K. Omata et al. / Catalysis Today 201 (2013) 7–11
11
Table 2
Conversion of glycerol and products yield.
Catalyst
Catal. wt. (g)
GLRb conv.a (%)
Yieldc (%)
ACRL
ACAL
PRAL
HACT
ACA
AA
0.1
0.5
<0.1
0.3
COx
Others
W–Nb–O (673 K)
W–Nb–O (973 K)
W–Nb–O (1273 K)
WO3/Nb2O5
WO3/ZrO2
H-ZSM-5
0.2
0.2
0.8
0.8
0.2
0.2
98.9
97.9
64.5
86.9
89.3
87.3
74.4
70.1
15.4
37.9
62.1
46.4
2.9
1.3
0.2
0.8
0.9
1.9
1.0
0.8
<0.1
0.2
0.6
1.4
0.4
3.0
3.6
3.3
5.0
1.8
0.7
0.3
0.6
0.2
0.1
0.3
3.8
2.0
0.3
0.6
0.7
1.6
15.4
19.1
44.0
43.5
14.4
33.6
0.6
0.3
a
Reaction time, 0–1 h.
GLR, glycerol.
b
c
ACRL, acrolein; ACAL, acetaldehyde; PRAL, propanal; HACT, hydroxyacetone; ACA, acetic acid; AA, acrylic acid.
Table 3
Conversion of glycerol and products selectivity.
Catalyst
Catal. wt. (g)
GLR conv. (%)
Selectivity (%)
ACRL
ACAL
PRAL
HACT
ACA
AA
COx
Others
W–Nb–O (973 K)a
W–Nb–O (1273 K)
0.05
0.8
0.8
59.5
64.5
59.1
29.7
23.9
30.5
0.3
0.3
0.3
0.2
0.1
0.2
2.9
5.6
3.9
<0.1
0.9
<0.1
<0.1
<0.1
<0.1
0.7
0.5
0.7
66.1
68.2
64.5
b
Cs–W–Nb–O (AT)b
a
Reaction time, 1–2 h.
Reaction time, 0–1 h.
b
100
that the deactivation rate in the W–Nb–O catalyst was less
than that in WO /ZrO2 or H-ZSM-5. These results indicate that
3
W–Nb–O is an efficient and potential catalyst of acrolein produc-
tion from glycerol in high yield. W–Nb–O (1273 K) in Nb W O
8
0
0
0
0
8
9
47
phase and Cs–W–Nb–O with orthorhombic structure in the crystal
structure showed different selectivity for glycerol transforma-
tion. These results suggest that structure of the a–b plane affects
not only the activity but also the catalyst selectivity. W–Nb–O
synthesized by hydrothermal method seems to assume a sim-
ilar surface structure as formed in Cs0.5[Nb2.5W2.5O14] and to
generate active and selective sites for glycerol transformation to
acrolein.
6
4
2
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decreasing rate of acrolein yield in W–Nb–O was appreciably
[
slower than that in WO /ZrO2 or H-ZSM-5 as can be seen in Fig. 5.
3
[
After 5 h on stream from starting the reaction, the acrolein yield of
WO /ZrO and H-ZSM-5 decreased to less than half. On the other
3
2
[
[
hand, W–Nb–O (673 K) could still achieve an acrolein yield of about
0%. This may be due to the acid amount per weight of W–Nb–O
973 K) which is lower than that of H-ZSM-5, we consider the long
6
(
lifetime of the W–Nb–O is not due to these properties. These results
suggest that the acid sites formed on the W–Nb–O surface structure
have not only excellent activity for the dehydration of glycerol to
acrolein but also superior property against deactivation.
[
[
[
[
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(
[
The complex metal oxides of W and Nb were synthesized with
2
a layered structure via a hydrothermal method. The W–Nb–O
catalysts gave acrolein yield higher than 70% in the glycerol
transformation. This catalytic performance was higher than that
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of the WO /ZrO2 or the H-ZSM-5. In addition, it was observed
3