Reduced vanadium and molybdenum oxides catalyze the equivalent formation of ethane and acetaldehyde from ethanol

Article abstract of DOI:10.1002/cctc.201300991

Catalytic tests for ethanol conversion were performed on vanadium and molybdenum oxides with different oxidation states. We found for the first time that equivalent amounts of ethane and acetaldehyde were formed catalytically over V₂O₃ and MoO₂. No influence of the reaction temperature was observed on the selectivity to ethane and acetaldehyde in the range of 533-653K over V₂O₃ and MoO₂. The reactions of methanol, 1-propanol, and 2-propanol also produced the corresponding alkanes and aldehydes in a 1:1 ratio. A reaction scheme for the formation of ethane and acetaldehyde from ethanol is proposed in which a hydrogen transfer reaction occurs between two ethanol molecules adsorbed on the adjacent metal cation-oxygen anion pair sites to form ethane, acetaldehyde, and water in one step. Good things come in twos: The co-formation of ethane and acetaldehyde from ethanol occurs over reduced vanadium and molybdenum oxide catalysts. The mechanism for this reaction is proposed to be a hydrogen transfer reaction between two ethanol molecules adsorbed on the metal cation-oxygen anion pair sites of reduced vanadium and molybdenum oxides.

Full text of DOI:10.1002/cctc.201300991

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DOI: 10.1002/cctc.201300991
Reduced Vanadium and Molybdenum Oxides Catalyze the
Equivalent Formation of Ethane and Acetaldehyde from
Ethanol
[
a]
Yoichi Nakamura, Toru Murayama, and Wataru Ueda*
Catalytic tests for ethanol conversion were performed on vana-
dium and molybdenum oxides with different oxidation states.
We found for the first time that equivalent amounts of ethane
The selectivities to ethane and acetaldehyde decreased and
the selectivity to ethylene increased over the reduced catalyst
because of the loss of active sites for the dehydrogenation of
[3]
and acetaldehyde were formed catalytically over V O3 and
ethanol. Other reports also show the relationship between
the selectivities to alkanes and aldehydes and the catalytic oxi-
dation states. Abu-Zied and El-Awad showed that the forma-
tion of ethane from ethanol over Cd-Cr-O catalysts proceeded
through the hydrogenation of ethylene produced by the dehy-
dration of ethanol. As the selectivity to ethane increased with
an increase in the selectivity to acetaldehyde and Cr is known
to form hydride species, CrÀH was proposed as the active spe-
cies in the hydrogenation of alcohols over Cr. In this reaction,
2
MoO . No influence of the reaction temperature was observed
2
on the selectivity to ethane and acetaldehyde in the range of
533–653 K over V O and MoO . The reactions of methanol,
2 3 2
1-propanol, and 2-propanol also produced the corresponding
alkanes and aldehydes in a 1:1 ratio. A reaction scheme for the
formation of ethane and acetaldehyde from ethanol is pro-
posed in which a hydrogen transfer reaction occurs between
two ethanol molecules adsorbed on the adjacent metal
cation–oxygen anion pair sites to form ethane, acetaldehyde,
and water in one step.
6+
3+
Cr was reduced from Cr to Cr during the catalysis because
of the absence of oxygen in the reaction stream. The reduced
[4]
Cr is highly active for the dehydration reaction. Mohamed
showed that ethane and methane were formed as major prod-
ucts over Fe-ion-exchanged mordenite. In this report, the for-
mation of ethane as a dominant product was explained mainly
Vanadium and molybdenum oxide catalysts have attracted
much attention because of their unique catalytic properties
and commercial application in various chemical processes.
These catalysts are known to be active as oxidation and acid
3+
[5]
by the high O-abstracting affinity of the Fe ions. Sumathi
et al. showed that the reducibility of the B site of ABB’O -type
3
[1]
catalysts in reactions such as the partial oxidation of alkanes
perovskite oxides (A=Ba, B=Pb, Ce, Ti, B’=Bi, Cu, Sb) played
an important role in the catalytic activity and selectivity in the
selective oxidation of benzyl alcohol. They showed that the
mechanism for the formation of toluene proceeded through
the hydrogenation of benzyl alcohol. The possibility that the
adsorbed hydrogen species formed from the dehydrogenation
of benzyl alcohol take up lattice oxide ions increases as the re-
[
2]
and dehydration of alcohols. In reports on the reaction of al-
cohols over vanadium and molybdenum oxide catalysts, the
catalytic reaction was performed in the presence of oxygen
and aldehydes, and carboxylic acid and CO were produced.
2
However, we found that ethane was formed from ethanol con-
version over vanadium and molybdenum oxides under N . The
2
[6]
formation of alkanes from the corresponding alcohols is not
normally a feature of the dehydration and dehydrogenation of
alcohols. There is no report that describes the formation of al-
kanes from alcohols over reduced vanadium or molybdenum
oxides. However, several reports describe the formation of al-
kanes from the corresponding alcohols, which are summarized
in Table 1.
ducibility of the B sites decreased.
On the other hand, some reports showed that almost the
same yield of alkanes and aldehydes were formed from corre-
sponding alcohols. Ohtani et al. showed that the simultaneous
formation of ethane and acetaldehyde occurred by the hydro-
genation of hemiacetal via the acetalization of ethanol and
acetaldehyde using acidified ethanol over TiO -PtO in a postir-
2
2
McMonagle and Moffat proposed that the formation of
ethane from ethanol over 12 molybdophosphates proceeds
through the secondary hydrogenation of ethylene formed by
the dehydration of ethanol because the selectivity to ethane
radiation dark reaction. The yield of ethane increased with de-
[7]
creasing yields of acetal and H2. Lobo et al. reported the for-
mation of propane and propionaldehyde in the same quantity
with H as the main product in the reaction of 1-propanol over
2
[8]
increased in the presence of H and the selectivity to acetalde-
Pt-supported catalysts (Pt/Al O , Pt/Ce O , Pt/TiO ). They pro-
2 3 2 3 2
2
hyde was always higher than that of ethane. In this study,
posed the mechanism for the formation of propane from
1-propanol to be through the hydrogenation of 1-propanol.
They indicated that the hydrogenation of propylene and the
shift of OH to other propanol molecules were unlikely because
propylene and diols were not observed. Jin et al. showed that
butane was formed from 1- and 2-butanol over Fe O , Fe O -
6+
5+
Mo in the catalyst was reduced to Mo during the reaction.
[a] Y. Nakamura, Prof. Dr. T. Murayama, Prof. Dr. W. Ueda
Catalysis Research Center
Hokkaido University
N-21, W-10, Sapporo (Japan)
Fax: (+81)117069163
2
3
2
3
ZrO , and Fe O -ZnO. They indicated that the formation of
2
2
3
E-mail: ueda@cat.hokudai.ac.jp
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Table 1. Formation of alkanes from the corresponding alcohols over various solid catalysts.
Catalyst
Reactant
T
Carrier
Conversion
[%]
Selectivity [%]
Alkene
Other products
Ref.
[K]
Alkane
Aldehyde
(
NH
Cd-Cr-O
Fe-ion-exchanged mordenite
TiO -PtO
4
)
3
PMo12
O
40
C
C
C
C
C
C
C
2
2
2
2
3
3
3
H
H
H
H
H
H
H
5
5
5
5
7
7
7
OH
OH
OH
OH
OH
OH
OH
498
673
673
RT
He
38.3
58.0
68.0
–
–
–
32.9
5.5
68.0
2.6
15.3
5.0
–
–
–
–
–
7.7
3.2
11.9
–
51.8
73.0
7.0
–
–
CH
[3]
[4]
[5]
[7]
[8]
[8]
[8]
[9]
[9]
[9]
[10]
[6]
this work
this work
N
N
–
2
2
4
, (C
2
H
5
)
2
O
2
3.7
hemiacetal
Pt-Al
Pt-Ti
Pt-Ce
Fe
Fe
Fe
Au-Pd/TiO
BaPb0.6Bi0.4
V
MoO
523
523
523
523
523
523
353
637
573
573
N
2
N
2
N
2
13.0
12.0
10.0
16.8
2.4
13.8
45.4
23.4
39.9
45.6
12.0
10.0
15.0
76.5
94.4
85.3
54.6
76.6
41.7
47.1
H
H
H
–
–
–
–
–
–
–
2
2
2
–
2
2
2
O
3
O
3
O
3
2-butanol
2-butanol
2-butanol
benzyl alcohol
benzyl alcohol
He
He
He
He
8.8
24.9
8.5
27.0
28.8
16.5
42.9
-ZnO
-ZrO
2
2
O
3
N
2
N
2
N
2
–
2
O
3
C
C
2
H
H
5
OH
OH
<1
1.3
2
2
5
butane from butanol proceeded through the nucleophilic sub-
to their oxidation states for the formation of alkane from the
corresponding alcohol. A reaction mechanism that leads to al-
kanes and aldehydes is proposed, in which a hydrogen transfer
reaction occurs between two ethanol molecules adsorbed on
adjacent metal cation–oxygen anion pair sites.
stitution (S 2) of the alcoholic hydroxyl ion by a hydride ion.
N
In the nucleophilic mechanism, the source of hydride ions
may be a hydrogen molecule that is adsorbed heterolytically,
[9]
which is produced by the dehydrogenation of butanol. Mee-
nakshisundaram et al. showed that nearly equal amounts of
toluene and benzaldehyde were formed from benzyl alcohol
on Au-Pd nanoparticles under He. They proposed a mechanism
for the formation of toluene and benzaldehyde through the
The product distribution for the conversion of ethanol on
vanadium and molybdenum oxide catalysts with different oxi-
dation states is given in Table 2. Over V O , ethane was not
2
5
formed, but a high selectivity to acetaldehyde of 64.7% was
observed with the complete transformation of ethanol at 0.1 h
time on stream. However, the formation of ethane in 37% se-
lectivity and decreases in the conversion and selectivity to
acetaldehyde were also observed at 2 h time on stream. With
a further increase of the time on stream, the selectivity to
ethane reached 45.7% at 9 h time on stream, and almost the
same selectivities to ethane and acetaldehyde with 42.5% se-
lectivity were observed at this time on stream. Other minor
products are attributed to C compounds. The formation of C
[
10]
disproportionation of benzaldehyde over Pd.
Rintramee et al. observed the formation of ethane in ethanol
temperature-programmed desorption (TPD) profiles of a Pt cat-
alyst at high temperatures and proposed the hydrogenation of
[
11]
ethylene to form ethane from ethanol. Ochoa et al. observed
ethane, acetaldehyde, and water at low temperatures in etha-
nol TPD profiles over ferrite catalysts, however, they suggested
that the reaction mechanism for the formation of ethane is
ethanol disproportionation and coupling of the methyl species
formed by the dissociation of
4
4
[
12]
acetaldehyde.
Several reaction schemes for
the formation of alkanes from
the corresponding alcohols have
been proposed, however, the re-
action mechanism and the rela-
tionship between the catalytic
states and catalytic activity for
the formation of alkanes are still
not clear.
[
a]
Table 2. Catalytic activity of V
2
O
x
and MoO
x
for the formation of products in ethanol conversion.
Selectivity [%]
Catalyst
Time on
Conversion
[%]
stream [h]
C2H6
C2H4
3
CH CHO
C H O C H
5
2
5
2
Other
2
V O
5
0.1
2
100.0
74.5
73.7
35.5
31.5
28.0
22.8
15.3
16.5
98.4
59.6
47.7
46.9
42.0
42.9
<1
10.5
1.1
0.9
1.2
0.6
64.7
43.7
42.5
82.8
53.2
44.4
46.1
43.3
41.7
65.5
36.4
28.2
48.5
47.5
47.1
0
0
0
0
0
0
0
0
0
24.8
18.2
10.9
8.3
37.0
45.7
7.7
37.7
42.7
41.8
41.4
39.9
<1
19.1
24.8
48.4
47.0
45.6
9
VO
2
0.1
2
8.5
9
0.9
10.0
12.1
15.3
18.3
0.3
12.0
5.2
2.0
In the present study, we found
that the reduced states of vana-
dium and molybdenum oxides
were active for the formation of
ethane and acetaldehyde in an
equivalent amount from ethanol.
The objective of the present
study is to understand the cata-
lytic properties of vanadium and
molybdenum oxides in relation
V2O3
MoO
MoO
0.1
2
9
0.1
2
9
<1
<1
<1
28.2
28.1
35.9
1.1
3
2
6.0
4.4
5.9
<1
<1
<1
0.1
2
1.1
1.3
4.4
6.0
9
À1
[
0
a] Reaction conditions: 573 K, catalyst 0.15 g, SiO
2
2.5 g, N
2
flow rate 21 mLmin , ethanol flow rate
À1
.24 mLmin
.
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compounds, such as ethyl acetate, n-butanol, crotonaldehyde,
and 2-butanone, as condensation products of acetaldehyde
was observed. A decrease of the selectivity to acetaldehyde
with increased time on stream over V O was caused by the re-
2
5
duction of vanadium oxide. In the initial time on stream, the
preferential formation of acetaldehyde occurred from the de-
hydrogenation of ethanol with the concomitant removal of lat-
tice oxygen atoms of V O because the catalytic reaction was
2
5
performed under N , which suggests that V O was reduced
2
2
5
during the catalytic reaction. This result indicates that the state
of V O after ethanol conversion at 9 h time on stream was dif-
2
5
ferent from that in the initial reaction period at 0.1 h time on
stream.
The decreased conversion was caused mainly by the reduc-
tion of V O as we observed an increased surface area of the
2
5
catalyst after the reaction. This result indicates that reduced va-
nadium oxide was active for the formation of ethane from eth-
anol. VO showed the formation of a small amount of ethane
2
with 7.7% selectivity at 0.1 h time on stream, which suggests
that the degree of reduction was not enough to form the
equivalent amount of ethane and acetaldehyde in the initial
reaction period. The selectivity to ethane was still lower than
that of acetaldehyde until 2 h time on stream, then almost the
same selectivity to ethane (42.7%) and acetaldehyde (44.4%)
was observed at 9 h time on stream.
These results show that V O and VO were reduced during
2
5
2
the reaction to the same surface state of V O , which is active
2
3
to form ethane and acetaldehyde in equal amounts. A similar
tendency of the change in the selectivities to ethane and acet-
aldehyde was observed over molybdenum oxides.
Figure 1. Reaction of ethanol from 533–653 K over a) V
2
O
3
and b) MoO
2
.
Conditions: catalyst 0.15 g, SiO
2
2.5 g, time on stream 3 h, N flow rate
2
À1
À1
2
1 mLmin , ethanol flow rate 0.24 mLmin . Conversion of ethanol (^) and
MoO showed a very high selectivity to acetaldehyde with
selectivity to ethane (^), ethylene (*), and acetaldehyde (
).
&
3
no formation of ethane at a time on stream of 0.1 h. Moreover,
ethylene with 28.2% selectivity and diethyl ether with 6.0% se-
lectivity were formed by the dehydration of ethanol over the
ethane and acetaldehyde over V O3 (Figure 1(a)) and MoO2
2
(Figure 1(b)). For both V O3 and MoO , the selectivities to
2
2
[
13]
acid sites of MoO3. However, the selectivity to ethane in-
creased and the selectivity to acetaldehyde decreased with in-
creased time on stream. At a time on stream of 9 h, almost the
same selectivities to ethane (24.8%) and acetaldehyde (28.2%)
ethane and acetaldehyde were almost the same and were un-
changed throughout the reaction temperature range or the
conversion range. If ethane and acetaldehyde were formed in
successive steps, the selectivities to ethane and acetaldehyde
would vary with the reaction temperature or conversion unless
the activation energies for the formation of ethane and acetal-
dehyde were the same for these steps. The results suggest
that ethane and acetaldehyde are formed in a single step from
a common intermediate.
were observed. This result indicates that MoO was also re-
3
duced during the catalytic reaction. In addition, the selectivity
to ethylene increased to 35.9% at 9 h time on stream. Ohno
et al. reported that a H MoO phase is formed by the partial re-
x
3
duction of MoO with H , which is active for the dehydration
3
2
[
14]
of 2-propanol. Therefore, in this case, a H MoO phase seems
To study the reaction scheme for alcohol conversion on re-
duced vanadium and molybdenum oxides, a catalytic reaction
was performed by using methanol, 1-propanol, and 2-propanol
over reduced vanadium oxide (Table 3). The formation of meth-
ane and formaldehyde with 42.9 and 43.2% selectivity, respec-
tively, was observed if methanol was used as the substrate. In
the case of 1-propanol, we observed the formation of propane
and propionaldehyde with 43.1 and 36.0% selectivity, respec-
tively. The formation of propane with 22.6% selectivity and
acetone with 19.4% selectivity was observed if 2-propanol was
used, and a higher selectivity to propylene of 55.9% was ob-
tained. Almost the same selectivities to alkanes and their corre-
sponding aldehydes were observed in all kinds of alcohols.
This result indicates that the equivalent formation of alkanes
x
3
to be formed on MoO during ethanol conversion, which may
x
act as protonic acid sites to promote the dehydration of etha-
nol.
However, MoO2 showed the same selectivity to ethane
(
48.4%) and acetaldehyde (48.5%) from the beginning of the
reaction.
From these results, we can conclude that
3
V
4
+
and Mo species are active for the equivalent formation of
ethane and acetaldehyde from ethanol.
The effects of the reaction temperature on the selectivities
to ethane and acetaldehyde were examined over V O3 and
2
MoO in the temperature range from 533–653 K (Figure 1). The
2
reaction temperature had no effect on the selectivities to
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[
a]
Experimental Section
Table 3. Reaction of various alcohols on reduced vanadium oxide as catalyst.
V O was prepared by the calcina-
[
b]
[c]
2
5
Reactant
Conversion
Selectivity to products [%]
tion of NH VO3 (99% Wako Purer
4
[
%]
MA
EE
EA
PE
PA
FA
ACA
ACT
PPA
Other
Chemical Industries) at 773 K for
CH
3
OH
OH
OH
CH(OH)CH
40.4
73.7
47.8
42.9
0
0.9
0
0
45.7
0
0
0
0
0
0
43.1
22.6
43.2
0
42.5
0
0
0
0
0
0
36.0
0
13.9
10.9
20.9
2.2
2
h in air. VO was purchased from
2
C
2
H
5
0
0
0
0
0
0
Wako Purer Chemical Industries.
V2O3 was prepared by the reduc-
tion of V O under a H2 stream
n-C
CH
3
H
7
3
2
100.0
0
0
55.9
0
19.4
2
5
À1
À1
À1
[a] Reaction conditions: V
2
O
x
0.15 g, SiO
2
2.5 g, 573 K, 4 h, flow rates: N
2
21 mLmin , ethanol 0.24 mLmin
,
(30 mLmin ) at 773 K for 2 h.
À1
À1
À1
methanol 0.74 mLmin , 1-propanol 0.41 mLmin , 2-propanol 0.80 mLmin . [b] Conversion of reactants.
c] MA: methane, EE: ethylene, EA: ethane, PE: propylene, PA: propane, FA: formaldehyde, ACA: acetaldehyde,
ACT: acetone, PPA: propionaldehyde.
MoO was prepared by the calcina-
3
[
tion of (NH ) Mo O (99% Wako
4
6
7
24
Purer Chemical Industries) at 773 K
in air. MoO was prepared by the
2
reduction of MoO3 under a H2
À1
and aldehydes occurs with corresponding alcohols, regardless
of the alcohol. Moreover, the result of the formation of meth-
ane from methanol suggests that the reaction mechanism for
the equivalent formation of alkanes and aldehydes is not the
hydrogenation of an olefin.
stream (30 mLmin ) at 773 K for 2 h and then treated again under
À1
a H /Ar stream (5% H , 30 mLmin ) at 773 K for 2 h.
2
2
Catalytic reactions were performed in a continuous-flow fixed reac-
tor. A mixture of catalyst (0.15 g) and SiO (2.5 g) as diluent was
2
placed in the reactor and heated to 573 K. Then, the catalytic reac-
Based on these results, we propose a plausible reaction
scheme for the co-formation of ethane and acetaldehyde from
ethanol on V O and MoO (Scheme 1). The simultaneous for-
tion was started by the introduction of EtOH (1.8%) with N carrier
2
gas into the reactor. N
internal standard.
gas was used both as the carrier gas and
2
2
3
2
mation of ethane and acetaldehyde proceeds through a hydro-
gen transfer reaction between two ethanol molecules ad-
sorbed on adjacent metal cation–oxygen anion pairs on re-
duced vanadium and molybdenum oxides.
Catalytic activity tests with other alcohols as reactants were con-
ducted by the same procedure with different flow rates of the re-
actants.
The products were analyzed by GC. Two gas chromatographs were
used: Shimazu GC-8A and GC-380. The GC-8A chromatograph was
equipped with a thermal conductivity detector and the column
was packed with Porapack-QS. The GC-380 chromatograph was
equipped with a thermal conductivity detector and flame-ioniza-
tion detector and two columns packed with Unicarbon and molec-
ular sieves (5A).
Keywords: alcohols · aldehydes · alkanes · molybdenum ·
vanadium
Scheme 1. Reaction scheme for the co-formation of ethane and acetalde-
hyde from ethanol over reduced vanadium and molybdenum oxides.
[1] S. Song, S. Jiang, R. Rao, H. Yang, A. Zhang, Appl. Catal. A 2011, 401,
215–219.
[
2] A. Benadda, A. Katrib, A. Barama, Appl. Catal. A 2003, 251, 93–105.
Cation sites of certain catalysts, such as ZrO , are known to
[3] J. B. McMonagle, J. B. Moffat, J. Catal. 1985, 91, 132–141.
2
act as Lewis acid sites, which are active for the hydrogen trans-
fer reaction between alcohols and aldehydes through a six-
[4] B. M. Abu-Zied, A. M. El-Awad, J. Mol. Catal. A 2001, 176, 227–246.
[
[
5] M. M. Mohamed, J. Mol. Catal. A 2003, 200, 301–3137.
6] R. Sumathi, K. Johnson, B. Viswanathan, T. K. Varadarajan, Appl. Catal. A
[
15]
membered transition state. Therefore, in the present case,
two ethanol molecules are adsorbed on a pair of cation–
oxygen anion sites on reduced vanadium and molybdenum
oxides. The H atoms on the hydroxyl groups may be stabilized
by H bonding with lattice O atoms. As a result, the six-mem-
1
998, 172, 15–22.
[7] B. Ohtani, M. KAkimoto, S. Nishimoto, T, Kagiya, J. Photochem. Photo-
biol. A 1993, 70, 265–272.
8] R. Lobo, C. L. Marshall, P. J. Dierich, F. H. Ribeiro, C. Akatay, E. A. Stach, A.
Mane, Y. Lei, J. Elam, J. T. Miller, ACS Catal. 2012, 2, 2316–2326.
9] T. Jin, H. Hattori, K. Tanabe, Chem. Lett. 1981, 1, 533–1534.
[
[
bered transition state is formed. The methylene H transfers to
[10] S. Meenakshisundaram, E. Nowicka, G. J. Hutchings, Faraday Discuss.
2010, 145, 341–356.
a
the positively charged C atom of methylene group of another
ethanol adsorbed on the adjacent site as a hydride ion. At the
same time, the H atom of the hydroxyl group transfers to the
hydroxyl group of the ethanol adsorbed at the adjacent site
accompanied by the cleavage of the CÀO bond of the ethanol
molecule. As a result, ethane and acetaldehyde are formed
simultaneously.
[
11] K. Rintramee, K. Fottinger, G. Rupprechter, J. Wittayakun, Appl. Catal. B
012, 115, 225–235.
2
[
12] J. V. Ochoa, C. Trevisanut, J. M. M. Millet, G. Busca, F. Cavani, J. Phys.
Chem. C 2013, 117, 23908–23918.
[13] F. Bertinchamps, E. M. Gaigneaux, Catal. Today 2004, 91, 105–110.
[
14] T. Ohno, Z. Sakai, H. Sakagami, N. Takahashi, T. Matsuda, Appl. Catal. A
010, 389, 52–59.
15] Y. Zhu, G. Chuah, S. Jaenicke, J. Catal. 2004, 227, 1–10.
2
[
Received: November 20, 2013
Published online on February 12, 2014
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