One-pot conversion of carbohydrates into gamma-valerolactone catalyzed by highly cross-linked ionic liquid polymer and Co/TiO2

Article abstract of DOI:10.1039/c4ra14363a

The acid catalytic conversion of carbohydrates into levulinate esters followed by metal catalytic hydrogenation is an important approach to obtain gamma-valerolactone (GVL) from biomass. In this work, we prepared the highly cross-linked polymer of divinylbenzene with acid ionic liquid (PDVB-IL) and supported Co on TiO₂ (Co/TiO₂), which were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental analysis. It was demonstrated that the PDVB-IL polymer could efficiently catalyze the esterification reaction of furfuryl alcohol (FAL), 5-hydroxymethylfurfural (HMF), and fructose with ethanol to produce the intermediate ethyl levulinate (EL), and the EL in the reaction mixture was directly hydrogenated to GVL over the Co/TiO₂ without requiring purification and with high yields.

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Graphical abstract:
The PDVB-IL polymer and Co/TiO2 is efficient and facilely recyclable
for one-pot conversion of FAL, HMF, and fructose into GVL.

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RSCPublishing
ARTICLE
One-pot conversion of carbohydrates into gamma-
valerolactonecatalyzed by highly cross-linkedionic
liquid polymer and Co/TiO2
Cite this: DOI: 10.1039/x0xx00000x
Received 00th January 2012,
Accepted 00th January 2012
Huacong Zhou, Jinliang Song, Xinchen Kang, Jiayin Hu, Yingying Yang, Honglei
Fan, QingleiMeng, Buxing Han*
DOI: 10.1039/x0xx00000x
www.rsc.org/
The acid catalytic conversion of carbohydrates intolevulinateesters followed by the metal
catalytic hydrogenation is an important approach to obtain gamma-valerolactone (GVL)
from biomass. In this work, we prepared the highly cross-linked acid ionic liquid polymer
(PDVB-IL) and the supported Co on TiO2 (Co/TiO2), which were characterized by Fourier
transform infraredspectroscopy (FTIR), scanning electron microscopy (SEM), transmission
electron microscopy (TEM), and elemental analysis. It was demonstrated that the PDVB-IL
polymer could efficiently catalyze the esterification reaction of furfuryl alcohol (FAL), 5-
hydroxymethylfurfural (HMF), and fructose with ethanol to produce the intermediate ethyl
levulinate (EL), and the EL in the reaction mixture could be directly hydrogenated to GVL
over the Co/TiO2 without the need of purification, and high yields were obtained.
the alcoholysis of FAL into ethyl levulinate (EL).24 Zhang et al.
developed a novel organic-inorganic hybrid solid acid catalyst
Introduction
for the conversion of FAL into alkyl levulinates.25
Comparatively, the one-pot conversion directly from FAL to
GVL is more attractive because no separation of the
intermediate alkyl levulinates was needed. Rode et al.
conducted the first attempt for the direct conversion of FAL to
GVL by the combination of acid ILs and different supported
noble metal catalysts.20The combination of acid resin
Ambelyst-15 and RANEY® Ni was also reported to be efficient
for the tandem conversion of FAL.18
Under the background of increasing demand for energy and
limited reserves of traditional fossil resources on earth,
exploring sustainable carbon source becomes a critical issue for
human society.1,
2
Biomass is a well-accepted green and
sustainable carbon source, which brings human light to
overcome the above problem.3-5 Lignocellulose, consisting
mainly of cellulose, hemicellulose, and lignin, is an abundant
and renewable carbon source and can be biologically or
chemically converted into various bulk chemicals, materials,
and fuel additives.1, 6-13 One of the useful chemicals obtained
from lignocellulose is gamma-valerolactone (GVL), which has
wide applications including fuel additive, solvent, liquid fuel,
and a precursor for the production of more valuable chemicals,
etc.1, 14-19
Although much progress has been achieved as above stated,
there are still many problems remaining to be solved for the
direct conversion of FAL to GVL. For example, for the
homogeneous catalysts, the most efficient catalyst reported up
to date except the mineral acids is sulfonic acid functionalized
ionic liquids. Its homogeneous property makes the recovery of
the catalyst troublesome and consumption of large amounts of
organic solvents, water, and energy.20 For the reported
heterogeneous catalysts, the humin by-products formed in the
acid catalytic process could easily be adsorbed on the surface of
the catalysts and deactivated them.24-26 The commonly used
method to regenerate the catalysts is coke burn-off, while it is
not suitable for the temperature-sensitive materials like resins.24
Most of the reported metal catalysts were metal-based ones
including the Ru, Rh, Pd, Ag, Ir, etc. The cost was high and the
One of the approaches to obtain GVL from biomass is the C5
sugar route with hemicellulose derived furfuryl alcohol (FAL)
as the initial or intermediate molecule.1,
20
Tandem acid
catalytic alcoholysis of FAL and subsequent metal catalytic
hydrogenation reaction is a key process in this route.21-23
Although the high efficiency of inorganic mineral acids, their
corrosion and recovery problems drive researchers to
investigate more economically and environmentally feasible
heterogeneous acid catalysts. Lange et al. has proved that the
strongly acidic resins and zeolites were effective catalysts for
This journal is © The Royal Society of Chemistry 2013
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reserve is very limited. The only reported non-noble metal was experiment, 5.40 g (40 mmol) 1,4-butane sultone and 0.94 g (10
RANEY® Ni, but it required the purification of the intermediate mmol) 1-vinylimidazole were added into a 25 mL one-necked flask
EL.18Obviously, more efforts are still desirable to improve the equipped with a magnetic stirrer. After reflux for 10 h at 70 ºC under
above aspects of the catalysts for GVL production.
N2 atmosphere with stirring, the reaction mixture was cooled down
Considering the above problems, in this work, we designed a and solid product was recovered by filtration. The product was
novel catalytic system consisted of thehighly cross- washed with diethyl ether to completely remove the unreacted
linkedpolymer of divinylbenzenewith acid ionic liquid (PDVB- reactants and then dried under vacuum overnight. A white zwitterion
IL) and supported Co on TiO2 (Co/TiO2) for the one-pot product was obtained with a yield of 98%. A stoichiometric amount
conversion of FAL into GVL (Scheme 1), which consisted of of sulfonic acid was subsequently added dropwise to the zwitterions
esterification of the carbohydrates with ethanol to EL and solution and the mixture was stirred at 80ºC for 6 h. After removal of
hydrogenation reaction of EL to GVL. It was demonstrated that water via evaporation, the viscous IL was obtained and dried under
1
this catalytic system could catalyze the conversion of FAL, vacuum overnight. The prepared IL was confirmed by H and 13C
1
HMF, and fructose into GVL efficiently without the NMR. H NMR (400 MHz, D2O): δ 8.84 (s, 1H), 7.58 (s, 1H), 7.40
purification of the intermediate EL. The ILs could be recycled (s, 1H), 6.93 (dd, J = 15.6, 8.7 Hz, 1H), 5.59 (dd, J = 15.6, 2.7 Hz,
easily due to the heterogeneous property. The PDVB-IL 1H), 5.21 (dd, J = 8.7, 2.7 Hz, 1H), 4.08 (t, J = 7.1 Hz, 2H), 2.88 –
polymer nearly did not adsorb humin, giving the catalyst a 2.63 (m, 2H), 2.03 – 1.73 (m, 2H), 1.56 (dt, J = 18.3, 7.8 Hz,
better reusability than that of the commercial Amberlyst-15.
2H).13C NMR (100 MHz, D2O): δ 134.30, 128.13, 122.72, 119.49,
109.25, 49.95, 49.18, 27.83, 20.82.
Preparation of the PDVB-IL polymer
The PDVB-IL polymer was prepared according to the previous
method with modification.27The synthesized IL was copolymerized
with DVB to form highly cross-linked polymer. In a typical
polymerization, 0.34 g prepared IL, 1.40 g DVB, and 40 mL ethanol
or ethanol/chloroform mixtures with different ratios were added into
a 100 mL three-necked round flask and heated to 70 ºC. The flask
was purged with nitrogen and then 0.08 g benzoyl peroxide was
added under stirring. The polymerization was allowed to proceed
under N2 atmosphere for 24 h. After cooling down, the product was
separated by centrifugation, washed thoroughly with ethanol and
water, and then dried under vacuum for use.
Preparation of supported cobalt
Scheme 1 Schematic diagram of the tandem conversion of FAL,
HMF, and fructose into GVL by the PDVB-IL polymer and
supported cobalt catalytic system.
The supported cobalt was prepared by the impregnation and
NaBH4 reduction method.20 In a typical procedure, 0.05 g
support was suspended in a solution containing a calculated
amount of Co(NO3)2•6H2O under ultrasonification, and the
mixture was stirred under room temperature for 2 h. Then 0.075
g NaBH4 dissolved in 10 mL water was added dropwise and the
system was stirred for half an hour. The supported cobalt was
then separated via centrifugation, washed by ethanol, and kept
in ethanol for use.
Experimental
Materials
Furfuryl alcohol (98%), 1-vinylimidazole (99%), silicon (IV) oxide
(amorphous fumed, S.A. 130-170 m2/g), Amberlyst-15 (H) ion
exchange resin, molecular sieve (zeolite Y, hydrogen), and celite
(HyfloSupercel) were from Alfa Aesar®. Divinylbenzene (DVB, m-
and p-mixture, 55% in EVB + DEB, stabilized with TBC), benzoyl
peroxide (BPO, 98%), 1,4-butane sultone (99%), ethyl levulinate
(98%), gamma-valerolactone (98%), and dodecane (99%) were
purchased from J&K Chemical. Titanium (IV) oxide Aeroxide® P25
was from Acros Organics. Cobalt nitrate hexahydrate, sodium
borohydride, MgO, ZrO2, and other chemicals were A. R. grade and
provided by Sinopharm Chemical Reagent Co. Ltd. H2 (99.99%)
was provided by Beijing Analytical Instrument Company.
Catalyst characterization
The PDVB-IL polymer was characterized by scanning electron
microscopy (SEM, HITACHI S-4800), Fourier transform
infrared spectroscopy (FTIR, Bruker Tensor 27 spectrometer),
and elemental analysis (EA, Flash EA 1112). The Co/TiO2 was
characterized by transmission electron microscopy (TEM,
JEOL JEM-1011).
Reaction
For the conversion of FAL into EL, typically, 0.25 g (2.4 mmol)
FAL, 0.18 g PDVB-IL polymer, and certain amount of ethanol
were added into a 10 mL Teflon-lined stainless steel autoclave
equipped with a magnetic stirrer. After removing the air via
Preparation of IL precursor
Sulfonic acid functionalized ionic liquid precursor was synthesized
according to the reported procedures with modification.20 In the
2 | J. Name., 2012, 00, 1-3
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vacuum pump, nitrogen of 1 atm was charged and the reactor the matrix, leading to the decreasing of the accessibility of the
was placed in a constant temperature oil bath of desired acid sites.27Thus the PDVB-IL polymer prepared in
temperature. After reaction, the reactor was cooled in ice water ethanol/chloroform with ratio of 30:10 (v/v) was used to study
and the organic phase was extracted from the mixture by ethyl the effects of reaction condition on the reaction.
acetate. The sample was analyzed by gas chromatograph (GC,
HP 4890) equipped with a flame ionization detector (FID), and
dodecane was used as the internal standard. Identification of the
products and reactants was done using a GC-MS (SHIMADZU-
QP2010) as well as by comparing the retention times to
respective standards in GC traces. The results are expressed in
mol% based on the total FAL loaded. In tandem reaction, the
catalyst in each step was separated via centrifugation and
washed once with ethanol for reuse. HMF and fructose
were converted under the same procedures with FAL.
The activity of the supported cobalt was evaluated via the
hydrogenation of EL. In a typical experiment, 1 g EL and 0.05
g of the prepared catalyst were introduced into the reactor. The
reaction was conducted under 130ºC and 3 MPa of hydrogen
pressure. The product was analysed as stated above.
Fig. 1 SEM images and size distributions of the PDVB-IL
polymer obtained in different solvents: neat ethanol (a),
ethanol/chloroform mixtures with volume (mL) ratios of
Results and Discussion
30/10(b), 20/20(c), and 10/30(d).
Preparation and characterization of the PDVB-IL polymer
The morphologies of the PDVB-IL polymer varied from dense
microspheres to irregular porous gel, depending strongly on the
solvent system (Fig. 1). The average sizes of the samples prepared in
mixed solvents with ethanol/chloroform ratios (v/v) of 40:0, 30:10,
and 20:20 were 360 nm, 500 nm, and 2.8 ꢀm, respectively (Fig. 1a,
1b, and 1c).The change of morphology can be explained by the
competition between the polymer chain growth rate and the phase
separation rate.27 Ethanol is a much poorer solvent for the polymer
than chloroform. Once the polymer was formed, the phase separation
occurred quickly, and the polymer shrunk and grew into the dense
microsphere in ethanol, while this process was limited with the
increasing of chloroform content, leading to the formation of larger
aggregated spheres or irregular porous structure.
FTIR spectroscopy and elemental analysis were carried out
to confirm the existence of IL segments in the polymer. As
shown in Fig. 2, the peaks at 1654 cm-1, 1174cm-1, and 1041
Fig. 2 FTIR spectra of the prepared IL and PDVB-IL polymer
obtained in the ethanol/chloroform with volume ratio of 30/10.
cm-1 attributed to C=N stretching vibrations of imidazole rings,
asymmetrical and symmetrical stretching of SO3, respectively,
appeared in the spectrum of the PDVB-IL polymer, proving the
existence of IL structure.27-29 Elemental analysis showed the
contents of IL segments increased with the increasing of
chloroform contents (Fig. 3). This may be attributed to that
higher chloroform concentration facilitated the diffusion of IL
in the polymer matrix and enhanced the probability of the
copolymerization of IL and DVB.27 When the obtained
polymers were used to convert FAL, the conversion of FAL
decreased with the increasing of IL contents and the EL yield
reached the highest value at the IL contents of ca. 3.1 wt% (Fig.
3). The decrease of the conversion of FALmay be attributed to
that the slower phase separation rate at higher chloroform
contents resulted in the embedment of more IL segments into
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Fig. 3 The IL contents and activity of PDVB-IL polymers
From above results, the formation of humin limited the
obtained under different ethanol/chloroform ratios. Reaction further improvement of the EL yields. It has been reported that
conditions: ethanol, 4 mL; FAL 0.25 g; PDVB-IL polymer, some organic solvents could inhibit the formation of humin to
0.18 g; N2, 1 atm; 130 ºC, 3 h.
some extent.26, 30, 31 Thus, several common solvents were used,
attempting to further improve the EL yields. The results were
shown in Fig. 5. For all the cases, FAL was totally converted
but with different EL yields. Unlike the reported results,30, 31
yields in acetonitrile and toluene were lower than that in pure
ethanol, and yield in THF was similar to that in pure ethanol.
Interestingly, the yield of the product in DMSO could reach60%
under the same conditions. During the experiments, we found
that the intermediate ethoxy FAL was not totally converted into
EL after reaction at 130 ºC for 12 hours. Increasing the reaction
time to 24 hours failed to fulfil the total conversion of the
intermediate, while improving the reaction temperature to 150
ºC succeeded in total conversion of the intermediate within 12
hours. The EL yield was increased to 75%, which was higher
than the common solid acids.24As reported in literatures,
DMSO could stabilize the furan structure in the reactantsand
suppress the condensation of the reactants and formation of by-
products, thus improving the selectivity of EL.32,33
Conversion of FAL and optimization
The effects of catalyst/substrate ratio, the amount of ethanol,
the concentration of substrate, and temperature on the reaction
were studied, and the results are presented in Fig. 4. It can be
seen from Fig. 4a that increasing the catalyst/substrate mole
ratio from 0.3% to 1.3% could significantly improve the EL
yield from 14% to 38% within 12 h, while further increasing
the catalyst/substrate ratio led to a slightly decrease in product
yield, resulting from the fast formation of humin by-products.
Increasing the volume of the solvent could improve the EL
yield, while increasing the concentration of FAL at a constant
solvent volume resulted in the decrease of the product yield
(Fig. 4b and 4c), which was consistent with the previous report
using other catalysts.20 Temperature is also an important factor
influencing the EL yield (Fig. 4d). A moderate EL yield of 33%
was obtained even under 90 ºC, and the yield increased up to 48%
at the temperature of 130 ºC. Further increasing the temperature
to 150 ºC resulted in the obvious drop in EL yield, which may
be attributed to that the side reactions were also accelerated
under higher temperature.Furthermore, in our experiments, we
found that the only co-product was the intermediate
methoxyfurfuryl alcohol formed by the reactant and ethanol
only detected under lower temperature or shorter reaction time,
and no other side-productsexcept humin were detected.
Fig. 5 Effects of solvents on the performance of the PDVB-IL
polymer. EtOH, ethanol; Ace: acetonitrile; Tol, toluene; THF:
tetrahydrofuran; DMSO: dimethyl sulfoxide. Reaction
conditions: ethanol, 2 mL; solvent: 6 mL; FAL 0.12 g; PDVB-
IL polymer, 0.18 g; N2, 1 atm; 130 ºC, 12 h. DMSO130 and
DMSO150 means the reaction was conducted at 130 and 150 ºC,
respectively.
In our experiments, it is interesting to find that the PDVB-IL
polymer nearly did not adsorb the humin by-products on its
surface, compared with the commercial acid resins, such as
Amberlyst-15. We detected the dry mass change of Amberlyst-
15 and the PDVB-IL polymer, and found that a mass increase
of ca. 5% after twice reactions occurred for Amberlyst-15 and
no obvious mass change for the PDVB-IL polymer after
reaction. The humin adsorption of the two catalysts could also
be seen simply through the colour change after the reaction (Fig.
6a, 6b). The reusability comparison between our PDVB-IL
polymer and Amberlyst-15 showed that the PDVB-IL polymer
exhibited a better performance in both FAL conversion and EL
Fig. 4 Effects of the catalyst/substrate mole ratios (a), the
volume of ethanol (b), the concentration of FAL (c), and
temperature (d) on the EL yield. The catalyst/substrate mole
ratios were the mole ratios of IL/FAL. Typical reaction
conditions were as follows until otherwise stated in above
figures: ethanol, 8 mL; FAL 0.12 g; PDVB-IL polymer, 0.18 g;
N2, 1 atm; 130ºC, 12 h.
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yield than that of Amberlyst-15 within 5 cycles (Fig. 6c). This
indicated that the weak adsorption for humin is favourable to
maintain the activity of the catalyst. We speculated that the
strong adsorption of Amberlyst-15 for the humin could be
related with its porous structures, which resulted in the
accumulation of by-products. It is worth noting that the PDVB-
IL polymer also suffered a decrease in activity at a speed
slower than that of Amberlyst-15. The sulphur contents in the
reaction solutions with pure ethanol as solvents without DMSO
were detected. No obvious sulphur content was detected after
the first catalysis reaction, while ca. 100 ppm of sulphur was
detected after the fifth run.Thus we speculated that partial
leaching of IL segmentsfrom the bulk polymer phase was the
main reason for the activity decrease of the catalyst.We
compared the FTIR spectra of the virgin and recycled PDVB-IL
catalysts after used three times and no obvious differences were
found, indicating that the main structures of PDVB-IL were
wellmaintained after the reaction (Fig. 7).
One-pot conversion of carbohydrates into GVL
After optimizing the reaction conditions of the PDVB-IL
polymer for catalytic conversion of FAL into EL, we conducted
the one-pot conversion of FAL into GVL. The supported cobalt
was attempted for the first time in the conversion of FAL into
GVL. The impregnation and NaBH4 reduction method was
used to load cobalt on various materials, and the hydrogenation
of EL to GVL was used to evaluate the activity (Table 1).
Among the materials investigated, TiO2 gave the highest GVL
yield (entry 8). Increasing the loading of cobalt on TiO2 could
significantly increase the GVL yield (entries 8—10). TEM
characterization of Co/TiO2 (20 wt% Co) showed that the Co
particles with a diameter of 50—150 nm were dispersed
uniformly in the TiO2 matrix without obvious aggregation (Fig.
8).
The tandem conversion of FAL into GVL was shown in the
diagram in Table 2. It can be seen that the catalytic system is
very efficient in the conversion of FAL with the intermediate
EL yield of 75% and the final GVL yield up to 69%, which was
even higher than that of the combination of noble Ru/C and
[BMIm-SH][HSO4].20 The activity maintained well in the
second run (entries1—2). A decrease in the GVL yield was
observed since the third recycle (entries 3—6). We detected the
cobalt contents in the reaction solutions. No obvious cobalt was
found after the first two recycles, but a content of ca. 70 ppm
was detected after the fifth run. Thus the deactivation of the
catalytic system may be attributed to the leaching of IL
segments, as analysis above, and subsequent partial cobalt
dissolution. We expanded our catalytic system to the
conversion of other carbohydrates, including HMF and fructose
(entries 7—8), and GVL yields of 62% and 55% were obtained,
respectively, which were comparable to the reported results
using Amberlyst-15 and RANEY® Ni as the catalyst system.18
Considering the raw carbohydrate may come from the
aqueous systems, we further investigated the effect of water on
our catalytic system. The results showed that serious coking
and no obvious products were detected in pure water due to the
instability of FAL in water. Thus we turned to the mixture of
water and ethanol/DMSO and found that a water content of 10%
(v/v) had no obvious influence on the high EL and GVL yields.
Fig.6 Optical images of the Amberlyst-15 resin (a) and PDVB-
IL polymer (b) before and after reaction and their
reusability(c).The catalysts were washed once with ethanol
before taking pictures. Reaction conditions: ethanol, 2 mL;
DMSO, 6 mL; FAL, 0.12 g; PDVB-IL polymer, 0.18 g or
Amberlyst-15, 0.2 g; N2, 1 atm; 130 ºC; 12 h. The catalysts
were washed once with ethanol before the next run.
Table 1 Screening of the supports for cobalt immobilizationa
Entry
Supports
Conversion/% Selectivity/% Yield/%
1
2
Control
MgO
ZrO2
8
16.8
31
84.3
94.1
94.4
94.6
94.1
70.4
97.9
92.1
91.0
91.8
6.8
15.8
29.2
13.3
14.8
16
3
4
Zeolite
SiO2
14.1
15.7
5
6
Amberlyst-15 22.8
7
Celite
TiO2
35.2
45.2
64.9
78.8
34.5
41.7
59.1
72.3
8
b
Fig.7 Comparison of FTIR spectra of the virgin and recycled
9
TiO2
c
PDVB-IL catalysts after used three times.
10
TiO2
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aTypical reaction conditions: EL, 1.0 g; supported cobalt (5
wt%), 0.05 g; H2, 3 MPa; 130 ºC; 3 h. bCobalt loading: 10 wt%;
cCobalt loading: 20 wt%.
Acknowledgements
The authors thank the National Natural Science Foundation of
China. This work was supported by National Natural Science
Foundation of China (21173234, 21133009, 21021003), and
Chinese Academy of Sciences (KJCX2.YW.H30).
Notes and references
Beijing National Laboratory for Molecular Sciences, CAS Key
Laboratory of Colloid and Interface and Thermodynamics, Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Tel/fax: 86-10-62562821. E-mail address: Hanbx@iccas.ac.cn.
1
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Fig.8 TEM image of Co/TiO2 with a Co loading of 20 wt%.
M. Y. He, Y. H. Sun and B. X. Han, Angew.Chem. Int. Ed., 2013, 52
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9620.
Table 2 One-pot conversion of carbohydrates into GVL in the
PDVB-IL polymer and Co/TiO2 catalyst systema
4
5
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Entry Substrate Conversion/% EL Yield/% GVL Yield/%
1b
2 b
3 b
4 b
5 b
6 b
7
FAL
>99
>99
97
75
74
66
61
52
35
73
65
69
66
56
48
33
18
62c
55
3
FAL
H. C. Zhou, J. L. Song, H. L. Fan, B. B. Zhang, Y. Y. Yang, J. Y. Hu,
FAL
Q. G. Zhu and B. X. Han, Green Chem., 2014, 16, 3870.
FAL
93
10 W. W. Zhu, H. M. Yang, J. Z. Chen, C. Chen, L. Guo, H. M. Gan, X.
G. Zhao and Z. S. Hou, Green Chem., 2014, 16, 1534.
FAL
90
FAL
70
11 H. B. Xie, H. W. Shen, Z. W. Gong, Q. Wang, Z. B. K. Zhao and F.
W. Bai, Green Chem., 2012, 14, 1202.
HMF
>99
12 H. B. Xie, Z. B. K. Zhao and Q. Wang, ChemSusChem, 2012,
13 M. Dashtban, A. Gilbert and P. Fatehi, RSC Adv., 2014, , 2037.
14 W. R. H. Wright and R. Palkovits, ChemSusChem, 2012, , 1657.
5, 901.
8
Fructose
>99
aReaction conditions: the first step, 1 mmol carbohydrate (FAL,
HMF, or fructose); 0.18 g PDVB-IL polymer; 2 mL ethanol, 6
mL DMSO; N2, 1 atm; 150 ºC; 12 hours. In the second step,
Co/TiO2 0.05 g; H2, 3 MPa; 130ºC; 6 hours. Yields were all
given as the mole percent of the initiate substrates.b Entries 1—
6, reusability of the catalytic systems for FAL: run times 1—6;
c 24 hours for the hydrogenation reaction.
4
5
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consisting of the PDVB-IL polymer and Co/TiO2 for the one-
pot conversion of FAL, HMF, and fructose into GVL via EL.
Under the optimized conditions, the yields of GVL can reach
69%, 62%, and 55% from FAL, HMF, and fructose,
respectively. The PDVB-IL polymer is facile to recycle due to
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humin. The obvious advantages of this catalytic system,
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