Vapor phase hydrogenation of 2-methylfuran over noble and base metal catalysts

Article abstract of DOI:10.1016/j.apcata.2014.01.054

Vapor phase hydrogenation of 2-methyl furan (2-MF) was carried out over barium-promoted copper chromite (Ba/Cu/Cr), Cu/Cr/Ni/Zn/Fe, Cu-Ru/C, 0.5 wt.% Pt/C (Pt/C), and 0.5 wt.% Pd/C (Pd/C) catalysts, respectively. The catalysts were characterized with respect to their specific surface areas by the N ₂ BET method and solid-state structures by X-ray diffraction (XRD). The XRD data confirmed the formation of a mixed oxide in the copper-chromite catalyst and the presence of small Pt and Pd crystals (<5 nm by TEM) in the carbon-supported catalysts. The 2-MF hydrogenation was performed in vapor phase at atmospheric pressure in a continuous flow fixed bed tubular reactor at 140-350 C employing the H₂/2-MF mole ratios in the 10-25 range. The results of 2-MF hydrogenation showed that the Ba/Cu/Cr, Cu/Cr/Ni/Zn/Fe, Cu-Ru/C and Pt/C catalysts were mainly active for furan ring opening leading mostly to 2-pentanone (2-PN) as well as small amounts of other products, such as 2-methyltetrahydrofuran (2-MTHF), 2-pentanol (2-PL), 1-pentanol (1-PL) and cracked hydrocarbons (butane and propane). On the other hand, the Pd/C catalyst was highly selective in 2-MF ring saturation leading to 2-MTHF as the main product below 220 C, whereas it became increasingly selective to 2-PN, the ring opening product, at higher temperatures.

Full text of DOI:10.1016/j.apcata.2014.01.054

Applied Catalysis A: General 475 (2014) 379–385
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Vapor phase hydrogenation of 2-methylfuran over noble and base
metal catalysts
Prakash Biswas1, Jiann-Horng Lin2, Jungshik Kang, Vadim V. Guliants∗
Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221-0012, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Vapor phase hydrogenation of 2-methyl furan (2-MF) was carried out over barium-promoted copper
chromite (Ba/Cu/Cr), Cu/Cr/Ni/Zn/Fe, Cu-Ru/C, 0.5 wt.% Pt/C (Pt/C), and 0.5 wt.% Pd/C (Pd/C) catalysts,
respectively. The catalysts were characterized with respect to their specific surface areas by the N2 BET
method and solid-state structures by X-ray diffraction (XRD). The XRD data confirmed the formation of a
mixed oxide in the copper-chromite catalyst and the presence of small Pt and Pd crystals (<5 nm by TEM)
in the carbon-supported catalysts. The 2-MF hydrogenation was performed in vapor phase at atmospheric
pressure in a continuous flow fixed bed tubular reactor at 140–350 ◦C employing the H2/2-MF mole ratios
in the 10–25 range. The results of 2-MF hydrogenation showed that the Ba/Cu/Cr, Cu/Cr/Ni/Zn/Fe, Cu-Ru/C
and Pt/C catalysts were mainly active for furan ring opening leading mostly to 2-pentanone (2-PN) as
well as small amounts of other products, such as 2-methyltetrahydrofuran (2-MTHF), 2-pentanol (2-PL),
1-pentanol (1-PL) and cracked hydrocarbons (butane and propane). On the other hand, the Pd/C catalyst
was highly selective in 2-MF ring saturation leading to 2-MTHF as the main product below 220 ◦C, whereas
it became increasingly selective to 2-PN, the ring opening product, at higher temperatures.
© 2014 Elsevier B.V. All rights reserved.
Received 21 September 2013
Received in revised form 29 January 2014
Accepted 30 January 2014
Available online 6 February 2014
Keywords:
Hydrogenation
Hydrogenolysis
2-Methylfuran
2-Methyltetrahydrofuran
2-Pentanone
Copper-chromium catalyst
Pt
Pd catalyst
1. Introduction
of furfural ring which is a principal component of a P-series fuel [2].
2-Methylfuran (2-MF) can be also produced by furfural hydrogena-
The catalytic transformation of biomass-derived oxygenated
aromatics, such as substituted furans, to value-added chemicals
and fuels is an important research area in green chemistry. It is
highly desirable to develop novel catalysts and methods that enable
control over the nature of functional groups in these biomass-
derived molecules. Selective hydrogenation and hydrogenolysis of
tion at higher temperature than that employed to make furfuryl
alcohol [3]. 2-MF appears as an unwanted by-product when furfuryl
alcohol is made from furfural by the vapor phase hydrogenation
over a copper-chromite catalyst at 135 ◦C and the yield of 2-MF
increases when the reaction temperature is raised to compensate
for the gradual reduction of catalytic activity [4]. The selectivity to
the desired product in these hydrogenation reactions depends on
the partial pressure of hydrogen and the nature of catalyst.
Hydrogenation of furan ring compounds over noble metals (Pt,
Pd, Ir) is well known in the literature [5–12]. The first reported
catalyst was platinum as a furfural hydrogenation catalyst in 1923
[13]. However, the fundamentals of surface reactions during hydro-
genation of these heterocycles on noble and base metal catalysts
are poorly understood as compared to elementary reaction steps
on these surfaces involving benzene ring molecules. Tracy et al.
[14] reported that furan, thiophene and pyrrole exhibit very dif-
ferent reaction pathways on Pd (1 1 1). Maris et al. [10,12] have
shown that by using cinchonidine (CD)-modified Pd/Al2O3, a chi-
rally modified metal catalyst, the enantioselective hydrogenation
can be effectively achieved for furan and benzofurancarboxylic acid.
Earlier studies in the literature [15–18] indicated that there was a
problem of catalyst deactivation, as both palladium black and Pd/C
deactivated rapidly due to carbon laydown.
C
C and C O bonds are important reactions for the conversion of
substituted furans to useful chemicals. The objective of hydrogenol-
ysis is to selectively break target C C and/or C O bonds, thereby
producing more valuable, desired products.
Furan, furfural and their derivatives are very important biomass-
derived aromatics that can be hydrogenated into a variety of
specialty chemicals, solvents and alternative fuels. Selective hydro-
genation of the C C bond in the furan ring of furfural leads to
the formation of tetrahydrofurfural, which can be converted into
a diesel fuel component by self-aldol condensation [1]. Methylte-
trahydrofuran can be also obtained by the selective hydrogenation
∗
Corresponding author. Tel.: +1 513 556 0203; fax: +1 513 556 3473.
E-mail address: Vadim.Guliants@uc.edu (V.V. Guliants).
Present address: Department of Chemical Engineering, Indian Institute of Tech-
1
nology Roorkee, Roorkee 247667, Uttarakhand, India.
2
Hydrogenation of olefinic and carbonyl groups of furan and
its derivatives over copper-chromite catalysts has been reported
Present address: Intel Corporation, 2501 NW 229th Avenue, RA3-355, Hillsboro,
OR 97124, USA.
0926-860X/$ – see front matter © 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.apcata.2014.01.054

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P. Biswas et al. / Applied Catalysis A: General 475 (2014) 379–385
[19–23]. Also, the cleavage of furan ring has been reported
over copper-chromite and Pt oxide catalysts at low temperature
and pressure [13,24]. Copper-chromite catalysts have been used
extensively in various industrial processes, such as the partial
hydrogenation of vegetable oils and fatty acids, as well as the
decomposition or dehydration of alcohols [25]. The utilization of
these catalysts in hydrogenation reactions stems from their ability
to selectively hydrogenate carbonyl bonds while leaving unsatu-
rated C C bonds virtually untouched [19]. Ruthenium catalysts are
frequently used for liquid phase hydrogenation of aromatic and car-
bonyl compounds [26–30]. Previously, it was reported that furan,
methylfuran, ␣,␣-dimethyl furan, ethylfuran and alkenefurans can
be converted to saturated derivatives in good yields over Raney
nickel catalysts under mild reaction conditions [31,32]. Papa et al.
[33] in their study of hydrogenolysis of furan derivatives over Raney
alloy and aqueous alkali found equal amounts of furan-ring hydro-
genation and hydrogenolysis products. At atmospheric pressure,
the hydrogenation of 2-alkylfurans over skeletal Cu-Al catalysts
leads to the furan ring opening by breaking the C O bond away
from the alkyl group, whereas at high hydrogen pressure the cleav-
age of both C C and C O bond takes place leading to the formation
of an aliphatic alcohol [34]. Paraffins were also observed over
skeletal Cu-Al catalysts, probably due to dehydration of aliphatic
alcohols followed by hydrogenation of olefin intermediates.
Therefore, these previous studies indicated that the nature
of hydrogenation products of furan, 2-MF and their derivatives
depends highly on the nature of catalysts and reaction conditions
employed. However, very few reports have appeared to date on
the topic of the vapor-phase hydrogenation of 2-MF [31,35,36] and
the current fundamental understanding of the molecular relation-
ships between the catalyst structure and the nature of alkylfuran
hydrogenation pathways.
as outlet to facilitate faster removal of reactor effluent. The cat-
alyst (0.2–2 g) was placed between quartz wool plugs inside the
reactor. Prior to these tests, the catalysts were treated in situ at
atmospheric pressure in the hydrogen flow of 20 cc/min, while the
temperature was progressively increased from ambient to 340 ◦C,
and then maintained for 2 h at 340 ◦C. A constant flow of 2-MF vapor
(Sigma–Aldrich, 99%) was established by passing Ar through a bub-
bler (Kontes Kimble Chase LLC, Kontes Article No. 652230-0000)
containing pure liquid 2-MF in a constant temperature bath (Fisher
Scientific, Cat No. 14-462-10, Model 210, USA), and mixing the
resulting 2-MF/Ar feed with hydrogen at the molar H2/2-MF ratios
in the 10–25 range. The 2-MF concentration in the feed was con-
trolled by the bath temperature. The reactor was mounted inside
a programmable electric furnace (Thermo Scientific, Lindberg/Blue
M) and the axial temperature profile in the reactor was measured
using a chromel–alumel thermocouple placed inside the catalyst
bed. The reaction temperature was varied from 130 to 350 ◦C. The
effluent was directly passed through the heated sampling valves to
online GC–MS (Shimadzu, GCMS QP-5000) to determine the prod-
ucts stream composition. All stainless steel lines after the bath and
the sampling valve of the GC-MS were heated to avoid condensation
of the 2-MF reactant and products.
The reactor effluent was analyzed by GC–MS equipped with a
capillary column (Supelco, 28473-U, SLB-5ms) of 30 m in length
and 0.25 ␮ film thickness using ultrapure helium (Wright Brother
Inc., Lot 9047-1) as the carrier gas. The injector and detector tem-
perature was maintained at 230 ◦C. The products were identified
using NIST Mass Spectrum Library 2008 (Shimadzu, Catalog No.
225-13290-91) and the total carbon balances agreed within 5%.
The 2-MF conversion, selectivity and yield of the products were
defined as:
Conversion (%) = [(Mole of 2-MF in the feed – Mole of 2-MF in the
product)/Mole of 2-MF in the feed] × 100
Selectivity (%) = (Mole of the individual product/Total moles of
the products) × 100
2. Experimental
Yield (%) = (Selectivity × Conversion)/100
2.1. Catalysts
The Cu/Cr/Ni/Zn/Fe = 43:45:8:3:1 (atomic ratio) catalyst was
prepared by the co-precipitation method as reported by Zheng
et al. [36] using Cu, Cr, Ni, Zn and Fe nitrates (Alfa Aesar, 99.9%,
USA) as precursors. The Cu-Ru/C catalyst was prepared by incipient
wetness impregnation method, where Ru and Cu were impreg-
nated sequentially onto carbon black support (Vulcan-XC72 GP
3907, Cabot Corporation Ltd., USA) at the atomic Ru:Cu ratio = 3:2.
RuCl3·3H2O (Alfa Aesar, 99.9%) and Cu(NO3)3·3H2O (Alfa Aesar,
99.9%, USA) were used as the respective sources and the total metal
content was 10 wt.%. The Ba/Cu/Cr, 0.5 wt.% Pt/C, and 0.5 wt.% Pd/C
catalysts were obtained from BASF, USA.
3. Results and discussion
3.1. Catalyst characterization
The BET surface areas of carbon-supported catalysts were higher
than those of the other catalysts. The BET surface areas of Pt/C
and Pd/C catalysts were 1182 m2/g and 1188 m2/g, respectively,
whereas their total pore volume was 0.71 cm3/g. The Ba/Cu/Cr,
Cu/Cr/Fe/Ni/Zn and Cu-Ru/C catalysts were dense showing signif-
icantly lower BET surface areas of 47 m2/g, 81 m2/g and 64 m2/g,
respectively, and low pore volumes.
The XRD pattern of the copper-chromite catalyst shown
in Fig. 1(A) agreed well with the pattern reported previously
[19,37,38]. The peaks at 35.4◦ and 63◦ 2Â correspond to cupric
chromite (CuCrO4), whereas the peaks at 37.4◦ and 41.5◦ corre-
spond to CuCrO2 and CuO, respectively [19]. A weaker peak was
detected at 22.3◦, which corresponds to Cr2O3 [37]. The XRD pattern
of the Cu/Cr/Fe/Ni/Zn catalyst, Fig. 1(B), corresponds to a disordered
structure. The diffraction peaks corresponding to the binary Fe, Ni
and Zn oxides were absent, suggesting that this catalyst proba-
bly contained an amorphous mixed metal oxide phase. The weak
peaks observed at 35.4◦ and 63◦ 2Â suggested the presence of either
CuCr2O4 (JCPDS #026-0509) or CuO (JCPDS #003-0898).
2.2. Catalyst characterization
The BET surface areas of the catalysts were determined by the
N2 physisorption at liquid N2 temperature employing a Micromer-
itics Tri-Star system. Prior to the measurements, the temperature
was slowly ramped to 200 ◦C and the catalysts outgassed for 8 h.
The phase composition of the catalysts was investigated by X-ray
diffraction (XRD) (Siemens D500, CuK␣). The TEM images were
collected using Philips CM 20 electron microscope.
2.3. Catalytic tests
The diffraction peak observed at 25.3◦ 2Â for the Cu-Ru/C, Pt/C
and Pd/C catalysts was assigned to that of the graphite phase (JCPDS
#41–1487). Other peaks belonging to RuO2, CuO, metallic Ru and
metallic Cu were not detected for the Cu-Ru/C catalyst suggest-
ing that the Ru- and Cu-containing phases were either disordered
The hydrogenation of 2-MF was performed at atmospheric pres-
sure in a continuous flow fixed bed tubular reactor employing
quartz tubes, 250 mm in length and 7 mm i.d. Another quartz tube
of 210 mm length and 3 mm i.d. attached to the first one served

P. Biswas et al. / Applied Catalysis A: General 475 (2014) 379–385
381
hydrocarbons (butane and pentane), 1-PL and 1-butanone (1-BN)
were also detected in some cases.
Fig. 3 shows the catalytic data for the hydrogenation of 2-MF
over the Ba/Cu/Cr catalyst at two different H2/2-MF mole ratios
at 130–300 ◦C. These data indicated that 2-PN, 2-MTHF, 1-PL and
2-PL were major products below 220 ◦C, while above 220 ◦C the
production of alcohols and 2-MTHF decreased with increasing reac-
tion temperature and no alcohols were observed above 250 ◦C.
Moreover, the yield of 2-PN decreased sharply from 66 to 20 mol.%
above 250 ◦C and the pentane yield was enhanced dramatically to
80 mol.% as the reaction temperature was increased to 300 ◦C.
These results indicated that the product distribution was highly
dependent on the reaction conditions used. Wilson [44] reported
that 2-MTHF, 2-PN and 2-PL were major 2-MF hydrogenation prod-
ucts over Ni-based catalysts, whereas Wojcik [31] showed that
2-MTHF, 1-PL and 2-PL were major products at 200 ◦C over a Cu-Cr
catalyst. Zheng et al. [36] have reported that 2-PN and 2-PL were the
major products, while 2-MTHF and 1-PL were the minor products
of 2-MF hydrogenation over the Cu-based catalyst.
In this study, the conversion of 2-MF over the Ba/Cu/Cr catalyst
increased with reaction temperature and reached 100% at 300 ◦C
and the H2/2-MF mole ratio of 10, while the yield of 2-PN reach
maximum of ca. 60 mol.% at 225 ◦C. A previous study of 2-MF hydro-
genation [44] also showed that the main hydrogenation product
over Ni-based catalysts at 100 ◦C was 2-MTHF with 86 mol.% yield,
but as the temperature was further increased the 2-MTHF yield
declined with a simultaneous increase in the yield of 2-PN. While
pure copper catalyst was found to be inactive in the 2MF hydro-
genation reaction, the copper-chromite catalyst showed 52% yield
of 2-PN at 340 ◦C. However, the Ba/Cu/Cr catalyst employed in the
present study showed a maximal 55 mol.% selectivity to 2-PN at
250 ◦C, whereas pentane was the main product at higher tempera-
tures.
Fig. 1. XRD patterns of fresh catalysts: (A) barium-promoted copper chromite; (B)
Cu/Cr/Fe/Ni/Zn; (C) Cu-Ru/C; (D) 0.5 wt.% Pt/C; (E) 0.5 wt.% Pd/C. The symbols are
representing the difference phases as indicated: (ꢀ) CuCr2O4, (+) CuCrO2, (*) Cuo,
(᭹) Cr2O3, (ଝ) Graphite, (ꢁ) CuO, (O) Pt, (↓) Pd.
or present below the XRD detection limit. The XRD pattern of the
Pt/C catalyst shown in Fig. 1(D) exhibited the characteristic diffrac-
tion peaks at 39◦, 46◦, 67◦ and 81◦ 2Â which correspond to the
(1 1 1), (2 0 0), (2 2 0) and (3 1 1) planes of the fcc Pt crystal structure,
respectively [38–40]. The XRD pattern of the Pd/C catalyst shown
in Fig. 1(E) similarly exhibited four weak peaks at 40◦, 47◦, 68◦ and
81◦ 2Â corresponding to the (1 1 1), (2 0 0), (2 2 0) and (3 1 1) reflec-
tions, respectively, of the fcc Pd structure [41–43]. The intensity of
Pt and Pd peaks was low suggesting their small crystal size [41].
Fig. 2 shows the TEM images of the Pt/C and Pd/C catalysts. The
low resolution TEM images showed the presence of roughly spher-
ical metal nanoparticles of less than 5 nm in diameter uniformly
distributed on carbon support. These TEM images confirmed the
small Pt and Pd particle size suggested by the XRD patterns of Pt/C
and Pd/C catalysts.
The yield of 2-PN dramatically decreased above 225 ◦C, while
the pentane yield increased reaching >80 mol.% at 300 ◦C. The com-
plete conversion of 2-MF was observed above 280 ◦C at the H2/2-MF
mole ratio of 20 with the maximum yield of 2-PN of ca. 70 mol.%
at 250 ◦C. However, its yield declined sharply above 250 ◦C, which
was accompanied by a significant increase in the yield of pen-
tane. The maximum yield of 2-PN at both H2/2-MF mole ratios was
observed at 225–250 ◦C, while pentane production was favored at
higher temperatures and higher H2/2-MF mole ratios. Therefore,
the product selectivity was highly dependent on the nature of cat-
alysts as well as the reaction conditions. It should be noted that
the yield of 1-PL and C3-C4 hydrocarbons was not significant over
the Ba/Cu/Cr catalyst above 250 ◦C, whereas significant amounts of
pentane were observed above 250 ◦C [45,46]. This result indicated
that the Ba/Cu/Cr catalyst promoted furan ring opening by break-
ing the C O bond at high temperatures. Liaw et al. [47] reported
3.2. Catalytic performance
The catalytic data during 2-MF hydrogenation were collected by
varying the reaction temperature, total feed flow rate, the H2/2-MF
mole ratio and the amount of catalyst, and shown in Figs. 3–7. The
main products observed were 2-PN, 2-PL and 2-MTHF, which are
products of both furan ring saturation as well as furan ring open-
ing reactions. Minor amounts of other products, such as cracked
Fig. 2. TEM images of fresh catalysts: (A) 0.5 wt.% Pt/C; (B) 0.5 wt.% Pd/C.

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P. Biswas et al. / Applied Catalysis A: General 475 (2014) 379–385
Fig. 3. Variation of 2-MF conversion and product yield over Ba/Cu/Cr catalyst at different temperature. (A) H2: 2MF = 10; (B) H2: 2MF = 15.
Fig. 4. Variation of 2-MF conversion and product yield over Cu/Cr/Ni/Zn/Fe catalyst at different temperature and H2 to 2-MF mole ratio: (A) H2: 2MF = 10; (B) H2: 2MF = 15.
Fig. 5. Variation of 2-MF conversion and product yield over Cu-Ru/C catalyst at different temperature and H2 to 2-MF mole ratio: (A) H2: 2MF = 10; (B) H2: 2MF = 20.
that Cr effectively promotes the hydrogenation of conjugated C
C
catalyst had little or no effect on furan ring below 175 ◦C for fur-
fural hydrogenation. However, the Ba/Cu/Cr catalyst employed in
this study facilitated furan ring opening rather than the ring satura-
tion reaction resulting in the high selectivity to 2-PN at atmospheric
pressure. The maximum yield of 2-PN (70 mol.%) was observed at
250 ◦C at the H2/2-MF mole ratio of 20 with 98% of 2-MF conversion.
bonds, while higher reactivity toward the C O bond is the spe-
cific property of copper catalysts. Burnette [48] demonstrated that
2-MF can be converted to 2-MTHF, 2-PN and 2-PL over partially
activated Raney nickel catalyst by hydrogenation at atmospheric
pressure and 200 ◦C. Wojcik [31] reported that the copper-chromite

P. Biswas et al. / Applied Catalysis A: General 475 (2014) 379–385
383
Fig. 6. Variation of 2-MF conversion and product yield over Pt/C catalyst at different temperature. (A) H2: 2MF = 10; (B) H2: 2MF = 25.
Fig. 7. Variation of 2-MF conversion and product yield over Pd/C catalyst at different temperature. (A) H2: 2MF = 10; (B) H2: 2MF = 25.
Therefore, excess hydrogen was beneficial for achieving a higher
yield of 2-PN over the Ba/Cu/Cr catalyst.
The product distribution over the Cu/Cr/Ni/Zn/Fe catalyst
demonstrated that significant quantities of both 2-PN and 2-
PL formed simultaneously by furan ring opening below 200 ◦C.
However, 2-PL formation decreased above 200 ◦C, while the 2-PN
yield increased and reached ca. 90 mol.% at 250 ◦C. Moreover, this
behavior did not depend significantly on the H2/2-MF mole ratio.
These observations may be due to the selective conversion of
2-MF to 2-PN as well as the conversion of 2-PL formed to 2-PN
by the reverse reaction. However, at higher temperatures, the
conversion of 2-MF to 2-PN was the dominant reaction and further
hydrogenation of 2-PN to 2-PL was not significant. The large excess
of hydrogen was not beneficial in terms of catalytic conversion
of 2-MF and 2-PN yield over the Cu/Cr/Ni/Zn/Fe catalyst. Some
2-MTHF was also detected besides 2-PN and 2-PL at all H2/2-MF
mole ratios and low temperatures (<175 ◦C). The results obtained
over the Cu/Cr/Ni/Zn/Fe catalyst indicated that both the ring
saturation and ring opening were favorable at low temperatures
(<175 ◦C), but ring opening became much more favorable at higher
temperatures leading to highly selective formation of 2-PN.
The results of catalytic hydrogenation of 2-MF over the
Cu/Cr/Ni/Zn/Fe catalyst at H2/2-MF = 10 and 15 are shown in Fig. 4.
At these H2/2-MF mole ratios, the 2-MF conversion was almost
100% above 225 ◦C, and even 80–98% below 225 ◦C at a lower
H2/2-MF ratio of 10, which may be due to a higher contact time
and the absence of inert support, such as carbon, in this catalyst.
2-PN and 2-PL were the primary products observed over the
Cu/Cr/Ni/Zn/Fe catalyst, whereas trace amounts of 2-MTHF and
1-PL were also detected. The yield of 2-PN increased while the
yield of 2-MTHF and 1-PL decreased with increasing temperature
over the range of H2/2-MF mole ratios investigated, whereas the
yield of 2-PL passed through a maximum at ∼200 ◦C. The yield
of 2-PN varied in the range of 15–90 mol.% at 130–250 ◦C for
both H2/2-MF mole ratios. The maximum yield to 2-PL (56 mol.%)
was observed at the H2/2-MF mole ratio of 15 at 200 ◦C. The
variation of the 2-PL yield with temperature indicated that the
formation of 2-PL was temperature-dependent. It was previously
reported that 2-PL is the product of 2-PN hydrogenation and
the conversion of 2-PN to 2-PL is an equilibrium reaction that
strongly favors 2-PN at atmospheric pressure over the entire
temperature range investigated [36]. According to Zheng et al.,
2-PN and 2-PL could be obtained with 57 and 25 mol.% yield at
250 ◦C. Our results indicated the same two major products; how-
ever, 2-PN can be obtained in a much higher yield (85 mol.%).
In the case of the Cu-Ru/C catalyst, the main product was 2-
PN and its yield reached a maximum at 225 ◦C at both high and
low H2/2-MF mole ratios (Fig. 5), while the yield of other prod-
ucts, such as 2-MTHF, 2-PL, 2-BN, and pentane, varied with reaction
temperature. The 2-MF conversion was 100% at 250 ◦C for all H2/2-
MF mole ratios studied. The Cu-Ru/C catalyst exhibited similar
catalytic performance to that reported by Wilson [44]. The main

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P. Biswas et al. / Applied Catalysis A: General 475 (2014) 379–385
product over this catalyst was 2-PN and some isomerized hydro-
carbons were observed at high temperatures (above 250 ◦C). For
the H2/2-MF mole ratio of 10, the conversion varied from 24 to
100% at 175–250 ◦C. At low reaction temperature (175 ◦C), the
yield of 2-PN, 2-MTHF and 2-PL was 13, 4 and 3%, respectively.
The formation of 1-PL was not observed over this catalyst, while
significant amounts of 2-butanone (2-BN) were detected above
250 ◦C. As the reaction temperature increased, so did the yield of
2-PN, whereas the yields of other products, 2-MTHF and cracking
products, i.e., butane, pentane and butanone, also showed temper-
ature dependence. The 2-MTHF yield decreased with increasing
reaction temperature, while the yield of the cracking products
increased indicating that the hydrogenation of 2-MF over the Cu-
Ru/C catalyst produces predominantly 2-MTHF at low temperature.
At higher reaction temperatures, 2-MTHF is further cracked to
produce shorter-chain hydrocarbons by C C bond hydrogenolysis.
Complete conversion of 2-MF was observed with a 70 mol.% yield
of 2-PN at the H2/2-MF mole ratio of 10 and above 250 ◦C, while
other products were obtained in less than 5 mol.% yield, with the
exception of 10 mol.% yield of 2-BN. Therefore, 2-MF is converted
selectively to 2-PN over the Cu-Ru/C catalyst at ca. 225 ◦C. To inves-
tigate the effect of hydrogen concentration on the catalytic activity
and product yield, 2-MF hydrogenation was carried out at a high
H2/2-MF mole ratio of 20. The results shown in Fig. 5(B) demon-
strated that the catalytic activity was not significantly affected in
the presence of a large excess of hydrogen, but the conversion of
2-MF and 2-PN yield were increased. Some cracking products, such
as butane, pentane and butanone, were also detected, whereas 2-
MTHF and 2-PL were not observed. The formation of the cracked
hydrocarbons may occur due to the C C bond hydrogenolysis of
2-MF in the presence of a large excess of hydrogen [45,46]. There-
fore, in comparison to the Ba/Cu/Cr and Cu/Cr/Ni/Zn/Fe catalysts,
the Cu-Ru/C catalyst was much more active and selective during
2-MF conversion to 2-PN at 225 ◦C and low H2/2-MF ratios.
The results of 2-MF hydrogenation over the Pt/C catalyst at the
H2/2-MF mole ratios of 10 and 25 and 150–250 ◦C are shown in
Fig. 6. The conversion of 2-MF ranged from 21 to 100% at the
H2/2-MF = 10 and the major products were 2-PN, 2-PL, 2-MTHF,
and cracking products, such as butane and pentane, indicating
that these transformations corresponded to both furan ring satu-
ration as well as ring opening reactions. The selectivity to these
hydrogenation products changed somewhat as the temperature
increased in the 150–250 ◦C range. The product selectivity trends
indicated that Pt metal is capable of promoting both furan ring sat-
uration and ring opening reactions. 100% conversion of 2-MF was
observed at 250 ◦C at the H2/2-MF = 10, while the product yields
were 69 mol.% (2-PN), 12 mol.% (butane and pentane), 10 mol.%
(2-PL), 4 mol.% (2-MTHF), and 5 mol.% (1-PL). Our results for the
0.5 wt.% Pt/C catalyst are in excellent agreement with those of
Shuikin et al. [49] which also reported 2-PN as the main product.
The conversion of 2-MF increased somewhat up to 200 ◦C at the
high H2/2-MF mole ratio of 25 accompanied by a slight increase
in the yield of cracked hydrocarbons. These results indicated that
the over hydrogenation was enhanced over the Pt/C catalyst in the
presence of a large excess of hydrogen, which contributed to the
higher yield of cracked hydrocarbons. The hydrogenolysis of 2-MF
was favored at high reaction temperatures, and significant quan-
tities of cracked products (up to 20 mol.% yield) were produced at
both low and high H2/2-MF mole ratios.
Fig. 8. Thermodynamic calculations of chemical equilibrium for 2-MF hydrogena-
tion at H2: 2MF = 10 and 100–350 ◦C.
reaction temperature increased above 200 ◦C, while the formation
of 2-PN and cracked hydrocarbons progressively increased at 100%
2-MF conversion. These results showed that the Pd/C catalyst is
very active and selective for furan ring hydrogenation in 2-MF to
2-MTHF at low reaction temperatures. Excellent agreement was
also observed with the results of a previous study that employed
0.5 wt.% Pd/C and demonstrated 84–97 mol.% yield of 2-MTHF up to
236 ◦C, whereas 2-PN formed increasingly above 273 ◦C [50]. Gaset
et al. [15] reported that tetrahydrofuran (THF) can be obtained in
high yield at low pressure over a charcoal-supported Pd catalyst.
Starr and Hixon [16] also found that furan could be converted to
THF quantitatively over palladous oxide-palladium black catalyst.
It should be noted that the product distribution during 2-MF
hydrogenation over the catalysts employed in this study signifi-
cantly deviated from that expected for the chemical equilibrium.
Fig. 8 shows the results of thermodynamic calculations for the
chemical equilibrium between 2-MF, 2-MTHF, 2-PN, and 2-PL for
the H2/2-MF feed ratio of 10 and 100–350 ◦C. The pure component
properties used in these calculations were taken from the Dort-
mund Data Bank [51]. The results of these calculations indicated
that 2-MF would be completely converted to products at equilib-
rium under these reaction conditions. However, 2-PN is expected
to be the most abundant product, whereas 2-MTHF and 2-PL would
be present only in trace quantities. Therefore, high yields of several
hydrogenation and hydrogenolysis products observed in this study
suggest the promise of these catalysts for catalytic transformation
of biomass-derived 2-methylfuran to value-added chemicals and
fuels.
4. Conclusions
Vapor-phase hydrogenation of 2-MF was carried out over
Ba/Cu/Cr, Cu/Cr/Ni/Zn/Fe, Cu-Ru/C, Pt/C and Pd/C catalysts as a func-
tion of temperature and H2/2-MF mole ratios. This study showed
that the Ba/Cu/Cr, Cu/Cr/Ni/Zn/Fe, Cu-Ru/C, and Pt/C catalysts were
active for both furan ring opening and ring saturation reactions.
However, 2-PN was the main hydrogenation product over these
four catalysts. On the other hand, the Pd/C catalyst was highly
active for the selective conversion of 2-MF to 2-MTHF at low tem-
peratures and low H2/2-MF ratio. A complete conversion of 2-MF
was observed even at 125 ◦C with a 98 mol.% yield of 2-MTHF. The
Ba/Cu/Cr catalyst was highly active and selective for the conversion
of 2-MF into pentane at high reaction temperatures. The catalytic
data confirmed that this catalyst facilitated the furan ring opening
The performance of the 0.5 wt.% Pd/C catalyst in 2-MF hydro-
genation is shown in Fig. 7. The Pd/C catalyst was found to behave
very differently as compared to other catalysts investigated. This
catalyst was very active and selective in the furan ring hydro-
genation that led to the complete conversion of 2-MF to 2-MTHF
even at low reaction temperatures (<200 ◦C) and low H2/2MF
ratio. However, the yield of 2-MTHF dramatically decreased as the

P. Biswas et al. / Applied Catalysis A: General 475 (2014) 379–385
385
rather than the ring saturation reaction. A large excess of hydro-
gen was beneficial for obtaining a higher yield of 2-PN over the
Ba/Cu/Cr catalyst. The results obtained over the Cu/Cr/Ni/Zn/Fe cat-
alyst demonstrated that both ring saturation and ring opening took
place at low temperatures (<200 ◦C), while ring opening became
more favorable at higher temperatures resulting in a selective for-
mation of 2-PN with a 90 mol.% yield at 250 ◦C, the yield of 2-PL
over this catalyst showed a maximum of 60 mol.% at 200 ◦C and
H2/2-MF mole ratio of 15. The yield of the 2-PN was not signifi-
cantly influenced by different H2/2-MF ratios, while they affected
the 2-PL formation. The use of excess hydrogen was not beneficial
to produce 2-PN in the case of the Cu/Cr/Ni/Zn/Fe catalyst. The Cu-
Ru/C catalyst showed high activity in both ring opening and ring
saturation reactions at low temperature. At high reaction temper-
atures, C C and C O scission products formed increasingly over
the Cu-Ru/C catalyst. The product selectivity trends over the Pt/C
catalyst showed that the Pt catalyst has the tendency to promote
both the furan ring opening and ring saturation reactions. Complete
conversion of 2-MF was observed even at 220 ◦C resulting in a prod-
uct mixture from both ring saturation and ring opening reactions.
Furthermore, the Pt/C catalyst enhanced the over hydrogenation
reaction in the presence of excess hydrogen, which contributed to
the higher yield of hydrocarbon products.
[13] A. Kaufman, J.C. Adams, J. Am. Chem. Soc. 45 (1923) 3029–3044.
[14] T.E. Caldwell, D.P. Land, Polyhedron 16 (1997) 3197–3211.
[15] G. Godawa, A. Gaset, P. Kalck, Y. Maire, J. Mol. Catal. A: Chem. 34 (2) (1986)
199–212.
[16] D. Starr, R.M. Hixon, J. Am. Chem. Soc. 56 (1934) 1595–1596.
[17] S.D. Jackson, A.S. Canning, E.M. Vass, S.R. Watson, Ind. Eng. Chem. Res. 42 (22)
(2003) 5489–5494.
[18] S.D. Jackson, I.J. Huntingdon, N.A. Hussain, S.R. Watson, Stud. Surf. Sci. Catal.
126 (1999) 453–456.
[19] R. Rao, A. Dandekar, R.T.K. Baker, M.A. Vannice, J. Catal. 171 (1997) 406–419.
[20] H.Y. Zheng, J. Yang, Y.L. Zhu, G.W. Zhao, React. Kinet. Catal. Lett. 82 (2) (2004)
263–269.
[21] W. Huang, H. Li, B. Zhu, Y. Feng, S. Wang, S. Zhang, Ultrason. Sonochem. 14
(2007) 67–74.
[22] L.W. Burnette, I.B. Johs, R.F. Holdren, R.M. Hixon, Ind. Eng. Chem. 40 (1948)
502–505.
[23] G. Seo, H. Chon, J. Catal. 67 (1981) 424–429.
[24] Adkins, Reactions of Hydrogen with Organic Compounds over Copper-
Chromite Oxide and Nickel Catalysts, University of Wisconsin Press, Madison,
1937.
[25] C.L. Thomas, Catalytic Processes and Proven Catalysts, Academic Press, New
York, 1970.
[26] P.N. Rylander, Engelhard Ind. Tech. Bull. 1 (1961) 133.
[27] P.N. Rytander, Catalytic Hydrogenation over Platinum Metals, Academic Press,
New York, 1967.
[28] A.P.G. Kiebaam, F. van Rantwijk, Hydrogenation and Hydrogenolysis in Syn-
thetic Organic Chemistry, Delft University Press, Delft, 1977.
[29] M. Freifelder, Catalytic Hydrogenation in Organic Synthesis, John Wiley, New
York, 1978.
[30] P.O.J. Koopman, A.P.G. Kieboom, H. Van Bekkum, Colloid. and Surface. 3 (1)
(1901) l–l12.
[31] S.H. Wojcik, Ind. Eng. Chem. 40 (1948) 210–216.
[32] L. Baijun, L. Lianhai, W. Bingchun, C. Tianxi, K. Iwatani, Appl. Catal. A: Gen. 171
(1998) 117–122.
[33] D. Papa, E. Schwenk, H.F. Ginsberg, J. Org. Chem. 16 (2) (1951) 253–261.
[34] I.F. Bel’skii, N.I. Shuikin, V.M. Shostakovskii, From Izvestiya Akademii Nauk
SSSR, Seriya Khimicheskaya 9 (1963) 1631–1635.
Therefore, high yields of hydrogenation and hydrogenolysis
products observed in this study indicated the promise of these
noble and base metal catalysts for catalytic transformation of
biomass-derived substituted furans to value-added chemicals and
fuels.
[35] M. He, D.Q. Zhou, H.L. Ge, M.Y. Huang, Y.Y. Jiang, Polym. Adv. Technol. 14 (2003)
273–277.
[36] H.Y. Zheng, Y.L. Zhu, B.T. Teng, Z.Q. Bai, C.H. Zhang, H.W. Xiang, Y.W. Li, J. Mol.
Catal. A: Chem. 246 (2006) 18–23.
[37] C. Liang, Z. Ma, L. Ding, J. Qiu, Catal. Lett. 130 (1–2) (2009) 169–176.
[38] R.B.C. Pillai, Catal. Lett. 26 (3–4) (1994) 365–371.
[39] P.L. Kuo, W.F. Chen, H.Y. Huang, I.C. Chang, S.A. Dai, J. Phys. Chem. B 110 (7)
(2006) 3071–3077.
[40] S. Vengatesan, H.J. Kim, S.K. Kim, I.H. Oh, S.Y. Lee, E.A. Cho, H.Y. Ha, T.H. Lim,
Electr. Acta 54 (2) (2008) 856–861.
Acknowledgment
The financial support of this research was provided from the
National Science Foundation under grant CBET-1236210.
References
[41] Y. Zhu, Y. Kang, Z. Zou, Q. Zhou, J. Zheng, B. Xia, H. Yang, Electrochem. Comm.
10 (2008) 802–805.
[1] G.W. Huber, J.N. Chheda, C.J. Barrett, J.A. Dumesic, Science 308 (2005)
1446–1450.
[42] L. Zhang, T. Lu, J. Bao, Y. Tang, C. Li, Electrochem. Comm. 8 (2006) 1625–1627.
[43] P. Canton, C. Meneghini, P. Riello, A. Balerna, A. Benedetti, J. Phys. Chem. B 105
(2001) 8088–8091.
[44] C.L. Wilson, J. Am. Chem. Soc. 70 (1948) 1313–1315.
[45] T. Miyazawa, S. Koso, K. Kunimori, K. Tomishige, Appl. Catal. A: Gen. 329 (2007)
30–35.
[46] E.P. Maris, R.J. Davis, J. Catal. 249 (2007) 328–337.
[47] B.J. Liaw, Y.Z. Chen, Appl. Catal. A: Gen. 196 (2000) 199–207.
[48] L.W. Burnette, Rubber Chem. Technol. 18 (1945) 284–285.
[49] N.I. Shuikin, I.F. Bel’skii, Doklady Akademii Nauk SSSR 116 (1957)
621–624.
[50] Zh. G. Yuskovets, N.V. Nekrasov, M.M. Kostyukovskii, M.V. Shimanskaya, S.L.
Kiperman, Kinetika i Kataliz 25 (6) (1984) 1361–1364.
[51] Dortmund Data Bank Explorer Version 2011, http://www.ddbst.com
[2] S.F. Paul, US Patent 6,309,430 (2001).
[3] S. Sitthisa, W. An, D.E. Resasco, J. Catal. 284 (2011) 90–101.
[4] L.E. Schniepp, H.H. Geller, R.W. Van Korff, J. Am. Chem. Soc. 69 (1947) 672–674.
[5] Z. Guo, H. Feng, H.C. Ma, Q.X. Kang, Z.W. Yang, Polym. Adv. Technol. 15 (2004)
100–104.
[6] J. Kijenski, P. Winiarek, T. Paryjczak, A. Lewicki, A. Mikołajska, Appl. Catal. A:
Gen. 233 (2002) 171–182.
[7] S. Kaiser, S.P. Smidt, A. Pfaltz, Angew. Chem. Int. Ed. 45 (2006) 5194–5197.
[8] Y. Inamura, Bull. Chem. Soc. Jpn. 43 (10) (1970) 3271–3279.
[9] S.K. Nandy, J. Liu, A.A. Padmapriya, Tetrahedron Lett. 49 (2008) 2469–2471.
[10] M. Maris, T. Mallat, E. Orglmeister, A. Baiker, J. Mol. Catal. A: Chem. 219 (2004)
371–376.
[11] M. Shirai, M. Arai, Langmuir 15 (4) (1999) 1577–1578.
[12] M. Maris, W.R. Huck, T. Mallat, A. Baiker, J. Catal. 219 (2003) 52–58.