Catalytic transformation of carbohydrates into 5-hydroxymethyl furfural over tin phosphate in a water-containing system

Article abstract of DOI:10.1016/j.cattod.2015.06.031

The dehydration of carbohydrates to produce 5-hydroxymethylfurfural (HMF) in the presence of tin salt and hydrogen phosphate is examined. The precipitate freshly formed from SnCl₄and (NH₄)₂HPO₄ shows a good performance in a water-dimethylsulfoxide (DMSO) mixed solvent. The highest HMF yield achieves 71% at 135 °C for 1 h. The tin valence number, the type of phosphate and the molar ratio of Sn/PO₄ affect the yield of HMF. In addition, the reaction time, temperature and water to DMSO ratio also influence the yield. Glucose and sucrose as the reactant are compared, and the reaction pathways are discussed.

Full text of DOI:10.1016/j.cattod.2015.06.031

Catalysis Today 264 (2016) 131–135
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Catalysis Today
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Catalytic transformation of carbohydrates into 5-hydroxymethyl
furfural over tin phosphate in a water-containing system
Min Zhanga, Xinli Tongb, Rui Maa, Yongdan Lia,∗
a Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Applied Catalysis Science and Technology and
State Key Laboratory for Chemical Engineering, School of Chemical Engineering, Tianjin University, Tianjin 300072, PR China
b School of Chemistry and Chemical Engineering, Tianjin University of Technology, Tianjin 300084, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 22 May 2015
Received in revised form 23 June 2015
Accepted 27 June 2015
Available online 8 August 2015
The dehydration of carbohydrates to produce 5-hydroxymethylfurfural (HMF) in the presence of tin salt
and hydrogen phosphate is examined. The precipitate freshly formed from SnCl4and (NH4)2HPO4 shows
a good performance in a water-dimethylsulfoxide (DMSO) mixed solvent. The highest HMF yield achieves
71% at 135 ◦C for 1 h. The tin valence number, the type of phosphate and the molar ratio of Sn/PO4 affect
the yield of HMF. In addition, the reaction time, temperature and water to DMSO ratio also influence the
yield. Glucose and sucrose as the reactant are compared, and the reaction pathways are discussed.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
5-Hydroxymethylfurfural
Tin phosphate
Fructose
Dehydration
Bio-fuel
1. Introduction
of 75% at 71% conversion. Tong et al. [18] reported that a 86% HMF
yield was achieved from fructose using FeCl3 as the catalyst in N-
At the present time, the liquid fuels and industrial chemicals are
mostly derived from the refining of fossil fuels, such as petroleum,
coal, and natural gas; however, the rapid consumption of the fos-
sil fuels and the increasingly serious environmental pollutions lead
to a great demand for the development of sustainable substitutes
of the fossil resources [1,2]. Biomass, which is self-produced by
the biosphere in great amount and CO2-neutral, provides potential
substitutes for the fuels and chemicals. Therefore efficient tech-
nologies for the transformation of biomass to fuels and chemicals
are becoming a hot topic in the chemical research [3–9]. Nowadays,
one of the focuses in the field is the dehydration of carbohy-
drates into 5-hydroxymethylfurfural (HMF), which is an important
platform molecule and can be converted to many value-added
derivatives [10–15].
Recently, intensive work on the synthesis of HMF from the
dehydration of fructose has been reported. Therein, mineral acids,
inorganic salts and solid acids have been frequently used as cat-
alysts in water, organic solvents or ionic liquids (ILs) [16]. For
example, Tuercke et al. [17] utilized HCl as the catalyst to dehy-
drate fructose to HMF in a continuous flow microreactor at 185 ◦C
and within 1 min residence time, and achieved a HMF selectivity
methyl-2-pyrrolidone (NMP) solvent. Ngee et al. [19] found that the
conversion of fructose to HMF can be successfully performed with
sulfated mesoporous niobium oxide (MNO-S) as the catalyst in a
water-DMSO, with an HMF yield of up to 88%. Furthermore, in the
dehydration of fructose to HMF, ILs can function both as catalyst
and solvent [20–22]. Moreau et al. [23] investigated the produc-
tion of HMF from sucrose under Amberlyst-15 in a binary solvent
composed of dimethyl sulfoxide (DMSO) and ILs, and achieved a
HMF yield of 80% in 24 h. Although high yields of HMF have been
produced in these systems, the exploration of new, efficient and
clean systems is still meaningful. Low cost and environmentally
friendly solvent and catalyst are critical for the success of a process
in industry [24].
In the synthesis of HMF, water-containing solvent has been con-
sidered the ideal and promising reaction medium for the large-scale
process. Various metal phosphates showed promising catalytic per-
formances in dehydration reactions [25,26]. Recently NbPO, AlPO,
TiPO and ZrPO were tested in glucose dehydration to HMF in water
solvent, in which the activity depends on the amount of strong acid
sites over the catalysts [27].
In this work, a novel approach for the dehydration of fructose is
investigated with the in situ generated tin phosphate as the cata-
lyst in a water-dimethylsulfoxide (DMSO) mixed solvent, and a 71%
yield of HMF is obtained at 135 ◦C for 1 h. The in situ generated tin
phosphate is more efficient than the prepared solid tin phosphate
∗
Corresponding author. Tel.: +86 22 27405613; fax: +86 22 27405243.
E-mail address: ydli@tju.edu.cn (Y. Li).
http://dx.doi.org/10.1016/j.cattod.2015.06.031
0920-5861/© 2015 Elsevier B.V. All rights reserved.

132
M. Zhang et al. / Catalysis Today 264 (2016) 131–135
Table 1
Dehydration of fructose into HMF with different catalysts and solvent.a
Entry
Catalysts
Mole ratio
Solvent
Yield, %
1
2
3
4
5
6
7
8
9
SnCl4-(NH4)2HPO4
SnCl4-(NH4)2HPO4
SnCl4-(NH4)2HPO4
SnPOb
1:2
1:2
1:2
–
1:2
1:2
1:1
1:0.5
–
DMSO:water (65:35, w/w)
DMSO:water (0:100, w/w)
DMSO:water (100:0, w/w)
DMSO:water (65:35, w/w)
DMSO:water (65:35, w/w)
DMSO:water (65:35, w/w)
DMSO:water (65:35, w/w)
DMSO:water (65:35, w/w)
DMSO water (65:35, w/w)
DMSO:water (65:35, w/w)
71
36
14
20
70
70
64
25
38
2
SnCl4-Na2HPO4
SnCl4-K2HPO4
SnCl4-(NH4)3PO4
SnCl2-(NH4)2HPO4
SnCl4
c
10
(NH4)2HPO4
–
a
Reaction condition: 1.0 g d-fructose, 30 mol % metal chloride, in 20 g of solvent, reaction time: 1 h, temperature: 135 ◦C.
0.5 g SnPO catalyst.
60 mol % hydrogen phosphate.
b
c
catalyst in the reaction. Moreover, the existence of water plays a
2.4. Characterization
key role in the reaction.
The XRD patterns of the phosphate catalysts after treat-
ment were recorded with a D8-Focus diffractometer (BrukerAXS),
employing CuK␣ radiation at 40 kV and 200 mA with a scan speed
of 5◦/min. The samples were prepared as follows: after stirring in
the mixed solvent for 10 min, the in situ generated catalyst samples
were filtrated and then dried at room temperature in a vacuum for
24 h. The FTIR adsorption spectra of the phosphate catalyst diluted
with KBr was recorded with a Nicolet Nexus-870 instrument with
a 4 cm−1 optical resolution. The samples tested with FTIR were the
same ones as those used in XRD. The particle size and distribution
of the in situ generated tin phosphate in the mixed solvent were
measured with a laser particle size analyzer at room temperature
(90PALS, Brookhaven Instruments Corp., the United States). In the
measurement, after adding chloride and hydrogen phosphate into
the solvent, all the samples were stirred for 10 min, and then were
quickly transferred into the cuvette for analysis.
2. Experimental
2.1. Reagents
Fructose, glucose, sucrose, SnCl4, SnCl2, Na2HPO4, K2HPO4,
(NH4)2HPO4, (NH4)3PO4 and DMSO were all of analytical grade
and bought in Tianjin Guangfu Fine Chemical Research Institute.
A standard sample of HMF was purchased from Aladdin Industrial
Corporation. Ultrapure water was supplied by an Ultrapure Water
System (electrical resistivity = 10–16 Mꢀ cm).
2.2. The preparation of catalyst
White tin phosphate was generated in situ with adding SnCl4
and (NH4)2HPO4 into the water-containing mixture, and directly
used as the catalyst without further treatment. A solid phos-
phate catalyst Sn–P–O was synthesized with the modification of
a reported process in literature [28]. A 0.6 M aqueous solution of
disodium hydrogen phosphate (Na2HPO4) was added dropwise to
a 0.3 M stirred aqueous solution of SnCl4 at room temperature.
The obtained precipitate was filtrated and washed with distilled
water to a pH 3–4 and then dried in vacuum at 100 ◦C. The material
was then treated with 1 M HNO3 for 24 h. After the treatment the
material was washed with water to a pH 4–5 and dried at 110 ◦C
overnight.
3. Results and discussion
The dehydration of fructose was first carried out as a model
reaction, presented as Scheme 1, using different catalysts in the
water-DMSO mixed solvent. The experimental results are listed in
Table 1. The highest HMF yield of 71 % was achieved within 1 h at
135 ◦C with the SnCl4 to (NH4)2HPO4 ratio equaling 1:2 as the cat-
alyst in the water-DMSO mixed solvent (entry1). However, when
the reaction was carried out only in pure water or pure DMSO, only
36% and 14% yields of HMF were obtained, respectively (entries 2
and 3). Moreover, when the prepared solid tin phosphate catalyst
was employed as the catalyst, the HMF yield is only 20% (entry 4). It
is probably due to that the tin phosphate solid catalyst has less acid
sites and lower specific surface area than the in situ generated tin
phosphate in the dehydration process. In addition, the effect of the
cations, like Na+ and K+, in the phosphate was also examined. As a
result, the HMF yields are both 70% when (NH4)2HPO4 was replaced
by Na2HPO4 or K2HPO4 with the same ratio to SnCl4 (entries 5 and
6). It exhibits that the cations NH4+, Na+ and K+ have little influ-
ence to the catalytic activity. The combination SnCl4-(NH4)3PO4
also gave excellent activity, and a yield of 64% HMF was obtained
(entry 7). Here, the lowering of the yield may be attributed to that
2.3. Dehydration reaction
All the dehydration reactions were carried out in a 250 mL
sealed stainless steal autoclave with magnetic stirring and auto-
matic temperature controlling. A typical procedure was presented
as follows: fructose (1 g), tin chloride (0.56 g, 30 mol% based on
fructose), (NH4)2HPO4 (0.42 g), water (7 g) and DMSO (13 g) were
successively added into the reactor. The reactor was purged with
N2, then preheated to the preset temperature with stirring, and kept
at the temperature for a period. After the reaction, the reactor was
cooled down in an ice bath and then the slurry was filtrated and
the solid was washed with ultrapure water. Therein, the volume
of the filtrated liquid was measured with a volumetric flask and
the HMF concentration was analyzed with an Agilent 1200 HPLC
equipped with both UV and refractive index detectors. Moreover,
the effect of reaction time, temperature and DMSO proportions on
the fructose dehydration was further studied through changing one
of those factors under similar conditions.
Scheme 1. Catalytic dehydration of fructose into HMF.

M. Zhang et al. / Catalysis Today 264 (2016) 131–135
133
80
70
60
50
40
30
20
10
0
Entry 8
SnCl -(NH ) HPO
4
4
4 2
SnCl -(NH ) PO
4
4 3
4
Entry 7
Entry 2
Entry 1
SnCl -(NH ) HPO
2
4 2
4
1600
1400
1200
1000
800
600
Wavenumber (cm-1)
1:1.5 1:2 1:2.5
1:0.5 1:1 1:1.5
Mol ratio Sn:P
1:0.25 1:0.5 1:1
Fig. 3. FTIR spectra in the region of structrual vibration of the phosphates.
Fig. 1. Effect of the mol ratio of Sn to P on the dehydration of fructose to HMF.
Reaction conditon: 1.0 g fructose, 30 mol% Sn, 20 g solvent, DMSO: water = (65:35,
w/w), 1 h, 135 ◦C.
Entry 2
Entry 8
100
80
60
40
20
Entry 9
a
Entry 4
Entry 9
Entry 8
100
1000
10000
100
80
Entry 7
b
Entry 1
Entry 7
60
Entry 8
Entry 2
Entry 1
40
200
250
300
Diameter (nm)
350
10
20
30
40
50
60
2θ (degree)
Fig. 4. The particle size distribution of the in situ generated tin phosphate catalysts
in different entries.
Fig. 2. XRD patterns of the tin phosphate catalysts used in different entries.
have higher activity than that with the size 1861 nm formed in pure
water and the size 2621 nm formed with only SnCl4 (entries 2 and
9 in Table 2). Fig. 3a and b also shows that entries 1 and 7 produce
almost the same particle size distribution, while entries 2 and 9
give very large but similar sized particles. Entry 8 produces a wide
particle size distribution within the range of 200–1000 nm.
The effect of the reaction temperature on the yield of HMF was
examined, and the results are illustrated in Fig. 5, which clearly
shows that the optimum temperature is 135 ◦C in either pure water
or the mixed solvent. Moreover, when the temperature increases
from 115 ◦C to 135 ◦C, the yield of HMF increased rapidly. How-
ever, with the further increase of the temperature from 135 ◦C to
145 ◦C the HMF yield drops slightly. It is also observed that when
the temperature increased from 115 ◦C to 145 ◦C, more and more
dark humans were generated and the color of the reaction liquid
became darker.
the basicity of (NH4)3PO4 is stronger than that of (NH4)2HPO4. Oth-
erwise, SnCl2 is found less active than SnCl4, and a yield of only
25% HMF was attained with the SnCl2 and (NH4)2HPO4 combina-
tion as the catalyst (entry 8). Visually, a milk white gel was formed
during the reaction when the combination SnCl4-(NH4)2HPO4 was
used, while white precipitation was generated when the combina-
tion of SnCl2-(NH4)2HPO4 was used as the catalyst. As comparison,
when only SnCl4 or (NH4)2HPO4 was employed as the catalyst in
the water-DMSO solvent, the yield of HMF was 38% or 2%, respec-
tively (entries 9–10). This shows that the synergy of SnCl4 and
(NH4)2HPO4 is important for the reaction. The molar ratio of Sn
and P is a critical parameter for all the catalyst samples. As shown
in Fig. 1, the optimal molar ratios of catalyst SnCl4-(NH4)2HPO4,
SnCl4-(NH4)3PO4 and SnCl2-(NH4)2HPO4 are 1:2, 1:1 and 1:0.5.
The in situ generated catalytic materials were purified and
characterized using different methods. The XRD patterns of these
catalysts in Fig. 2 indicate that all the catalysts typically exhibit
an amorphous structure. A broad band in the range of about 20o-
30o is observed for all the samples. The FT-IR spectra of these solid
catalysts were shown in Fig. 3. The broad band in the range of
The effect of the reaction time under the optimized
SnCl4:(NH4)2HPO4 ratio and reaction temperature was also
Table 2
1100–1200 cm−1 is attributed to the O
P O asymmetric stretch-
The effective particle size of in situ generated tin phosphate from Table 1 in the
solvent.
ing of phosphate. The particle size and the distribution of the in
situ generated tin phosphate are shown in Fig. 4 and Table 2. It
can be seen that the in situ generated materials, whose particle
sizes–are distributed from 268 nm to 447 nm in the mixed solvent,
Catalyst
Entry 1
285
Entry 2
1861
Entry 7
268
Entry 8
474
Entry 9
2621
Particle Size/nm

134
M. Zhang et al. / Catalysis Today 264 (2016) 131–135
70
60
50
40
30
20
10
0
in water
70
60
50
40
30
20
10
0
in water-DMSO mixture
115
120
125
130
135
140
145
0
5
15 25 35 45 55 65 75 85 95 100
DMSO Proportion (%)
o
Temperature ( C)
Fig. 5. Effect of reaction temperature on the dehydration of fructose to HMF. Reac-
tion conditon: 1.0 g fructose, 30 mol% SnCl4-(NH4)2HPO4 (1:2), 20 g solvent, DMSO:
water = (65:35, w/w), 1 h in mixed solvent and 2 h in water.
Fig. 7. Effect of DMSO proportions on the dehydration of fructose into HMF. Reaction
conditon: 1.0 g fructose, 30 mol % SnCl4-(NH4)2HPO4 (1:2), 135 ◦C and time = 1 h.
Table 3
Dehydration of sugars into HMF with different tin phosphate as catalysts.
80
in water
in water-DMSO mixture
Entry
Reactant
Catalysts
Yield, %
70
60
50
40
30
20
10
0
1
2
3
4
GLUCOSE
GLUCOSE
SUCROSE
SUCROSE
SnCl4-(NH4)2HPO4
SnCl4-(NH4)3PO4
SnCl4-(NH4)2HPO4
SnCl4-(NH4)3PO4
11
33
45
44
Reaction condition: 1.0 g glucose or sucrose, water/DMSO (w/w) = 35: 65, in 20 g of
solvent, reaction temperature: 135 ◦C, time: 1 h.
was 32% in aqueous media, and was increased gradually along with
the increase of the DMSO percentage in the mixed solvent to the
maximum yield of the HMF 71% with a 65% ratio of DMSO, and then
the HMF yield was decreased with the further increase of the ratio
of DMSO and only a 14% HMF yield was obtained in pure DMSO.
Most importantly, DMSO is an aprotic basic solvent which hinders
the deep dehydration of fructose to formic acid and levulinic acid
and the polymerization into humins. Nevertheless, it is difficult to
form tin phosphate catalyst in the pure DMSO solvent, so that the
yield of HMF becomes low when the ratio of DMSO is too high.
The dehydration of glucose and sucrose to HMF using the
SnCl4-(NH4)2HPO4 and the SnCl4-(NH4)3PO4 combinationsin the
water-DMSO solvent was also examined. The results are listed
in Table 3. The HMF yield in the reaction of glucose with SnCl4-
(NH4)2HPO4 as catalyst is only 11%, which is much lower than
the HMF yield of 33% obtained with the SnCl4-(NH4)3PO4 cat-
alyst (entries 1–2). However, for the reaction of sucrose, the
catalytic activities of SnCl4-(NH4)2HPO4 and SnCl4-(NH4)3PO4 cat-
alyst systems are similar, with the HMF yields being 45% and 44%,
respectively (entries 3–4). Scheme 2 illustrates the process for the
conversion of sucrose to HMF. Herein, fructose, glucose and sucrose
are converted to each other with isomerization reactions and can
be in equilibrium [29].
0.5
1.0
1.5
Time (h)
2.0
2.5
3.0
Fig. 6. Effect of reaction time on the dehydration of fructose to HMF. Reaction con-
diton: 1.0 g fructose, 30 mol% SnCl4-(NH4)2HPO4 (1:2), 20 g solvent, DMSO: water
(65:35 w/w), 135 ◦C.
evaluated in two solvents, water and water/DMSO mixture, and
the results are presented in Fig. 6. The trend of changing of the
HMF yields in water and in the mixed solvent is different. In
water-DMSO mixed solvent the HMF yield was gradually increased
during the beginning 0.5-1.0 h period and reached the maximum
value of 71 % after1 h, and then HMF yield remained unchanged
in the following period up to 3 h, indicating a protecting effect
of DMSO on the product HMF. While in water the yield of HMF
reaches the maximum of 43% at 2 h, after that the HMF yield
decreases to 33% in the next 1 h.
The effect of the water and DMSO ratio was tested in the dehy-
dration reaction and the results are depicted in Fig. 7. The HMF yield
Scheme 2. General conversion route of sucrose to HMF.

M. Zhang et al. / Catalysis Today 264 (2016) 131–135
135
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The financial support from the Ministry of Science and Tech-
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Natural Science Foundation of China under contract number
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