CHEMSUSCHEM
COMMUNICATIONS
DOI: 10.1002/cssc.201402033
Molybdenum Carbide as a Highly Selective Deoxygenation
Catalyst for Converting Furfural to 2-Methylfuran
[a]
[b]
[b]
[c]
Ke Xiong, Wen-Sheng Lee, Aditya Bhan,* and Jingguang G. Chen*
[
12]
[13,14]
Selectively cleaving the C=O bond outside the furan ring of
furfural is crucial for converting this important biomass-derived
molecule to value-added fuels such as 2-methylfuran. In this
work, a combination of density functional theory (DFT) calcula-
tions, surface science studies, and reactor evaluation identified
ring intact. Copper-
and nickel-based
catalysts have
been reported as active towards the conversion of furfural into
2-methylfuran. However, the copper chromite catalyst required
for making 2-methylfuran is toxic while the yield of 2-methyl-
furan on monometallic nickel catalysts is less than 15%. Resas-
molybdenum carbide (Mo C) as a highly selective deoxygena-
co et al. reported that adding iron into Ni/SiO could improve
2
2
[14]
tion catalyst for converting furfural to 2-methylfuran. These re-
the yield of 2-methylfuran. This was achieved, however, at
relatively high temperature (ca. 523 K). Other common deoxy-
genation catalysts include precious metals such as rutheni-
sults indicate the potential application of Mo C as an efficient
2
catalyst for the selective deoxygenation of biomass-derived
oxygenates including furanics and aromatics.
[15]
[16]
[17]
[18]
um,
rhodium,
palladium,
rhenium,
and cobalt or
[19]
nickel molybdenum (CoMo, NiMo) sulfide catalysts. The pre-
cious-metal catalysts suffer from low selectivity due to undesir-
able side reactions involving CÀC bond cleavage and also from
the limited abundance of precious metals, which might
become a cost issue for large-scale applications for biomass
conversion. On the other hand, the CoMo and NiMo sulfide
catalysts require high operating temperatures and additional
Biomass upgrading is a promising alternative in order to meet
[
1–3]
recent energy and environment challenges.
Several furanic
molecules have been introduced as platform chemicals in bio-
[
4]
mass conversion. These furanic molecules can be produced
by hydrolyzing and dehydrating
[20]
cellulose and hemicellulose, which
separation units because of the possible leaching of sulfur.
comprise more than 55 wt% of the
Molybdenum carbide (Mo C) is emerging as a hydrodeoxyge-
2
[1]
components of raw biomass. Fur-
fural (Scheme 1) is one of the most
important biomass-derived furanic
molecules, as described in previous
nation (HDO) catalyst. It has been demonstrated to possess
high activity towards HDO and high CÀO scission selectivity
compared to CÀC scission in the study of small oxygenates
Scheme 1. Molecular structure
of furfural.
[21]
[22]
such as ethanol and propanal. A recent report suggested
that Mo C is more stable compared to tungsten carbide (W C)
[
5,6]
reports.
Furfuryl alcohol, which
2
2
[20]
can be obtained by selectively hydrogenating the C1=O1 bond
in the HDO of guaiacol. However, the fundamental reason
[
7–10]
[11]
of furfural,
is a desirable compound for producing resins.
behind the selective HDO activity of Mo C is not well under-
2
Another desirable compound is 2-methylfuran, from the selec-
tive cleavage of the C1=O1 bond, which has a high energy
density, a high blending research octane number (RON), and
has been shown to be a promising fuel additive for gasoline in
stood. Because different oxygen-containing functional groups
usually coexist in biomass molecules, furfural, which contains
carbon–oxygen bonds both outside and inside the furan ring,
should be an excellent probe molecule for studying the selec-
[
6]
a recent 90000 km road test.
tive HDO activity of Mo C for biomass molecules.
2
The conversion of furfural to 2-methylfuran requires selective
In this work we report the unique HDO properties of Mo2C
for selectively cleaving the C=O bond outside the furan ring of
furfural, while leaving the CÀO bond inside the ring intact.
Density functional theory (DFT) calculations predict that furfu-
deoxygenation of the C1=O1 bond while leaving the furan
[
a] K. Xiong
Catalysis Center for Energy Innovation (CCEI)
ral adsorbs onto the Mo C surface in a configuration that
2
favors selective cleavage of the C1=O1 bond while leaving the
furan ring intact. This favorable bonding configuration was
confirmed by using surface vibrational spectroscopy over
Department of Chemical and Biomolecular Engineering
University of Delaware
Newark, DE, 19716 (USA)
[
b] Dr. W.-S. Lee, Prof. A. Bhan
a well-characterized Mo C surface, and the production of 2-
2
Department of Chemical Engineering and Materials Science
University of Minnesota
Minneapolis, MN, 55455 (USA)
methylfuran was detected by temperature programmed de-
sorption (TPD) experiments. Finally, the promising results on
model surfaces were extended to flow reactor evaluation on
E-mail: abhan@umn.edu
[c] Prof. J. G. Chen
porous Mo C catalysts, confirming the production of 2-methyl-
2
Department of Chemical Engineering
Columbia University
New York, NY, 10027 (USA)
E-mail: jgchen@columbia.edu
furan with high selectivity at relatively low temperatures.
DFT calculations of binding energies of furfural and several
related molecules, including furan, 2-methylfuran, and furfuryl
alcohol, were performed on a close-packed Mo C(0001) sur-
Supporting Information for this article is available on the WWW under
http://dx.doi.org/10.1002/cssc.201402033.
2
face. A DFT calculation of furfural on a typical precious-metal
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2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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