H. Bosch and P.J. G e l l i n g s , Appl. Catal.. 8 (1983) 369-382. C.R. Adams, J. Catal.. 10 (1968) 355-361. R.K. G r a s s e l l i , J.D. B u r r i n g t o n , D.D. Suresh, M.S. F r i e d r i c h and M.A.S. Hazle. J. Catal.. 68 (1981) 109-120. M. A i , J. Catal., ( i n press). M. Ai. i n T. Seiyama and K. Tanabe (Eds.), Proc. 7 t h I n t . Congr. Catal.. Tokyo, June 30 - J u l y 4, 1980. Kodansha. Tokyo/Elsevier, Amsterdam. 1981, pp. 1060-1 069. M. A i , J. Catal., 40 (1975) 318-326 and 327-333. M. A i , B u l l . Japan P e t r o l . I n s t . . 18 (1976) 50-54. M. Ai. B u l l . Chem. SOC. Japan, 49 (1976) 1328-1334. M. A i . J. Catal., 52 (1978) 16-24.
265 (1) which have V. CORTlS CORBERAN ( I n s t . C a t a l i s i s y Petroquimica. Spain): been y o u r i n i t i a l c r i t e r i a f o r t h e s e l e c t i o n o f m e t a l l i c c a t i o n s , and a t o m i c (2) The r a t i o s between them, f o r t h e c a t a l y s t c o m p o s i t i o n s you have used. systems you have used a r e w e l l known by t h e i r p r o p e r t i e s i n t h e c a t a l y t i c s e l e c t i v e o x i d a t i o n o f o l e f i n s and t h e o v e r a l l t e n d e n c i e s f i n a l l y found f o r t h i s r e a c t i o n ( f o r example, a d d i t i o n o f t e l l u r i u m ) p a r a l l e l t h o s e p r e v i o u s l y known f o r s e l e c t i v e o x i d a t i o n s o f o l e f i n s . Would you have expect, a p r i o r i , d i f f e r e n t tendencies, and i f so, why?
M. A 1 (Tokyo I n s t . Tech., Japan): (1) I had no i n i t i a l c r i t e r i o n : we t e s t e d v a r i o u s k i n d s o f s i n g l e and b i n a r y o x i d e systems and, then, we s e l e c t e d some t e r n a r y systems b a s i n g on t h e i n f o r m a t i o n o b t a i n e d f r o m t h e t e s t s o f b i n a r y ( 2 ) Many k i n d s o f mixed o x i d e systems have been known t o be e f f e c t i v e oxides. as c a t a l y s t f o r o x i d a t i o n of o l e f i n s . T h i s s t u d y i n d i c a t e s a t l e a s t t h a t a l l I expected, a o f them a r e n o t e f f e c t i v e f o r o x i d a t i o n o f P(-methylstyrene. p r i o r i , d i f f e r e n t tendencies, because Bi-Mo-type c a t a l y s t s a r e n o t e f f e c t i v e f o r t h i s oxidation. R.K. GRASSELLI (Mobil Research and Develop., USA): You s t a t e i n y o u r conclus i o n s t h a t Sb-based c a t a l y s t w h i l e e f f e c t i v e f o r t h e o x i d a t i o n o f I - b u t e n e t o butadiene are n o t e f f e c t i v e f o r t h e o x i d a t i o n o f d-methylstyrene t o atropoaldehyde, a p p a r e n t l y i n c o n t r a s t t o Mo-Te-Ti. Mo-Te-W, and Mo-Te-Fe based c a t a l y s t s I should l i k e t o remind you t h a t o u r work which you k i n d l y whichyou s t u d i e d , quoted as r e f e r e n c e 8, c l e a r l y showed t h a t d - m e t h y l s t y r e n e i s e f f e c t i v e l y conv e r t e d t o atropoaldehyde w i t h Nb-U-Sb based c a t a l y s t s , i n f a c t t h e s e l e c t i v i t i e s which we r e p o r t e d w i t h o u r antimony based c a t a l y s t s r i v a l y o u r b e s t systems, w h i l e I agree t h a t c a t a l y t i c systems must be o p t i m i z e d f o r each g i v e n r e a c t i o n . There i s no a p r i o r i reason t o e x c l u d e antimony f o r t h e o x i d a t i o n o f d - m e t h y l styrene.
M.AI (Tokyo I n s t . Tech.,
Japan): I c o u l d n o t g e t a good performance w i t h Sb, Mo-Sb, and Mo-Te-Sb oxides, b u t I d i d n o t t r y t o t e s t w i t h U-Sb o x i d e s because you had a l r e a d y t e s t e d w i t h them. Therefore, I t h i n k t h a t y o u r a r e reason. What parameter i s f o r you a measure J. KIJENSKI (Warsaw P o l i t e c h n i k a , Poland): o f a c i d i t y o r b a s i c i t y of m o l e c u l e and a l l o w you t o c o n s i d e r a p a r t i c u l a r r e a c t i o n as e.g., "acid-base'' process?
M. A 1 (Tokyo I n s t . Tech., Japan): I have n o t s p e c i a l o p i n i o n about t h e d e f i n i t i o n o f acid-base. Indeed, o r d i n a r y i n d i c a t o r / t i t r a t i o n method i s n o t a p p l i c a b l e f o r o x i d a t i o n c a t a l y s t s because o f t h e i r d a r k c o l o r . On t h e o t h e r hand, t h e gas phase a d s o r p t i o n method c o n t a i n s some problems. Therefore, a t p r e s e n t t h e measurement o f c a t a l y t i c a c t i v i t y f o r acid-base c a t a l y z e d model r e a c t i o n s seems t o be t h e most combinient. though t h e r e remains arguments about t h e d e f i n i t i o n and s t r e n g t h o f acid-base. B. GRZYBOWSKA ( I n s t . Catal. S u r f a c e Chem.. Poland): ( 1 ) I n t h e Me-Mo-Te t e r n a r y o x i d e systems t h e r e e x i s t w e l l d e f i n e d compounds (e.g., telluromolybdates o f Co. Mn, N i , Cd) s y n t h e s i z e d and c h a r a c t e r i z e d by S l o c z y n s k i ( r e f . 1) and by F o r z a t t i . T r i f i r 6 . and V i l l a ( r e f . 2 ) . They have shown t o be a c t i v e a l s o i n a r o m a t i c hydrocarbon o x i d a t i o n ( r e f , 3). There e x i s t a l s o w e l l d e f i n e d phases i n Mo-Te-0 system. Both acid-base and o x i d i z i n g p r o p e r t i e s w i l l depend s t r o n g l y on phase c o m p o s i t i o n o f y o u r c a t a l y s t s and mode o f mutual arrengement o f t h e phases and n o t o n l y on t h e presence o f p a r t i c u l a r i o n s i n p r e d e f i n e d environment. I b e l i e v e t h a t t h e s e f a c t s should be t a k e n i n t o account when (2) Adding some comments t o t h e q u e s t i o n c o n s i d e r i n g t h e o x i d a t i o n mechanism. l e t me remind t h a t some a u t h o r s c o n s i d e r t h e i o n i z a t i o n of Prof. K i j e n s k i : p o t e n t i a l o f a molecule as a measure o f a c i d i t y , b a s i c i t y [see r e v i e w s by Ruckenstein e t a1 ( r e f . 4)]. ( 3 ) The d i s c u s s i o n on r e l a t i o n between oneI n t h e case o f e l e c t r o n and t w o - e l e c t r o n (acid-base) p r o p e r t i e s i s s t i l l open.
266
s o l i d f o r i n s t a n c e t h e r e a r e some a t t e m p t s t o r e c o n c i l e t h e b o t h p r o p e r t i e s ( r e f . 5) - showing t h a t s u r f a c e o n e - e l e c t r o n a c c e p t o r s t a t e s can be i d e n t i c a l and i n v o l v e t h e same o r b i t a l s as Lewis a c i d i c s i t e s , p r o v i d e d t h e a c c e p t o r l e v e l l i e s below t h e Fermi energy l e v e l . 1 J. S l o c z y n s k i , Z. Anorg. A l l g . Chem., 438 (1978) 287. 2 P. F o r z a t t i , F. T r i f i r 6 , P.L. V i l l a , J. Catal., 55 (1978) 52. 3 B. Grzybowska, M. Czerwenka, J. S l o c z y n s k i , Catal., Today, 1 (1987) 157. 4 D.B. Dadyburjor, S.S. Jewur, E. Ruckenstein, Catal. Rev., 19 (1979) 293. 5 S.R. Morrison, Surf. Sci., 50 (1975) 329. M.AI
(Tokyo I n s t . Tech.,
Japan):
Thank You f o r y o u r comments.
J. K I J E N S K I (Warsaw P o l i t e c h n i k a . Poland): Comment t o t h e remark o f P r o f . Grzybowska: I n o n i z a t i o n energy c a n n o t be c o n s i d e r e d as a measure o f a c i d i t y o r b a s i c i t y w h i c h a r e i o n i c , i.e., two e l e c t r o n p r o p e r t i e s . There i s no g e n e r a l p a r a l l e l i s m between t h e b a s i c i t y and e l e c t r o n donor p r o p e r t i e s .
J. HABER ( I n s t . C a t a l . S u r f a c e Chem., Poland): (1) What i s t h e r e p r o d u c t i v i t y o f y o u r r e s u l t s . The d a t a seem t o - b e c o n s i d e r a b l y spread which may i n d i c a t e ( 2 ) One o f t h e i m p o r t a n t s i d e t h e i r dependence on u n c o n t r o l l e d f a c t o r s . r e a c t i o n s o f m e t h y l s t y r e n e i s c e r t a i n l y cracking which w i l l o c c u r on more a c i d i c c a t a l y s t s and w i l l r i v a l u a t e t h e m e c h a n i s t i c c o n c l u s i o n s . D i d you t r y t o d e t e r m i n e t h e c o n t r i b u t i o n f r o m c r a c k i n g by c a r r i n g t e s t experiments i n t h e absence o f oxygen. M. A1 (Tokyo I n s t . Tech., Japan): ( 1 ) I d i d n o t f i n d t h a t t h e r e p r o d u c t i v i t y o f t h i s o x i d a t i o n i s s p e c i a l l y low. However, p h e n y l a c r o l e i n i s n o t s t a b l e , i.e., i t t e n d s t o p o l y m e r i z e t o dimer and t r i m e r . Indeed, I cannot measure t h e amount o f t h e s e polymers. Therefore, " o t h e r " may c o n s i t m a i n l y o f polymers. (2) I n t h e p r e d e c i n g work ( r e f . 9 i n t h e t e x t ) , t h e e f f e c t o f oxygen concentrat i o n was s t u d i e d . The consumption o f d - m e t h y l s t y r e n e i n c r e a s e s almost i n p r o p o r t i o n a l t o t h e oxygen c o n c e n t r a t i o n . Therefore, t h e cracking may be s m a l l a t l e a s t o v e r t h e Mo-Te-based c a t a l y s t s .
257
VAPOR-PHASE OXIDATION OF ALPHA-METHYLSTYRENE TO PHENYLACROLEIN
M. A1 Research L a b o r a t o r y o f Resources U t i l i z a t i o n , Tokyo I n s t i t u t e o f Technology, Yokohama 227 (Japan)
4259 Nagatsuta, Midori-ku, ABSTRACT
V a r i o u s Mo-Te-based t e r n a r y o x i d e s were t e s t e d as c a t a l y s t s f o r t h e vaporphase a i r o x i d a t i o n o f P t - m e t h y l s t y r e n e t o f o r m p h e n y l a c r o l e i n (atropoaldehyde). The b e s t c a t a l y s t performances were found w i t h Mo/Te/Ti, Mo/Te/W, and Mo/Te/Fe oxides: t h e one-pass y i e l d o f p h e n y l a c r o l e i n a t t a i n e d 63 mol% a t t h e ol-methyls t y r e n e c o n v e r s i o n o f 96.5 %. The c a t a l y t i c f u n c t i o n s o b t a i n e d w i t h t h e s e c o m b i n a t i o n s o f o x i d e s were a l s o i n v e s t i g a t e d i n t h e l i g h t o f b o t h acid-base and o x i d i z i n g f u n c t i o n s o b t a i n e d f r o m t h e c a t a l y t i c a c t i v i t y f o r d e h y d r a t i o n dehydrogenation o f 2-propanol and o x i d a t i o n o f 1-butene. INTRODUCTION Propylene i s o x i d i z e d t o a c r o l e i n w i t h a v e r y h i g h s e l e c t i v i t y o v e r Bi-Moand Sb-based mixed-oxide c a t a l y s t s . i.e.,
F u r t h e r , m e t h y l - s u b s t i t u t e d propylene,
n-butene and isobutene, a r e o x i d i z e d t o b u t a d i e n e and m e t h a c r o l e i n ,
r e s p e c t i v e l y , o v e r s i m i l a r t y p e o f mixed-oxide c a t a l y s t s .
However, i n t h e
o x i d a t i o n o f a r o m a t i c compounds, t h e s e c a t a l y s t s cannot u s u a l l y e x h i b i t an e x c e l l e n t performance.
Indeed, i n t h e o x i d a t i o n o f ethylbenzene t o s t y r e n e ,
t h e c a t a l y s t s proposed t o be e f f e c t i v e a r e d i f f e r e n t f r o m t h o s e used i n t h e o x i d a t i o n o f p r o p y l e n e and butenes ( r e f . 1 ) . benzaldehyde, V-P o x i d e s ( r e f . 2),
I n the o x i d a t i o n o f toluene t o
Mo-P o x i d e s ( r e f . 3 ) . Mo-P-based
o x i d e s ( r e f . 4), Mo-based o x i d e s ( r e f .
5).
and V-Ti o x i d e s ( r e f .
ternary
6) have been
proposed t o be e f f e c t i v e . As f o r t h e o x i d a t i o n o f p h e n y l - s u b s t i t u t e d propylene, i.e., [2-phenylpropene]
t o f o r m d - p h e n y l a c r o l e i n [ atropoaldehyde,
d-methylstyrene
2-phenylpropenal ]
( a b b r e v i a t e d h e r e a f t e r as PhA), t h e r e have been v e r y few s t u d i e s .
Adams ( r e f .
7 ) r e p o r t e d t h a t Bi-Mo o x i d e i s n o t e f f e c t i v e : t h e y i e l d o f PhA i s about 3 mol% a t t h e d - m e t h y l s t y r e n e c o n v e r s i o n o f 45 %. Recently, G r a s s e l l i e t a l . ( r e f . 8) r e p o r t e d a 30 mol% y i e l d o f PhA a t t h e c o n v e r s i o n o f 50 % o v e r Nb-promoted Sb-U oxides. I n t h e p r e c e d i n g s t u d y ( r e f . 9).
i t was found t h a t t h e b e s t performance f o r
t h e p r o d u c t i o n o f PhA i s o b t a i n e d w i t h Moo3 among t h e v a r i o u s s i n g l e - o x i d e s t e s t e d and t h a t Mo/Te atomic r a t i o = 10/4 o x i d e e x h i b i t s t h e b e s t performance among t h e v a r i o u s Mo-based b i n a r y o x i d e s t e s t e d .
The y i e l d o f PhA a t t a i n e d
258 48.5 mol% a t t h e c o n v e r s i o n o f 96.3 %. I t was a l s o found t h a t d - m e t h y l s t y r e n e i s much more r e a c t i v e t h a n p r o p y l e n e and butenes. I n t h i s study, f o r purpose o f e x p l o r i n g more e f f e c t i v e c a t a l y s t s f o r t h i s p a r t i a l o x i d a t i o n , v a r i o u s o x i d e s were combined w i t h t h e Mo/Te atomic r a t i o = 10/4 o x i d e and t h e i r c a t a l y t i c p r o p e r t i e s were t e s t e d .
Then, t h e f u n c t i o n s o f
o x i d e r e q u i r e d f o r c a t a l y z i n g t h i s o x i d a t i o n r e a c t i o n were i n v e s t i g a t e d . EXPERIMENTAL Catalysts The c a t a l y s t s used i n t h i s s t u d y were Mo/Te/X ( X i s t h e t h i r d component) a t o m i c r a t i o = 10/4/x ( x = 0 t o 16) t e r n a r y oxides.
They were supported on 8-
t o 20-mesh s i z e pumice o r i g i n a t i n g from v o l c a n i c stone c o n s i s t i n g o f macropores
2
( p a c k i n g d e n s i t y = ca. 0.4 g/ml and s p e c i f i c s u r f a c e area = 0.3 t o 0.6 m /g). F o r example, t h e Mo/Te/W = 10/4/8 c a t a l y s t was prepared as f o l l o w s . (NH ) 4 6
Mo7024.4H20 (35.3 g ) was d i s s o l v e d i n h o t w a t e r and 41.8 g o f (NH4)10W,2041'
5H20 was a l s o d i s s o l v e d i n a n o t h e r h o t w a t e r u s i n g o x a l i c acid.
The two s o l u -
t i o n s were mixed and 18.0 g o f H6Te06 was d i s s o l v e d t o t h e s o l u t i o n .
Excess
w a t e r was evaporated o f f w i t h s t i r r i n g w i t h t h e a i d o f h o t a i r c u r r e n t , y i e l d i n g a s t i c k y syrup.
T h e r e a f t e r , 100 m l o f t h e pumice was added t o t h e s t i c k y
s y r u p and t h e m i x t u r e was evaporated t o dryness w i t h s t i r r i n g w i t h t h e a i d o f h o t a i r current.
The o b t a i n e d s o l i d was evaporated a g a i n i n an oven a t 200°C
f o r 4 h and t h e n i t was c a l c i n e d a t 450°C f o r 6 h i n a stream o f a i r . R e a c t i o n procedures The vapor-phase c o n t a c t o x i d a t i o n o f d - m e t h y l s t y r e n e was conducted w i t h 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 system. cm l o n g and 1.8 cm i.d.,
The r e a c t o r was made o f a s t e e l tube, 50
mounted v e r t i c a l l y and immersed i n a l e a d bath.
Air
was i n t r o d u c e d f r o m t h e t o p o f t h e r e a c t o r . w i t h d - m e t h y l s t y r e n e b e i n g i n j e c t e d i n t o t h e p r e h e a t i n g s e c t i o n o f t h e r e a c t o r by means o f a s y r i n g e pump. Unless o t h e r w i s e i n d i c a t e d , t h e f e e d r a t e s were f i x e d as f o l l o w s : a i r , 400 m l ( a t 20°C)/min (ca.
i n air).
1.0 mol/h);
d - m e t h y l s t y r e n e . 11.9 mmol/h (ca. 1.19 mol%
The e f f l u e n t gas f r o m t h e ' r e a c t o r was l e d s u c c e s s i v e l y i n t o f o u r
c h i l l e d scrubbers c o n t a i n i n g 2-propanol pounds. (120 m l ) .
A f e t r 1 h time-on-stream,
t o r e c o v e r t h e 2-propanol-soluble
com-
t h e c o n t e n t o f t h e scrubbers was c o l l e c t e d
The r e a c t i o n p r o d u c t s and unreactedd-methylstyrene were analysed by
gas chromatograph: a 1-m column o f M o l e c u l a r s i e v e 13X f o r CO; a 6-m column o f p r o p y l e n e carbonate f o r C02; a 2-m column o f PEG 20M a t 160°C f o r d - m e t h y l s t y rene, benzaldehyde, and 2-propanol;
a 1-m column o f AT-1200 t H3P04 a t 160°C
f o r PhA, benzaldehyde. m a l e i c anhydride,
and benzoic acid.
The amount o f t o t a l
a c i d was a l s o checked by t i t r a t i o n w i t h 0.1 N NaOH u s i n g a pH meter.
The
259 amount was u s u a l l y i n accord w i t h t h e sum o f maleic anhydride and benzoic a c i d measured by gas chromatograph. Since PhA i s n o t a v a i l a b l e as a chemical agent, t h e i d e n t i f i c a t i o n was performed by means o f GC-MS ( H i t a c h i H-80) and t h e q u a n t i t y was determined on t h e b a s i s o f t h e approximation t h a t t h e peak area o f PhA recorded i n gas chromatograph ( F I D ) i s equal t o t h a t o f cinnamaldehyde [p-phenylacrolein,
3-phenyl-
propenal 1. The y i e l d and s e l e c t i v i t y o f a p a r t i c u l a r product were defined as mole percentage y i e l d and s e l e c t i v i t y on a carbon-account-fo; o f carbon oxides [COX].
basis.
As f o r t h e y i e l d
t h e COX accompanied w i t h t h e formation o f benzoic acid,
benzaldehyde, and maleic anhydride was excluded.
RESULTS AND DISCUSSION Performances o f t h e Mo-Te-based
t e r n a r y oxide c a t a l y s t s
The r e s u l t s obtained over 10 g-portions o f Mo-Te-based t e r n a r y oxide catal y s t s a t t h e o p t i m a l r e a c t i o n temperatures are l i s t e d i n Table 1, according t o t h e c l a s s i f i c a t i o n o f oxide i n view o f both acid-base and o x i d i z i n g f u n c t i o n s ( r e f . 9,lO).
The r e s u l t s may be summarized as follows.
( 1 ) The a d d i t i o n o f W03, Ti02, and Fep03 t o t h e Mo/Te = 10/4 oxide enhances markedly b o t h t h e o x i d a t i o n a c t i v i t y and s e l e c t i v i t y t o PhA.
The presence
o f an optimum amount was observed f o r each t h i r d component. ( 2 ) The b e s t r e s u l t s are obtained w i t h t h e Mo/Te/Ti = 10/4/4 oxide: t h e onepass y i e l d of PhA a t t a i n s 63.0 mol% a t t h e d - m e t h y l s t y r e n e conversion o f 96.5 %.
(3) The second best r e s u l t s a r e obtained w i t h t h e Mo/Te/W = 10/4/8 oxide: t h e PhA y i e l d a t t a i n s 59.5 mol% a t t h e conversion o f 98.4
4.
(4) The t h i r d b e s t r e s u l t s are obtained w i t h t h e Mo/Te/Fe = 10/4/4 oxide: t h e PhA y i e l d a t t a i n s 58.0 mol% a t t h e conversion o f 96.7 %.
(5) The a d d i t i o n o f Zr02,
Bi20g, and Co304 enhances t h e o x i d a t i o n a c t i v i t y , b u t
i t enhances t h e s e l e c t i v i t y o n l y a l i t t l e . (6) The e f f e c t o f V205 i s small.
( 7 ) The a d d i t i o n of U308. SnO2. ZnO. NiO, and Mn02 enhances t h e o x i d a t i o n a c t i v i t y , b u t i t decreases t h e s e l e c t i v i t y .
(8) The a d d i t i o n o f an a c i d i c oxide such as P205, B203, and Sb205 decreases markedly t h e o x i d a t i o n a c t i v i t y and i t does n o t improve t h e s e l e c t i v i t y . Performances o f t h e b i n a r y oxide c a t a l y s t s For understanding t h e f u n c t i o n o f each component i n t h e Mo/Te/W, Mo/Te/Ti. and Mo/Te/Fe t e r n a r y oxides, t h e c a t a l y s t performance f o r t h e o x i d a t i o n o f d-methylstyrene obtained over each b i n a r y oxide c o n s i s t i n g o f t h e t e r n a r y
260
TABLE 1 Performances o f Mo-Te-based t e r n a r y o x i d e c a t a l y s t s * Catalyst atomic r a t i o Mo
T ("C)
Conv
(2)
PhA
Baci
Y i e l d (mol%) Bald MA COX
450 460
81.5 90.0
18.5 20.5
12.5 13.8
15.9 17.1
5.6 7.0
4.1 6.4
24.9 15.2
23.0 23.0
other
'PhA (mol%)
Mo/Te
1014
430 440
92.5 96.3
45.0 48.5
11.3 13.7
2.5 2.0
2.1 2.0
4.4 5.0
27.2 25.1
48.5 50.5
Mo/Te/P Mo/Te/B Mo/Te/Sb Mo/Te/Zr
101414 101414 101414 101414
468 500 490 415
95.7 58.5 78.0 91.4
44.0 26.5 42.0 51.5
12.4 3.9 8.2 11.5
4.3 2.5 7.7 5.0
4.5 2.0 3.0 4.5
8.1 3.3 4.8 7.0
22.4 20.3 12.7 11.9
46.0 45.0 54.0 56.0
Mo/Te/W
101412
395 400
88.8 95.9
52.5 55.5
11.9 14.6
3.0 5.2
3.4 3.3
4.7 3.7
13.3 13.6
59.1 57.9
101414
390 410
54.0 93.5
37.0 53.5
6.0 11.3
2.4 4.5
1.5 1.6
1.8 5.0
5.3 17.6
69.0 57.0
101418
385 390 395
89.0 96.2 98.4
58.5 58.5 59.5
12.3 13.2 16.9
3.0 3.6 4.2
2.6 2.5 2.9
3.8 4.4 4.9
8.8 14.0 10.0
66.0 61 .O 60.5
1014116
375 38 5
51 .O 85.5
21.8 28.2
8.7 16.3
3.6 8.4
2.9 5.0
3.0 7.8
11.0 19.8
43.0 33.0
Mo/Te/V
101414
435 440
88.5 95.0
46.5 45.5
15.8 14.1
6.7 7.1
2.5 2.5
2.9 6.0
14.1 19.8
52.5 48.0
Mo/Te/U
101414
400
94.7
44.1
14.1
4.8
4.7
4.8
22.2
46.5
Mo/Te/Ti 101412
440 4 50
83.7 88.3
47.8 49.3
8.1 9.3
3.6 4.8
3.2 2.8
2.6 4.1
18.4 18.0
57.0 56.0
101414
390 400
83.5 96.5
59.3 63.0
13.7 15.0
2.4 3.6
3.5 3.2
2.3 3.8
2.3 7.4
71 .O 65.0
101418
400 41 0
90.6 96.7
50.5 56.8
12.8 15.7
2.4 4.8
3.2 3.2
5.5 5.6
16.2 10.6
56.0 59.0
Mo/Te/Sn 101414
390
90.0
27.0
12.3
3.6
7.2
24.7
14.7
30.3
Mo/Te/Fe 101414
420 430 375 385
89.0 96.7 86.5 90.0
56.8 58.0 40.7 44.1
11.4 13.3 22.0 18.5
4.0 3.6 9.6 8.4
3.4 3.5 4.5 3.0
0.6 0.6 1.4 3.7
12.8 17.2 8.3 12.3
64.0 60.0 47.0 49.0
Mo/Te/Bi 101414 Mo/TelZn 101414 Mo/Te/Ni 101414
395 41 0 390
83.2 96.2 96.4
47.6 47.2 40.5
9.6 16.0 15.8
3.0 4.8 4.2
2.1 5.0 4.6
7.5 4.7 10.5
13.3 18.5 20.8
57.2 49.0 41.8
Mo/Te/Co 101414
390 400
82.0 94.8
46.1 49.3
14.7 14.7
2.4 3.6
0.7 3.6
6.0 7.7
12.1 15.9
56.2 52.0
Mo/Te/Cr 10/4/4 Mo/Te/Mn 101414
405 41 0
89.6 92.7
40.2 36.3
17.4 15.3
4.8 5.4
5.0 4.1
7.0 10.7
15.0 20.9
44.6 39.1
101418
*
T = temperature, PhA = phenylacrolein, Baci = benzoic hyde, MA = maleic anhydride, COX = carbon oxides, o t h e r of d-methylstyrene) - ( sum o f t h e y i e l d s of PhA t Baci SphA = s e l e c t i v i t y t o PhA, amount o f c a t a l y s t used = 10
acid, Bald = benzalde= [ ( o v e r a l l conversion
t Bald t COX)], g.
261 TABLE 2 Comparison o f t h e performances of t h e t e r n a r y oxides w i t h those of b i n a r y oxides Cata 1y s t
T
Conv
atomic r a t i o
("C)
(X)
PhA
Baci
Bald
MA
1014 1014 1014 101418
440 400 410 395
96.3 88.0 95.8 98.4
48.5 32.5 46.2 59.5
13.7 11.5 18.6 16.9
2.0 4.8 9.6 4.2
2.0 4.1 4.0 2.9
5.0 12.9 4.0 4.9
25.1 22.2 13.4 10.0
50.5 37.0 48.3 60.5
Mo/Te Ti/Te Mo/Ti Mo/Te/Ti
1014 1014 1014 101414
440 410 350 400
96.3 52.0 89.0 96.5
48.5 23.3 6.4 63.0
13.7 4.9 9.4 15.0
2.0 2.4 5,4 3.6
2.0 2.1 15.3 3.2
5.0 14.7 31.4 3.8
25.1 4.6 21.1 7.4
50.5 45.0 7.2 65.0
Mo/Te Fe/Te Mo/Fe Mo/Te/Fe
1014 1014 1014 10/4/4
440 345 370 430
96.3 33.0 79.4 96.7
48.5 1.7 18.1 58.0
13.7 0. 14.7 13.3
2.0 4.8 7.8 3.6
2.0 0. 6.5 3.5
5.0 17.5 4.9 0.6
25.1 9.0 27.4 17.2
50.5 5.1 22.8 60.0
Mo/Te W/Te Mo/W Mo/Te/W
Y i e l d (mol%)
COX
other
'PhA (molX)
~
~~
Abbreviations a r e t h e same as f o r Table 1. The amount o f c a t a l y s t used i s 10 g. oxides were compared w i t h those obtained over t h e t e r n a r y oxides. The t e s t s The r e s u l t s a r e shown i n
were performed u s i n g 10 g-portion o f t h e c a t a l y s t s . Table 2. The r e s u l t s may be summarized as follows.
W03 by i t s e l f i s n o t e f f e c t i v e as a c a t a l y s t f o r t h i s o x i d a t i o n ( r e f . 9) and Te02 has no o x i d a t i o n a c t i v i t y .
However, t h e combination o f t h e two
oxides generates a h i g h o x i d a t i o n a c t i v i t y , b u t t h e s e l e c t i v i t y t o PhA i s lower and t h e formation of COX i s much g r e a t e r than those obtained w i t h t h e MoITe oxide.
On t h e o t h e r hand, t h e a d d i t i o n o f W03 t o Moog enhances
markedly both t h e o x i d a t i o n a c t i v i t y and s e l e c t i v i t y :
t h e performance o f
t h e Mo/W = 1014 oxide i s comparable w i t h t h a t o f t h e Mo/Te = 1014 oxide. Therefore. i t i s considered t h a t t h e a d d i t i o n o f Te02 improves t h e Mo/W oxide much as i t improves t h e Moo3 alone c a t a l y s t . The performances o f t h e T i I T e and Fe/Te oxides are much lower than t h a t o f t h e W/Te oxide.
Further. t h e a d d i t i o n o f Ti02 and Fe203 t o Moo3
increases t h e o x i d a t i o n a c t i v i t y , b u t i t decreases t h e s e l e c t i v i t y t o PhA. However, an e x c e l l e n t c a t a l y t i c performance i s obtained by t h e a d d i t i o n o f Te02 t o t h e MoITi and Mo/Fe oxides, suggesting t h a t t h e presence o f Moo3 and Te02 i s e s s e n t i a l f o r a c a t a l y s t t o be e f f e c t i v e f o r t h i s o x i d a t i o n . Acid-base p r o p e r t i e s of t h e c a t a l y s t s The acid-base p r o p e r t i e s of t h e t e r n a r y and b i n a r y oxide c a t a l y s t s were studied.
Simce t h e c a t a l y s t s are colored, t h e i n d i c a t e r / t i t r a t i o n method i s
262 TABLE 3 C a t a l y t i c a c t i v i t y f o r d e h y d r a t i o n and dehydrogenation o f 2-propanolQ
S
Catalyst
( X 10
mol/h
2
m )
(m2/g)
r P
ra
ralr P
0.61 2.4 1.1 1.05
7.0 2.3 15.4 8.6
15.7 2.0 26.5 20.0
2.3 0.9 1.7 2.4
Ti/Te 1014 Mo/Ti 1014 Mo/Te/Ti 10/4/4
3.7 8.6 0.9
0.18 28.7 13.3
1 .o 7.6 18.6
5.7 0.26 1.4
1014 Fe/Te MoIFe 1014 Mo/Te/Fe 101414
24.6 1.6 0.45
0.11 15.7 4.6
0.96 15.6 8.7
8.6 1.0 1.9
atomic r a t i o Mo/Te W/Te Mo/W MoITelW
*
1014 1014 1014 101414
S, s u r f a c e area:
n o t applicable.
r
P'
r a t e o f dehydration:
Therefore,
ra, r a t e o f dehydrogenation.
t h e p r o p e r t i e s were e s t i m a t e d i n d i r e c t l y from t h e
c a t a l y t i c a c t i v i t i e s f o r a c i d - and base-catalyzed t e s t - r e a c t i o n s .
As a measure
of t h e a c i d i c p r o p e r t y , t h e a c t i v i t y f o r d e h y d r a t i o n o f 2-propanol
t o propylene,
and as a measure o f t h e b a s i c p r o p e r t y , t h e ( a c t i v i t y f o r o x i d a t i v e dehydrog e n a t i o n o f 2-propanol t o a c e t o n e ) / ( a c t i v i t y r a t i o , were employed (refs.11-14).
f o r d e h y d r a t i o n o f 2-propanol)
The a c t i v i t i e s were measured under t h e
f o l l o w i n g c o n d i t i o n s : temperature, 220°C; 2-propanol c o n c e n t r a t i o n ,
1.3 mol%
i n a i r : f e e d r a t e o f a i r , 400 ml/min. The r e s u l t s a r e l i s t e d t o g e t h e r w i t h t h e s p e c i f i c s u r f a c e area i n T a b l e 3. They may be summarized as f o l l o w s . ( 1 ) The o x i d e s which a r e poor i n t h e a c i d i c p r o p e r t y a r e n o t e f f e c t i v e as c a t a l y s t s f o r t h e f o r m a t i o n o f PhA; f o r example, t h e T i / T e and Fe/Te o x i d e s . ( 2 ) The o x i d e s which a r e poor i n t h e b a s i c p r o p e r t y a r e n o t e f f e c t i v e i n t h e o x i d a t i o n : f o r example, t h e Mo/Ti.
W/Te.
and Mo/Fe oxides.
( 3 ) The a d d i t i o n o f Te02 suppresses t h e a c i d i c p r o p e r t y and enhances t h e b a s i c property, t o a c e r t a i n extent. ( 4 ) The possession o f a c e r t a i n l e v e l i n b o t h t h e a c i d i c and b a s i c p r o p e r t i e s seems t o be r e q u i r e d t o achieve a good performance i n t h e o x i d a t i o n . Performances i n t h e o x i d a t i o n o f 1-butene. To know t h e c h a r a c t e r i s t i c f e a t u r e s o f t h e t e r n a r y o x i d e s which show a good performance i n t h e o x i d a t i o n o f & - m e t h y l s t y r e n e . t h e performances o f t h e s e o x i d e s i n t h e o x i d a t i o n o f 1-butene were s t u d i e d .
The r e a c t i o n was conducted
under t h e f o l l o w i n g c o n d i t i o n s ; 1-butene c o n c e n t r a t i o n , 2.03 molz i n a i r : f e e d
263
TABLE 4 Performances i n t h e o x i d a t i o n o f 1-butene" Cata 1ys t Atomic r a t i o
T
Conv
("C)
Y i e l d (mol%) 'qH6
'C H
(moWj
Acid
Mo/W
1014
440 460
27.7 39.0
20.2 22.6
74 58
Mo/Te/W
10/4/4
440 460 480
66.3 79.4 88.8
60.3 65.9 64.7
14.4
91. 83 73.
72.0
5.4
38.0
60.0 75.4 92.1 94.5
55.0 65.5 66.5 55.0
Mo/Ti
1014
360
Mo/Te/Ti
101414
420 440 460 480
~~
',
~
7.5 92. 87. 72. 58.
25.5
~
Mo/Fe
1014
440 460
47.5 57.0
11.3 12.0
24. 21.
Mo/Te/Fe
10/4/4
460 480
34.0 41 .O
33.0 39.5
97. 96.5
*ScqH6,
s e l e c t i v i t y t o butadiene;
amount o f c a t a l y s t used, 20 g.
Acid was measured by t h e t i t r a t i o n and t h e amount was c a l c u l a t e d as a c e t i c a c i d o r maleic anhydride. r a t e o f a i r , 280 ml/min:
amount o f c a t a l y s t used, 20 g.
The y i e l d s o f
butadiene and a c i d (mainly a c e t i c a c i d and maleic anhydride) and t h e select i v i t y t o butadiene are l i s t e d i n Table 4. The r e s u l t s may be summarized as follows.
(1) The t e r n a r y oxides which show a h i g h s e l e c t i v i t y i n t h e o x i d a t i o n o f pr-methylstyrene t o PhA, show a very h i g h s e l e c t i v i t y i n t h e o x i d a t i o n o f 1-butene t o butadiene, too.
A t a h i g h conversion, a f a i r amount o f
a c e t i c a c i d and maleic anhydride i s formed.
Possibly, they may be formed
by t h e consecutive o x i d a t i o n o f butadiene. (2) The Mo/Ti and Mo/Fe oxides are n o t e f f e c t i v e i n t h e o x i d a t i o n o f 1-butene t o butadiene much as i n t h e o x i d a t i o n o f ac-methylstyrene t o PhA. s e l e c t i v i t y t o butadiene decreases i n t h e o r d e r o f Mo/W)
Mo/Fe)
The Mo/Ti.
This order i s i n c o n f o r m i t y w i t h t h a t o f t h e s e l e c t i v i t y t o PhA. (3) The a d d i t i o n o f Te02 t o t h e Mo/W oxide enhances t h e c a t a l y t i c a c t i v i t y i n o x i d a t i o n o f both d-methylstyrene and 1-butene.
Whereas, t h e a d d i t i o n o f
Te02 t o t h e Mo/Ti and Mo/Fe oxides s t r o n g l y decreases t h e a c t i v i t y i n t h e both o x i d a t i o n reactions.
The Te02 enhances t h e basic p r o p e r t y o f t h e
Mo/W oxide, whereas i t suppresses t h e a c i d i c p r o p e r t y o f t h e Mo/Ti and Mo/Fe oxides (Table 3).
264
Discussion The a d d i t i o n o f Te02 t o t h e Mo/Ti and Mo/Fe o x i d e s decreases markedly t h e o x i d a t i o n a c t i v i t y . T h i s may be a s c r i b e d t o t h e decrease i n t h e s u r f a c e area. Since b o t h a-methylstyrene and PhA a r e b a s i c compounds, t h e o x i d a t i o n o f d - m e t h y l s t y r e n e t o PhA i s a "base
+ base
t y p e r e a c t i o n " ( r e f . 10).
Therefore,
t h e possession o f b o t h a c i d i c and b a s i c p r o p e r t i e s i n a p r o p e r l e v e l i s r e q u i r e d as a c a t a l y s t f o r t h i s t y p e o f p a r t i a l o x i d a t i o n ( r e f s . 10.11.13). The Mo/Te/Ti,
Mo/Te/W,
and Mo/Te/Fe t e r n a r y o x i d e s may b e s t f i t t h e r e q u i r e d
balance and/or l e v e l o f t h e two o p p o s i t e p r o p e r t i e s . The presence of Moo3 i n t h e c a t a l y s t may be e s s e n t i a l t o have a c i d i c and redox p r o p e r t i e s .
The W03. Ti02, and Fe203 p l a y a r o l e i n enhancing t h e a c i d i c
p r o p e r t y , b u t t h e p r o p e r t y may be t o o s t r o n g t o suppress t h e s i d e - r e a c t i o n s ; f o r example, c o n s e c u t i v e o x i d a t i o n o f b a s i c p r o d u c t s and C-C bond f i s s i o n . The a d d i t i o n o f Te02 t o t h e Mo-based b i n a r y o x i d e s suppresses t h e a c i d i c p r o p e r t y t o a p r o p e r l e v e l and a l s o enhances t h e b a s i c p r o p e r t y . I t s h o u l d be noted t h a t t h e o x i d e s which show a good performance i n t h e
o x i d a t i o n o f 1-butene t o butadiene.
do n o t always show a good performance a l s o
i n t h e o x i d a t i o n o f d - m e t h y l s t y r e n e t o PhA.
F o r example, 8i-Mo-
and Sb-based
o x i d e s a r e e f f e c t i v e f o r o x i d a t i o n t o butadiene, b u t a r e n o t e f f e c t i v e f o r t h e o x i d a t i o n o f +methylstyrene
A t present.
t o PhA.
i t i s s t i l l hard t o e x p l a i n t h e reason.
We f e e l t h a t a more
s t r i c t l e v e l o f acid-base p r o p e r t i e s , which we c a n n o t measure now, i s r e q u i r e d t o a c h i e v e a good performance i n t h e o x i d a t i o n o f d - m e t h y l s t y r e n e . REFERENCES 1 2 3 4 5 6 7 8 9 10 11 12 13 14
G. Emig and H. Hofman. J. Catal.. 84 (1983) 15-26. M. A i , Kogyo Kagaku Zasshi. 73 (1970) 946-950: Chem. Abst., 73 (1970) 76790k. M. A i , Kogyo Kagaku Zasshi. 74 (1971) 1636-1639: Chem. Abst. 75 (1971) 109992~. M. A i , Nippon Kagaku K a i s h i , (1972) 1151-1156: Chem. Abst., 77 (1972) 66559k. N.K. Nag, T. Frasen and P. Mars, J. Catal., 68 (1981) 77-85. A.J. Van Hengstum, J.E. Ommen. H. Bosch and P.J. G e l l i n g s , Appl. Catal.. 8 (1983) 369-382. C.R. Adams, J. Catal.. 10 (1968) 355-361. R.K. G r a s s e l l i , J.D. B u r r i n g t o n , D.D. Suresh, M.S. F r i e d r i c h and M.A.S. Hazle. J. Catal.. 68 (1981) 109-120. M. A i , J. Catal., ( i n press). M. Ai. i n T. Seiyama and K. Tanabe (Eds.), Proc. 7 t h I n t . Congr. Catal.. Tokyo, June 30 - J u l y 4, 1980. Kodansha. Tokyo/Elsevier, Amsterdam. 1981, pp. 1060-1 069. M. A i , J. Catal., 40 (1975) 318-326 and 327-333. M. A i , B u l l . Japan P e t r o l . I n s t . . 18 (1976) 50-54. M. Ai. B u l l . Chem. SOC. Japan, 49 (1976) 1328-1334. M. A i . J. Catal., 52 (1978) 16-24.
265 (1) which have V. CORTlS CORBERAN ( I n s t . C a t a l i s i s y Petroquimica. Spain): been y o u r i n i t i a l c r i t e r i a f o r t h e s e l e c t i o n o f m e t a l l i c c a t i o n s , and a t o m i c (2) The r a t i o s between them, f o r t h e c a t a l y s t c o m p o s i t i o n s you have used. systems you have used a r e w e l l known by t h e i r p r o p e r t i e s i n t h e c a t a l y t i c s e l e c t i v e o x i d a t i o n o f o l e f i n s and t h e o v e r a l l t e n d e n c i e s f i n a l l y found f o r t h i s r e a c t i o n ( f o r example, a d d i t i o n o f t e l l u r i u m ) p a r a l l e l t h o s e p r e v i o u s l y known f o r s e l e c t i v e o x i d a t i o n s o f o l e f i n s . Would you have expect, a p r i o r i , d i f f e r e n t tendencies, and i f so, why?
M. A 1 (Tokyo I n s t . Tech., Japan): (1) I had no i n i t i a l c r i t e r i o n : we t e s t e d v a r i o u s k i n d s o f s i n g l e and b i n a r y o x i d e systems and, then, we s e l e c t e d some t e r n a r y systems b a s i n g on t h e i n f o r m a t i o n o b t a i n e d f r o m t h e t e s t s o f b i n a r y ( 2 ) Many k i n d s o f mixed o x i d e systems have been known t o be e f f e c t i v e oxides. as c a t a l y s t f o r o x i d a t i o n of o l e f i n s . T h i s s t u d y i n d i c a t e s a t l e a s t t h a t a l l I expected, a o f them a r e n o t e f f e c t i v e f o r o x i d a t i o n o f P(-methylstyrene. p r i o r i , d i f f e r e n t tendencies, because Bi-Mo-type c a t a l y s t s a r e n o t e f f e c t i v e f o r t h i s oxidation. R.K. GRASSELLI (Mobil Research and Develop., USA): You s t a t e i n y o u r conclus i o n s t h a t Sb-based c a t a l y s t w h i l e e f f e c t i v e f o r t h e o x i d a t i o n o f I - b u t e n e t o butadiene are n o t e f f e c t i v e f o r t h e o x i d a t i o n o f d-methylstyrene t o atropoaldehyde, a p p a r e n t l y i n c o n t r a s t t o Mo-Te-Ti. Mo-Te-W, and Mo-Te-Fe based c a t a l y s t s I should l i k e t o remind you t h a t o u r work which you k i n d l y whichyou s t u d i e d , quoted as r e f e r e n c e 8, c l e a r l y showed t h a t d - m e t h y l s t y r e n e i s e f f e c t i v e l y conv e r t e d t o atropoaldehyde w i t h Nb-U-Sb based c a t a l y s t s , i n f a c t t h e s e l e c t i v i t i e s which we r e p o r t e d w i t h o u r antimony based c a t a l y s t s r i v a l y o u r b e s t systems, w h i l e I agree t h a t c a t a l y t i c systems must be o p t i m i z e d f o r each g i v e n r e a c t i o n . There i s no a p r i o r i reason t o e x c l u d e antimony f o r t h e o x i d a t i o n o f d - m e t h y l styrene.
M.AI (Tokyo I n s t . Tech.,
Japan): I c o u l d n o t g e t a good performance w i t h Sb, Mo-Sb, and Mo-Te-Sb oxides, b u t I d i d n o t t r y t o t e s t w i t h U-Sb o x i d e s because you had a l r e a d y t e s t e d w i t h them. Therefore, I t h i n k t h a t y o u r a r e reason. What parameter i s f o r you a measure J. KIJENSKI (Warsaw P o l i t e c h n i k a , Poland): o f a c i d i t y o r b a s i c i t y of m o l e c u l e and a l l o w you t o c o n s i d e r a p a r t i c u l a r r e a c t i o n as e.g., "acid-base'' process?
M. A 1 (Tokyo I n s t . Tech., Japan): I have n o t s p e c i a l o p i n i o n about t h e d e f i n i t i o n o f acid-base. Indeed, o r d i n a r y i n d i c a t o r / t i t r a t i o n method i s n o t a p p l i c a b l e f o r o x i d a t i o n c a t a l y s t s because o f t h e i r d a r k c o l o r . On t h e o t h e r hand, t h e gas phase a d s o r p t i o n method c o n t a i n s some problems. Therefore, a t p r e s e n t t h e measurement o f c a t a l y t i c a c t i v i t y f o r acid-base c a t a l y z e d model r e a c t i o n s seems t o be t h e most combinient. though t h e r e remains arguments about t h e d e f i n i t i o n and s t r e n g t h o f acid-base. B. GRZYBOWSKA ( I n s t . Catal. S u r f a c e Chem.. Poland): ( 1 ) I n t h e Me-Mo-Te t e r n a r y o x i d e systems t h e r e e x i s t w e l l d e f i n e d compounds (e.g., telluromolybdates o f Co. Mn, N i , Cd) s y n t h e s i z e d and c h a r a c t e r i z e d by S l o c z y n s k i ( r e f . 1) and by F o r z a t t i . T r i f i r 6 . and V i l l a ( r e f . 2 ) . They have shown t o be a c t i v e a l s o i n a r o m a t i c hydrocarbon o x i d a t i o n ( r e f , 3). There e x i s t a l s o w e l l d e f i n e d phases i n Mo-Te-0 system. Both acid-base and o x i d i z i n g p r o p e r t i e s w i l l depend s t r o n g l y on phase c o m p o s i t i o n o f y o u r c a t a l y s t s and mode o f mutual arrengement o f t h e phases and n o t o n l y on t h e presence o f p a r t i c u l a r i o n s i n p r e d e f i n e d environment. I b e l i e v e t h a t t h e s e f a c t s should be t a k e n i n t o account when (2) Adding some comments t o t h e q u e s t i o n c o n s i d e r i n g t h e o x i d a t i o n mechanism. l e t me remind t h a t some a u t h o r s c o n s i d e r t h e i o n i z a t i o n of Prof. K i j e n s k i : p o t e n t i a l o f a molecule as a measure o f a c i d i t y , b a s i c i t y [see r e v i e w s by Ruckenstein e t a1 ( r e f . 4)]. ( 3 ) The d i s c u s s i o n on r e l a t i o n between oneI n t h e case o f e l e c t r o n and t w o - e l e c t r o n (acid-base) p r o p e r t i e s i s s t i l l open.
266
s o l i d f o r i n s t a n c e t h e r e a r e some a t t e m p t s t o r e c o n c i l e t h e b o t h p r o p e r t i e s ( r e f . 5) - showing t h a t s u r f a c e o n e - e l e c t r o n a c c e p t o r s t a t e s can be i d e n t i c a l and i n v o l v e t h e same o r b i t a l s as Lewis a c i d i c s i t e s , p r o v i d e d t h e a c c e p t o r l e v e l l i e s below t h e Fermi energy l e v e l . 1 J. S l o c z y n s k i , Z. Anorg. A l l g . Chem., 438 (1978) 287. 2 P. F o r z a t t i , F. T r i f i r 6 , P.L. V i l l a , J. Catal., 55 (1978) 52. 3 B. Grzybowska, M. Czerwenka, J. S l o c z y n s k i , Catal., Today, 1 (1987) 157. 4 D.B. Dadyburjor, S.S. Jewur, E. Ruckenstein, Catal. Rev., 19 (1979) 293. 5 S.R. Morrison, Surf. Sci., 50 (1975) 329. M.AI
(Tokyo I n s t . Tech.,
Japan):
Thank You f o r y o u r comments.
J. K I J E N S K I (Warsaw P o l i t e c h n i k a . Poland): Comment t o t h e remark o f P r o f . Grzybowska: I n o n i z a t i o n energy c a n n o t be c o n s i d e r e d as a measure o f a c i d i t y o r b a s i c i t y w h i c h a r e i o n i c , i.e., two e l e c t r o n p r o p e r t i e s . There i s no g e n e r a l p a r a l l e l i s m between t h e b a s i c i t y and e l e c t r o n donor p r o p e r t i e s .
J. HABER ( I n s t . C a t a l . S u r f a c e Chem., Poland): (1) What i s t h e r e p r o d u c t i v i t y o f y o u r r e s u l t s . The d a t a seem t o - b e c o n s i d e r a b l y spread which may i n d i c a t e ( 2 ) One o f t h e i m p o r t a n t s i d e t h e i r dependence on u n c o n t r o l l e d f a c t o r s . r e a c t i o n s o f m e t h y l s t y r e n e i s c e r t a i n l y cracking which w i l l o c c u r on more a c i d i c c a t a l y s t s and w i l l r i v a l u a t e t h e m e c h a n i s t i c c o n c l u s i o n s . D i d you t r y t o d e t e r m i n e t h e c o n t r i b u t i o n f r o m c r a c k i n g by c a r r i n g t e s t experiments i n t h e absence o f oxygen. M. A1 (Tokyo I n s t . Tech., Japan): ( 1 ) I d i d n o t f i n d t h a t t h e r e p r o d u c t i v i t y o f t h i s o x i d a t i o n i s s p e c i a l l y low. However, p h e n y l a c r o l e i n i s n o t s t a b l e , i.e., i t t e n d s t o p o l y m e r i z e t o dimer and t r i m e r . Indeed, I cannot measure t h e amount o f t h e s e polymers. Therefore, " o t h e r " may c o n s i t m a i n l y o f polymers. (2) I n t h e p r e d e c i n g work ( r e f . 9 i n t h e t e x t ) , t h e e f f e c t o f oxygen concentrat i o n was s t u d i e d . The consumption o f d - m e t h y l s t y r e n e i n c r e a s e s almost i n p r o p o r t i o n a l t o t h e oxygen c o n c e n t r a t i o n . Therefore, t h e cracking may be s m a l l a t l e a s t o v e r t h e Mo-Te-based c a t a l y s t s .