Study on the reaction pathway in decarbonylation of biomass-derived 5-hydroxymethylfurfural over Pd-based catalyst

Article abstract of DOI:10.1016/j.molcata.2016.05.012

An extensive product distribution is firstly examined in the process of 5-hydroxymethylfurfural (HMF) decarbonylation over Pd-based catalysts and some interesting results are obtained. The main side reactions are due to the high activity of the furan ring-branched hydroxymethyl, which could go through hydrogenolysis, dehydrogenation and etherification. The H₂ source was carefully explored and determined to be the hydroxymethyl dehydrogenation. The reactivity of the main intermediates was separately investigated and their evolution pathway was obtained. Noticeably, it is demonstrated that the elimination of the furanic ring-branched hydroxymethyl (in HMF or furfuryl alcohol) is completed by sequential dehydrogenation and decarbonylation via the intermediate of aldehyde (2, 5-diformylfuran or furfural). A comprehensive reaction pathway for HMF decarbonylation is proposed, which is significant for designing highly selective decarbonylation catalysts.

Full text of DOI:10.1016/j.molcata.2016.05.012

Accepted Manuscript
Title: Study on the reaction pathway in decarbonylation of
biomass-derived 5-hydroxymethylfurfural over Pd-based
catalyst
Author: Qingwei Meng Hongyan Zheng Yulei Zhu Yongwang
Li
PII:
S1381-1169(16)30184-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2016.05.012
MOLCAA 9887
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
30-3-2016
12-5-2016
13-5-2016
Please cite this article as: Qingwei Meng, Hongyan Zheng, Yulei Zhu, Yongwang
Li, Study on the reaction pathway in decarbonylation of biomass-derived 5-
hydroxymethylfurfural over Pd-based catalyst, Journal of Molecular Catalysis A:
Chemical http://dx.doi.org/10.1016/j.molcata.2016.05.012
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Study on the reaction pathway in decarbonylation of
biomass-derived 5-hydroxymethylfurfural over Pd-based
catalyst
Qingwei Meng , Hongyan Zheng , Yulei Zhu a,c,*, Yongwang Li a,c
a,b
c
a State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese
Academy of Sciences, Taiyuan 030001, PR China
b University of Chinese Academy of Sciences, Beijing 100039, PR China
c Synfuels China Co., Ltd., Beijing 101407, PR China
*
Corresponding author at: State Key Laboratory of Coal Conversion, Institute of
Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China.
Tel.: +86 351 7117097; fax: +86 351 7560668.
E-mail address: zhuyulei@sxicc.ac.cn (Y. Zhu).
1

Graphical abstract
Highlights



An extensive product distribution is firstly examined in decarbonylation of HMF.
The H source was determined to be the hydroxymethyl dehydrogenation.
2
The elimination path of –CH OH is sequential dehydrogenation and
2
decarbonylation.


The reactivity of the main intermediates was separately investigated.
A comprehensive reaction pathway for HMF decarbonylation is proposed.
2

Abstract
An extensive product distribution is firstly examined in the process of 5-
hydroxymethylfurfural (HMF) decarbonylation over Pd-based catalysts and some
interesting results are obtained. The main side reactions are due to the high activity of
the furan ring-branched hydroxymethyl, which could go through hydrogenolysis,
dehydrogenation and etherification. The H source was carefully explored and
2
determined to be the hydroxymethyl dehydrogenation. The reactivity of the main
intermediates was separately investigated and their evolution pathway was obtained.
Noticeably, it is demonstrated that the elimination of the furanic ring-branched
hydroxymethyl (in HMF or furfuryl alcohol) is completed by sequential
dehydrogenation and decarbonylation via the intermediate of aldehyde (2, 5-
diformylfuran or furfural). A comprehensive reaction pathway for HMF
decarbonylation is proposed, which is significant for designing highly selective
decarbonylation catalysts.
Keywords: 5-hydroxymethylfurfural; Decarbonylation; Reaction pathway; Pd
1
. Introduction
Furfuryl alcohol (FOL) has been widely used for fine chemicals and polymer
industries. The main applications of FOL are the production of thermostatic resins
resistant to acids, bases and certain solvents; liquid resins for galvanic bath tub;
synthetic fibers; farm chemicals; foundry binders; adhesives for plywood and
furniture; also other fine chemical products such as Vitamin C and tetrahydrofurfuryl
alcohol [1-5]. Presently, FOL is produced by hydrogenation of furfural (FAL). FAL
and HMF, which are converted from Polymers of C
5
sugars and C
6
sugars
respectively, are two important platform chemicals in the process of biomass
conversion [6, 7]. The conversion technology of furfural has been already well
3

developed [7-11], while the production and application of HMF is limited to the
development in its process chemistry. Decarbonylation of HMF to FOL provided
another way to utilize the C sugars.
6
The liquid-phase decarbonylation of HMF has been subjected to several studies
which mainly focused on screening of catalysts or optimizing of the catalytic system,
targeting a high decarbonylation yield [12-15]. Though an optimal FOL yield (94%)
was obtained over an homogeneous compound [IrCl(cod)]
heterogeneous Pd/SBA-15 [14], the byproducts was not analyzed in detail. Moreover,
the high cost of the catalysts limits their application for large scale practices. Pd/Al
2
PCy
3
[13] or
2
O
3
has been widely used in the catalytic conversion, including hydrogenation [16-22] and
hydrogenolysis [23] reactions, hydrodechlorination [24-27] reaction, oxidation [28-31]
and reduction [32-34] reactions, reforming [35] and isomerization [36] reactions.
Pd/Al
interaction in Pd/Al
sites on Pd and the abundant Lewis acid sites on Al
selectivity [35, 36]. Moreover, Pd/Al is available commercially [38], applicable
for industrial practice. Noticeably, Pd/Al is efficient for decarbonylation reaction
39], but has not been used for HMF decarbonylation [12]. A clear understanding of
2
O
3
exhibited high catalytic activity [29, 32, 37] and the strong metal-support
leads to a good stability [26, 27]. The synergy of the metallic
could induce high specific
2
O
3
2
O
3
2
O
3
2
O
3
[
the reaction mechanism and the origin of by-products are significantly important for
the catalytic design for selectivity enhancement of the desired products. The reaction
pathway in the process of HMF decarbonylation over Pd/Al
report.
2
3
O was focused in this
Though the product distribution and the reaction pathway in the process of HMF
decarbonylation has not been reported in the open literature, the reaction route of
hydrogenation of HMF [40-42] and FAL [43-45] has been studied a lot and can
provide some guidance. In the process of catalytic conversion of HMF to 2, 5-
dimethylfuran (DMF), 5-methylfurfural (MFAL) is the necessary intermediate [40, 42,
4
6], which is similar with decarbonylation process. In previous works, some results
on the behaviour of furfural hydrogenation and its intermediates (such as FOL,
tetrahydrofurfuryl alcohol) over Cu-based catalysts were also reported [43, 47].
However, more reactions are involved and much bevaviour of the intermedaites
evolution are different in the HMF decarbonylation. Furthermore, the transformation
4

path in HMF decarbonylation could also provide significant references for the
conversion path of HMF or FAL into a series of value added furan-derived
compounds through hydrogenation or oxidation reactions.
The aim of this work is to shed light on the product distribution and the reaction
mechanism in the process of HMF decarbonylation, thus to provide an instruction for
designing highly selective catalysts. The H source was carefully explored and was
2
determined to mainly from the dehydrogenation of the furan ring-branched
hydroxymethyl, though with small amount of water gas shift reaction (WGS).
Furthermore, the elimination mechanism of the furanic ring-branched hydroxymethyl
was determined to be sequential dehydrogenation and decarbonylation via the
intermediate of aldehyde. The evolution pathway of HMF and its main intermediates
over Pd/Al
2
3
O was investigated detailedly and its applicability to Pd/C was also tested
in order to obtain general results. As a result, the reaction pathway in the process of
HMF decarbonylation was firstly proposed.
2
. Experimental
2
.1 Preparation of catalysts
Pd/γ-Al
Firstly, the parent γ-Al
palladium nitrate for 5h. Then the precursors were dried at 80 ℃ for 16 h and
calcinated at 400 ℃for 2 h. The loading of Pd/Al and Pd/C is 1 wt%. The resulting
2
O
3
and Pd/C were prepared by incipient wetness impregnation method.
2
O
3
or C powders were impregnated in aqueous solution of
O
2 3
catalysts were shaped by a tablet machine and crushed into granules of 20-40 mesh
for activity test.
2
.2 Characterization
The amount of H
2
adsorption on catalysts during reduction was approximately
on Auto Chem. II 2920
equipment (Micromeritics, USA) with mass spectra. Prior to each measurement, 200
mg sample was reduced in situ by flowing H at 200 ℃ for 2 h, cooling to 50 ℃ under
continuous flow of H , and then purged with Ar for 0.5 h. TPD was conducted from
00 ℃ to 800 ℃ at a heat rate of 10 ℃/min. Quantification was conducted by injecting
a series of a certain amount of H , acquiring an standard curve and then comparing the
measured by thermal programmed desorption (TPD) of H
2
2
2
1
2
measured peak area with the standard curve.
5

X-ray photoelectron spectroscopy (XPS) of calcined and reduced Pd/Al
2
3
O was
measured on an AXIS ULTRA DLD (Kratos U. K.) spectrometer with Al Kα
radiation and a multichannel detector. The binding energies were calibrated with the
C
1S peak at 284.6 eV as the reference.
o
TEM of reduced Pd/Al
2
O
3
and used Pd/Al
2
O after reaction of HMF at 180 C for
3
1
6h was performed with a field-emission transmission electron microscopy (FETEM,
JEM-2011F) operating at 200 kv voltages. The pre-treated samples were suspended in
ethanol with ultrasonic dispersion and deposited on copper grids amorphous carbon
films. The average diameter of Pd nanoparticles was determined using the following
equation [48].
3
Σ n •di
i
d
Pd
=
Σ n •di
2
i
2
.3 Activity test
The catalytic tests were performed in a 50 ml stainless steel autoclave at a stirring
speed of 300 rpm. Prior to reaction, the samples were reduced with pure H
2
flow at
2
00 ℃ for 2 h. In a typical run, the solvent (1, 4-dioxane), reactant and the catalysts
were introduced into the autoclave. After purge with N for several times, the reaction
2
mixture was heated to 180 ℃. After reaction, the autoclave was cooled down rapidly
by ice-water bath. The gas was collected and analyzed by two GC (models 6890N,
Agilent, USA) with a FID and a TCD detector respectively. The liquid was filtered
and the mixture was analyzed by a GC (models 6890N, Agilent) equipped with a FID
detector. The conversion and the selectivity were calculated by the area normalization
method. The yield of FOL, 2-methylfuran (2-MF), FAL, 5-methylfurfural (MFAL)
and HMF was also examined by an internal standard method with 1, 4-dioxane as the
internal standard. The results calculated by the two methods were consistent.
3
. Results and discussions
3
.1 Reactivity of 5-hydroxymethylfurfural
XPS spectrum of Pd (3d3/2, 3d5/2) for calcined Pd/Al
2
3
O (Fig. 1) appears at 342.6
and 337.3 ev respectively, which is in good agreement with the values for Pd (II) state
49]. While the binding energy of 3d3/2 at 340.3 ev and 3d5/2 at 335.0 ev for reduced
[
Pd/Al
2
O
3
is consistent with the presence of zero-valence Pd [50]. It indicates that the
6

Pd-based catalysts could be reduced under the reduction conditions. Thus, it is
considered that the Pd (0) species are proposed as responsible for the observed
reactivity. The solvent was investigated previously and HMF exhibited good stability
in 1, 4-dioxane [14]. Thus, 1, 4-dioxane was selected as the solvent to study the
reaction mechanism in this work. Table 1 shows the conversion of HMF and products
distribution in process of decarbonylation over Pd/Al
are all active for decarbonylation of HMF, exhibiting similar conversion values at 180
oC. Pd/C exhibits better selectivity of FOL than Pd/Al
due to lower selectivity of
2
O
3
and Pd/C. The two catalysts
2
O
3
difurfuryl ether (DFE) and polymers. This difference of selectivity may be derived
from the different acidity of the two catalysts. An extensive product distribution was
generated on the catalysts, which mainly falls into four categories: (1) furan ring-
connecting DFE; (2) C
dimethylfuran (DMF) and 2, 5-diformylfuran (DFF); (3) C
methylfuran (2-MF), FAL and FOL; (4) C furan. DFE indicates the etherification of
FOL, as the acidic Al support could promote dehydration of hydroxyl group [51,
2]. On account of the carbon number, MFAL and DMF are deduced to from the
6
furan derivatives: 5-methylfurfural (MFAL), 2, 5-
5
furan derivatives: 2-
4
2
O
3
5
hydrogenation/hydrogenolysis of HMF, while DFF demonstrates the dehydrogenation
of hydroxymethyl in HMF. Generally, FAL and 2-MF indicates the cracking of one
branced ‘C-C’ bond on the furan ring, while the apperance of furan demonstrates the
cracking of the two branched ‘C-C’ (C2 and C5) in HMF. The selectivity of DFF is
decreased with rising temperature and that of FAL and furan shows an adverse
tendency. This indicates that FAL and furan could be produced by decarbonylation of
DFF, as high temperature is in favour of decarbonylation. As a result, the first
conversion step of HMF can be concluded as scheme 1. Pd/Al
several times to investigate the deactivation for decarbonylation of HMF (Table S1).
Though Pd/Al exhibits gradual deactivation, the products distribution is similar in
these runs with decreased selectivity of side products. From TEM results showed in
Fig. 2, the mean particle size of reduced Pd/Al is 5.3 nm, while it is increased to
.6 nm after reaction, indicating slight sintering of palladium. This is consistent with
the slight deactivation in stability results (Table S1).
2
O
3
was reused for
2
O
3
O
2 3
6
3
.2 The origins of hydrogen involved in the side reactions.
7

As quite amount of hydrogenation products are formed without external H
figuring out the H source is the top priority to depict the reaction pathway. The H
might be derived from three ways: (1) WGS (Scheme 2(d)), (2) H adsorbed on
2
,
2
2
2
catalysts during reduction, and (3) dehydrogenation of the products. Trace water
involved in WGS could be introduced by the dehydration step of hydrogenolysis, the
moist biomass HMF or the solvent. The quantitative data of H amount, including the
2
consumption amount and the generation amount from the three sources in the process
of HMF conversion (reactions in Table 1), is compared in Table 2. Assuming that
FAL and furan were produced through dehydrogenation or sequential decarbonylation
of the furan ring-branched hydroxymethyl, the H
of dehydrogenation could be evaluated by the summing amount of DFF, FAL and
furan. The H amount produced through the WGS could be evaluated by the ratio of
CO and CO in the tail gas after decarbonylation of HMF. The H amount adsorbed
on the surface in the process of catalysts reduction could be approximately evaluated
by the characterization of H -TPD. From the results in Table 2, it is evident that the
amount from adsorption on catalyst and WGS is quite insufficient to involve in the
hydrogenation side reactions for both catalysts. While the H amount calculated from
2
amount generated from the pathway
2
2
2
2
H
2
2
dehydrogenation could compensate for the insufficiency. This further verified that
FAL and furan might be formed by the dehydrogenation route. It can be concluded
that the dehydrogenation of the furan ring-branched hydroxymethyl is the main H
source, while the WGS and H adsorption on the surface during the catalysts
reduction also provide small amount of H
2
2
2
.
3
.3 Reactivity of furfural, furfuryl alcohol and 5-methylfurfural
FAL and FOL are used as model compounds to investigate the conversion
pathways of the furan ring-branched -CHO and –CH
2
OH respectively. Table 3 reports
and Pd/C, which show similar
the catalytic data of tests with FAL over Pd/Al
O
2 3
o
product distribution at 180 C. Furan is the main product, indicating that FAL goes
mainly through decarbonylation. Besides, small amount of FOL and 2-MF are also
produced, demonstrating the hydrogenation and the sequential hydrogenolysis path of
FAL. The yield both of furan and 2-MF increases with the rise of temperature, as high
temperature is beneficial to decarbonylation and hydrogenolysis. The H involved in
2
the hydrogenation/hydrogenolysis side reactions might mainly derive from WGS. H ,
2
8

CO and CO were all detected in the tail gas (Table S2), indicating the occurrence of
2
WGS. It can be deduced that, similar with the main decarbonylation pathway of FAL,
DFF mainly goes through decarbonyaltion as well. As a result, FAL can be produced
by DFF decarbonylation. As DFF is the dehydrogenation product, the hydrogenation
of the –CHO in DFF can be negligible. Therefore, the main reaction pathway of FAL
and DFF can be described as Scheme 2(a).
The conversion of FOL (Table 4) is characterized by low conversion values with
o
both catalysts, which show similar product distribution at 180 C. The generation of
2
-MF indicates the hydrogenolysis of FOL and the product DFE demonstrates the
etherification of FOL. The higher yield both of 2-MF and DFE over Pd/Al than
that over Pd/C may due to the stronger acidity of Pd/Al . Besides, FAL and furan
2
O
3
2
O
3
are also produced. The forming of FAL provides a direct evidence for the
dehydrogenation pathway of FOL, which is similar with dehydrogenation of HMF to
DFF. It can be concluded that FAL can come from DFF decarbonylation or FOL
dehydrogenation. References have reported that tetrahydrofurfuryl alcohol [47] over
Ni-based catalyst and FOL [43] over Cu-based catalyst can eliminate CO and H
produce tetrahydrofuran and furan respectively. To make the elimination pathway of
the branched –CH OH more clear, 0.2 MPa N (RT) was used to make it possible to
2
to
2
2
obtain the tail gas after reaction of FOL at 180 ℃ (Table 4). As a result, CO was
detected (see Table S3) and is in approximately equimolecular portion with furan.
Therefore, furan can be produced by sequential dehydrogenation and decarbonylation
of FOL through the intermediate FAL. This is consistent with the dehydrogenation
data in Table 2. The occurrence of WGS was also detected (Table S3), providing the
2
H source for hydrogenolysis of FOL. The conversion pathway of FOL can be
described as Scheme 2(b).
In all the catalytic tests, MFAL (Table 5) gave rise to mainly 2-MF and small
amount of furan and DMF. It is demonstrated that decarbonylation is the main
pathway of MFAL. The formation of DMF indicates the sequential hydrogenation and
hydrogenolysis path of the branched –CHO in MFAL. The H
2
involved in
hydrogenolysis of MFAL might also mainly come from WGS (Table S4 see the tail
gas composition). The main reaction pathway of MFAL can be described as Scheme
2
(c). Conclusively, 2-MF can be generated both by MFAL decarbonylation and
9

hydogenolysis of FOL. However, the concentration of MFAL is quite low when HMF
is used as reactant and the H involved in hydrogenolysis is mainly derived from
2
dehydrogenation of the hydroxymethyl (Table 2). Therefore, 2-MF is probably mainly
produced by FOL hydrogenolysis.
In all the tail gas composition (Table S1, Table S2 and Table S3), the percent of
CO
2
with Pd/C is lower than that with Pd/Al
2
3
O , indicating lower WGS activity of
Pd/C. The amount of hydrogenolysis products on Pd/C is lower than that on Pd/Al
2
O
3
for tests of FAL, FOL and MFAL (Table 3, Table 4, Table 5), because of both its
lower acidity and lower WGS activity.
3
.4 Reactivity of 2, 5-dimethylfuran, 2-methylfuran and furan
With both catalysts, DMF, 2-MF and furan (Table 6) are very stable, with low yield
of lower weight molecules. The branched methyl in DMF and 2-MF could be break,
while 2-MF also gave rise to trace FOL at higher temperature. The yield of methanol
or ethanol in the tests of furan is higher than that in the test of DMF and 2-MF. On
this basis, it may be hypothesized that methanol and ethanol is generated by ring-
opening of furan.
On the basis of the experimental results in this work, a proper pathway of HMF
decarbonylation is proposed in Scheme 3. The broken lines represent a minor pathway.
4
. Conclusions
In summary, the versatile product distribution in HMF decarbonylation is resulted
from the high activity of the hydroxymethyl in HMF or FOL. Moreover,
dehydrogenation of the furan ring-branched hydroxymethyl makes the main H source
leading to hydrogenation/hydrogenolysis side reactions. The WGS reaction and H
adsorption on catalysts during reduction also provide small amount of H . The
2
2
2
elimination of the furanic ring-branched hydroxymethyl (in HMF or FOL) is
completed by sequential dehydrogenation and decarbonylation via the intermediate of
1
0

aldehyde (DFF or FAL). 2-MF is probably mainly derived from FOL hydrogenolysis.
Etherification of FOL occurred only over the acidic Pd/Al . The branched methyl
2
O
3
in 2-MF and DMF can also be elimination at low conversion, and methanol is
produced by ring-opening of furan. These results are helpful to understand the
mechanism and reaction pathway of HMF decarbonylation, and to provide an
instruction for design of new catalytic formulations.
Acknowledgements
The authors gratefully acknowledge the financial support of the Major State Basic
Research Development Program of China (973 Program) (no. 2012CB215305).
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1
3

Fig. 1 XPS patterns of calcined and reduced Pd/Al
2
3
O .
1
4

Fig. 2 Particle sizes of catalysts: (a) reduced Pd/Al
2
O
3
; (b) used Pd/Al
2
3
O after
o
reaction of HMF at 180 C for 16h.
1
5

Scheme 1. The evolution direction of HMF.
1
6

Scheme 2. The proposed reaction pathway for the intermediates.
1
7

Scheme 3. Proper reaction pathway proposed for HMF decarbonylation.
1
8

Table 1 Catalytic data for the tests of HMF decarbonylation.a
Selectivity
Conv.
T(℃)
fura DM MFA 2-
Other
sb
(%)
FOL DFF FAL
DFE
n
F
L
MF
2.2
4.3
5.9
6.7
2.5
1
1
1
2
1
40
60
80
00
80c
11.9
30.6
56.3
75.7
54.6
77.7 8.0
72.0 4.3
64.5 1.9
3.6
6.9
8.6
8.8
8.7
-
3.3
2.2
1.6
1.7
2.0
-
-
5.2
8.6
6.2
15.3
1.3
-
1.8
2.0
2.1
1.4
-
1.7
4.3
1.9
7.6
3.6
-
57.6
-
80.5 1.7
a Conditions: 1.2 g HMF, 25 g 1,4-dioxane, 0.25 g catalyst, N atmospheric pressure
2
o
(
room temperature=RT), T=180 C, t=16h.
b Others = methanol, ethanol (trace) and polymers.
c Catalyst: 1% Pd/C
HMF=5-hydroxymethylfurfural, FOL=furfuryl alcohol, DFF=2, 5-diformylfuran,
FAL=furfural, DMF=2, 5-dimethylfuran, MFAL=5-methylfurfural, 2-MF=2-
methylfuran, DFE= difurfuryl ether.
1
9

Table 2 Quantitative data of H amount for reactions in Table 1.
2
T
H
2
/Hydrogenation H
2
/Dehydrogenatio H /WGS
2
H
2
/H
2
-TPDd
o
a
nb
c
Cat.
( C
(mmol)
)
(mmol)
(mmol)
(mmol)
0.066
1
0
1
0
4
6
0
0
0
1
.14
.37
.68
.00
0.13
0.33
0.66
0.94
0.64
0.088
0.089
0.10
Pd/Al O
2
0
.012
3
18
0
2
0
1
0
0
8
Pd/C
0.51
0.048
0.010
a H
b Calculated from the summing amount of DFF, FAL and furan.
c Calculated based on the amount of CO and CO in the tail gas.
d Calculated from the quantitative data of H -TPD.
2
involved in hydrogenation side reactions.
2
2
2
0

Table 3 Catalytic data for the tests of furfural.a
Yield (%)b
fura 2-
FOL
3.8 1.5
T
Conv.
(%)
Sample
(℃)
others
trace
0.2
1
40 5.4
-
Pd/Al
Pd/C
2
O
3
180 43.6
00 78.6
180 40.1
40.5 1.6
75.1 2.4
39.5 0.2
1.3
1.0
0.2
2
0.4
0.3
a Conditions: 1.2 g FAL, 25 g 1,4-dioxane, 0.25 g catalyst, N atmospheric pressure
2
o
(
RT), T=180 C, t=16h.
b Others = methanol, ethanol (trace) and polymers.
FAL=furfural, 2-MF=2-methylfuran, FOL=furfuryl alcohol.
2
1

Table 4 Catalytic data for the tests of furfuryl alcohol.a
Conv. Yield (%)b
T
Sample
(℃)
(%)
fura 2-
FAL DFE others
1
1
40 10.8
80 9.3
0.12 5.0
1.1
0.5
1.0
2.4
3.5
-
2.7
1.6
5.0
2.2
3.3
5.2
Pd/Al
Pd/C
2
O
3
1
2
80c 17.7
00 25.1
1.3
5.2
3.5
-
4.4
10.8 0.9
2.0 3.4
5.0
180c 7.5
trace
a Conditions: 1.2 g FOL, 25 g 1,4-dioxane, 0.25 g catalyst, N atmospheric pressure
2
o
(
RT), T=180 C, t=16h.
b others = methanol, ethanol (trace) and polymers.
c N :0.2 MPa (RT).
FOL=furfuryl alcohol, 2-MF=2-methylfuran, FAL=furfural, DFE= difurfuryl ether.
2
2
2

Table 5 Catalytic data for the tests of 5-methylfurfural.a
Yield (%)b
T
Conv.
(%)
Sample
(℃)
fura 2- FAL DM others
1
40 5.1
-
4.5
-
-
0.6
4.5
-
Pd/Al
Pd/C
2
O
3
180 55.9
00 83.2
180 53.5
-
49.6
-
2
0.8
1.7
78.3 1.30 2.7
50.8 0.9
0.2
0.1
-
a Conditions: 1.2 g MFAL, 25 g 1,4-dioxane, 0.25 g catalyst, N atmospheric pressure
2
o
(
RT), T=180 C, t=16h.
b others = methanol, ethanol (trace) and polymers.
MFAL=5-methylfurfural, 2-MF=2-methylfuran, FAL=furfural, DMF=2, 5-
dimethylfuran.
2
3

Table 6 Catalytic data for the tests of 2, 5-dimethylfuran, 2-methylfuran and furan.a
T
Yield
Feed
Cat.
(
℃) Methanol Ethanol furan
2-MF
FOL
1
40 trace
trace
trace
trace
0.1
0.2
0.2
0.2
0.2
0.1
trace
-
trace
-
Pd/Al
Pd/C
Pd/Al
Pd/C
Pd/Al
Pd/C
2
2
2
O
3
O
3
O
3
DMF
180 trace
180 trace
0.1
-
0.2
-
1
40 0.1
-
-
-
-
-
-
-
2
-MF
180 trace
180 trace
0.1
0.4
0.2
-
-
1
40 0.3
trace
0.2
furan
180 1.0
180 0.2
-
-
trace
-
-
a Conditions: 1.2 g substrate, 25 g 1,4-dioxane, 0.25 g catalyst, N atmospheric
2
o
pressure (RT), T=180 C, t=16h.
DMF=2, 5-dimethylfuran, 2-MF=2-methylfuran, FOL=furfuryl alcohol.
2
4