5-HMF production from glucose using ion exchange resin and alumina as a dual catalyst in a biphasic system

Article abstract of DOI:10.1039/c9ra09997b

5-HMF is a platform chemical that can be used in many applications such as biofuels, monomers, industrial feed stocks, etc. In this work 5-HMF was synthesized from glucose in a biphasic system using a batch reactor. Aluminium oxide and ion exchange resin were used as catalysts in this system. The organic solvent and aqueous solvent were methyl isobutyl ketone (MIBK) and 1-methyl-2-pyrrolidinone (NMP). The effect of operating conditions for synthesis of 5-HMF on the yield and selectivity of 5-HMF was studied including aqueous-to-organic phase ratio, NMP-to-water ratio, catalyst dosage, ratio of catalyst, and reaction time. The optimal conditions were at the reaction temperature of 120 °C and reaction time of 480 min, aqueous-to-organic phase ratio of 7 : 3, NMP-to-water ratio of 4 : 1, 0.3 g of catalyst, and the catalyst ratio of 1 : 2. The conversion of glucose, yield of 5-HMF, and selectivity of 5-HMF were 94.036%, 84.92%, and 90.48%, respectively.

Full text of DOI:10.1039/c9ra09997b

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5-HMF production from glucose using ion
exchange resin and alumina as a dual catalyst in
a biphasic system
Cite this: RSC Adv., 2020, 10, 9492
Supakrit Pumrod,a Amaraporn Kaewchada,b Supacharee Roddechaa
a
*
and Attasak Jaree
5-HMF is a platform chemical that can be used in many applications such as biofuels, monomers, industrial
feed stocks, etc. In this work 5-HMF was synthesized from glucose in a biphasic system using a batch
reactor. Aluminium oxide and ion exchange resin were used as catalysts in this system. The organic
solvent and aqueous solvent were methyl isobutyl ketone (MIBK) and 1-methyl-2-pyrrolidinone (NMP).
The effect of operating conditions for synthesis of 5-HMF on the yield and selectivity of 5-HMF was
studied including aqueous-to-organic phase ratio, NMP-to-water ratio, catalyst dosage, ratio of catalyst,
and reaction time. The optimal conditions were at the reaction temperature of 120 ꢀC and reaction time
of 480 min, aqueous-to-organic phase ratio of 7 : 3, NMP-to-water ratio of 4 : 1, 0.3 g of catalyst, and
the catalyst ratio of 1 : 2. The conversion of glucose, yield of 5-HMF, and selectivity of 5-HMF were
94.036%, 84.92%, and 90.48%, respectively.
Received 29th November 2019
Accepted 18th February 2020
DOI: 10.1039/c9ra09997b
rsc.li/rsc-advances
catalysts have been reported.7–10 Avantium (chemical company)
developed a large scale production of HMF and FDCA from
carbohydrates through chemical catalysis.11 This work focused
on the conversion of glucose to 5-HMF because it is the most
abundant C6 sugar in nature. This process involves isomeriza-
tion of glucose over base or Lewis acid sites followed by dehy-
dration reaction over Brønsted acid catalysts as shown in
Fig. 2.12
In the 1990s, Kuster13 synthesized 5-HMF from fructose in
a catalyst-free system by using water as a solvent and found that
the conversion of fructose was quite low because 5-HMF can
readily undergo rehydration with the surrounding water mole-
cules producing levulinic acid and formic acid. In addition,
polymerization of glucose, fructose, and 5-HMF can result in the
1. Introduction
5-Hydroxymethylfurfural is a versatile platform chemical that
can be used to produce various building-block compounds such
as furanic polyesters, polyamides, and polyurethanes due to the
presence of both hydroxyl and aldehyde functional groups in
the molecule.1,2 For example, 5-HMF can be oxidized over
a metallic catalyst for the production of 2,5-furan dicarboxylic
acid (FDCA), a chemical that can be used as raw material for the
production of polyethylene furanoate (PEF). PEF offers similar
physical, mechanical and chemical properties compared to
polyethylene terephthalate (PET). Hence, it has a potential to
partially substitute for terephthalic acid, which is used for the
production of polyethylene terephthalate. 5-HMF can be
hydrogenated to produce dihydroxymethyltetra hydrofuran
(DHMTHF), a monomer for polymer synthesis, or other appli-
cations such as precursor for production of 1,6-hexanediol.
Etherication of 5-HMF to 5-alkoxymethylfurfural ethers and
hydrogenolysis of 5-HMF to dimethylfuran (DMF) have been
proposed for liquid transportation fuels production.3–6 The
main derivatives of 5-HMF are shown in Fig. 1.
Due to the great potential of 5-HMF production from
carbohydrates such as cellulose, glucose and fructose, many
studies on the development of 5-HMF synthesis using different
aCenter of Excellence on Petrochemical and Materials Technology, Department of
Chemical Engineering, Faculty of Engineering, Kasetsart University, Chatuchak,
Bangkok, 10900, Thailand. E-mail: fengasj@ku.ac.th
bDepartment of Agro-Industrial, Food and Environmental Technology, King Mongkut's
University of Technology North Bangkok, Bansue, Bangkok, 10800, Thailand
Fig. 1 Derivative of 5-HMF.
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resin with sulfonic group and aluminium oxide (Al2O3) was used
as Brønsted acid and Lewis acid, respectively. The effect of reac-
tion time, N-methyl-2-pyrrolidone–water ratio in aqueous phase,
aqueous–organic phase ratio, the amount of catalyst, ratio of
catalysts (cation-exchange resin and aluminium oxide) on the
conversion of glucose as well as yield and selectivity of 5-HMF was
investigated. NaCl was added to increase immiscibility between
aqueous and organic phase, and nally layered as two phases. The
HMF product which in situ occurred in aqueous phase was
extracted to the organic phase and the side reaction was termi-
nated. Results were also compared with the literature data in
terms of reaction conditions, yield of 5-HMF, and selectivity of 5-
HMF.
Fig. 2 Synthesis HMF from glucose.
formation of humins which is a by-product as shown in Fig. 3.
The synthesis of 5-HMF was also studied by using homoge-
neous acid catalyst such as hydrochloric acid (HCl) and sulfuric
acid (H2SO4).14,15 Li et al. obtained the yield of 5-HMF of 62.45%
from the conversion of glucose using hydrochloric acid and
ꢀ
sulfuric acid as catalyst at the reaction temperature of 140 C
and reaction time of 60 min.16 The Brønsted bases were used as
catalyst but monosaccharides were unstable under such
conditions leading to the formation of by-products. However,
there are some drawbacks associated with the application of
homogeneous catalyst including the separation of product and
solvent, by-product formation, and corrosion of equipment.
These issues lead to the increased production cost. To alleviate
these problems, the use of heterogeneous catalyst with high
polarity solvent such as dimethyl sulfoxide or DMSO, tetrahy-
drofuran or THF17,18 and 1-ethyl-3-methylimidazolium chloride,
[BMM][Cl] was proposed.19 Degirmenci et al. studied glucose
dehydration into 5-HMF using Lewis acidic metal chlorides
(MeClx)/ionic liquid/SBA-15 as catalyst and obtained the glucose
conversion of 46% and the yield of 5-HMF of 22% at 150 ꢀC with
the reaction time of 3 h.20 However, the product–solvent sepa-
ration is necessary to recycle the solvent as well as to obtain
high purity product. Besides, the yield of 5-HMF was relatively
low compared to that of the homogeneous catalyst system. As an
alternative to the use of ionic liquid, Musau et al. studied the
synthesis of 5-HMF using cation-exchange resin (Diaion PK216)
and dimethylsulfoxide as solvent.21 The conversion of glucose of
approximately 90% was obtained at the reaction temperature of
90 ꢀC and the reaction time of 600 min. N-Methyl-2-pyrrolidone
(NMP) was also successfully applied as solvent for the synthesis
of 5-HMF from glucose in a biphasic system using cation-
exchange resin as catalyst.22 The conversion of glucose of 90%
and 5-HMF yield of 83% were achieved at the reaction temper-
2. Material & methods
2.1 Material
All chemicals including 1-methyl-2-pyrrolidinone (NMP),
acetonitrile (HPLC grade), and 5-hydroxymethylfurfural (AR
grade) for HPLC calibration were purchased from Sigma-
Aldrich. Methyl isobutyl ketone (AR grade) was purchased
from Merck. D-Glucose (AR grade) was purchased from Fisher
Scientic. Aluminium oxide was purchased from APS. Ion-
exchange resin (DIAION® RCP160M) catalyst was supplied by
Mitsubishi Chemical Corporation.
2.2 Catalyst characterization
In this work, dual catalyst was used to synthesize 5-HMF from
glucose in a biphasic system. Two types of acid catalyst in the
form of cation exchange resin with sulfonic, –HSO3 functional
groups and aluminium oxide (Al2O3) were used for the conver-
sion of glucose to 5-HMF. The total number of acid sites on the
ion-exchange resin and aluminium oxide surfaces was deter-
mined by acid–base back neutralization titration method and
NH3-TPD, respectively. The catalysts were suspended in 0.1 M
sodium hydroxide aqueous solution and stirred for 4 h followed
by ultrasonication for 1 h at room temperature. The concentra-
tion of OH– ions in the mixture was calibrated by a standard
solution of 0.1 M hydrochloric acid. Phenolphthalein was used as
an indicator for this titration. The titration continued until the
mixture was neutralized. The catalyst was also characterized by X-
ray diffraction (XRD), Fourier Transform Infrared Spectropho-
tometer (FTIR) and N2 adsorption–desorption.
ꢀ
ature of 90 C and reaction time of 12 h.
In this study, 5-HMF was produced by using dual heteroge-
neous catalyst in a biphasic system. High porosity cation-exchange
Fig. 3 Reaction scheme for 5-HMF production from glucose.
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located at 25.6ꢀ, 35.2ꢀ, 43.4ꢀ, 52.6ꢀ and 57.5ꢀ indicated that
traces of a-alumina was present in the catalyst. The percentages
of alpha-alumina and gamma-alumina were 34.9% and 65.1%,
respectively.
2.3 Synthesis of 5-HMF from glucose
The synthesis of 5-HMF was performed in a closed system. The
reactor was a round-bottom glass reactor equipped with a reux
condenser. For a typical experiment, glucose, aluminium oxide,
cation-exchange resin, NaCl, N-methyl-2-pyrrolidone, water and
MIBK were loaded in the reactor at ambient temperature. The
glass reactor was then placed in an oil bath with internal circu-
lation for temperature control at 120 ꢀC. During experiment, the
reacting mixture and catalyst were continuously stirred. Aer
a certain period of reaction time has elapsed, the reaction was
quenched by placing the glass reactor in an ice bath at 0 ꢀC
immediately. The solution was ltered by vacuum ltration. The
organic layer and aqueous layer were separated and analyzed by
high performance liquid chromatography (HPLC).
To investigate the functional groups which involve the
exchanging ion of cation-exchange resin, FTIR (PERKIN ELMER
Spectrum One) was used. The FTIR spectrum is presented in
Fig. 5. The peak located at 3500 cmꢂ1 contributed to the O–H
stretching and the C]C stretching was indicated at 1700 cmꢂ1
.
In addition, the peaks at 1200 and 1000 cmꢂ1 were associated
with the S]O stretching. Therefore, sulfonic functional groups
were present on the cation-exchange resin.
The surface area of catalyst was studied by N2-sorption
technique. As summarized in Table 1, it was found that the
surface areas of aluminium oxide and cation-exchange resin
were 74.8 and 48.5 m2 gꢂ1, respectively. This surface area was
similar to that of the Amberlyst-15 used for the synthesis of
hydroxymethylfurfural by Tuteja et al., who reported the
conversion of glucose and the yield of hydroxymethylfurfural at
the optimal conditions of 82% and 37%, respectively.23 The
acidity of catalyst was measured by titration and NH3-TPD
method. It was found that the acidity of cation-exchange resin
2.4 Product analysis
The liquid samples collected from batch experiments were
analyzed by high performance liquid chromatography (HPLC).
The Sugar HMP column (3.5 mm, 4.6 ꢁ 100 mm) was used to
determine the amount of glucose by using RI detector (model
YL9170, YL Instrument). The column temperature was main-
tained by a column oven (model TCM-004076, Waters) at 60 ꢀC,
and mobile phase was 0.005 M sulfuric acid solution at a ow
rate of 0.4 ml minꢂ1. The amount of 5-HMF in both layers was
determined using UV detector (model 2550, Varian) at the
wavelength of 320 nm. The ACE Excel 5 Super C18 reverse phase
column (4.6 mm ꢁ 250 mm, 5 mm particle size, Advanced
Chromatography Technologies) was held at 30 ꢀC and the
mobile phase was acetonitrile : water (10 : 90 (v/v)) at the ow
rate of 0.7 ml minꢂ1. The injector (model 7125, Rheodyne)
volume of the sample (ltered through 0.45 mm Nylon syringe
lter membrane) was 20 mL. The analysis was repeated three
times. The conversion of glucose, the yield of 5-HMF, and the
selectivity of 5-HMF were calculated as follows:
and aluminium oxide were 6.77 and 0.91 mmol gꢂ1
respectively.
,
3.2 Effect of aqueous : organic phase ratio
In a biphasic system, MIBK has been applied to prevent unde-
sired reactions of 5-HMF in the aqueous phase. Compared to
butanol and THF, MIBK offers better partitioning effect by
transferring 5-HMF into the organic phase.28 Therefore, the
NMP/H2O and MIBK were used in this study. The NMP/H2O and
MIBK volume ratio was varied from 5 : 5 to 2 : 8 and the total
volume of mixture was constant at 10 ml. The amount of catalyst
and catalyst ratio was constant at 0.4 g and 1 : 1, respectively.
The reaction time, temperature and NMP/H2O ratio were held
constant at 360 min, 120 ꢀC and 3 : 1, respectively. Fig. 6 shows
the effect of aqueous and organic phase ratio on the yield of 5-
HMF, conversion of glucose, and selectivity toward 5-HMF. It
Conversion of glucose
Conv. (%) ¼ (1 ꢂ (moles of glucose unreacted/moles
of starting glucose units)) ꢁ 100%
(1)
Yield of 5-HMF
YHMF (%) ¼ (moles of HMF produced/moles of
starting glucose units) ꢁ 100%
(2)
(3)
Selectivity of 5-HMF
SHMF (%) ¼ (YHMF/Conv.) ꢁ 100%
3. Result and discussion
3.1 The characterization of catalyst
First, the composition of aluminium oxide was determined by
using XRD technique (Bruker D8 Advance). As shown in Fig. 4,
the peaks were found at 2q of 25.6ꢀ, 32.9ꢀ, 35.2ꢀ, 37.7ꢀ, 43.4ꢀ,
45.5ꢀ, 52.6ꢀ, 57.5ꢀ, and 67.2ꢀ, respectively. The peaks which Fig. 4 XRD pattern of aluminium oxide.
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Fig. 5 FTIR spectrum of cation exchange resin.
Table 1 Surface areas of catalyst
Fig. 6 Effect of aqueous : organic phase ratio. Reaction conditions:
0.1 g of glucose, 0.2 g of cation exchange resin, 0.2 g of aluminium
oxide, 0.4 g of sodium chloride, NMP : H2O 3 : 1, 120 ꢀC and 360 min.
Catalyst
SBET (m2 gꢂ1
)
Source
phase were 3 and 7 ml. As shown in Fig. 7, it was found that
increasing the NMP/H2O volume ratio from 1 : 1 to 2 : 1 resulted
in a marked increase in the glucose conversion, yield of 5-HMF,
and selectivity of 5-HMF. This was due to the tautomerism of
fructose in NMP that favors the formation of fructofuranose.
This form of fructose is relatively active towards the formation
of 5-HMF compared to other forms.28 Therefore, the isomeri-
zation of glucose was shied to the product formation. Further
increasing the NMP/H2O volume ratio to 4 : 1 resulted in almost
a linear increase for both 5-HMF yield and selectivity while the
glucose conversion appeared to level off around 85%. This was
because NMP acted as an aqueous phase modier preventing
the formation of humin in water. Similar results were also re-
ported by Chheda et al. who studied the conversion of fructose
to 5-HMF by ion exchange resin as catalyst in biphasic system.
This reduced the possibility of 5-HMF undergoing rehydration
to form other by-products.17 Horvat et al. explained that the
addition of water to the 2, 3-carbon positions on 5-HMF resulted
in the undesired reactions (polymerization reactions) which can
form humin.30 Furthermore, the addition of water to 4, 5-carbon
positions led to the formation of levulinic acid and formic acid.
Therefore, the benecial effect of NMP on 5-HMF formation is
related to its ability to minimize ring opening of these carbon
atoms. In this system, there were four different tautomeric
forms of D-fructose (two pyranoids and two furanoids). The
furanoid form is promoted in DMSO and NMP due to the
similar molecular structure. The dehydration of fructose in this
from can undergo dehydration to selectively produce 5-HMF.
However, further increasing of NMP/H2O ratio from 4 : 1 to 1 : 0
resulted in a negative effect on the glucose conversion, yield and
selectivity of 5-HMF from 83.85% to 72.84%, 53.99% to 36.58%
and 66.77% to 37.16%, respectively. This was due to the transfer
of NMP into the organic phase and also the hydrophilic nature
of the sulfonic group of the cation exchange resin. Conse-
quently, the activity of RCP160M was reduced substantially.
This was in line with the work by Chen et al., who studied the
Aluminium oxide
Cation exchange resin
Amberlyst-15
Zirconium dioxide
Titanium dioxide
Fe3O4@SiO2–SO3H
SiO2–ATS–PTA
74.8
48.5
50
17
100
This work
This work
24
25
25
26
27
106.8
290.55
was found that at aqueous and organic phase ratio between 5 : 5
and 3 : 7 decreasing the volume ratio of aqueous phase to
organic phase boosted the conversion of glucose and the yield
of 5-HMF. This was due to the transfer of 5-HMF from aqueous
phase to organic phase, preventing the undesired reaction
(rehydration) of 5-HMF in the aqueous phase. The excess
amount of water in the system can lead to the formation of
levulinic acid and formic acid. However, lowering the aqueous-
to-organic phase ratio from 3 : 7 to 2 : 8 decreased the 5-HMF
yield and selectivity from 33.61% to 39.38% and 15.96% to
18.2%, respectively. It was probable that the part of the aqueous
phase dissolved into the excess MIBK and vice versa. Hence, in
the aqueous phase, the concentration of NMP (phase modier)
was affected as well as the glucose concentration, promoting the
conversion of glucose to other by-products. A similar effect was
reported for the study of the conversion of glucose into 5-HMF
using different solvents and catalysts.29 Kuster et al.13 reported
that cross-polymerization during the dehydration of fructose to
produce 5-HMF resulted in the formation of humins, especi-
cally in aqueous systems.
3.3 Effect of NMP/H2O ratio
To improve the reaction performance for the synthesis of 5-
HMF, the effect of NMP/H2O volume ratio was investigated. The
NMP/H2O volume ratio was varied from 1 : 1 to 4 : 1 while the
reaction time and temperature were held as constant at 360 min
ꢀ
and 120 C, respectively. The volumes of aqueous and organic
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Fig. 7 Effect of NMP : H2O volume ratio. Reaction conditions: 0.1 g of Fig. 8 Effects of catalyst amount. Reaction conditions: 0.1 g of
glucose, 0.2 g of cation exchange resin, 0.2 g of aluminium oxide, 0.4 g glucose, 0.4 g of sodium chloride, aqueous : organic phase volume
of sodium chloride, aqueous : organic phase volume 3 : 7, 120 ꢀC and 3 : 7, NMP : H2O 4 : 1, 120 ꢀC and 360 min.
360 min.
1 : 1 to 1 : 2 resulted in a slight increase of glucose conversion
and the yield of 5-HMF to 94.04% and 71.23%, respectively,
conversion of glucose to 5-HMF by using porous coordination
while the selectivity of 5-HMF was approximately the same.
polymer as heterogeneous catalysts.31
With two-thirds of catalyst being aluminium oxide, the isom-
erization proceeded rapidly. Despite the fact that the amount
3.4 Effect of catalyst amount
of cation-exchange resin was decreased from 0.15 to 0.10 g at
The inuence of catalyst dosage on the activity was investigated
by varying the total amount of catalyst in the range of 0.10–
0.40 g. Other parameters were kept constant. All experiments
were carried out with the ratio between cation exchange resin
and Al2O3 of 1 : 1, NMP : MIBK ratio of 3 : 7, 0.4 g NaCl , and
0.1 g glucose at 120 ꢀC for 360 min. As shown in Fig. 8, the yield
of 5-HMF increased from 24.68% to 64.86% with increasing the
amount of catalyst up to 0.30 g. Further increasing the amount
of catalyst resulted in a slight decrease for both yield and
selectivity of 5-HMF. It was possible that excess active site
provided by the high catalyst loading simultaneously induced
side reactions to some degree. Thus, the optimal catalyst
amount in this system was 0.30 g. Similar results were reported
by Elsayed et al. for the dehydration of glucose to 5-HMF using
core–shell Fe3O4@SiO2–SO3H magnetic nanoparticles.32
this ratio, the effect of equilibrium shiing prevailed. Further
decreasing the catalyst ratio to 1 : 3 resulted in a marked
decline in the yield and selectivity of 5-HMF while the
conversion of glucose increased slightly. Conceivably, the
increased amount of alumina at this ratio enhanced the
formation of humin from glucose. For the catalyst ratio of
0 : 1, we observed a substantial decline in the glucose
conversion, yield of 5-HMF, and selectivity of 5-HMF. This was
due to lack of Brønsted acid sites necessary for the dehydra-
tion of fructose. Hence, both glucose and fructose were
3.5 Effect of catalyst ratio
The effect of catalyst ratio was evaluated with the constant
reaction time of 360 min and the reaction temperature of
ꢀ
120 C. The catalyst ratio was studied from 1 : 0 to 0 : 1 while
the total amount of catalyst was kept constant at 0.30 g. As
shown in Fig. 9, a dramatic increase in terms of glucose
conversion, 5-HMF yield, and 5-HMF selectivity was observed
when the catalyst ratio was changed from 1 : 0 to 1 : 1. This
was due to the fact that ion-exchange resin (Brønsted acid) was
not effective for isomerization reaction. The presence of
aluminium oxide (Lewis acid) allowed the isomerization of
glucose to proceed more efficiently. This reaction was also
enhanced by the dehydration of fructose and the transfer of 5-
Fig. 9 Effect of catalyst ratio and Brønsted : Lewis acid sites ratio.
Reaction conditions: 0.1 g of glucose, 0.4 g of sodium chloride,
aqueous : organic phase volume 3 : 7, NMP : H2O 4 : 1, 120 ꢀC and
HMF into the organic phase. Lowering the catalyst ratio from 360 min.
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3.6 Effect of reaction time
ꢀ
A set of experiments were performed at 120 C with the aque-
ous : organic phase volume ratio of 3 : 7, NMP/H2O 4 : 1, 0.1 g of
ion exchange resin and 0.2 g of aluminium oxide while the
reaction time was varied from 120–600 min. As shown in Fig. 10,
the conversion of glucose, 5-HMF yield, and 5-HMF selectivity
increased almost linearly with increasing reaction time from
120 min to 360 min. Further increasing the reaction time to
480 min resulted in a slight increase of 5-HMF yield and
selectivity while the conversion of glucose was approximately
constant. This might be caused by the slow transfer of 5-HMF
from aqueous phase into the organic phase. However, at the
reaction time of 600 min, the yield and selectivity of 5-HMF
dropped to 54.65% and 55.57%, respectively. This can be
explained that a great extent of 5-HMF was further converted to
by-products due to the prolonged reaction time.33 Therefore, the
optimal conditions were as follows: 0.1 g of glucose, 0.4 g of
sodium chloride, catalyst ratio of 1 : 2, aqueous : organic phase
volume ratio of 3 : 7, NMP : H2O of 4 : 1, reaction temperature
Fig. 10 Effects of reaction time. Reaction conditions: 0.1 g of glucose,
0.4 g of sodium chloride, catalyst ratio of 1 : 2, aqueous : organic
phase volume ratio of 3 : 7, NMP : H2O of 4 : 1, reaction temperature
of 120 ꢀC.
ꢀ
of 120 C, and reaction time of 480 min. The glucose conver-
sion, 5-HMF yield, and 5-HMF selectivity were 93.85%, 84.92%,
and 90.48%, respectively.
3.7 Reuse of catalyst
To examine the stability of our catalyst, the system was scaled
up with the aqueous : organic phase of 6 : 14, NMP/H2O 4 : 1,
0.8 sodium chloride, ion exchange resin 0.2 g and aluminium
oxide 0.4 g. The experiments were carried out at the reaction
ꢀ
temperature and reaction time of 120 C and 360 min, respec-
tively. The yields of the 5-HMF reduced from 84.92% to 71.15%
aer ve consecutive runs as shown in Fig. 11. The total acidity
of ion exchange resin decreased to 5.48 mmol gꢂ1 aer 3 runs
and nally decreased to 4.06 mmol gꢂ1 aer 5 runs. The change
of catalytic activity was presumably attributed to the adsorption
and accumulation of oligomeric products on the acid sites of
catalyst.
Fig. 11 Effect of catalyst reuse.
3.8 Comparison of catalyst performance
polymerized to form other by-products. A similar behavior was
The performance of catalyst for 5-HMF production from glucose
was evaluated at the optimal operating conditions and
compared with the literature data. The comparison was
summarized in Table 2. It was found that synthesis 5-HMF from
glucose in a monophasic system using homogeneous catalyst
˜
´
reported by Nunez et al., who used g-Al2O3 as acid catalyst for
the dehydration of glucose to 5-HMF. Therefore, the optimal
catalyst ratio of 1 : 2 will be used for all subsequent
experiments.
Table 2 Catalyst performance for 5-HMF synthesis from glucose
Solvent
Catalyst
Temp (ꢀC)
Time (min)
HMF yield (%)
5-HMF selectivity (%)
Ref.
H2O
H2O
[BMIM]Cl
[EMim]BF4
NaCl–H2O/THF
NaCl–H2O–DMSO/MIBK
H2O–NaCl/MIBK
H2O–NMP–NaCl/MIBK
H3PO4
H3PO4/(NH4)2HPO4
GeCl4
180
180
140
100
180
140
195
120
20
20
30
180
240
600
30
12.4
23
48
61
45.3
53
—
—
34
27
35
14
36
33
37
53.33
56
45.3
66.25
64.29
93.85
SnCl4
PTA–PCP(Cr)–SO3H$Cr(III)
PBnNH3Cl
10Al-MCM
63
84.92
RCP160M
480
This work
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provided relatively low selectivity and yield of 5-HMF. The use of
ionic liquid and heterogeneous catalyst was able to enhance the
synthesis of 5-HMF. However, this system requires a separation
process to purify the product as well as to recycle the catalyst.
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4. Conclusions
In this study, the potential of dual catalyst as a mixture of ion
exchange and aluminium oxide for the synthesis 5-HMF from
glucose in a biphasic system was successfully demonstrated.
The NMP-to-water ratio enhanced the conversion of glucose,
yield and selectivity of 5-HMF. However, pure NMP as the
aqueous solvent turned the system into single phase. Increasing
the amount of catalyst promoted the synthesis of 5-HMF. Excess
catalyst also facilitated undesired side reactions. The ratio of
Lewis acid and Brønsted acid of 2 : 1 was suitable for a series of
isomerization and dehydration. The reaction time of 8 h was
sufficient to obtain high yield of 5-HMF without a signicant
loss through other side reactions. The glucose conversion, yield
and selectivity of 5-HMF of 84.92%, 90.48%, and 93.85%,
respectively, were obtained at the optimal conditions.
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Conflicts of interest
There are no conicts to declare.
Acknowledgements
The authors would like to thank Mitsubishi Chemical Corpo-
ration for providing the Ion-exchange resin (DIAION®
RCP160M) catalyst for this study. The nancial support from
the Agricultural Research Development Agency (Public Organi-
zation), grant number CRP6205031540, is acknowledged.
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