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Synthesis of Higher Alcohols from Syngas over Ni—Mo Catalysts. Effect of Methanol or Ethylene
A. Holmen et al. (Editors), Natural Gas Conversion 1991 Elsevier Science Publishers B.V., Amsterdam
349
SYNTHESIS OF HIGHER ALCOHOLS FROM SYNGAS OVER Ni-Mo CATALYSTS.
EFFECT
OF METHANOL OR ETHYLEN 3. BARRAULT'* and L. FROBST'
' L a b o r a t o i r e de Catalyse en Chimie Organique, U.R.A. C.N.R.S. 40, Avenue du Recteur Pineau 66022 P o i t i e r s C$dex (France) 2U.F. S. C. (Brasil)
-
-
Chemistry
Department,
66000 F l o r i a n o p o l i s ,
DO 350,
Santa Catarina,
SUMMARY B i m e t a l l i c Ni-Mo c a t a l y s t s promoted w i t h potassium supported on manganese oxide or more p a r t i c u l a r l y on z i n c oxide are a c t i v e and select i v e f o r t h e conversion o f syngas i n t o l i g h t alcohols. These a l c o h o l s c o u l d be v i a a CO i n s e r t i o n i n t o a m e t a l - a l k y l bond or v i a an h y d r o f o r m y l a t i o n type r e a c t i o n . Indeed t h e r a t e o f hydrocarbon and s p e c i a l l y o f a l c o h o l formation a r e g r e a t l y enhanced by t h e a d d i t i o n o f o l e f i n s . INTRODUCTION Some works r e l a t e d t h e s y n t h e s i s o f oxygenated compounds from carbon o x i d e ( s ) i n t h e presence o f n i c k e l c a t a l y s t s . T. Hayasaka and a l .
(ref.1)
showed t h a t t h e support played a s i g n i f i c a n t r o l e on t h e c a t a l y t i c prop e r t i e s of
nickel.
Methanol
and C2+
Tatsumi and a l . found t h a t t h e a d d i t i o n
o f an a l c a l i n e element or/and a group increased
the
formation
of
superficial
particles
of
VIII metal t o molybdenum c a t a l y s t
a l c o h o l from syngas
2 , 3 ) . According
(ref.
t h i s s e l e c t i v i t y c o u l d be t h e r e s u l t o f t h e formation
Mo-NI
; the
formed when n i c k e l
~ i l methanol e is t h e o n l y product i n t h e
i s supported on t i t a n i a ,
presence o f Ni-ZnO c a t a l y s t s . T.
t o these authors,
a l c o h o l s are
alloy
presence
i n the
of
vicinity
potassium
o f n i c k e l and molybdenum
decreasing
the
reduction r a t e
o f molybdenum oxide. The c a t a l y s t s u r f a c e w i l l present two types o f a c t i v e c e n t e r s b o t h i n m e t a l l i c and oxide
states.
On t h e f i r s t
type t h e r e w i l l occur a
d i s s o c i a t i v e adsorption o f CO w h i l e on t h e o t h e r CO w i l l be m o l e c u l a r l y adsorbed and used e i t h e r
for
methanol
formation
of
for
insertion i n
hydrocarbon species r e s u l t i n g i n t h e f o r m a t i o n o f higher alcohols. main d i f f i c u l t i e s of
i)the s u p e r f i c i a l s i t e d e n s i t y ,
types o f s i t e s and
ii)t h e r a t i o between t h e two
iii) t h e homogeneity i n the d i s t r i b u t i o n o f these
a c t i v e centers.
*
The
i n the p r e p a r a t i o n o f such c a t a l y s t s are the c o n t r o l
Author t o whom correspondence should be adressed.
350 In t h i s study,
we r e p o r t r e s u l t s o b t a i n e d w i t h nickel-molybdenum
s u p p o r t e d e i t h e r on a r e d u c i b l e o x i d e (MnOx) or on a b a s i c o x i d e (ZnO). Moreover we i n v e s t i g a t e d t h e e f f e c t s o f m e t h a n o l and e t h y l e n e i n o r d e r t o explain the modification of the s e l e c t i v i t y . METHODS C a t a l y s t s were p r e p a r e d by a c o p r e c i p i t a t i n g ( r e f . 4 ) or impregnat i n g n i c k e l , nickel-molybdenum, or Ni/Mo a l c a l i n e p r e c u r s o r s on s u p p o r t s . The powders were h e a t e d i n a o v e n a t 12OOC f o r 12h b e f o r e c a l c i n a t i o n in
a i r a t 45OOC f o r 4h. Z i n c o x i d e ( 3 3 m2g-’) 2 -1 (53 m g ) were u s e d a s s u p p o r t s .
and manganese d i o x i d e
The s y n t h e s i s r e a c t i o n was c a r r i e d o u t i n a tubular reactor, p r e s s u r e (5-MR)
stainless
-
steel
c o n t a i n i n g 10 o r 2 0 g p e l l e t i z e d c a t a l y s t s , u n d e r p l a c e d i n a flow a p p a r a t u s . B e f o r e r e a c t i o n , c a t a l y s t s
nere r e d u c e d by H2 u n d e r a t m o s p h e r i c p r e s s u r e a t a t e m p e r a t u r e between 4 O O O C and 500OC. A l l t h e p r o d u c t s were a n a l y z e d i n t h e g a s p h a s e t h r o u g h
h e a t e d l i n e s or i n t h e l i q u i d p h a s e a f t e r c o o l i n g down t o 2OoC, u s i n g g a s c h r o m a t o g r a p h y methods (TCD and FID) ( r e f . 5 ) . RESULTS 1 ) N i c k e l and molybdenum s u p p o r t e d o n ZnO o r Mn02
Whatever t h e s u p p o r t , T a b l e 1 shows t h a t n i c k e l c a t a l y s t s a r e more a c t i v e t h a n molybdenum c a t a l y s t s .
Nevertheless
the alcohol s e l e c t i v i t y
is much more i m p o r t a n t w i t h molybdenum t h a n w i t h n i c k e l . c a n o b s e r v e w i t h Mo-supported
catalysts that
p r o d u c t w i t h Mo-ZnO c a t a l y s t s and manganese d i o x i d e i s u s e d
as a
Moreover we
i ) methanol is t h e major
i i ) h i g h e r a l c o h o l s a r e formed when support.
(Even w i t h Ni-Mn02 c a t a l y s t s
t h e r e is a s i g n i f i c a n t f r a c t i o n o f C2+ a l c o h o l s ) .
A t t h e same time it c a n a l s o be n o t i c e d t h a t
c2
and C3 h y d r o c a r b o n s
a r e formed e s p e c i a l l y when N i and Mo a r e s u p p o r t e d on manganese d i o x i d e
2 ) E f f e c t o f t h e a d d i t i o n o f molybdenum t o s u p p o r t e d n i c k e l c a t a l y s t s A l l t h e r e s u l t s i n T a b l e 2 were o b t a i n e d a f t e r c a t a l y s t s t a b i l i z a t i o n (30 t o 50 h o u r s ) . When Mn02 is u s e d a s s u p p o r t , a d e c r e a s e o f h y d r o c a r b o n s e l e c t i v i t y and an i n c r e a s e o f molybdenum t o n i c k e l .
alcohol s e l e c t i v i t y a r e observed a f t e r addition of I n t h e c a s e of
ZnO s u p p o r t e d c a t a l y s t s t h e same
phenomena c a n b e n o t i c e d a s t h e s e w i t h n i c k e l c a t a l y s t s .
In both cases
a s y n e r g e t i c e f f e c t i n C2+ a l c o h o l f o r m a t i o n i s o b t a i n e d a f t e r a d d i t i o n
351
TABLE 2 E f f e c t of molybdenum a d d i t i v e or t h e c a t a l y t i c p r o p e r t i e s of Ni(Co) supported on Mn02 or ZnO i n (CO, H2) r e a c t i o n .
Reaction
c o n d i t i o n s : P = 5.0 MPa, H
Catalyst
21(-0 = 2 , T = 25ooc, W/F = 1 g h 1-1
Ni3k7-MnO2
Ni3M07-ZnO
21.4 7.6
25.6 0.2
4.0 4.0
Ni3M07K1-Zn0 Ni7M03-Zn0 Co 3Mo 7 -ZnO
Selectivity ( C atom % )
CH4 C2H4
19.5 7.4
20.0
10.0
3.4
9.4
-
1.3
5.6
4.5
2.0
5.8
3.5
c4+ MeOH
14.0 29.5
3.9 41.4
8.0 19.4
2.3 49.7
4.5 47.2
EtOH nprOH
15.8 2.3
9.2 4.0
19.5 14.9
10.6 2.1
6.5 1.8
50.0
33.0
42.0
‘96 C3H6
19.6 4.4 8.1 4.1
............................................................................... S e l e c t i v i t y C02 ( % )
50.0
36.0
352
of molybdenum which i s p a r t i c u l a r l y important with Mn02 - supported c a t lysts. On t h e o t h e r hand t h e i n c r e a s e of n i c k e l c o n t e n t (7% i n s t e a d of 3%) o r t h e replacedment o f n i c k e l by c o b a l t d e c r e a s e s t h e a c t i v i t y : alcohols/hydrocarbons,
without changing s i g n i f i c a n t l y t h e r a t i o
but
d e c r e a s i n g t h e C2+ a l c o h o l s e l e c t i v i t y .
3 ) I n f l u e n c e of K a d d i t i o n to Ni-Mo/ZnO c a t a l y s t a d d i t i o n of
After a catalyst
the total
g r e a t l y enhanced
a small
percentage
a c t i v i t y and
(Table 2).
Indeed
potassium t o s u c h
(1%) of
t h e C2+
alcohol s e l e c t i v i t y a r e
the r a t i o
(C2+/C,)alcohols
from 0.32 t o 1.8 Moreover i t can a l s o be observed t h a t
varies
i ) the ratio
ii) t h e o l e f i n f r a c t i o n i n C2+ hydrocarbons (c.?+/cl) hydrocarbons and a r e i n c r e a s e d ( f o r s i m i l a r CO c o n v e r s i o n s ) by t h e presence o f potassium (Table 2 ) ; s o t h a t t h e formation of C2+ a l c o h o l s could be d i r e c t l y r e l a t e d t o t h a t of o l e f i n s . Moreover when i n c r e a s i n g t h e c o n t a c t time, t h e hydrocarbons s e l e c t i v i t y and t h e methanol s e l e c t i v i t y d e c r e a s e when t h e
c2+ a l c o h o l
formation s i g n i f i c a n t l y i n c r e a s e s .
4 ) I n f l u e n c e o f methanol o f e t h y l e n e on t h e a l c o h o l formation On account of t h e above r e s u l t s , t h e
c2+
a l c o h o l s could be formed
e i t h e r by 0x0 r e a c t i o n s of o l e f i n s or by homologation o f methanol (and o t h e r a l c o h o l s ) though t h i s r e a c t i o n is more improbable. Moreover previous
work
c a r r i e d o u t i n our
laboratory
with o t h e r c a t a l y s t s
show
t h a t oxygenated compounds would b e formed by CO i n s e r t i o n i n t o a "metalcarbon
bond" ( 6 ) .
The i n v e s t i g a t i o n s on t h e e f f e c t o f methanol i n t h e (CO, H2) r e a c t i o n showed t h a t whatever t h e c a t a l y s t used f o r t h e r e a c t i o n t h e C2+ alcohol
formation is not modified.
W e observed only
some changes i n
t h e hydrocarbon r e p a r t i t i o n ( r e f . 5). On t h e c o n t r a r y t h e a d d i t i o n of e t h y l e n e during t h e syngas t r a n s formation a f f e c t s t h e a l c o h o l s e l e c t i v i t y and p r o d u c t i v i t y . I n presence of molybdenum c a t a l y s t s e s p e c i a l l y with Mo-ZnO, methanol was t h e major product b e f o r e t h e a d d i t i o n o f e t h y l e n e (Table 1 ) . After
i)
adding C2H4 t o syngas ( p a r t i a l p r e s s u r e
0.131,
o f n propanol and a l s o of C3 hydrocarbons was ii)
a significant increase
obtained (Table 3 ) .
With Ni-Mo c a t a l y s t s s i m i l a r r e s u l t s a r e observed b u t t h e r e s u l t s
p r e s e n t e d i n Table 3 g i v e rise t o more comments
: Indeed with c a t a -
l y s t s supported on Mn02 t h e i n c r e d s e o f n propanol s e l e c t i v i t y is very s i g n i f i c a n t b u t t h e r e a c t i v i t y of e t h y l e n e i s less so than with c a t a l y s t s supported on z i n c oxide.
On t h e s e l a t t e r c a t a l y s t s we observed
b o t h a s i g n i f i c a n t i n c r e a s e of a c t i v i t y and of C3 (hydrocarbon + a l c o h o l )
353 TABLE 3 I n f l u e n c e o f e t h y l e n e i n (Co, H2) r e a c t i o n . r e a c t i o n c o n d i t i o n s : P = 5.0 MPa, H2/C0 = 2,
T = 25OoC, W/F = 1 g h 1-I.
a) Ethylene percentage i n reagents (CO + H2 + C2H4). b ) SC02 =
C02/C02 + C hyd.
c ) Ethylene/ethane r a t i o d u r i n g t h e r e a c t i o n .
Catalyst
Mol 0-ZnO
Ni3M07-MnOq
E t h y l e n e ( a ) (%)
0
A c t i v i t y (X103)
0.3
1.2
0.06
0.08 2.3
0
13
13
Ni3Mo7-ZnO
0
Ni3Mo7K1 -ZnO 13
13
0
12.0
1.1
2.0 3.8
mole h-lg-lcatal. Selectivity
CH4
19.1
2.1
23.4
1.2
21.8
5.0
28.4
C atom (%)
C3H6
1.3
9.3
7.5
1.3
6.3
2.6
1.4
3.9
5.0
6.2
2.0
23.0
-
-
2.3
1.0
3.8
5.8
11.0
0.6
5.9
2.0
4.3
1.6
-
5.6
4.9
0.8
3.4
7.3
-
3.2
&OH 70.0
Without(C02 and C2 j C3H8 CC4 C5-C7
12.0
33.3
11.7
21.8
8.1
46.0
3.4
EtOH
1.4
0.5
17.3
9.2
21.8
9.4
10.0
2.0
nprOH
0.8
42.0
2.5
74.8
16.9
40.0
4.4
72.0
(C4-Cg)OH
-
-
-
-
20.3
-
4.0
Selectivity C O ~ ( ~ )
30.0 0.27
C,H,/C,H,(~)
4.5 1.65
50.0 1.9
0.8 50.0 11.5
2.2
4.5 14.3
3.7
36.0 0.02
0.035
TABLE 4 I n f l u e n c e o f e t h y l e n e on r a t i o of f o r m a t i o n of C3 hydrocarbons and n propanol. ( b ) and ( a ) before and a f t e r e t h y l e n e a d d i t i o n .
Reactions c o n d i t i o n s : see
Table 3. Catalyst
Ni3M07-Mn02 Ni3Mo7-ZnO
Ni3Mo7KI-ZnO
Rate o f propene and propane formation
Rate o f n propanol formation
mole h - l g - ’ c a t a l (X104)
mole h-lg-lcatal.
(b)
2.25
(a)
1.0
(b)
0.45
31.0
(a)
2.0
14.4
(b)
1 .o
2.5
(a)
4.3
48.0
10-2
0.75 60.0
( ~ 1 0 ~ )
354 s e l e c t i v i t y . The i n c r e a s e o f C3 h y d r o c a r b o n s e l e c t i v i t y is more s i g n i f i c a n t w i t h Mo-ZnO c a t a l y s t t h a n w i t h NiMo(K)-ZnO c a t a l y s t s , which s u g g e s t s t h a t n i c k e l or mixed (Ni-Mo) sites a r e n e c e s s a r y for CO i n s e r I n f a c t when n i c k e l i s added t o Mo-ZnO, n p r o p a n o l s e l e c t i v i t y
tion.
i s l a r g e l y i n c r e a s e d t o t h e d e t r i m e n t o f p r o p a n e and propene. Moreover
when p o t a s s i u m is added t o Ni-Mo/ZnO,
(C5-C7)
and
C2H4
into
s y n g a s so t h a t t h e r e i s a l w a y s a r e l a t i o n between h y d r o c a r b o n
and
higher
alcohols
alcohol
productions.
ethylene addition particularly
higher hydrocarbons
are formed a f t e r i n t r o d u c t i o n o f
(C,-C,)
Table 4 shorn
on t h e r a t e s o f
on t h e r a t e o f
t h e very s i g n i f i c a n t e f f e c t p r o p e n e and propane
of
f o r m a t i o n and
n p r o p a n o l f o r m a t i o n which is i n c r e a s e d
by a 70 t o 80 f a c t o r d e p e n d i n g o n t h e c a t a l y s t .
This r e s u l t c l e a r l y
d e m o n s t r a t e s t h e r e a c t i v i t y of o l e f i n s i n 0x0 t y p e r e a c t i o n s w i t h n i c k e l molybdenum c a t a l y s t s . L a s t l y i t is i n t e r e s t i n g a l s o t o n o t e t h a t t h e s e s p e c i f i c p r o p e r t i e s may b e t h e r e s u l t o f t h e low h y d r o g e n a t i n g p r o i n c o m p a r i s o n of c h a i n g r o w t h v i a h y d r o c a r b o n s p e c i e s o r / a n d
perties
CO i n s e r t i o n .
The r e s u l t s o f T a b l e 3 i n d i c a t e t h a t C2H,+ added t o s y n g a s
never
during the reaction
is
e n t i r e l y hydrogenated
a s was i n d i c a t e d
i n numerous works p u b l i s h e d p r e v i o u s l y .
CONCLUSION I n t h i s work we e m p h a s i z e d t h e d e t e r m i n i n g e f f e c t o f t h e s u p p o r t
of molybdenum and o f a l c a l i n e o n t h e a c t i v i t y and t h e s e l e c t i v i t y o f nickel
c a t a l y s t s i n syngas conversion.
Both a s e l e c t i v i t y i n
(C,-C3)
a l c o h o l s h i g h e r t h a n 60% and a s i g n i f i c a t i v e p r o d u c t i v i t y a r e o b t a i n e d with
d N i Mo
clearly
K/ZnO c a t a l y s t .
demonstrated
that
The e x p e r i m e n t s c a r r i e d out w i t h e t h y l e n e
i) h i g h e r
o l e f i n i n 0x0 t y p e r e a c t i o n and
alcohol
formation
i i ) hydrocarbons
can
involve
( i - e p r o p e n e and
p r o p a n e ) c a n b e formed v i a r e a c t i o n o f e t h a n e or C2 s u r f a c e s p e c i e s w i t h C1
fragment s u r f a c e a s p r e v i o u s l y proposed
by B a s s e t
and c o l l .
( r e f . 7 , 8). According
t o models o f promoted nickel-molybdenum o x i d e s p r o p o s e d 9 ) t h e s i m u l t a n e o u s f o r m a t i o n o f mixed o x i d e s
i n the literature (ref.
close t o o r d e c o r a t e d by some n i c k e l p a r t i c l e s c o u l d e x p l a i n t h e s p e c i f i c p r o p e r t i e s of such c a t a l y s t s .
But t h e r o l e o f t h e s u p p o r t is n o t
c l e a r ; p r e l i m i n a r y XPS c h a r a c t e r i z a t i o n s showing s i g n i f i c a n t m o d i f i c a t i o n s o f t h e s u r f a c e c o m p o s i t i o n w i t h t h e change o f s u p p o r t ( r e f . 10).
355 REFERENCES 1 2 3 4
5 6 a)
7
b)
8
9 10
Hayasaka, Y. Ohbayashi, S . Uchiyama and N. Kawata i n Proc. gth I n t . Cong. Ca ta l. , Calgary, Canada, 3une 26-3uly 1 , 1988, M.3. P h i l l i p s and M. Ternan (Ed) 2 (1988) 521. T. Tatsumi, A. Muramatsu and H. Tominaga, A p p l . Catal., 34 (1987) 77. T. Tatsumi, A. Muramatsu, K. Yokota and H. Tominaga, 3. C a t a l . , 115 (1989) 388. M.P. Astier, G. D j i and S.3. Teichner, Ann. Chim. F r . , 12 (1987) 337. L. Probs t , t h e s i s , P o i t i e r s (Fra nc e ), 1989. H. Derule, t h e s i s P o i t i e r s (Fra nc e ) 1989. M. Blanchard, H. Derule and P. Canesson, Catal. Lett., 2 (1989) 319. M. Leconte, A. Theolier and 3.M. Basset, 3. Mol. C a t a l . , 28 (1985) 217. E. Rodriguez, M. Leconte, 3.M. B a sset, K. Tanaka, 3. C a t a l . , 119 (1989) 230. H. Topsoe, B.S. Clausen, C a ta l. Rev., Sci. Eng. 26(3-4) (1984) 395. 3. B a r r a u l t , L. Probst, unpublished results. T.
349
SYNTHESIS OF HIGHER ALCOHOLS FROM SYNGAS OVER Ni-Mo CATALYSTS.
EFFECT
OF METHANOL OR ETHYLEN 3. BARRAULT'* and L. FROBST'
' L a b o r a t o i r e de Catalyse en Chimie Organique, U.R.A. C.N.R.S. 40, Avenue du Recteur Pineau 66022 P o i t i e r s C$dex (France) 2U.F. S. C. (Brasil)
-
-
Chemistry
Department,
66000 F l o r i a n o p o l i s ,
DO 350,
Santa Catarina,
SUMMARY B i m e t a l l i c Ni-Mo c a t a l y s t s promoted w i t h potassium supported on manganese oxide or more p a r t i c u l a r l y on z i n c oxide are a c t i v e and select i v e f o r t h e conversion o f syngas i n t o l i g h t alcohols. These a l c o h o l s c o u l d be v i a a CO i n s e r t i o n i n t o a m e t a l - a l k y l bond or v i a an h y d r o f o r m y l a t i o n type r e a c t i o n . Indeed t h e r a t e o f hydrocarbon and s p e c i a l l y o f a l c o h o l formation a r e g r e a t l y enhanced by t h e a d d i t i o n o f o l e f i n s . INTRODUCTION Some works r e l a t e d t h e s y n t h e s i s o f oxygenated compounds from carbon o x i d e ( s ) i n t h e presence o f n i c k e l c a t a l y s t s . T. Hayasaka and a l .
(ref.1)
showed t h a t t h e support played a s i g n i f i c a n t r o l e on t h e c a t a l y t i c prop e r t i e s of
nickel.
Methanol
and C2+
Tatsumi and a l . found t h a t t h e a d d i t i o n
o f an a l c a l i n e element or/and a group increased
the
formation
of
superficial
particles
of
VIII metal t o molybdenum c a t a l y s t
a l c o h o l from syngas
2 , 3 ) . According
(ref.
t h i s s e l e c t i v i t y c o u l d be t h e r e s u l t o f t h e formation
Mo-NI
; the
formed when n i c k e l
~ i l methanol e is t h e o n l y product i n t h e
i s supported on t i t a n i a ,
presence o f Ni-ZnO c a t a l y s t s . T.
t o these authors,
a l c o h o l s are
alloy
presence
i n the
of
vicinity
potassium
o f n i c k e l and molybdenum
decreasing
the
reduction r a t e
o f molybdenum oxide. The c a t a l y s t s u r f a c e w i l l present two types o f a c t i v e c e n t e r s b o t h i n m e t a l l i c and oxide
states.
On t h e f i r s t
type t h e r e w i l l occur a
d i s s o c i a t i v e adsorption o f CO w h i l e on t h e o t h e r CO w i l l be m o l e c u l a r l y adsorbed and used e i t h e r
for
methanol
formation
of
for
insertion i n
hydrocarbon species r e s u l t i n g i n t h e f o r m a t i o n o f higher alcohols. main d i f f i c u l t i e s of
i)the s u p e r f i c i a l s i t e d e n s i t y ,
types o f s i t e s and
ii)t h e r a t i o between t h e two
iii) t h e homogeneity i n the d i s t r i b u t i o n o f these
a c t i v e centers.
*
The
i n the p r e p a r a t i o n o f such c a t a l y s t s are the c o n t r o l
Author t o whom correspondence should be adressed.
350 In t h i s study,
we r e p o r t r e s u l t s o b t a i n e d w i t h nickel-molybdenum
s u p p o r t e d e i t h e r on a r e d u c i b l e o x i d e (MnOx) or on a b a s i c o x i d e (ZnO). Moreover we i n v e s t i g a t e d t h e e f f e c t s o f m e t h a n o l and e t h y l e n e i n o r d e r t o explain the modification of the s e l e c t i v i t y . METHODS C a t a l y s t s were p r e p a r e d by a c o p r e c i p i t a t i n g ( r e f . 4 ) or impregnat i n g n i c k e l , nickel-molybdenum, or Ni/Mo a l c a l i n e p r e c u r s o r s on s u p p o r t s . The powders were h e a t e d i n a o v e n a t 12OOC f o r 12h b e f o r e c a l c i n a t i o n in
a i r a t 45OOC f o r 4h. Z i n c o x i d e ( 3 3 m2g-’) 2 -1 (53 m g ) were u s e d a s s u p p o r t s .
and manganese d i o x i d e
The s y n t h e s i s r e a c t i o n was c a r r i e d o u t i n a tubular reactor, p r e s s u r e (5-MR)
stainless
-
steel
c o n t a i n i n g 10 o r 2 0 g p e l l e t i z e d c a t a l y s t s , u n d e r p l a c e d i n a flow a p p a r a t u s . B e f o r e r e a c t i o n , c a t a l y s t s
nere r e d u c e d by H2 u n d e r a t m o s p h e r i c p r e s s u r e a t a t e m p e r a t u r e between 4 O O O C and 500OC. A l l t h e p r o d u c t s were a n a l y z e d i n t h e g a s p h a s e t h r o u g h
h e a t e d l i n e s or i n t h e l i q u i d p h a s e a f t e r c o o l i n g down t o 2OoC, u s i n g g a s c h r o m a t o g r a p h y methods (TCD and FID) ( r e f . 5 ) . RESULTS 1 ) N i c k e l and molybdenum s u p p o r t e d o n ZnO o r Mn02
Whatever t h e s u p p o r t , T a b l e 1 shows t h a t n i c k e l c a t a l y s t s a r e more a c t i v e t h a n molybdenum c a t a l y s t s .
Nevertheless
the alcohol s e l e c t i v i t y
is much more i m p o r t a n t w i t h molybdenum t h a n w i t h n i c k e l . c a n o b s e r v e w i t h Mo-supported
catalysts that
p r o d u c t w i t h Mo-ZnO c a t a l y s t s and manganese d i o x i d e i s u s e d
as a
Moreover we
i ) methanol is t h e major
i i ) h i g h e r a l c o h o l s a r e formed when support.
(Even w i t h Ni-Mn02 c a t a l y s t s
t h e r e is a s i g n i f i c a n t f r a c t i o n o f C2+ a l c o h o l s ) .
A t t h e same time it c a n a l s o be n o t i c e d t h a t
c2
and C3 h y d r o c a r b o n s
a r e formed e s p e c i a l l y when N i and Mo a r e s u p p o r t e d on manganese d i o x i d e
2 ) E f f e c t o f t h e a d d i t i o n o f molybdenum t o s u p p o r t e d n i c k e l c a t a l y s t s A l l t h e r e s u l t s i n T a b l e 2 were o b t a i n e d a f t e r c a t a l y s t s t a b i l i z a t i o n (30 t o 50 h o u r s ) . When Mn02 is u s e d a s s u p p o r t , a d e c r e a s e o f h y d r o c a r b o n s e l e c t i v i t y and an i n c r e a s e o f molybdenum t o n i c k e l .
alcohol s e l e c t i v i t y a r e observed a f t e r addition of I n t h e c a s e of
ZnO s u p p o r t e d c a t a l y s t s t h e same
phenomena c a n b e n o t i c e d a s t h e s e w i t h n i c k e l c a t a l y s t s .
In both cases
a s y n e r g e t i c e f f e c t i n C2+ a l c o h o l f o r m a t i o n i s o b t a i n e d a f t e r a d d i t i o n
351
TABLE 2 E f f e c t of molybdenum a d d i t i v e or t h e c a t a l y t i c p r o p e r t i e s of Ni(Co) supported on Mn02 or ZnO i n (CO, H2) r e a c t i o n .
Reaction
c o n d i t i o n s : P = 5.0 MPa, H
Catalyst
21(-0 = 2 , T = 25ooc, W/F = 1 g h 1-1
Ni3k7-MnO2
Ni3M07-ZnO
21.4 7.6
25.6 0.2
4.0 4.0
Ni3M07K1-Zn0 Ni7M03-Zn0 Co 3Mo 7 -ZnO
Selectivity ( C atom % )
CH4 C2H4
19.5 7.4
20.0
10.0
3.4
9.4
-
1.3
5.6
4.5
2.0
5.8
3.5
c4+ MeOH
14.0 29.5
3.9 41.4
8.0 19.4
2.3 49.7
4.5 47.2
EtOH nprOH
15.8 2.3
9.2 4.0
19.5 14.9
10.6 2.1
6.5 1.8
50.0
33.0
42.0
‘96 C3H6
19.6 4.4 8.1 4.1
............................................................................... S e l e c t i v i t y C02 ( % )
50.0
36.0
352
of molybdenum which i s p a r t i c u l a r l y important with Mn02 - supported c a t lysts. On t h e o t h e r hand t h e i n c r e a s e of n i c k e l c o n t e n t (7% i n s t e a d of 3%) o r t h e replacedment o f n i c k e l by c o b a l t d e c r e a s e s t h e a c t i v i t y : alcohols/hydrocarbons,
without changing s i g n i f i c a n t l y t h e r a t i o
but
d e c r e a s i n g t h e C2+ a l c o h o l s e l e c t i v i t y .
3 ) I n f l u e n c e of K a d d i t i o n to Ni-Mo/ZnO c a t a l y s t a d d i t i o n of
After a catalyst
the total
g r e a t l y enhanced
a small
percentage
a c t i v i t y and
(Table 2).
Indeed
potassium t o s u c h
(1%) of
t h e C2+
alcohol s e l e c t i v i t y a r e
the r a t i o
(C2+/C,)alcohols
from 0.32 t o 1.8 Moreover i t can a l s o be observed t h a t
varies
i ) the ratio
ii) t h e o l e f i n f r a c t i o n i n C2+ hydrocarbons (c.?+/cl) hydrocarbons and a r e i n c r e a s e d ( f o r s i m i l a r CO c o n v e r s i o n s ) by t h e presence o f potassium (Table 2 ) ; s o t h a t t h e formation of C2+ a l c o h o l s could be d i r e c t l y r e l a t e d t o t h a t of o l e f i n s . Moreover when i n c r e a s i n g t h e c o n t a c t time, t h e hydrocarbons s e l e c t i v i t y and t h e methanol s e l e c t i v i t y d e c r e a s e when t h e
c2+ a l c o h o l
formation s i g n i f i c a n t l y i n c r e a s e s .
4 ) I n f l u e n c e o f methanol o f e t h y l e n e on t h e a l c o h o l formation On account of t h e above r e s u l t s , t h e
c2+
a l c o h o l s could be formed
e i t h e r by 0x0 r e a c t i o n s of o l e f i n s or by homologation o f methanol (and o t h e r a l c o h o l s ) though t h i s r e a c t i o n is more improbable. Moreover previous
work
c a r r i e d o u t i n our
laboratory
with o t h e r c a t a l y s t s
show
t h a t oxygenated compounds would b e formed by CO i n s e r t i o n i n t o a "metalcarbon
bond" ( 6 ) .
The i n v e s t i g a t i o n s on t h e e f f e c t o f methanol i n t h e (CO, H2) r e a c t i o n showed t h a t whatever t h e c a t a l y s t used f o r t h e r e a c t i o n t h e C2+ alcohol
formation is not modified.
W e observed only
some changes i n
t h e hydrocarbon r e p a r t i t i o n ( r e f . 5). On t h e c o n t r a r y t h e a d d i t i o n of e t h y l e n e during t h e syngas t r a n s formation a f f e c t s t h e a l c o h o l s e l e c t i v i t y and p r o d u c t i v i t y . I n presence of molybdenum c a t a l y s t s e s p e c i a l l y with Mo-ZnO, methanol was t h e major product b e f o r e t h e a d d i t i o n o f e t h y l e n e (Table 1 ) . After
i)
adding C2H4 t o syngas ( p a r t i a l p r e s s u r e
0.131,
o f n propanol and a l s o of C3 hydrocarbons was ii)
a significant increase
obtained (Table 3 ) .
With Ni-Mo c a t a l y s t s s i m i l a r r e s u l t s a r e observed b u t t h e r e s u l t s
p r e s e n t e d i n Table 3 g i v e rise t o more comments
: Indeed with c a t a -
l y s t s supported on Mn02 t h e i n c r e d s e o f n propanol s e l e c t i v i t y is very s i g n i f i c a n t b u t t h e r e a c t i v i t y of e t h y l e n e i s less so than with c a t a l y s t s supported on z i n c oxide.
On t h e s e l a t t e r c a t a l y s t s we observed
b o t h a s i g n i f i c a n t i n c r e a s e of a c t i v i t y and of C3 (hydrocarbon + a l c o h o l )
353 TABLE 3 I n f l u e n c e o f e t h y l e n e i n (Co, H2) r e a c t i o n . r e a c t i o n c o n d i t i o n s : P = 5.0 MPa, H2/C0 = 2,
T = 25OoC, W/F = 1 g h 1-I.
a) Ethylene percentage i n reagents (CO + H2 + C2H4). b ) SC02 =
C02/C02 + C hyd.
c ) Ethylene/ethane r a t i o d u r i n g t h e r e a c t i o n .
Catalyst
Mol 0-ZnO
Ni3M07-MnOq
E t h y l e n e ( a ) (%)
0
A c t i v i t y (X103)
0.3
1.2
0.06
0.08 2.3
0
13
13
Ni3Mo7-ZnO
0
Ni3Mo7K1 -ZnO 13
13
0
12.0
1.1
2.0 3.8
mole h-lg-lcatal. Selectivity
CH4
19.1
2.1
23.4
1.2
21.8
5.0
28.4
C atom (%)
C3H6
1.3
9.3
7.5
1.3
6.3
2.6
1.4
3.9
5.0
6.2
2.0
23.0
-
-
2.3
1.0
3.8
5.8
11.0
0.6
5.9
2.0
4.3
1.6
-
5.6
4.9
0.8
3.4
7.3
-
3.2
&OH 70.0
Without(C02 and C2 j C3H8 CC4 C5-C7
12.0
33.3
11.7
21.8
8.1
46.0
3.4
EtOH
1.4
0.5
17.3
9.2
21.8
9.4
10.0
2.0
nprOH
0.8
42.0
2.5
74.8
16.9
40.0
4.4
72.0
(C4-Cg)OH
-
-
-
-
20.3
-
4.0
Selectivity C O ~ ( ~ )
30.0 0.27
C,H,/C,H,(~)
4.5 1.65
50.0 1.9
0.8 50.0 11.5
2.2
4.5 14.3
3.7
36.0 0.02
0.035
TABLE 4 I n f l u e n c e o f e t h y l e n e on r a t i o of f o r m a t i o n of C3 hydrocarbons and n propanol. ( b ) and ( a ) before and a f t e r e t h y l e n e a d d i t i o n .
Reactions c o n d i t i o n s : see
Table 3. Catalyst
Ni3M07-Mn02 Ni3Mo7-ZnO
Ni3Mo7KI-ZnO
Rate o f propene and propane formation
Rate o f n propanol formation
mole h - l g - ’ c a t a l (X104)
mole h-lg-lcatal.
(b)
2.25
(a)
1.0
(b)
0.45
31.0
(a)
2.0
14.4
(b)
1 .o
2.5
(a)
4.3
48.0
10-2
0.75 60.0
( ~ 1 0 ~ )
354 s e l e c t i v i t y . The i n c r e a s e o f C3 h y d r o c a r b o n s e l e c t i v i t y is more s i g n i f i c a n t w i t h Mo-ZnO c a t a l y s t t h a n w i t h NiMo(K)-ZnO c a t a l y s t s , which s u g g e s t s t h a t n i c k e l or mixed (Ni-Mo) sites a r e n e c e s s a r y for CO i n s e r I n f a c t when n i c k e l i s added t o Mo-ZnO, n p r o p a n o l s e l e c t i v i t y
tion.
i s l a r g e l y i n c r e a s e d t o t h e d e t r i m e n t o f p r o p a n e and propene. Moreover
when p o t a s s i u m is added t o Ni-Mo/ZnO,
(C5-C7)
and
C2H4
into
s y n g a s so t h a t t h e r e i s a l w a y s a r e l a t i o n between h y d r o c a r b o n
and
higher
alcohols
alcohol
productions.
ethylene addition particularly
higher hydrocarbons
are formed a f t e r i n t r o d u c t i o n o f
(C,-C,)
Table 4 shorn
on t h e r a t e s o f
on t h e r a t e o f
t h e very s i g n i f i c a n t e f f e c t p r o p e n e and propane
of
f o r m a t i o n and
n p r o p a n o l f o r m a t i o n which is i n c r e a s e d
by a 70 t o 80 f a c t o r d e p e n d i n g o n t h e c a t a l y s t .
This r e s u l t c l e a r l y
d e m o n s t r a t e s t h e r e a c t i v i t y of o l e f i n s i n 0x0 t y p e r e a c t i o n s w i t h n i c k e l molybdenum c a t a l y s t s . L a s t l y i t is i n t e r e s t i n g a l s o t o n o t e t h a t t h e s e s p e c i f i c p r o p e r t i e s may b e t h e r e s u l t o f t h e low h y d r o g e n a t i n g p r o i n c o m p a r i s o n of c h a i n g r o w t h v i a h y d r o c a r b o n s p e c i e s o r / a n d
perties
CO i n s e r t i o n .
The r e s u l t s o f T a b l e 3 i n d i c a t e t h a t C2H,+ added t o s y n g a s
never
during the reaction
is
e n t i r e l y hydrogenated
a s was i n d i c a t e d
i n numerous works p u b l i s h e d p r e v i o u s l y .
CONCLUSION I n t h i s work we e m p h a s i z e d t h e d e t e r m i n i n g e f f e c t o f t h e s u p p o r t
of molybdenum and o f a l c a l i n e o n t h e a c t i v i t y and t h e s e l e c t i v i t y o f nickel
c a t a l y s t s i n syngas conversion.
Both a s e l e c t i v i t y i n
(C,-C3)
a l c o h o l s h i g h e r t h a n 60% and a s i g n i f i c a t i v e p r o d u c t i v i t y a r e o b t a i n e d with
d N i Mo
clearly
K/ZnO c a t a l y s t .
demonstrated
that
The e x p e r i m e n t s c a r r i e d out w i t h e t h y l e n e
i) h i g h e r
o l e f i n i n 0x0 t y p e r e a c t i o n and
alcohol
formation
i i ) hydrocarbons
can
involve
( i - e p r o p e n e and
p r o p a n e ) c a n b e formed v i a r e a c t i o n o f e t h a n e or C2 s u r f a c e s p e c i e s w i t h C1
fragment s u r f a c e a s p r e v i o u s l y proposed
by B a s s e t
and c o l l .
( r e f . 7 , 8). According
t o models o f promoted nickel-molybdenum o x i d e s p r o p o s e d 9 ) t h e s i m u l t a n e o u s f o r m a t i o n o f mixed o x i d e s
i n the literature (ref.
close t o o r d e c o r a t e d by some n i c k e l p a r t i c l e s c o u l d e x p l a i n t h e s p e c i f i c p r o p e r t i e s of such c a t a l y s t s .
But t h e r o l e o f t h e s u p p o r t is n o t
c l e a r ; p r e l i m i n a r y XPS c h a r a c t e r i z a t i o n s showing s i g n i f i c a n t m o d i f i c a t i o n s o f t h e s u r f a c e c o m p o s i t i o n w i t h t h e change o f s u p p o r t ( r e f . 10).
355 REFERENCES 1 2 3 4
5 6 a)
7
b)
8
9 10
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