Syntheses of 5-hydroxymethylfurfural through glucose dehydration in diphasic solvent system on ZrO2 and SO42-/TiO2-SiO2 catalyst

Article abstract of DOI:10.1080/15533174.2014.963237

Synthesis of 5-hydroxymethylfurfural (5-HMF) from glucose in water-dimethyl sulfoxide diphasic system using solid base ZrO₂ and SO₄^2-/TiO₂-SiO₂ catalysts was studied. The effects of calcining temperature, Ti/Si ratio in SO₄^2-/TiO₂-SiO₂, catalyst dosage, and mass ratio of ZrO₂ and SO₄^2-/TiO₂-SiO₂ mixture on 5-HMF yield were evaluated. Both the base and acid catalyst exhibited best performance when calcined at 450°C. The optimal Ti/Si ratio was found to be 4:1. ZrO₂ and SO₄^2-/TiO₂-SiO₂ mixture worked much better than ZrO₂ or SO₄^2-/TiO₂-SiO₂ alone. The optimal catalyst dosage was found to be 20% of the glucose amount (w). Instrumental characterization of the catalysts indicate that mild base and acid sites are suitable for conversion of glucose to 5-HMF, and the base and acid catalysts in the mixture do not interact chemically to a noticeable extend that influences the functionality. The water-organic diphasic system proved to be efficient in catalytic transformation of glucose to 5-HMF.

Full text of DOI:10.1080/15533174.2014.963237

Synthesis and Reactivity in Inorganic, Metal-Organic, and
Nano-Metal Chemistry
ISSN: 1553-3174 (Print) 1553-3182 (Online) Journal homepage: http://www.tandfonline.com/loi/lsrt20
Syntheses of 5-Hydroxymethylfurfural Through
Glucose Dehydration in Diphasic Solvent System
2
4
−
on ZrO and SO /TiO -SiO Catalyst
2
2
2
Yunpu Wang, Yuhuan Liu, Liu Yang, Roger Ruan, Pingwei Wen & Yiqin Wan
To cite this article: Yunpu Wang, Yuhuan Liu, Liu Yang, Roger Ruan, Pingwei Wen & Yiqin Wan
(
2016) Syntheses of 5-Hydroxymethylfurfural Through Glucose Dehydration in Diphasic Solvent
2−
4
System on ZrO and SO /TiO -SiO Catalyst, Synthesis and Reactivity in Inorganic, Metal-
2
2
2
Organic, and Nano-Metal Chemistry, 46:2, 177-184, DOI: 10.1080/15533174.2014.963237
To link to this article: http://dx.doi.org/10.1080/15533174.2014.963237
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Date: 12 October 2015, At: 23:25

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry (2016) 46, 177–184
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2014.963237
Syntheses of 5-Hydroxymethylfurfural Through Glucose
2
¡
Dehydration in Diphasic Solvent System on ZrO and SO /
2
4
TiO -SiO Catalyst
2
2
1
1,2
1
1,2
2
1
YUNPU WANG , YUHUAN LIU , LIU YANG , ROGER RUAN , PINGWEI WEN , and YIQIN WAN
1
Nanchang University, Engineering Research Center for Biomass Conversion, Ministry of Education, Nanchang, P. R. China
Nanchang University, State Key Laboratory of Food Science and Technology, Nanchang, P. R. China
2
Received 29 November 2013; accepted 23 August 2014
Synthesis of 5-hydroxymethylfurfural (5-HMF) from glucose in water-dimethyl sulfoxide diphasic system using solid base ZrO and
2
2
¡
2¡
SO4 /TiO -SiO catalysts was studied. The effects of calcining temperature, Ti/Si ratio in SO /TiO -SiO , catalyst dosage, and
mass ratio of ZrO and SO /TiO -SiO mixture on 5-HMF yield were evaluated. Both the base and acid catalyst exhibited best
performance when calcined at 450 C. The optimal Ti/Si ratio was found to be 4:1. ZrO and SO /TiO -SiO mixture worked
much better than ZrO or SO /TiO -SiO alone. The optimal catalyst dosage was found to be 20% of the glucose amount (w).
2
2
4
2
2
2
4
¡
2
2
2
ꢀ
2¡
2
4
2
2
2
¡
2
4
2
2
Instrumental characterization of the catalysts indicate that mild base and acid sites are suitable for conversion of glucose to 5-HMF,
and the base and acid catalysts in the mixture do not interact chemically to a noticeable extend that influences the functionality. The
water-organic diphasic system proved to be efficient in catalytic transformation of glucose to 5-HMF.
Keywords: solid base, solid acid, glucose, 5-HMF
Introduction
enediol is transformed to 3-deoxyhexose which is further
dehydrated to 5-HMF. During the reaction process, the reac-
With declining fossil reserves and growing concerns over tion is prone to aggregation that results in soluble polymer
global warming, conversion of biomass to value-added chem- and insoluble materials, such as humin, levulinic acid, formic
[
1]
icals is receiving intensive interests in recent years. Among acid, and other by-products, which can significantly affect
[
11]
biomass resources, saccharides and glucose are important the yield of 5-HMF. Therefore, we must select the appro-
[2,3]
economical and practical chemical feedstocks.
Catalytic priate reaction conditions to improve the efficiency of prepar-
transformation of hexoses into furans, which involves several ing 5-HMF from hexoses.
steps such as dehydration, hydrolysis, isomerization, reform-
Recently, many researchers attempted to develop low
ing, aldol condensation and so on, is an interesting cost, high selectivity, and environmentally friendly cata-
[
4,5]
[7]
approach.
The furanic chemicals include 5-hydroxyme- lysts for transforming saccharides to 5-HMF.
The
thylfurfural (5-HMF), 2, 5-diformylfuran, and 2,5-furandi- research results show that hundreds of inorganic and
[
12]
carboxylic acid (2,5-FDCA), among others. These chemicals organic matters can be used for preparation of 5-HMF.
can be used as starting materials of new value-added products Compared with homogeneous catalysts, heterogeneous cat-
[
6,7]
as well as replace oil-derived chemicals.
5-HMF as a dehy- alysts can be easily separated and when recycled possess
[
13]
dration product of hexoses is considered an important renew- better selectivity.
Solid acid catalysts have been widely
Take glucose as an example, the used, however, many by-products were generated during
possible reaction pathway of dehydration of hexose to 5- the process of 5-HMF preparation, which reduced the 5-
[8,9]
able platform chemical.
[
10]
[14]
[15]
HMF
is shown in Figure 1. First, glucose is changed to HMF yield and conversion rate.
Watanabe et al.
sug-
1
,2-enediol through isomerization, where enol structure is gested that solid acid TiO promoted the generation of 5-
2
considered to be the key to 5-HMF preparation. Second, 1,2- HMF while solid base ZrO2 promoted isomerization of
[
16]
glucose in hot compressed water at 473 K. Ohara et al.
studied the syntheses of 5-HMF and levoglucosan through
selective dehydration of glucose using solid acid Amberly-
Address correspondence to Yuhuan Liu, the Engineering
Research Center for Biomass Conversion, Ministry of Educa-
tion, Nanchang University, 235 Nanjing Road, Nanchang City,
Jiangxi Province, P. R. China. E-mail: liuyuhuan@ncu.edu.cn
Color versions of one or more of the figures in the article can be
found online at www.tandfonline.com/lsrt.
1
5 and solid base hydrotalcite. Their results showed that
solid base promoted isomerization of glucose while solid
acid promoted the generation of 5-HMF. As summarized
recently, combining solid acid and solid base can improve
5
-HMF yield.

1
78
Wang et al.
Fig. 1. The possible reaction pathway of glucose dehydration to 5-HMF.
Reactions for syntheses of 5-HMF can take place in water purchased from Sigma-Aldrich Co. DF-1 oil bath was pur-
[
17,18]
or organic solvent.
Water is a benign environmentally chased from JiangSu Huanyu Scientific Instrument Co. SX2-
friendly solvent, but it is not the best solvent for saccharides 25-10 muffle furnace was purchased from Shanghai Experi-
dehydration because of low yield and low selectivity of 5- mental Instrument Co.
[
19,20]
HMF.
Compared with water, organic dissolvent such as
dimethyl sulfoxide (DMSO), acetonitrile, and polyethylene
glycol can improve the selectivity of saccharides transforma- Catalysts Preparation
tion, and shorten reaction time and restrain humin generation
[
21]
Preparation of solid base catalyst ZrO . The 1 mol/L
2
because of their higher boiling points. Due to hexose’s low
solubility in organic solvents, the water-organic diphasic sys-
tem has been studied. Results showed that the diphasic sys-
ZrOCl¢8H O solution was prepared by dissolving
2
ZrOCl¢8H O in distilled water and its pH was adjusted to 9–
2
[
22–24] 10 by adding ammonia solution. The solution was allowed to
tem improved 5-HMF yield, especially in organic phase.
In this article, studies on syntheses of 5-HMF via dehydra-
tion of glucose in water-DMSO diphasic system on mixed
solid base catalyst ZrO and solid acid catalyst SO
SiO are discussed. DMSO with a high boiling point and
ꢀ
age at 30–40 C for 12 h, washed with distilled water to
¡
ꢀ
remove Cl (test with AgNO detection), and dried at 110 C
3
2
¡
for 3 h followed by grinding. The resultant powder was
2
4
/TiO2-
ꢀ
finally calcined at 400–600 C for 3 h.
2
high dissolubility in water was used in our studies because it
favors reaction selectivity and limits production of
Preparation of solid acid catalyst SO42 /TiO -SiO . The
¡
2
2
[
21,22]
1
mol/L Ti(SO ) and NaSiO solution was prepared by dis-
solving the salts in distilled water according to different
rations of V(Ti(SO ) ): V(Na SiO ), and its pH was adjusted
to 8~9 by adding ammonia solution to adjust the pH to,
allowed to age at 30–40 C for 12 h, washed with distilled
humans.
Low cost solid base ZrO2 and solid acid
2
4 2 3
2
¡
SO4 /TiO -SiO were selected due to their outstanding per-
2
formances on isomerization and dehydration of hexose,
4 2
2
3
[
15,25]
respectively.
The effects of catalyst dosage, ratio of n
ꢀ
(
Ti): n(Si), and catalyst calcining temperature on 5-HMF
2
¡
water to remove SO (test with BaCl detection), and dried
at 110 C for 3 h followed by grinding. The resultant powder
yield were investigated, and catalysts were characterized.
4
2
ꢀ
was, soaked in 1 M sulfuric acid for 12 h, and finally calcine
ꢀ
at 400–600 C for 3 h.
Experimental
Catalyst characterization. Solid base ZrO2 catalyst was
Materials and Reagents
characterized using XRD and CO -TPD-MS techniques.
2
Glucose, DMSO, sodium silicate, ammonia solution, m- XRD analysis was performed with Cu radiation with XRD
nitrotoluene, nitrobenzene, p-nitrochlorobenzene, and 2,4- DI SYSTEM (Bede Co., England). CO -TPD-MS analysis
2
2
¡
dinitrofluorobrnzene were purchased from Tianjin DaMao was used to determine alkalinity of ZrO . Solid acid SO
/
2
4
Chemical Co. Zirconium(IV) oxychloride octahydrate, tita- TiO -SiO catalyst was characterized using FT-IR (Nicolet
2
2
nium(IV) sulfate, and sulfuric acid were purchased from 5700) and Hammett indicator method. FT-IR spectra were
¡
1
Sinopharm Chemical Reagent Co. Ltd. 5-HMF was recorded over the range from 400–4000 cm
on FT-IR

Syntheses of 5-Hydroxymethylfurfural
179
Nicolet 5700 after catalyst was mixed with KBr powder and Table 1. Effects of ZrO dosage on 5-HMF yield
2
compressed into pellets.
5
-HMF yield (%)
Dosage of
Average §
Analysis of 5-HMF
ZrO (%)
1
2
3
SD (%)
2
The 5-HMF was measured using a UV spectroscope (Lab-
tech UV9100 ultraviolet spectrophotometer). Samples were
taken from the reactions using mini-pipettor and diluted with
distilled water, and the absorbance (ABS) of solution was
then measured at wavelength 284 nm on the spectroscope.
The 5-HMF content was determined as
0
5
9.33
8.46
23.17
34.43
35.75
40.17
9.78
26.11
31.44
34.72
39.99
9.19 § 0.55
23.65 § 1.84
32.35 § 1.47
36.23 § 1.47
41.24 § 1.64
21.67
31.18
38.22
43.56
1
1
2
0
5
0
The experiments were repeated three times. The calcining temperature of
ꢀ
ZrO
2
was 450 C.
ABS
-HMF yield D ABS
ð5-HMF after reactionÞ
5
£ 100%
ðGlucose before reactionÞ
HMF formed without any catalysts but formation of 5-HMF
increased with increasing ZrO2.
General Procedure for Conversion of Glucose to 5-HMF
0 g of distilled water to 25 g glucose to prepare 50% glucose
Effects of ZrO calcining temperature on 5-HMF yield. Cal-
2
cining temperature as an important factor affects the struc-
ture of solid catalysts. We prepared ZrO2 at 5 different
5
solution in a three-necked flask with condensation apparatus
Figure 2). The volume of the glucose solution was accurately
ꢀ
calcining temperatures (400, 450, 500, 550, 600 C). The
(
ꢀ
results (Table 2) indicate that calcining temperature of 450 C
measured. DMSO was then added to the 50% glucose solu-
tion (volume ratio of DMSO:50% glucose solution D 2:1) to
form diphasic solution. To start a reaction, an designated
amount of base or acid catalysts, and both catalysts was
produced highest yield of 5-HMF yield when ZrO dosage
2
was 20%. Based on the results from the previous sections, we
concluded that the best reaction condition should include the
ꢀ
ꢀ
use 20% ZrCO calcined at 450 C.
2
added to the flask which was heated in an oil bath at 140 C
for 12 h with stirring (Figure 2).
Characterization of solid base catalyst ZrO . The ZrO par-
2
2
ticles formed certain structure after drying and calcination,
which determines the performance of the catalyst. To study
the structure-performance relationship, we obtained the
Results and Discussion
Conversion of Glucose to 5-HMF on Solid Base ZrO2
XRD spectra of ZrO calicined at different temperatures
2
ꢀ
ꢀ
Effect of ZrO dosage on 5-HMF yield. The effects of solid (400–600 C) as shown in Figure 3. At 400 and 450 C, there
base catalyst dosage (% of glucose weight) in the diphasic sys- were many tetragonal regions of ZrO , or t-ZrO . With
2
2
2
tem were studied, and the results are shown in Table 1. 5- increasing temperature, the t-ZrO2 regions decreased (or
became more intact) until monoclinic regions ZrO (m-ZrO )
2
2
ꢀ
[26]
appeared beginning at 500 C. There was a large proportion
of m-ZrO region at 600 C. According to the previous sec-
tion, ZrO exhibited the best activity when calcined at 450 C,
ꢀ
2
ꢀ
2
and we therefore concluded that t-ZrO region were much
2
more beneficial for 5-HMF formation from glucose than
m-ZrO2.
Table 2. Effects of ZrO calcining temperature on 5-HMF yield
2
5
-HMF yield (%)
Calcining
temperature ( C)
Average §
ꢀ
1
2
3
SD (%)
4
4
5
5
6
00
50
00
50
00
38.85
41.86
36.82
34.33
25.02
34.14
38.81
39.17
30.85
22.88
36.81
43.05
38.70
32.83
21.43
36.60 § 1.93
41.24 § 1.79
38.23 § 1.02
32.67 § 1.42
23.11 § 1.47
Fig. 2. Reaction equipment of preparing 5-HMF. (1: Oil bath, 2:
necks flask, 3: Condense pipe).
3
The experiments were repeated three times.

1
80
Wang et al.
ꢀ
Fig. 4. CO -TPD-MS spectrum of ZrO calcined at 450 C.
2
2
ꢀ
Fig. 3. XRD spectrums of ZrO at different temperature ( : m-
2
Effects of SO42 /TiO -SiO calcining temperature on 5-HMF
¡
ZrO , *: t-ZrO ).
2
2
2
2
yield. Two opposite processes were expected to take place
during calcination of SO4 /TiO -SiO . Firstly, SO
2
¡
2¡
4
inter-
2
2
We further tested the alkalinity of the ZrO calcined at acted with mental oxide and generated strong acid sites, sec-
2
ꢀ
[27]
4
50 C using CO -TPD-MS method.
The CO -TPD-MS ondly, the strong acid degraded and released SO at very
2 2
2
spectrum (Figure 4) shows that there were two weak CO2 high temperature, which not only decreased acid sites but
desorption peaks, or in other words, two weak base sites on also led to low BET surface of the catalysts. From the 5-
its surface, suggesting that mild alkalinity promotes glucose HMF yield data (Table 4), we found that calcining tempera-
ꢀ
isomerization.
ture of 450 C produced best yield. The effects of calcining
2
¡
temperature on bonds and acidity of SO4 /TiO -SiO and
2
2
their relationship to catalytic activity will be further discussed
subsequently.
2
¡
/
Conversion of Glucose to 5-HMF on Solid Acid SO4
TiO -SiO
2
2
2¡
Effect of n(Ti):n(Si) in SO4 /TiO -SiO on 5-HMF
2
2
2
¡
2¡
Effects of SO4 /TiO -SiO dosage on 5-HMF yield. Simi- yield. Additional n(Ti):n(Si) ratios in SO
lar experiments were conducted to study the effects of solid were studied to determine an optimal SO
/TiO -SiO
-SiO com-
2
2
2
4
2
2
2
¡
/TiO
4
2
2
¡
acid catalyst SO4 /TiO -SiO on 5-HMF formation. It was position. Table 5 shows that a ratio of 4:1 was the best.
2
2
found that 5-HMF yield increased with increasing dosage of According to experiments in the previous sections, 20%
2
¡
2¡
ꢀ
SO4 /TiO -SiO (Table 3). Compared with the section SO
/TiO
-SiO
with n(Ti):n(Si) at 4:1 and calcined at
2
2
4
2
2
“
Effect of ZrO dosage on 5-HMF yield,” we concluded that 450 C produced the highest 5-HMF yield on the acid
2
2
¡
ZrO was a better catalyst than SO /TiO -SiO , which catalyst.
2
4
2
2
may be attributed to the fact that ZrO is an amphoteric
2
[
25]
2¡
4
oxide that possesses Lewis acid sites and Lewis base sites
Characterization of solid acid catalyst SO /TiO -SiO .
2 2
2
¡
[28]
2¡
while SO4 /TiO -SiO has strong acid sites only.
The Figure 5 shows the FT-IR spectra of SO4 /TiO -SiO at dif-
2
2
2 2
ꢀ
existence of mild acid and base sites on ZrO is believed to be ferent calcining temperatures ranging from 400 to 600 C. The
beneficial to the formation of 5-HMF from glucose.
2
¡
1
absorption peak around 950 cm is attributed to the Ti-O-Si
Table 4. Effect of SO42 /TiO -SiO calcining temperature on 5-
¡
2
¡
Table 3. Effect of SO4 /TiO -SiO dosage on 5-HMF yield
2
2
2
2
HMF yield
Calcining
5
-HMF yield (%)
2
5
-HMF yield (%)
2
2
¡
Dosage of SO4
TiO -SiO (%)
/
Average
§ SD (%)
9.19 § 0.55
11.87 § 1.04
17.68 § 1.19
22.00 § 1.20
29.47 § 1.65
Average
§ SD (%)
24.12 § 1.47
33.56 § 1.30
29.47 § 1.93
23.75 § 1.11
19.78 § 1.21
1
3
2
2
ꢀ
temperature ( C)
1
3
0
5
1
1
2
9.33
10.53
19.27
23.51
31.11
8.46
9.78
12.03
17.23
20.57
27.22
4
4
5
5
6
00
50
00
50
00
26.05
32.24
28.97
22.89
21.18
23.82
35.33
32.04
25.31
19.94
22.49
33.11
27.40
23.05
18.22
13.05
16.44
21.92
30.08
0
5
0
The experiments were repeated three times. The calcining temperature of
2¡
ꢀ
SO
4
/TiO
2
-SiO
2
was 500 C, n(Ti):n(Si)D2:1.
The experiments were repeated three times. n(Ti):n(Si)D2:1.

Syntheses of 5-Hydroxymethylfurfural
181
2¡
Table 5. Effect of n(Ti), n(Si) in SO4 /TiO -SiO on 5-HMF
2
2
yield
5
-HMF yield (%)
Average
n(Ti):n(Si)
1
2
3
§ SD (%)
1:1
2:1
4:1
1:2
1:4
26.98
32.24
40.02
19.87
24.99
30.11
35.33
36.79
22.55
28.06
28.86
33.11
35.84
20.94
24.44
28.65 § 1.29
33.56 § 1.31
37.55 § 1.74
21.12 § 1.10
25.83 § 1.59
The experiments were repeated three times.
stretching vibration. The presence of Ti-O-Si indicates that
TiO and SiO were linked by chemical bond not physical
2
2
¡
1
2¡
4
mix. The peak at around 1066 cm was Si-O-Si stretching Fig. 6. FT-IR analysis of SO
/TiO
-SiO
with different n(Ti):n
2
2
¡
1
vibration, and the one at 1240 cm
was SDO vibration (Si).
¡
1
which appeared above 1220 cm that the way of combina-
2
¡
tion between SO
and metal oxide was chelate double coor-
4
[
29,30]
¡1
dination.
The small peak at around 1640 cm was O-H 5-HMF Formation From Glucose in the Presence of Both
deformation vibration arising from absorption of water on Solid Acid and Solid Base Catalysts
surface metal. Figure 6 shows the FT-IR spectra of the acid
5
-HMF was directly produced from glucose by a simple one-
ꢀ
catalysts with different n(Ti):n(Si) ratio (calcined at 450 C).
¡
1
pot reaction including hydrolysis, isomerization and dehydra-
tion using ZrO and SO /TiO -SiO shown in Figure 7.
The peaks at around 950 cm varied noticeably with differ-
ent ratios of n(Ti):n(Si).
2
¡
2
4
2
2
The acidity of solid acid catalyst, an important factor in
the catalyst’ activity, was determined using Hammett indica-
tors including m-nitrotoluene, nitrobenzene, p-nitrochloro- Effects of mass ratio of ZrO and SO /TiO -SiO on 5-
2
¡
2
4
2
2
benzene, and 2,4-dinitrofluorobrnzene in cyclohexane HMF yield. As discussed earlier, solid base catalysts pro-
2
¡
solvent. The test results for SO4 /TiO -SiO calcined at dif- mote glucose isomerization while solid acid catalysts facili-
2
2
2
¡
[15]
ferent temperatures are shown in Table 6. SO /TiO -SiO
exhibited little acidity when calcined at 400 C but greater oxide, possessing both Lewis acid and base sites and has the
acidity when calcined at higher temperatures. As discussed ability to promote the isomerization and dehydration pro-
previously, SO4 /TiO -SiO demonstrated highest activity cesses at the same time, the isomerization is reversible and
when calcined at 450 C. We therefore concluded that mild thus, adding strong solid acid SO4 /TiO -SiO to the reac-
tate 5-HMF formation.
Although ZrO is an amphoteric
4
ꢀ
2
2
2
2
¡
[27]
2
2
ꢀ
2¡
2
2
acidity favors glucose transformation and 5-HMF tion system will enhance dehydration, ensuring that the reac-
generation.
tions are directed to the formation of stable 5-HMF
[
31]
product. The mass ratio of acid:base is therefore critical to
the optimal 5-HMF formation. Nine acid-base rations were
tested in our study and the results are shown in Figure 8
(starting with 10% acid catalyst and adding more base cata-
lyst stepwise, starting with 10% base catalyst and adding
more acid catalyst stepwise). The highest 5-HMF yield was
obtained with base:acid ratio of 4:3 (Figure 8). Adding more
acid to the fixed base catalyst reduced the 5-HMF yield
2
¡
Table 6. Acidity determination of SO4 /TiO -SiO2
2
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
4
00 450 500 550 600
Indicator
H0
C
C
C
C
C
m-nitrotoluene
nitrobenzene
p-nitrochlorobenzene
¡11.99
¡12.14
¡12.70
§
¡
¡
¡
C
C
§
§
C
C
C
C
C
C
C
C
C
C
C
§
2
,4-dinitrofluorobrnzene ¡14.52
2¡
Fig. 5. FT-IR analysis of SO4 /TiO -SiO at different tempera- nC o: t Cc oh la on rg ce h. anged obviously, §: Color changed not obviously, ¡: Color did
2
2
ture ([n(Ti):n(Si)D4:1].n(Si)D4:1).

1
82
Wang et al.
Fig. 7. 5-HMF formation from glucose in the presence of ZrO
2
2¡
and SO4 /TiO -SiO in one pot.
2
2
Fig. 10. Effects of ZrO calcining temperature on 5-HMF yield
2
2¡
ꢀ
when SO4 /TiO -SiO was calcined at 450 C (green: ZrO
2
2
2
2¡
only, purple: ZrO C SO /TiO -SiO ).
2
4
2
2
2
¡
probably due to the fact that SO /TiO -SiO helps convert
4
2
2
[
32,33]
5-HMF to humins.
2
¡
Effects of total dosage of ZrO and SO /TiO -SiO on 5-
2
4
2
2
2
¡
HMF yield. The effects of dosage of ZrO or SO /TiO2-
2
4
2
¡
SiO only, and mixture of ZrO and SO /TiO -SiO (fixed
2
2
4
2
2
ratio of 4:3) on 5-HMF yield are illustrated in Figure 9. The
-HMF yield increased with increasing dosage. The mixture
5
2
¡
of ZrO and SO /TiO -SiO performed much better than
ZrO or SO /TiO -SiO alone. It appears that ZrO and
SO4 /TiO -SiO did not interact with each other despite the
2
4
2
2
2
¡
2
4
2
2
2
2
¡
2
2
Fig. 8. Effects of mass ratio between solid acid and solid base on
-HMF yield (green: m(solid acid):m(solid base), purple: m(solid
base):m(solid acid)).
fact that they possess opposite chemical properties. They
seem to perform their primary functions independently
within the system. Our finding is consistent with work
5
[
16,34]
reported in the literature.
2
¡
2¡
Fig. 9. Effects of total dosage of ZrO and SO /TiO -SiO on Fig. 11. Effects of SO4 /TiO -SiO calcining temperature on 5-
2
4
2
2
2
2
2
¡
ꢀ
2¡
4
5
-HMF yield (green: no catalysts or ZrO only, grey: SO
TiO -SiO only, purple: ZrO and SO /TiO -SiO ).
/
HMF yield when ZrO was calcined at 450 C (grey: SO
/
2
4
2
2
¡
2¡
TiO -SiO only, purple: ZrO C SO /TiO -SiO ).
2
2
2
4
2
2
2
2
2
4
2
2

Syntheses of 5-Hydroxymethylfurfural
183
SO4 /TiO -SiO mixture proved to be much better than the
2
¡
2
2
catalysts used individually. The calcining temperature, Ti/Si
2
¡
ratio in SO4 /TiO -SiO , and catalyst dosage had strong
2
2
impact of 5-HMF yields. With the water-organic diphasic
system and under optimal catalyst conditions, the transfor-
mation of glucose to 5-HMF can reach more than 85%.
Funding
This work was supported by the following projects: Key Pro-
grams of the National Laboratory (No. SKLF-ZZB-201312),
the National Natural Science Foundation of China (No.
2
1266022, 21306076), the National High Technology
Research and Development Program 863 (2012AA101800-
3, 2012AA021205-6, 2012AA021704), and Foundation for
0
2
¡
the Youth of Jiangxi Province (GJJ13017).
Fig. 12. Effects of n(Ti):n(Si) in SO /TiO -SiO on 5-HMF
4
2
2
2
¡
2¡
yield when ZrO2 and SO4 /TiO -SiO (grey: Only SO4
TiO -SiO , purple: ZrO and SO /TiO -SiO ).
/
2
2
2
¡
2
2
2
4
2
2
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