Phosphorus pentoxide/metal chloride mediated efficient and facile catalytic conversion of fructose into 5-hydroxymethylfurfural

Article abstract of DOI:10.1039/c8ra07027j

Phosphorus pentoxide (P₂O₅)/metal chloride mixtures could significantly improve 5-HMF yield and selectivity for the catalytic conversion of fructose under mild conditions, whereas neither P₂O₅ nor tested metal chloride alone gave reasonable performances. A maximum 5-HMF yield of 75% with ～85% selectivity could be achieved within 30 min at 80 °C.

Full text of DOI:10.1039/c8ra07027j

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Phosphorus pentoxide/metal chloride mediated
efficient and facile catalytic conversion of fructose
into 5-hydroxymethylfurfural†
Cite this: RSC Adv., 2018, 8, 32533
a
a
a
b
a
Songyan Jia, * Xinjun He, Jiao Ma, Zhanwei Xu, Kangjun Wang
b
and Z. Conrad Zhang
*
Received 22nd August 2018
Accepted 15th September 2018
Phosphorus pentoxide (P
2 5
O )/metal chloride mixtures could significantly improve 5-HMF yield and
selectivity for the catalytic conversion of fructose under mild conditions, whereas neither P
2
O
5
nor
DOI: 10.1039/c8ra07027j
tested metal chloride alone gave reasonable performances. A maximum 5-HMF yield of 75% with ꢀ85%
ꢁ
rsc.li/rsc-advances
selectivity could be achieved within 30 min at 80 C.
ꢁ
Utilization of alternative energy sources has emerged as an 120 C in polar organic solvents, while reaction time still
important worldwide strategy to compensate for depleting fossil remains 1–3 h; (3) the viscosity of ionic liquid limits its appli-
fuels. Renewable biomass has attracted extensive attention for cation at low temperatures; (4) cost and time for the preparation
1–4
the production of biobased chemicals over the last decades. 5- of some functionalized materials is an issue. Therefore, efficient
Hydroxymethylfurfural (5-HMF) is a representative platform and facile conversion of fructose under mild conditions
5–7
compound derived from carbohydrates. 5-HMF can be con- remains an important research subject.
verted into high value-added chemicals by a variety of processes, The conversion of fructose into 5-HMF at low temperatures
8–11
ꢁ
with the potential of sustainable development.
(25–50 C) had been mainly achieved in ionic liquid based
Currently, 5-HMF is primarily produced through conversion media, in which 5-HMF yields of ꢀ40–80% were available.
of carbohydrates such as fructose, glucose and oligosaccha- However, relatively long reaction time (e.g. 4–12 h) was
23–26
rides. Among these carbohydrates, fructose is the most reactive mandatory for a reasonable 5-HMF yield.
In addition,
feedstock and extensively investigated, although glucose is a common ionic liquid, 1-butyl-3-methylimidazolium chloride,
5
–9
more abundant in nature. Indeed, the conversion of glucose was used as a solvent in the works above. This ionic liquid has
ꢁ
25
into 5-HMF is considered as a two-step tandem reaction a melting point at ꢀ70 C, indicating that additional opera-
including “isomerization of glucose into fructose” and “dehy- tions are necessary to lower the viscosity at low temperatures. A
1
2–14
dration of fructose into 5-HMF”.
conversion of fructose is an essential step for 5-HMF conversion under mild conditions.
production. In this work, we investigated approaches to achieve the
Pioneering works have demonstrated that fructose can be effective conversion of fructose into 5-HMF under mild condi-
effectively converted into 5-HMF with mineral acids, metal salts, tions. Dimethyl sulfoxide (DMSO) was used as a solvent due to
Therefore, efficient solvent with low viscosity is more desirable for fructose
15–19
27
zeolites and other functionalized acidic materials.
A number its ability of suppressing side reactions. A variety of metal
of reaction media such as polar organic solvents, ionic liquids chlorides were preliminarily employed as the catalysts because
and water—organic solvent biphasic solvents have been shown they could efficiently catalyze the production of 5-HMF from
2
0–22
to be benign to the conversion of fructose.
However, most fructose in an ionic liquid at moderate temperatures as previ-
12
reported technologies still face some questions as follows: (1) ously reported.
high temperatures at 150–180 C are necessary for biphasic
systems; (2) reaction temperature can be decreased to around metal chloride catalysts in DMSO at 80 C for 30 min. As shown
ꢁ
The conversion of fructose was rst evaluated over different
ꢁ
in Fig. 1, the reaction with SnCl $5H O showed a maximum
4
2
conversion of 43%, while the 5-HMF yield and selectivity
$6H
O resulted in a little amount of 5-HMF, most
catalysts did not actually work at all, implying that more severe
conditions were necessary for 5-HMF synthesis with the metal
chlorides alone. According to literatures, fructose undergoes
a
College of Chemical Engineering, Shenyang University of Chemical Technology, reached only 14% and 33%, respectively. Although CrCl
Shenyang, Liaoning, 110142, China. E-mail: jiasongyan@126.com; Tel:
2
O
3
3 2
and AlCl $6H
+
86-24-89386342
b
State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy,
Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian,
Liaoning, 116023, China. E-mail: zczhang@yahoo.com; Tel: +86-411-84379462
28–30
†
Electronic supplementary information (ESI) available. See DOI: acid catalyzed dehydration to yield 5-HMF.
0.1039/c8ra07027j
The three metal
1
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Fig. 1 Screening tests on the conversion of fructose into 5-HMF with
metal chlorides as catalysts (reaction conditions: fructose 60 mg;
metal chloride 10 mol% to fructose; DMSO 1 mL; 80 C; 30 min).
Fig. 3 Effect of P
2
O
5
loadings on the conversion of fructose with
ꢁ
a constant loading of NiCl
0 mg; NiCl $6H
2
$6H
2
O (reaction conditions: fructose
ꢁ
6
2
2
O 10 mol% to fructose; DMSO 1 mL; 80 C; 30 min).
4 2 3 2 3 2
salts, SnCl $5H O, CrCl $6H O and AlCl $6H O, may be more
3
1
acidic than other tested metal salts in solutions, which lead to
the formation of 5-HMF.
P
2
O
5
and tested metal chloride as catalysts (Fig. 2). The 5-HMF
selectivity stayed at about 80% in the presence of P accom-
panied by most metal chlorides except ZnCl . Analysis of
2 5
O
As discussed above, the production of 5-HMF undergoes acid
2
28–30
catalyzed dehydration of fructose.
acid catalysis as well as water removal. Phosphorus pentoxide
) as an anhydride is acidic and hygroscopic, which is
potentially appropriate for the dehydration of fructose. Based
on that, P was also investigated as a catalyst in this work. As
seen in Fig. 2, P showed a superior activity to SnCl $5H
alone with 5-HMF yield and selectivity of 21% and 57%,
respectively, possibly because P O could provide acidity and/or
Efforts should be put on
products showed that no or only trace amount of rehydration
products such as levulinic acid were produced in the above
reactions (Fig. S2†). In consideration of reaction performance
and catalyst cost, NiCl $6H O was selected as a representative
2 2
chloride for subsequent investigations.
2 5
(P O
2 5
O
2
O
5
4
2
O
Fig. 3 and 4 showed the effect of catalyst compositions on the
2 2
conversion of fructose. The loading of either NiCl $6H O or
P2O5 was set to be constant for examination. A slightly
decreased 5-HMF yield was observed when 5 mol% P O was
2
5
32,33
absorb the in situ formed water.
2 5
However, higher P O
2
5
loadings did not increase the 5-HMF yield much (Fig. S1†). The
slightly decreased 5-HMF selectivity demonstrated that more
side reactions occurred. Unexpectedly, both 5-HMF yield and
selectivity were signicantly improved when using mixtures of
added. The reaction performance remained basically
unchanged with increasing P O loading. In addition, tuning
2
5
the loading of NiCl
sion. The above results demonstrated the importance of
synergistic effect between P and metal chlorides. However,
2 2
$6H O did not obviously affect the conver-
2 5
O
Fig. 2 Conversion of fructose into 5-HMF with mixtures of P
2 5
O and
metal chloride as catalysts (reaction conditions: fructose 60 mg; P
2
O
5
2 2
Fig. 4 Effect of NiCl $6H O loadings on the conversion of fructose
1
8
0 mol% to fructose; metal chloride 10 mol% to fructose; DMSO 1 mL; with a constant loading of P
2
O
5
(reaction conditions: fructose 60 mg;
ꢁ
ꢁ
0 C; 30 min).
2
P O
5
10 mol% to fructose; DMSO 1 mL; 80 C; 30 min).
32534 | RSC Adv., 2018, 8, 32533–32537
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Table 1 Results on the effect of anions of nickel salts on the
a
conversion of fructose
Fructose
conv. (%)
5-HMF
yield (%)
5-HMF
sel. (%)
Entry
Catalyst
1
2
3
4
P
2
P
2
P
2
P
2
O
5
O
5
O
5
O
5
37
88
65
47
21
75
46
33
57
85
71
70
+ NiCl
+ Ni(NO
2
+ NiSO $6H O
2
$6H
2
O
3
)
2
$6H O
2
4
a
Reaction conditions: fructose 60 mg; P
2
O
5
10 mol% to fructose; Ni
ꢁ
fraction 10 mol% to fructose; DMSO 1 mL; 80 C; 30 min.
the reactivity could not be simply correlated with the catalyst
compositions. The loadings of P O and NiCl $6H O were set to
2 5 2 2
be 10 mol% (to fructose) for further studies as a better 5-HMF
yield was obtained at this catalyst composition.
The effect of anions of nickel salts on the conversion of
fructose was then investigated. As seen in Table 1 (entries 2–4),
the reactions with NiCl $6H O, Ni(NO ) $6H O and NiSO -
2
2
3 2
2
4
$
6H O exhibited different performances although they all
2
showed improved 5-HMF yield and selectivity compared to the
one with P alone. As reported, the production of 5-HMF from
2 5
O
fructose underwent a 2-deoxy-2-halo intermediate, which was
through a oxocarbenium precursor followed by the nucleophilic
34
attack by a halide ion. It is proposed that fructose underwent
such a mechanism as well in this work, accounting for the
performance in the presence of NiCl $6H O. Ni(NO ) $6H O
2
2
3 2
2
and NiSO $6H O showed decreased activities probably because
4
2
of the higher steric hindrance of nitrate and sulfate anions.
Moreover, the reactions with different chromium salts further
demonstrated the similar effect of the anions (Table S1†).
Fig. 5 Effect of reaction temperature and time on the conversion of
fructose (reaction conditions: fructose 60 mg; P O 10 mol% to
2 5
Highly concentrated conversion process is more desirable, fructose; NiCl $6H O 10 mol% to fructose; DMSO 1 mL).
2
2
since using dilute solutions for biomass renery may limit the
efficacy. Fig. S3† illustrated the effect of initial fructose loading
on the reaction performance. When a less amount of fructose
conversion was achieved from 5-fold and 10-fold scaling-up
tests, respectively, demonstrating the potential for a large
scale production.
(40 mg) was added, slightly higher 5-HMF yield (77%) and
selectivity (88%) was obtained than that with 60 mg of fructose,
Inulin is a kind of fructan material, which can be obtained
from natural biomass such as Jerusalem artichoke and chicory.
Table S2† presented the conversion of inulin in the studied
system. 5-HMF with a yield of ꢀ45% was facilely produced at
which was attributed to the stabilization of 5-HMF by sufficient
35
solvation effect of DMSO. However, increasing fructose
loading may result in more byproducts and humins. These
compounds could be formed by 5-HMF self-condensation or
ꢁ
36,37
80 C, and elevating reaction temperature can accelerate the
coupling with other compounds,
HMF yield and selectivity.
leading to decreased 5-
formation of 5-HMF as discussed above.
Glucose is of high abundance in nature, and therefore has
To get an optimized 5-HMF yield, the conversion of fructose
5–9
a great potential for 5-HMF synthesis. It is generally difficult
was examined as a function of time at different temperatures
ꢁ
to convert glucose into 5-HMF because the stability of six
(
Fig. 5). The reaction could proceed steadily at 70 C, while
12
membered pyran ring of glucose limits its conversion. It is
a relatively long time up to 90 min was required to obtain
a reasonable 5-HMF yield. Since the production of 5-HMF from
accepted that glucose should be rst isomerized into fructose
12–14
38,39
prior to the production of 5-HMF.
In order to get a reason-
fructose is mainly endothermic,
it is expected that elevating
able yield of 5-HMF, the conversion of glucose was investigated
temperatures lead to fast reaction rate and improved reaction
performance. The conversion was almost completed within
ꢁ
at 100 C. However, as seen in Table S3,† the studied system did
ꢁ
not work for the production of 5-HMF although the conversion
3
9
0 min at 80 C, and the time could be shortened to 15 min at
ꢁ
could be improved with mixtures of P
The tiny yield of 5-HMF indicated that metal chlorides such as
CrCl $6H O and AlCl $6H O did not enable the isomerization
of glucose into fructose under tested conditions.
2 5
O and metal chlorides.
0 C. A maximum 5-HMF yield of ꢀ80% was achievable under
such mild conditions.
3
2
3
2
Preliminary scaling-up tests were also carried out. Aer
ꢁ
3
0 min at 80 C, a 5-HMF yield of 74% with about 90% fructose
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a
Table 2 Results on the control experiments
Conflicts of interest
Fructose
conv. (%)
5-HMF
yield (%)
There are no conicts to declare.
Entry
Catalyst
1
2
P
P
P
P
H
H
2
2
2
2
O
O
O
O
5
5
5
5
37
88
33
29
6
9
66
4
21
75
18
16
2
3
52
0
+ NiCl
2
$6H
2
O
Acknowledgements
b
3
c
4
The authors thank for the support from the Natural Science
Foundation of Liaoning Province (China) (No. 2015020633),
Department of Education of Liaoning Province (China) (No.
L2015421), the National Natural Science Foundation of China
(No. 21673229, 21721004, 21706255) and the CAS/SAFEA Inter-
national Partnership Program for Creative Research Teams.
d
5
3
PO
PO
4
d
6
3
4
+ NiCl
2
$6H
2
O
7
P
NaH
Na HPO
2
O
5
+ NaCl
d
8
2
PO
4
d
9
2
4
5
0
a
2 5
Reaction conditions: fructose 60 mg; P O 10 mol% to fructose; metal
b
ꢁ
2
chloride 10 mol% to fructose; DMSO 1 mL; 80 C; 30 min. 4 mL of H O
c
d
(67 mol% to fructose) was added. 8 mL of H
2
O was added. Catalyst
2
0 mol% to fructose (equivalent to the mole of phosphorus in P ).
2
O
5
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