Very efficient conversion of glucose to 5-hydroxymethylfurfural in DBU-based ionic liquids with benzenesulfonate anion

Article abstract of DOI:10.1039/c4gc00311j

Efficient conversion of glucose to 5-hydroxymethylfurfural (HMF), an important platform molecular for fuels and chemicals, is a promising topic in green chemistry. In this work, several new DBU-based (DBU = 1,8-diazabicyclo[5. 4.0]undec-7-ene) ionic liquids (ILs) with benzene sulfonate (BS) anion were synthesized and used as the solvents for the dehydration of glucose to HMF. It was found that all the ILs were excellent solvents for the dehydration of glucose to form HMF using CrCl₃ as the catalyst. The effects of various factors, such as kind of catalysts, catalyst amount, reaction time and reaction temperature, on the yields of HMF were studied systematically in the Et-DBUBS/CrCl₃ catalytic system. The yield of HMF from glucose could reach 83.4% under the optimized reaction conditions, and the reasons for the high yield were investigated on the basis of control experiments. The Et-DBUBS/CrCl₃ system could be reused at least five times without considerable reduction in the efficiency. Further study indicated that the catalytic system was also very efficient for transformation of fructose, inulin, and cellobiose to HMF. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4gc00311j

Green Chemistry
View Article Online
View Journal | View Issue
PAPER
Very efficient conversion of glucose to
5-hydroxymethylfurfural in DBU-based ionic
liquids with benzenesulfonate anion
Cite this: Green Chem., 2014, 16,
3935
Lingqiao Wu, Jinliang Song,* Binbin Zhang, Baowen Zhou, Huacong Zhou,
Honglei Fan, Yingying Yang and Buxing Han*
Efficient conversion of glucose to 5-hydroxymethylfurfural (HMF), an important platform molecular for
fuels and chemicals, is a promising topic in green chemistry. In this work, several new DBU-based (DBU =
1,8-diazabicyclo[5.4.0]undec-7-ene) ionic liquids (ILs) with benzene sulfonate (BS) anion were syn-
thesized and used as the solvents for the dehydration of glucose to HMF. It was found that all the ILs were
excellent solvents for the dehydration of glucose to form HMF using CrCl3 as the catalyst. The effects of
various factors, such as kind of catalysts, catalyst amount, reaction time and reaction temperature, on the
yields of HMF were studied systematically in the Et-DBUBS/CrCl3 catalytic system. The yield of HMF from
glucose could reach 83.4% under the optimized reaction conditions, and the reasons for the high yield
were investigated on the basis of control experiments. The Et-DBUBS/CrCl3 system could be reused at
least five times without considerable reduction in the efficiency. Further study indicated that the catalytic
system was also very efficient for transformation of fructose, inulin, and cellobiose to HMF.
Received 21st February 2014,
Accepted 20th May 2014
DOI: 10.1039/c4gc00311j
www.rsc.org/greenchem
dehydration of glucose, including Lewis acid catalysts,6 tanta-
lum compounds,7 boric acid,8 ionic liquids (ILs),9 ion
Introduction
Diminishing fossil fuel reserves and growing concern about exchange resins,10 zeolites,11 chromium(0) nanoparticles,12
global warming have led to increasing interest in searching for Sn-Mont catalyst,13 bifunctional SO42−/ZrO2 catalysts,14 meso-
sustainable alternatives to fossil resources for chemicals and porous tantalum phosphate,15 and so on.
energy supply.1 Much attention has been paid to the conver-
Among the above catalysts, Lewis acid catalysts are an
sion of biomass into various valuable chemicals in recent important type of catalyst for the dehydration of glucose to
years.2 Dehydration of carbohydrates (e.g. glucose, fructose, produce HMF. For example, it has been reported that chro-
inulin, cellobiose and cellulose) into 5-hydroxymethylfurfural mium(II) chloride could catalyze the dehydration of glucose to
(HMF) is one of the most promising and successful routes HMF with good yields of about 70% using 1-ethyl-3-methylimid-
because HMF is considered as an important platform chemical azolium chloride ([EMIM]Cl) as reaction solvent.16 Hu et al.
derived from biomass3 and can be used to produce fine chemi- reported that a 62% yield of HMF was achieved from glucose
cals, liquid fuels and materials, which are mainly derived from in 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4)
petroleum currently.4
catalyzed by SnCl4.17 Furthermore, germanium(IV) chloride
Although high yields of HMF could be easily obtained from was found to be an effective catalyst for the production of
dehydration of fructose using various catalytic systems,5 the HMF from glucose in 1-butyl-3-methylimidazolium chloride
production of HMF from glucose is more attractive because ([BMIM]Cl) with a yield of 48.4%.18 Other Lewis acids, such as
glucose could be easily obtained through the hydrolysis of lanthanide chlorides,19 hafnium(IV) chloride,20 scandium
cellulose, which is inedible and the amount produced is very chloride,21 aluminum chloride,22 aluminum alkyls and
large. However, dehydration of glucose to produce HMF is alkoxides,23 could also be used to catalyze the dehydration of
more difficult than fructose and much effort has been devoted glucose to form HMF in various reaction solvents. Although
to the transformation of glucose into HMF. Up to now, various excellent results have been obtained, development of efficient
catalysts have been developed for the production of HMF from catalytic systems to enhance the efficiency and yield of the
reaction is still highly desirable.
Additionally, solvents have an important effect on the
activity and selectivity for the formation of HMF from the
Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese
dehydration of glucose. The dehydration of glucose has been
Academy of Sciences, Beijing 100190, China. E-mail: Hanbx@iccas.ac.cn,
conducted in traditional organic solvents,24 water,25 multiphase
songjl@iccas.ac.cn; Tel: 86-10-62562821
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3935–3941 | 3935

View Article Online
Paper
Green Chemistry
(98%), AlCl3, CrCl3·6H2O (98%) and CrCl2 (98%) were pur-
chased from Alfa Aesar. Glucose (99%) and inulin (95%) were
provided by J&K Scientific Ltd. Benzyl chloride, MnCl2·4H2O,
NiCl2·6H2O, SnCl4·5H2O, acetonitrile, ethyl acetate, KOH,
benzenesulfonic acid (70% water solution) and diethyl ether
were A. R. grade and were provided by Sinopharm Chemical
Reagent Beijing Co., Ltd. Bromoethane, allyl bromide and
butyl bromide of C. P. grade were purchased from Sinopharm
Chemical Reagent Beijing Co., Ltd. All chemicals were used
as received. Potassium benzene sulfonate was synthesized
through the reaction between KOH and benzenesulfonic
acid.
Synthesis of ILs with the BS anion
Scheme 1 Synthesis of the DBU-based ILs with BS anion and their
structures.
To synthesize ILs with the BS anion, the corresponding ILs
with halogen anion (Cl or Br) were firstly synthesized. 0.5 mol
of DBU and 0.8 mol of halohydrocarbon were added to 500 mL
ethyl acetate in a flask of 1000 mL. The reaction mixture was
stirred at room temperature for 48 h. After the reaction, the ILs
with halogen anion were obtained by filtering, washing with
diethyl ether, and drying at 40 °C for 24 h under vacuum.
Then, the ILs with halogen anion (Cl or Br) obtained above
(0.3 mol) and potassium benzene sulfonate (0.35 mol) were
added to acetonitrile (800 mL) in a beaker of 1000 mL
equipped with a magnetic stirrer. The reaction mixture was
stirred at room temperature under 48 h. After the reaction, the
reaction mixture was filtered to remove the solid salts. Then,
the filtrate was heated at 80 °C under vacuum to remove aceto-
nitrile to get the ILs with the BS anion. The synthesized ILs
were characterized as follows.
systems26 and ILs.27 Among these solvents, ILs are very attrac-
tive for the dehydration reaction because of their unusual
properties, such as high thermal and chemical stability, non-
flammability, negligible vapor pressure, adjustable func-
tions.28 Up to now, some ILs have been successfully used as
the reaction solvents for the dehydration of glucose to produce
HMF, including [EMIM]Cl,16 [BMIM]Cl,29 [EMIM]BF4,17
Bu-DBUCl,30 etc. However, the type of ILs for the reaction is
limited and enhancing the yield of the product is of great
importance. Therefore, it is still highly desirable to develop
new and easily prepared ILs as efficient reaction media for the
transformation of glucose into HMF.
In this work, we synthesized several DBU-based (DBU = 1,8-
diazabicyclo[5.4.0]undec-7-ene) ILs with the benzene sulfonate
(BS) anion (Scheme 1). Interest in these ILs stems from their
facile synthesis from commercially available and relatively
inexpensive starting materials, excellent air/water and thermal
stability. More importantly, the existence of the BS anion may
increase the activity and selectivity of the reaction through the
formation of hydrogen bonds between BS and glucose. Indeed,
it was found that these DBU-based ILs could be used as very
efficient reaction media for the dehydration of glucose to form
HMF catalyzed by CrCl3·6H2O (abbreviated as CrCl3 in the fol-
lowing). Furthermore, the DBU-based ILs/CrCl3 catalytic
system could be also used in the production of HMF from
other carbohydrates, such as fructose, inulin, and cellobiose.
To the best of our knowledge, this is the first application of
DBU-based ILs with BS anion in the conversion of carbo-
hydrates into HMF, and the HMF yield from glucose obtained
in our catalytic systems was very high, which could reach up to
83.4%.
Et-DBUBS. White solid; 1H NMR (D2O, 300 MHz) δ (ppm)
7.81–7.54 (m, 5H), 3.57–3.40 (m, 8H), 2.79–2.76 (m, 2H),
2.04–1.94 (m, 2H), 1.70–1.68 (m, 6H), 1.20–1.16 (m, 3H);
13C NMR δ (ppm) 166.1, 142.3, 131.5, 129.0, 125.3, 54.4, 48.6,
48.4, 46.0, 28.4, 28.0, 27.5, 25.5, 23.2, 19.6, 12.8.
Al-DBUBS. Light yellow solid; 1H NMR (D2O, 300 MHz)
δ (ppm) 7.82–7.51 (m, 5H), 5.88–5.77 (m, 1H), 5.26 (q, J =
9.0 Hz, 2H), 4.10–4.07 (m, 2H), 3.58–3.36 (m, 6H), 2.71–2.68
(m, 2H), 2.05–1.97 (m, 2H), 1.70–1.60 (m, 6H). 13C NMR
δ (ppm) 166.9, 142.5, 131.5, 130.9, 128.9, 125.3, 116.9, 54.9,
54.7, 48.7, 46.7, 28.0, 27.9, 25.5, 22.5, 19.5.
Bu-DBUBS. Light yellow oil; 1H NMR (D2O, 300 MHz)
δ (ppm) 7.80–7.51 (m, 5H), 3.54–3.52 (m, 2H), 3.45–3.37 (m,
6H), 2.76 (d, J = 9.01 Hz, 2H), 2.05–1.93 (m, 2H), 1.71–1.35 (m,
8H), 1.35–1.22 (m, 2H), 0.90 (t, J = 5.7 Hz, 3H); 13C NMR
δ (ppm) 166.2, 142.6, 131.5, 128.9, 125.3, 54.4, 53.2, 48.6, 46.7,
30.0, 28.0, 27.6, 25.5, 22.7, 19.5, 19.1, 13.0.
Bn-DBUBS. Transparent oil; 1H NMR (D2O, 300 MHz)
δ (ppm) 7.82–7.77 (m, 2H), 7.51–7.34 (m, 6H), 7.23 (d, J = 6.90
Hz, 2H), 4.69 (s, 2H), 3.58–3.39 (m, 6H), 2.70 (t, J = 5.40, 2H),
2.05–1.97 (m, 2H), 1.63 (d, J = 2.70, 4H), 1.47 (d, J = 5.10, 2H);
13C NMR δ (ppm) 167.1, 142.6, 135.1, 131.4, 129.1, 128.9,
Experimental section
Materials
Fructose (99%), cellobiose (98+%), cellulose (microcrystalline), 128.1, 126.4, 125.3, 56.0, 54.8, 48.8, 47.4, 28.2, 27.9, 25.4, 22.2,
starch (soluble), (1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) 19.5.
3936 | Green Chem., 2014, 16, 3935–3941
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
General procedures of the reaction for HMF generation
HMF was tested at 100 °C for 3 h in Et-DBUBS, and the results
are summarized in Table 1. Among the catalysts tested, CrCl3
(entry 1), SnCl4·5H2O (entry 2) and CrCl2 (entry 3) had high
activity for the reaction and CrCl3 was the best for the reaction.
The yield of HMF could reach 78.6% in the presence of CrCl3
in IL Et-DBUBS. In addition, some results of typical catalytic
systems used in the production of HMF from glucose were also
given in Table 1 (entries 6–9). It can be seen that the catalytic
system of this work is very efficient. Based on the results dis-
cussed above, we chose CrCl3 as the dehydration catalyst
to study effect of reaction parameters on the reaction in
Et-DBUBS.
All the experiments were carried out in a 5 mL flask in an oil
bath. Only the procedures for the synthesis of HMF from
glucose in an IL are discussed because those for other sugars
were similar. Typically, desired amounts of glucose and cata-
lyst were added to the preheated Et-DBUBS in the flask and
sealed with a glass stopper. The reaction mixture was stirred at
the desired temperature. After a suitable reaction time, the
mixture was cooled to room temperature immediately. Then,
all the samples were analyzed by HPLC to obtain the HMF
yield. Each reaction was repeated at least two times, and the
average yield was reported. In the experiment to test the reusa-
bility, 0.5 mL of deionized water was added into the reaction
system after the reaction. Then the produced HMF was
extracted with diethyl ether. After extraction, the Et-DBUBS/
CrCl3 system was heated to 80 °C to remove the water under
vacuum. Then, the Et-DBUBS/CrCl3 system was directly used
for the next run by adding new glucose.
Influence of catalyst amount
In order to investigate the appropriate amount of catalyst, the
influence of the amount of CrCl3 on the dehydration of
glucose into HMF was examined in Et-DBUBS at 100 °C with a
reaction time of 3 h, and the results are given in Fig. 1. It can
be seen that the yield of HMF reached a maximum when the
amount of catalyst was 10 mol%. Further increase of the
amount of catalyst resulted in a slight decrease of HMF yield.
These results demonstrated that a lower catalyst amount led to
a relatively slow reaction, and excess catalyst amount could
cause the side reactions to humins or other compounds.22
Therefore, 10 mol% of catalyst based on glucose was the
optimal catalyst amount for the reaction uner our reaction
conditions.
HMF analysis
The amount of HMF was analyzed by HPLC with a Shimadzu
LC-15C pump,
a Shimadzu UV-Vis SPD-15C detector at
282.0 nm, and a Supelcosil LC-18 5ìm column at 35 °C. Before
analysis, the reaction mixture was diluted to 1000 mL.
A methanol–water solution (50/50 v/v) was used as the mobile
phase at a flow rate of 0.8 mL min−1
.
Effect of reaction temperature
Results and discussion
We studied the effect of reaction temperature on the de-
hydration of glucose to HMF in the Et-DBUBS/CrCl3 system
with a reaction time of 3 h and the results are shown in Fig. 2.
The yield of HMF reached 82.2% when the temperature
increased from 80 °C to 110 °C and then slowly decreased to
80.7% when the reaction temperature increased to 120 °C. In
the reaction system, the reaction temperature affected the reac-
tion in two opposite ways. Firstly, the dehydration of glucose
Synthesis of the ILs with the BS anion
The routes to synthesize the DBU-based ILs with the BS anion
and their structures are presented in Scheme 1. The synthetic
procedures and the characterization are discussed in detailed
in the Experimental section.
Catalyst screening in Et-DBUBS
Some metal salts in ILs have been demonstrated to be efficient was accelerated by increasing temperature, which was favor-
catalysts for the conversion of glucose to HMF.16 In our study, able to obtaining high HMF yield. Secondly, the side reactions,
the activity of various catalysts for the conversion of glucose to such as polymerization and rehydration of HMF,15 were also
Table 1 Catalytic activity of different metal catalysts in Et-DBUBSa
Entry
Catalyst
Solvent
Temperature (°C)
Yieldb (%)
Selectivity (%)
1
2
3
4
5
6
CrCl3
SnCl4·5H2O
CrCl2
Et-DBUBS
Et-DBUBS
Et-DBUBS
Et-DBUBS
Et-DBUBS
Et-DBUBS
Bu-DBUCl
[EMIM]Cl
[EMIM]BF4
DMSO
100
100
100
100
100
100
100
100
100
150
78.6
69.1
62.2
47.4
1.2
0
64
71
61
34.2
84.2
69.6
63.4
52.3
—
—
—
—
—
AlCl3
NiCl2·6H2O
MnCl2·4H2O
CrCl3·6H2O
CrCl2
SnCl4
FPILs
7c
8d
9e
10f
—
a Reaction conditions: 1 g Et-DBUBS, 0.1 g glucose, 10 mol% (based on glucose) catalyst, reaction time 3 h. b HMF yields were determined by
HPLC. c The data was obtained from ref. 30. d The data was obtained from ref. 16. e The data was obtained from ref. 17. f The data was obtained
from ref. 31.
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3935–3941 | 3937

View Article Online
Paper
Green Chemistry
Fig. 1 Influence of the amount of catalyst on HMF yield. Reaction con-
ditions: 1 g Et-DBUBS, 0.1 g glucose, reaction temperature 100 °C, reac-
tion time 3 h.
Fig. 3 Effect of reaction time on dehydration of glucose to the HMF in
ILs/CrCl3 catalytic system. Reaction conditions:
1 g solvent, 0.1 g
glucose, 10 mol% (based on glucose) CrCl3, reaction temperature
110 °C.
yield of HMF, i.e., the rate of generation of the product HMF,
the rate of formation of by-products directly from the reactant
(glucose), and the rate of the conversion of HMF to by-pro-
ducts. To elucidate the effect of the conversion of HMF to by-
products on the yield, we studied the transformation of HMF
(10 wt%) in Et-DBUBS/CrCl3 and [BMIM]Cl/CrCl3 under the
same conditions shown in Fig. 3. The results demonstrated
that conversion of HMF was negligible at 2 h. These control
experiments indicated that the third factor above was not the
reason for the higher yield of HMF in our catalytic system.
Fig. 3 shows that the maximum yield in both systems occurred
at 2 h. Meanwhile, our experiments showed that the times for
the complete conversion of glucose in the two ILs were the
same. Therefore, it can be deduced that the rate of formation
of by-products directly from glucose in Et-DBUBS/CrCl3 was
slower, which was the main reason for the very high yield of
HMF in the system.
Fig. 2 Effect of reaction temperature on the conversion of glucose to
HMF in Et-DBUBS/CrCl3 system. Reaction conditions: 1 g Et-DBUBS,
0.1 g glucose, 10 mol% CrCl3 (based on glucose), reaction time 3 h.
accelerated by rising temperature. The competition of the two
opposite factors resulted in the highest yield at 110 °C.
Effect of reaction time
Effect of amount of glucose
We studied the influence of reaction time at different reaction
temperature (Fig. 3). From Fig. 3, we can see that when the
reaction was conducted at 110 °C, the yield increased dramati-
cally with time at the beginning, and reached the maximum
83.4% at 2 h. The yield was unchanged as the reaction time
increased from 2 h to 3 h.
The effect of the amount of glucose on the HMF yield was
investigated as the amount of CrCl3 was fixed at 10 mol%
(based on glucose). As shown in Fig. 4, the HMF yield
decreased from 84.4% to 68.4% when the amount of glucose
increased from 50 mg to 200 mg. This may result mainly from
the increasing concentration of CrCl3 and glucose in
Et-DBUBS, which could increase the side reactions such as
polymerization and rehydration of products, and humin was
the main by-product.22
Possible reason for the high yield in Et-DBUBS
[BMIM]Cl/CrCl3 is a very efficient catalytic system with high
HMF yield.16,32 We believe that the reaction pathway of the
reaction in our reaction system is the same as that reported by
The reusability of the CrCl3·6H2O/Et-DBUBS system
Zhao and co-workers.16 In order to study the possible reason In this work, we also investigated the reusability of the
for the high yield in the Et-DBUBS/CrCl3 catalytic system, we Et-DBUBS/CrCl3 catalytic system. After the reaction, the
also carried out the reaction in [BMIM]Cl/CrCl3, and the product was extracted by diethyl ether, and the catalytic system
results obtained in this work were consistent with that was used directly for the next run after drying, as described in
reported by Zhao and co-workers.16 The yields of HMF in the the Experimental section. It can be seen from Fig. 5 that the
two catalytic systems under the same reaction conditions are Et-DBUBS/CrCl3 system could be reused at least five times
compared in Fig. 3. Three main factors affected the maximum without considerable reduction in reaction efficiency.
3938 | Green Chem., 2014, 16, 3935–3941
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
Table 3 Dehydration of different substrates in Et-DBUBS catalyzed by
a
CrCl3
Entry
Substrate
Time (h)
Temperature (°C)
Yieldb (%)
1
2
3
4
5
6
7
8
Fructose
Glucose
Inulin
2
2
2
4
2
4
2
2
110
110
110
110
110
110
110
110
91.3
83.4
77.9
87.5
68.3
74.8
1.4
Inulin
Cellobiose
Cellobiose
Starch
Cellulose
0.3
a Reaction conditions: 1 g Et-DBUBS, 0.1 g substrate, 10 mol% (based
on hexose unit) CrCl3. b HMF yield is determined by HPLC.
Fig. 4 Effect of mass of glucose on the HMF yield. Reaction conditions:
1 g Et-DBUBS, 10 mol% (based on glucose) CrCl3, reaction temperature
110 °C, reaction time 2 h.
(entries 1–4) and Et-DBUBS generated the best result with
83.4% HMF yield (entry 1), which was higher than the typical
results reported in the literature (entries 7–10, Table 1). From
Table 2, we can also know that the yield of HMF decreased
with increasing chain length on the nitrogen atom of DBU in
the ILs (entries 1 and 3). The low efficiency in Bn-DBUBS may
result from the steric hindrance due to the existence of the
benzyl group, which may affect the isomerization of glucose.
From entries 3 and 7, it can be seen that the ILs with BS anion
gave higher HMF yields than ILs with Cl anion. In addition,
Et-DBUBS could give a higher HMF yield than [EMIM]Br and
[EMIM]BF4 (entries 5 and 6).
Dehydration of different substrates
Based on the results obtained from the dehydration of
glucose, transformation of other carbohydrates into HMF was
also studied in the Et-DBUBS/CrCl3 system under suitable con-
ditions and the results are shown in Table 3. As expected, fruc-
tose gave the best result with a HMF yield of 91.3% (entry 1) in
our catalytic system. Except for fructose, inulin and cellobiose
also gained a good HMF yield of 87.5% and 74.8%, respectively
(entries 4 and 6).
Fig. 5 Reusability of Et-DBUBS/CrCl3 system. Reaction conditions: 1 g
Et-DBUBS, 0.1 g glucose, 10 mol% (based on glucose) CrCl3, reaction
temperature 110 °C, reaction time 2 h.
Table 2 Effect of different solvents for the conversion of glucose to
HMFa
Time
(h)
Temperature
(°C)
Yieldb
(%)
Selectivity
(%)
Entry
Solvent
1
2
3
4
5
6
7c
Et-DBUBS
Al-DBUBS
Bu-DBUBS
Bn-DBUBS
[EMIM]Br
[EMIM]BF4
Bu-DBUCl
2
2
2
2
2
2
3
110
110
110
110
110
110
100
83.4
78.5
70.1
72.4
52.3
1.3
83.7
80.4
74.0
72.6
52.4
1.3
Conclusion
Several DBU-based new ILs, Et-DBUBS, Al-DBUBS, Bu-DBUBS
and Bn-DBUBS, have been synthesized, and used as solvents in
the synthesis of HMF from the dehydration of glucose cata-
lyzed by CrCl3. In the Et-DBUBS/CrCl3 catalytic system, the
HMF yield can be as high as 83.4%. One of the main reasons
for the very high yield of the product is that the rate of gene-
ration of by-products directly from glucose in Et-DBUBS/CrCl3
was slow. The Et-DBUBS/CrCl3 catalytic system can be reused
at least five times without considerable reduction in HMF
yield. In addition, satisfactory results were also obtained when
fructose, inulin and cellobiose were used as the feedstocks to
produce HMF. The efficient, simple, cheaper and reusable
catalytic system has great potential for application to produce
HMF from the dehydration of carbohydrates.
64.0
—
a Reaction conditions: 1 g solvent, 0.1 g glucose, 10 mol% (based on
glucose) CrCl3. b HMF yields were determined by HPLC. c The data
were obtained from ref. 30.
Effect of various DBU-based ILs with BS anion
Table 2 shows the results of the synthesis of HMF from
glucose catalyzed by CrCl3 in various new ILs prepared (shown
in Scheme 1) as reaction solvents. The four ILs were all
effective solvents for the production of HMF from glucose
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3935–3941 | 3939

View Article Online
Paper
Green Chemistry
6 J. B. Binder and R. T. Raones, J. Am. Chem. Soc., 2009, 131,
1979–1985.
Acknowledgements
The authors thank the National Natural Science Foundation of
China. This work was supported by National Natural Science
Foundation of China (21173234, 21133009, U1232203,
21021003), and Chinese Academy of Sciences (KJCX2.YW.H30).
7 F. Yang, Q. Liu, M. Yue, X. Bai and Y. Du, Chem. Commun.,
2011, 47, 4469–4471.
8 T. Ståhlberg, S. Rodriguez-Rodriguez, P. Fristrup and
A. Riisager, Chem. – Eur. J., 2011, 17, 1456–1464.
9 Y. Qu, C. Huang, Y. Song, J. Zhang and B. Chen, Bioresour.
Technol., 2012, 121, 462–466.
10 V. Heguaburu, J. Franco, L. Reina, C. Tabarez, G. Moyna
and P. Moyna, Catal. Commun., 2012, 27, 88–91.
Notes and references
1 (a) G. W. Huber, S. Iborra and A. Corma, Chem. Rev., 2006, 11 (a) I. Jiménez-Morales, J. Santamaría-González, A. Jiménez-
106, 4044–4098; (b) Y. Roman-Leshkov, C. J. Barrett,
Z. Y. Liu and J. A. Dumesic, Nature, 2007, 447, 982–985;
(c) A. Corma, S. Iborra and A. Velty, Chem. Rev., 2007, 107,
2411–2502; (d) H. de Lasa, E. Salaices, J. Mazumder and
R. Lucky, Chem. Rev., 2011, 111, 5404–5433;
López and P. Maireles-Torres, Fuel, 2014, 118, 265–271;
(b) M. Moliner, Y. Román-Leshkov and M. E. Davis,
Proc. Natl. Acad. Sci. U. S. A., 2010, 107, 6164–6168;
(c) J. S. Kruger, V. Nikolakis and D. G. Vlachos, Appl. Catal.,
A, 2014, 469, 116–123.
(e) V. V. Ordomsky, V. L. Sushkevich, J. C. Schouten, 12 J. He, Y. Zhang and E. Y.-X. Chen, ChemSusChem, 2013, 6,
J. van der Schaaf and T. A. Nijhuis, J. Catal., 2013, 300,
37–46.
2 (a) F. W. Lichtenthaler, Acc. Chem. Res., 2002, 35, 728–737;
61–64.
13 J. J. Wang, J. W. Ren, X. H. Liu, J. X. Xi, Q. N. Xia, Y. H. Zu,
G. Z. Lu and Y. Q. Wang, Green Chem., 2012, 14, 2506–2512.
(b) D. M. Alonso, S. G. Wettstein and J. A. Dumesic, Chem. 14 A. Osatiashtiani, A. F. Lee, D. R. Brown, J. A. Melero,
Soc. Rev., 2012, 41, 8075–8098; (c) C. O. Tuck, E. Pérez,
I. T. Horváth, R. A. Sheldon and M. Poliakoff, Science, 2012,
G. Morales and K. Wilson, Catal. Sci. Technol., 2014, 4, 333–
342.
337, 695–699; (d) L. Bui, H. Luo, W. R. Gunther and 15 I. Jiménez-Morales, A. Teckchandani-Ortiz, J. Santamaría-
Y. Román-Leshkov, Angew. Chem., Int. Ed., 2013, 52, 8022–
8025; (e) M. Y. He, Y. H. Sun and B. X. Han, Angew. Chem.,
González, P. Maireles-Torres and A. Jiménez-López, Appl.
Catal., B, 2014, 144, 22–28.
Int. Ed., 2013, 52, 9620–9633; (f) J. L. Song, H. L. Fan, J. Ma 16 H. Zhao, J. E. Holladay, H. Brown and Z. C. Zhang, Science,
and B. X. Han, Green Chem., 2013, 15, 2619–2635; 2007, 316, 1597–1600.
(g) T. Wang, M. W. Nolte and B. H. Shanks, Green Chem., 17 S. Q. Hu, Z. F. Zhang, J. L. Song, Y. X. Zhou and B. X. Han,
2014, 16, 548–572. Green Chem., 2009, 11, 1746–1749.
3 (a) M. Bicker, S. Endres, L. Ott and H. Vogel, J. Mol. Catal. 18 Z. Zhang, Q. Wang, H. Xie, W. Liu and Z. K. Zhao, Chem-
A: Chem., 2005, 239, 151–157; (b) J. N. Chheda, G. W. Huber SusChem, 2011, 4, 131–138.
and J. A. Dumesic, Angew. Chem., Int. Ed., 2007, 46, 7164– 19 T. Ståhlberg, M. G. Sørensen and A. Riisager, Green Chem.,
7183; (c) M. E. Zakrzewska, E. Bogel-Łukasik and R. Bogel- 2010, 12, 321–325.
Łukasik, Chem. Rev., 2011, 111, 397–417; (d) S. Subbiah, 20 L. Hu, Y. Sun, L. Lin and S. J. Liu, Biomass Bioenergy, 2012,
S. P. Simeonov, J. M. S. S. Esperança, L. P. N. Rebelo and
C. A. M. Afonso, Green Chem., 2013, 15, 2849–2853.
4 (a) H. Rasmussen, H. R. Sørensen and A. S. Meyer, Carbo-
47, 289–294.
21 X. Zhou, Z. Zhang, B. Liu, Z. Xu and K. Deng, Carbohydr.
Res., 2013, 375, 68–72.
hydr. Res., 2014, 385, 45–57; (b) Y. Román-Leshkov, 22 Y. Yang, C. W. Hu and M. M. Abu-Omar, J. Mol. Catal. A:
M. Moliner, J. A. Labinger and M. E. Davis, Angew. Chem., Chem., 2013, 376, 98–102.
Int. Ed., 2010, 49, 8954–8957; (c) H. Ning, J. L. Song, 23 D. Liu and E. Y.-X. Chen, Appl. Catal., A, 2012, 435–436, 78–85.
M. Q. Hou, D. Z. Yang, H. L. Fan and B. X. Han, Sci. China: 24 J. J. Wang, W. Xu, J. Ren, X. Liu, G. Lu and Y. Wang, Green
Chem., 2013, 56, 1578–1585; (d) R. J. van Putten, J. C. van
Chem., 2011, 13, 2678–2681.
der Waal, E. de Jong, C. B. Rasrendra, H. J. Heeres and 25 (a) T. Deng, X. Cui, Y. Qi, Y. Wang, X. Hou and Y. Zhu,
J. G. de Vries, Chem. Rev., 2013, 113, 1499–1597.
5 (a) C. Moreau, A. Finiels and L. Vanoye, J. Mol. Catal. A:
Chem. Commun., 2012, 48, 5494–5496; (b) S. De, S. Dutta
and B. Saha, Green Chem., 2011, 13, 2859–2868.
Chem., 2006, 253, 165–169; (b) T. S. Hansen, J. Mielby and 26 (a) Y. Román-Leshkov, J. N. Chheda and J. A. Dumesic,
A. Riisager, Green Chem., 2011, 13, 109–114; (c) A. J. Crisci,
M. H. Tucker, M. Y. Lee, S. G. Jang, J. A. Dumesic and
S. L. Scott, ACS Catal., 2011, 1, 719–728; (d) H. Xie,
Z. K. Zhao and Q. Wang, ChemSusChem, 2012, 5, 901–905;
Science, 2006, 312, 1933–1937; (b) Z. Zhang, B. Du,
L. J. Zhang, Y. X. Da, Z. J. Quan, L. J. Yang and X. C. Wang,
RSC Adv., 2013, 3, 9201–9205; (c) B. Saha and
M. M. Abu-Omar, Green Chem., 2014, 16, 24–38.
(e) X. Qi, H. Guo, L. Li and R. L. Smith, ChemSusChem, 27 (a) W. Liu and J. Holladay, Catal. Today, 2013, 200, 106–
2012, 5, 2215–2220; (f) J. L. Song, B. B. Zhang, J. H. Shi,
J. Ma, G. Y. Yang and B. X. Han, Chin. J. Chem., 2012, 30,
116; (b) J. Shi, H. Gao, Y. Xia, W. Li, H. Wang and C. Zheng,
RSC Adv., 2013, 3, 7782–7790.
2079–2084; (g) R. Liu, J. Chen, X. Huang, L. Chen, L. Ma 28 J. P. Hallett and T. Welton, Chem. Rev., 2011, 111, 3508–
and X. Li, Green Chem., 2013, 15, 2895–2903.
3576.
3940 | Green Chem., 2014, 16, 3935–3941
This journal is © The Royal Society of Chemistry 2014

View Article Online
Green Chemistry
Paper
29 B. Saha, S. De and M. Fan, Fuel, 2013, 111, 598–605.
31 H. Li, Q. Zhang, X. Liu, F. Chang, Y. Zhang, W. Xue and
30 J. L. Song, B. B. Zhang, J. H. Shi, H. L. Fan, J. Ma,
S. Yang, Bioresour. Technol., 2013, 144, 21–27.
Y. Y. Yang and B. X. Han, RSC Adv., 2013, 3, 20085– 32 G. Yong, Y. Zhang and J. Y. Ying, Angew. Chem., Int. Ed.,
20090.
2008, 47, 9345–9348.
This journal is © The Royal Society of Chemistry 2014
Green Chem., 2014, 16, 3935–3941 | 3941