5-Hydroxymethylfurfural and levulinic acid derived from monosaccharides dehydration promoted by InCl3 in aqueous medium

Article abstract of DOI:10.1016/j.molcata.2014.07.007

Indium trichloride (InCl₃) was used as catalyst for the conversion of monosaccharides into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) in aqueous medium. 5-HMF yield of 60% (10 min) and LA yield of 57% (60 min) were achieved from glucose at 180 °C with 2.5 mol% of InCl ₃, and 5-HMF yield of 79% (15 min) and LA yield of 45% (60 min) were obtained from fructose under the same conditions. Moreover, the isomerization process between glucose and fructose was investigated through the comparative studies of glucose/fructose mixture with different ratios as substrates. It was found that InCl₃ could not only catalyze the isomerization of glucose to fructose as well as the reverse direction, but also have the positive effects on the dehydration and conversion of monosaccharides. Based on this, a catalytic mechanism of dehydration of glucose and fructose promoted by InCl ₃ was proposed.

Full text of DOI:10.1016/j.molcata.2014.07.007

Accepted Manuscript
Title: 5-Hydroxymethylfurfural and levulinic acid derived
from monosaccharides dehydration promoted by InCl in
3
aqueous medium
Author: Yue Shen Jiankui Sun Yuxuan Yi Bo Wang Feng Xu
Runcang Sun
PII:
S1381-1169(14)00299-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2014.07.007
MOLCAA 9189
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
31-3-2014
23-6-2014
3-7-2014
Please cite this article as: Y. Shen, J. Sun, Y. Yi, B. Wang, F. Xu, R. Sun, 5-
Hydroxymethylfurfural and levulinic acid derived from monosaccharides dehydration
promoted by InCl in aqueous medium, Journal of Molecular Catalysis A: Chemical
3
(2014), http://dx.doi.org/10.1016/j.molcata.2014.07.007
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5-Hydroxymethylfurfural and levulinic acid derived from
monosaccharides dehydration promoted by InCl in aqueous medium
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a
a
a
a,
a
a,b,
Yue Shen, Jiankui Sun, Yuxuan Yi, Bo Wang, * Feng Xu, Runcang Sun *
a
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Beijing Key Laboratory of Lignocellulosic Chemistry, College of Materials Science
and Technology, Beijing Forestry University, Beijing 100083, PR China
b
State Key Laboratory of Pulp and Paper Engineering, South China University of
Technology, Guangzhou 510640, PR China
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*Corresponding author. Tel.: +86 10 62336592; fax: +86 10 62336903.
E-mail address: mzlwb@bjfu.edu.cn (B. Wang) and rcsun3@bjfu.edu.cn (R.C. Sun).
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Abstract: Indium trichloride (InCl ) was used as catalyst for the conversion of
monosaccharides into 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) in
aqueous medium. 5-HMF yield of 60% (10 min) and LA yield of 57% (60 min) were
o
achieved from glucose at 180 C with 2.5 mol % of InCl , and 5-HMF yield of 79% (15
3
min) and LA yield of 45% (60 min) were obtained from fructose under the same
conditions. Moreover, the isomerization process between glucose and fructose was
investigated through the comparative studies of glucose/fructose mixture with different
ratios as substrates. It was found that InCl could not only catalyze the isomerization of
3
glucose to fructose as well as the reverse direction, but also have the positive effects on
the dehydration and conversion of monosaccharides. Based on this, a catalytic
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mechanism of dehydration of glucose and fructose promoted by InCl was proposed.
Keywords: 5-Hydroxymethylfurfural, Levulinic acid, Monosaccharides, Dehydration,
Isomerization, InCl3.
1. Introduction
The impending exhaustion of petroleum reserves and deterioration of the global
climate have spurred research into utilizing biomass, which is the sustainable carbon
resource and widely distributed in nature, as an ideal clean substitute for the industrial
production of fuels and useful chemicals [1-3]. In the utilization of biomass for
chemicals, the manufacture of 5-hydroxymethylfurfural (5-HMF) and levulinic acid
(LA) through the carbohydrate dehydration is an important process [4,5]. As one of the
top-twelve biomass-derived compounds and a versatile intermediate, 5-HMF is very
useful not only for the production of the furan derivatives, which are potentially useful
for fine chemicals, promising liquid transportation fuel, and numerous polymers, but
also for important molecules such as 5-hydroxy-4-keto-2-pentenoic acid and LA [6-8].
Particularly, LA/esters from the decomposition of 5-HMF can be used as platform
chemicals to produce a variety of important products, e.g., acrylate polymers and fuel
additives [9]. Up until now, different feedstocks have been used to produce 5-HMF [10].
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Examples
include
monosaccharides,
disaccharides,
or
more
complex,
high-molecular-weight polysaccharides or raw lignocellulosic biomass [11,12]. Current
methods presented in literatures are focused on monosaccharides, which allow the
investigation and understanding of process mechanisms easily. Additionally, The
dehydration of monosaccharides to 5-HMF is a convenient and efficient method in the
preparation of 5-HMF from biomass.
In recent years, some synthesis and chemistry even kinetic studies of 5-HMF have
been reviewed [13,14]. High yields of 5-HMF have been reported using a variety of
catalysts in the dehydration of monosaccharides. Traditional acid catalysts, such as
mineral acids [15], solid acids [16], heteropolyacids [17], and strong acid ion-exchange
resins [18], etc. have been tested. Furthermore, metal salts including lanthanide
chlorides [19], chromium chlorides [20], and zinc chlorides [21] have also received
considerable attentions. Zhao et al. have studied the effect of a large number of metal
chlorides on the conversion of glucose, in which chromium (II) chloride was found to
be uniquely effective, and gained a yield of 5-HMF as high as 70% [22]. In addition, Hu
et al. [23] found the common Lewis acid SnCl could efficiently convert glucose and
4
fructose into 5-HMF followed by a combined catalyst system SnCl -TBAB developed
4
by Tian et al. [24], in which a remarkable catalytic effect in the production of 5-HMF
from selective conversion of glucose was obtained. Later, Zhang et al. reported the
dehydration of fructose and a yield of 5-HMF arrived at 92% using GeCl as catalyst in
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[BMIM]Cl [25]. Considering the findings in the above context, there is still a
considerable incentive for the development of effective alternative Lewis acid catalysts
[26]. Meanwhile, an ongoing objective in the development of synthesis and chemistry
of 5-HMF is exploiting the low-toxicity, cheap, and easily handled catalytic system. In
the past, InCl has emerged as an easy-handling and eco-friendly Lewis acid catalyst
3
that imparts high regio-selectivity and chemo-selectivity in various chemical
transformation, due to its air and water compatibility, operational simplicity, and
remarkable ability to suppress side reactions in acid-sensitive substrates [27-29]. Li et al.
found that InCl -ionic liquid catalytic system was effective for the conversion of
3
cellulose to 5-HMF [30]. However, the expensive ionic liquid restricted its extensive
application. This poses the challenges to investigate the catalytic activity of InCl for
3
the conversion of biomass in aqueous medium.
In this work, the reaction conditions of glucose were systematically screened by
altering the reaction temperature, catalyst dosage, and reaction time. The aim was to
seek a suitable reaction temperature and catalyst dosage for the dehydration of
monosaccharides to 5-HMF in majority. The dehydrations of fructose and the mixture of
glucose/fructose with different ratios were also investigated under the optimized
conditions. Meanwhile, the catalytic mechanism of InCl for the conversion of
3
monosaccharides was proposed on the basis of the experimental data.
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2. Experimental
2.1 Materials
Glucose, fructose, InCl ·4H O, tetrahydrofuran (THF), and NaCl were purchased
3
2
from Beijing Chemicals Co. Ltd. (Being, China). 5-HMF (AR, 99%) and LA (AR, 98%)
were obtained from Acros Organics. All the chemicals were of analytical grade and used
as received.
2.2 General procedure for the reaction
All the reaction experiments were carried out in 40 mL water. A typical procedure
for the dehydration of monosaccharides was as follows: glucose (1.0 g, 5.6 mmol) and
InCl (30 mg, 0.14 mmol) in 20 mL water were charged into the reactor (50 mL). The
3
o
reactor was sealed and stirred at 180 C. The reaction time began to be calculated when
the reaction system reached the certain temperature. After the reaction, the reactor was
taken from the stove and quenched in an ice cool water bath. The liquid samples were
collected, filtered, and diluted to 20 mL for analysis. The solid products were collected
and dried in a vacuum oven overnight to constant weight for analysis. THF was used as
100 an extracting medium with an organic-to-aqueous volume ratio of 3:1 when biphasic
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01 systems were studied. The aqueous phase can be recycled and the catalyst InCl can be
02 reused.
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04 2.3 Analytical methods
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06
The amount of products in the liquid samples were quantitatively analyzed by
07 high-performance liquid chromatography (HPLC; Agilent 1200, USA) with a Bio-Rad
08 Aminex HPX-87H analytical column and a refractive index detector. The eluent was 5
-
1
09 mM sulfuric acid solution with a volumetric flow rate of 0.5 mL min . Column
o
o
10 temperature was set at 50 C. The temperature of RI detector was 40 C and injection
11 volume was 10 μL. The amount of each compound was determined using calibration
12 curves obtained by external standard method based on the equation. 5-HMF: y =
13 64285x + 485, levulinic acid: y = 51635x + 2089. In addition, the amount of products
14 was also analyzed by HPLC fitted with a Lichrospher C18 column and an ultraviolet
o
15 detector at 284 nm. The column oven temperature was set at 25 C, and mobile phase
-
1
16 was methanol/water = 35:65 (v/v) at a flow rate of 0.8 mL min . The elemental
17 composition of the solid products was determined using a Vario EL Elemental Analyzer
18 (Elementar, Germany). The structure of the solid products was analyzed using a
19 scanning electron microscope (SEM) with a Hitachi S-3400N ΙΙ (Hitachi, Japan)
20 instrument at an accelerate voltage of 5 KV.
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The conversion of monosaccharides such as glucose and the yields of products were
22 evaluated on a carbon basis respectively as shown below:
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24
25 C=(1-Moles of glucose / Moles of starting amount of glucose) × 100%
26 Products yields (mol%):
Glucose conversion (mol%):
127 Y=(Moles of 5-HMF or levulinic acid / Moles of starting amount of glucose) × 100%
128
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29 3. Results and Discussion
30
31 3.1. Catalytic behaviors of InCl
3
for the conversion of glucose
32
33
To obtain the optimum conditions for glucose dehydration, variables for the
34 dehydration process, such as reaction temperature, reaction time, and catalyst dosage,
35 were studied in the reactors with InCl as catalyst. Initially, experiments were carried
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o
o
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36 out at 60 C, 90 C, 120 C, 150 C, 180 C, and 210 C, respectively (Fig. 1). When the
o
37 temperature was below 120 C, traces of 5-HMF and LA were detected. Higher reaction
o
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38 temperatures clearly produced higher 5-HMF and LA yields (from 150 C to 210 C),
39 which indicated that temperature has a positive effect on the dehydration of glucose.
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140
141 Fig. 1. Effect of temperature on the dehydration of glucose in aqueous medium
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1
1
1
1
1
42 catalyzed by InCl
43 (20 mL) for 2 min.
44 Fig. 2 shows the effect of reaction temperature and time on glucose dehydration. As
3 3
. Conditions: glucose (1.0 g) using InCl (30 mg, 2.5 mol%) in water
45 the figures show, the reaction temperature and time had large effects on both the glucose
46 dehydration and product selectivity. It was observed that glucose conversion increased
o
o
o
47 rapidly as the reaction time extending from 2 to 60 min at 150 C, 180 C, and 210 C
48 respectively, and then remained relatively stable (Fig. 2a). Nearly 100% of glucose
o
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49 conversion was achieved at 210 C for 2 min reaction time, 53% at 180 C, and 44% at
o
50 150 C over the same period when 2.5 mol % InCl was introduced. As for the products,
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o
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51 the yields of 5-HMF increased at 150 C and 180 C when the reaction time was less
52 than 10 min, then it started to decrease with the reaction time prolonged (Fig. 2b). In
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53 contrast, the LA yields increased (Fig. 2c) along with reaction time lasting at 150 C and
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54 180 C. These findings were in accordance with the rehydration of 5-HMF in the
55 dehydration of glucose which was catalyzed by InCl ; glucose was converted to 5-HMF
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56 as the main initial product and the produced 5-HMF was further converted to LA
o
57 (Scheme 1). The low temperature of 180 C led to a 5-HMF yield of 60% (10 min)
o
58 accompanied by 57% of LA yield (60 min). While at the higher temperature of 210 C,
59 as the reaction time was prolonged, the yields of both 5-HMF and LA decreased, though
60 the yield of LA had a slight increase at the beginning stage. These results show that the
o
61 optimal temperature is 180 C in the catalytic conversion of glucose to 5-HMF and LA.
162
163
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164
165 Fig. 2. Effect of temperature and reaction time on the dehydration of glucose in aqueous
1
66 medium catalyzed by InCl
67 in water (20 mL).
3 3
. Conditions: glucose (1.0 g) using InCl (30 mg, 2.5 mol%)
1
168
1
69 Scheme 1. Formation of 5-HMF and LA from glucose and fructose.
70 The dosage of InCl is also an important parameter that determines the 5-HMF and
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1
1
3
71 LA yields. Fig. 3 shows how varying the amount InCl (0.83 mol%, 2.5 mol%, and 4.2
3
72 mol%) affects the dehydration of glucose. As shown in Fig. 3a, the conversion of
73 glucose could reach a constant level in a shorter period of time with the increase of
1
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74 InCl dosage. The 5-HMF yield of 27% was obtained at a reaction time of 10 min using
75 0.83 mol% InCl , and it increased to 60% and 80% during the same reaction time when
3
76 using 2.5 mol% and 4.2 mol% InCl , respectively (Fig. 3b). This significant increase
3
77 can be attributed to the increase in the availability of the catalyst active sites.
78 Subsequently, they showed a smoothly decreased in the 5-HMF yield after the sharp
79 increase in initial stage along with reaction time going on. Correspondingly, the yield of
80 LA increased rapidly no matter how many catalysts were used (Fig. 3c) in accordance
81 with Fig.3b and Scheme 1, which indicated that the rehydration of 5-HMF was more
82 rapid than its generation. It should be noted that the LA yield was not the best among
83 the three catalyst amounts when 4.2 mol% of InCl was added. In contrast, 2.5 mol%
3
84 InCl could achieve better result during the same reaction time, which implied that the
3
85 conversion of glucose to byproducts was probably more rapid than the generation of
86 5-HMF. These data show that the optimal InCl dosage is 2.5 mol% in the catalytic
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87 process for the dehydration of glucose to 5-HMF and LA in consideration of the
88 expenses of the experiment.
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189
190
191
192 Fig. 3. Effect of catalyst dosage and reaction time on the dehydration of glucose in
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193 aqueous medium catalyzed by InCl . Conditions: glucose (1.0 g) in water (20 mL) at
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94 180 C.
95
In addition, insoluble humins were found in all the dehydration of glucose.
96 Moreover, the soluble polymers, the precursors of insoluble humins, were also formed,
97 which could be quantitatively analyzed by HPLC to understand when and how the
98 polymerization started [31]. Patil et al. [32,33] found that an intermediate was produced
99 from 5-HMF, and aldol addition or condensation of 2, 5-dioxo-6-hydroxyhexanal, was
00 primarily responsible for the growth of humins, which gave an infrared spectroscopic
01 study of the adsorption of carbonyl group. Additionally, the presence of humins was
02 confirmed by elemental analysis on the solid residue after the reaction. It was shown
03 that the residues were a mixture consisting mainly of humins (typical composition: C,
04 62.1; H, 4.2). This was similar to the results of previous reports [34]. Meanwhile,
05 further evidence for the formation of humins was obtained by SEM. The typical SEM
06 images of glucose applied in this study and the humins obtained are given
07 comparatively (Fig. 4). On the basis of their visual appearance, higher temperature and
08 over-using of catalysts promoted the tendency of formation of carbon fiber.
209
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(a)
(b)
11 Fig. 4. SEM images of glucose particles (a) and the humins (b) obtained after the
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12 reaction (180 C, 4.2 mol%, 20 min).
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14 3.2. Catalytic behaviors of InCl
3
for the conversion of fructose
15
16
Given that InCl rendered the solution fairly acidic, catalyzed the glucose
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17 isomerization, and formed fructose as the primary product [22, 35, 36], the fructose
18 dehydration reaction was used to provide insight into the glucose-to-fructose
19 isomerization under our reaction conditions. The results from starting with fructose as a
20 reactant using InCl as a catalyst for the dehydration are shown in Table 1. Fructose not
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21 only isomerized to glucose but also dehydrated to 5-HMF in a parallel path (Scheme 1).
22 In comparison to glucose (Fig. 2), the dehydration of fructose to 5-HMF and LA are
23 faster than that of glucose. The maximum 5-HMF yield derived from fructose was
24 higher (80%) than that from glucose (60%) (Table 1, entry 4). These differences in the
25 5-HMF yields originated from their distinct structures (Scheme 1). It should be noted
26 that the dehydration of fructose produced much less soluble polymers than that of
27 glucose, which also resulted in the higher yields of 5-HMF from fructose. This can be
28 explained by the following the proposed mechanism for glucose (aldose) to fructose
29 (ketose) isomerization.
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30
To further maximize the yield of 5-HMF from fructose, a biphasic system was used
31 to extract 5-HMF continuously from the aqueous media. Román -Leshkov et al. [37]
32 found that addition of NaCl in the aqueous phase not only improved the partition
33 coefficient of 5-HMF between the organic and aqueous phases, but also inhibited the
34 generated 5-HMF from further rehydration to LA. In this study, THF and 25 wt.% of
35 NaCl were added to form the biphasic system in the fructose dehydration. It can be seen
36 that a high 5-HMF yield of ~88% along with a ~3% yield of LA from fructose have
o
37 been achieved in 60 min at 180 C in the biphasic system (Table 1, entry 8). Moreover,
38 the recycle of the aqueous phase and reusage of the catalyst InCl could be achieved
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39 through the modifiable biphasic system. To our delight, the catalyst could be reused at
o
40 least for three times at 180 C for 60 min just with nearly no activity lose. These results
41 show that InCl can be used directly for the conversion of monosaccharides to 5-HMF
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42 without coupling with other acid catalysts.
43 Table 1
a
44 Conversion of fructose into 5-HMF and LA .
Entry T(min) Yield of glucose (%) Conv. (%) Yield of 5-HMF (%) Yield of LA (%)
b
1
2
3
4
2
1.7
2.0
3.2
4.1
74.8
97.6
100
100
67.7
72.2
76.5
79.8
13.0
16.5
17.2
20.9
5
10
15
1
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5
6
7
8
20
30
60
60
4.5
5.2
4
100
100
100
100
72.3
60.1
54.8
87.8
24.6
35.3
41.2
c
3.7
2.9
a
b
c
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2
2
2
2
2
2
2
2
2
2
2
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45
Reaction conditions:1.0 g fructose and 30 mg InCl
3
in 20 mL of water at 180 C.
46
47
The results were obtained by HPLC analysis.
THF was used as the organic solvent with the organic-to-aqueous phase volume ratio
48 of 3:1, and 25 wt.% of NaCl in the aqueous media.
49
50 3.3. Dehydration mechanism of glucose and fructose catalyzed by InCl
3
51
52
As above mentioned InCl showed high activity for not only the isomerization of
3
53 glucose to fructose but also the dehydration of fructose to 5-HMF and LA. For further
54 exploring the practicality and verifying the conclusion, a cascade of comparative studies
55 for 5-HMF synthesis using glucose, fructose, and their mixture as substrates were
56 investigated (Table 2). It was found that the isomerization from glucose to fructose was
57 easier than the reversible process under the same conditions (Table 2, entries 1 and 3,
58 entries 2 and 4). That is to say, k ＞ k in Scheme 1. At the same time, the conversion
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59 of fructose was better than that of glucose, and higher 5-HMF yields and lower LA
60 yields were also obtained under the same condition. Paine et al. [38] has proposed a
1
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61 common mechanism for this complex process during the dehydration of glucose using
1
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62
C labeled glucose. He explained the production of 5-HMF as secondary products in
63 this reaction, which was also supported by the fact that fructose was indeed observed by
64 HPLC. Additionally, the dehydration of the mixture of glucose/fructose with different
65 ratios was also carried out (Table 2, entries 5 to 9). Of the results listed in Table 2, as the
66 fructose ratio in the mixed substrates was increased, more and more fructose was
67 detected. Due to the higher activity of fructose than glucose, which was confirmed by
68 the higher yields of 5-HMF and LA, the conversions of total sugars gradually decreased.
69 This was also on account of the growing ratio of fructose, which suppressed the shift of
70 isomerization equilibrium from glucose to fructose, leading to the high concentration of
71 glucose in the reaction mixture.
72 Table 2
a
73 Conversion of monosaccharides into 5-HMF and LA .
Entry Substrate
Ratio of
T
Glu
Fru
Conv.
(%)
Yield
5-HMF (%)
52.0
of Yield of
b
Glu to Fru (min)
(mg)
181.2
86.1
20.3
32.0
13.9
(mg)
45.4
60.4
24.4
0
LA (%)
1
Glucose
Glucose
Fructose
Fructose
1: 0
1: 0
0: 1
0: 1
5
81.9
91.4
97.6
100
21.5
27.0
16.0
17.0
37.8
2
3
4
5
10
5
59.8
72.0
10
10
76.0
c
c
Glu + Fru 2: 1
17.6
96.9
62.6
1
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7
8
9
Glu + Fru 3: 2
Glu + Fru 1: 1
Glu + Fru 2: 3
Glu + Fru 1: 2
10
10
10
10
16.8
23.0
31.5
43.0
17.2
36.1
36.6
43.0
97.6
94.1
93.2
91.4
63.3
66.1
69.4
71.8
40.2
43.0
43.3
43.5
a
b
c
o
2
74
75
76
77
Reaction conditions: 1.0 g mixture and 30 mg InCl
3
in 20 mL of water at 180 C.
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
The results were obtained by HPLC analysis.
The conversions (%) from entries 5 to 9 were evaluated on a glucose basis.
Based on the well-established mechanism of the dehydration of monosaccharides
78 [35], a plausible reaction mechanism of the formation of 5-HMF and LA catalyzed by
79 InCl is proposed as Scheme 2. When InCl interacted with glucose at room temperature,
3
3
80 chloride atoms interacted with the hydrogen atoms combined with the intermediate a
o
81 formed. Then, the mixture was heated to 180 C for reaction. Heating would enhance
82 the interaction between the indium atom and oxygen atoms to convert a into b. Only
83 one indium atom remained coordination to the oxygen atoms of the closed-chain
84 glucose molecule. This is an important step in ring-opening and subsequent glucose
85 (aldose)-to-fructose (ketose) isomerization. The intermediate b could induce the
86 formation of the complex c, which consisted of glucose in straight-chain form, and was
87 further converted into enediol intermediate d. As described above, the formation of this
88 stable five-membered-ring chelate structure of indium atom with the two neighboring
89 hydroxyl groups in glucose played an important role in the catalytic reaction. The latter
1
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290 intermediate d was further transformed into fructose which could be dehydrated to form
291 5-HMF quickly. Finally, three water molecules were lost and 5-HMF was produced,
292 which was comparatively easy owing to the appearance of the conjugated double bond.
293
294 Scheme 2. Possible mechanism of Lewis acid-mediated intra-molecular hydride shift in
2
2
2
95 glucose and fructose isomerization and subsequent fructose dehydration to 5-HMF.
96
97 4. Conclusion
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98
99
An efficient catalytic synthesis of 5-HMF and LA from monosaccharides has been
00 successfully established in aqueous medium promoted by InCl
3
. 60% 5-HMF yield (10
o
01 min) and 57% LA yield (60 min) were obtained from glucose at 180 C with 2.5 mol%
02 InCl , while 79% 5-HMF yield (15 min) and 45% LA yield (60 min) were obtained
3
03 from fructose under the optimized conditions. It showed that fructose has the faster
04 conversion to 5-HMF, and the relatively more LA was obtained using glucose as
05 substrate under the same condition. The comparative studies of glucose/fructose mixture
06 manifested that the isomerization from glucose to fructose was easier than the reversible
07 process. As the fructose ratio in the mixed substrates was increased, the conversions of
08 total sugars gradually decreased, but the higher yields of 5-HMF and LA were obtained.
09 Moreover, a catalytic mechanism of monosaccharides dehydration was proposed. The
10 system can be efficiently reused for three times.
11
12 Acknowledgements
13
14
This work was financially supported by the New Century Excellent Talents in
15 University (NCET-13-0671), National Natural Science Foundation of China (31170556),
16 Beijing Higher Education Young Elite Teacher Project (YETP0765), Fundamental
17 Research Funds for the Central Universities (TD2011-11), National Science and
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0
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18 Technology Program of the Twelfth Five-Year Plan Period (2012BAD32B06), the State
19 Forestry Administration (201204803), and Major State Basic Research Development
20 Program of China (973 Program, No. 2010CB732204).
21
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83 Highlights:
84
85 InCl presented a remarkable catalytic effect on the dehydration of monosaccharides
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86 into 5-HMF and LA.
87 Fructose has the faster conversion to 5-HMF, and relatively more LA was obtained
88 using glucose.
89 The isomerization from glucose to fructose was easier than the reversible process.
390
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