The physicochemical properties of a room-temperature liquidus binary ionic liquid mixture of [HNMP][CH3SO3]/[Bmim]Cl and its application for fructose conversion to 5-hydroxymethylfurfural

Article abstract of DOI:10.1039/c8ra03604g

Via heating first and then cooling, binary ionic liquid (IL) mixture of N-methyl-2-pyrrolidonium methylsulfonate ([HNMP][CH₃SO₃]) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) could form a liquid at room temperature. The glass-transition temperature (T_g) characterized by DSC depends on its composition with T_g being as low as -63 °C. The physicochemical properties of the binary IL mixtures also vary with the composition. With the increase of the mole fraction of [Bmim]Cl, the hydrogen-bond accepting ability (β) of the binary IL mixture increases, but the hydrogen-bond donating ability (α) deceases. In this binary IL mixture, fructose could be effectively converted into 5-hydroxymethylfurfural (HMF) at room temperature. The HMF yields at a given time are found to be well correlated with the physicochemical properties of the binary mixture, especially the α and β values. Under specified conditions, the present IL mixture as medium for fructose dehydration into HMF is comparable to the medium formed by ILs and alcohol, where the alcohols have negative effect on the HMF formation.

Full text of DOI:10.1039/c8ra03604g

RSC Advances
View Article Online
View Journal | View Issue
PAPER
The physicochemical properties of a room-
temperature liquidus binary ionic liquid mixture of
HNMP][CH SO ]/[Bmim]Cl and its application for
Cite this: RSC Adv., 2018, 8, 18784
[
3
3
fructose conversion to 5-hydroxymethylfurfural
Yuyan Xiao and Xirong Huang
*
Via heating first and then cooling, binary ionic liquid (IL) mixture of N-methyl-2-pyrrolidonium
methylsulfonate ([HNMP][CH SO ]) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) could form
3
3
g
a liquid at room temperature. The glass-transition temperature (T ) characterized by DSC depends on its
ꢁ
composition with T
g
being as low as ꢀ63 C. The physicochemical properties of the binary IL mixtures
also vary with the composition. With the increase of the mole fraction of [Bmim]Cl, the hydrogen-bond
accepting ability (b) of the binary IL mixture increases, but the hydrogen-bond donating ability (a)
deceases. In this binary IL mixture, fructose could be effectively converted into 5-hydroxymethylfurfural
Received 26th April 2018
Accepted 17th May 2018
(HMF) at room temperature. The HMF yields at a given time are found to be well correlated with the
physicochemical properties of the binary mixture, especially the a and b values. Under specified
conditions, the present IL mixture as medium for fructose dehydration into HMF is comparable to the
medium formed by ILs and alcohol, where the alcohols have negative effect on the HMF formation.
DOI: 10.1039/c8ra03604g
rsc.li/rsc-advances
14
being much lower than its component IL. For the viscosity of
a DSIL, a linear or non-linear change of viscosity with the
Introduction
15,16
Ionic liquids (ILs) are organic salts with melting point below composition could be also observed.
The changes
ꢁ
1
00 C. Compared with traditional molecular solvents, ILs can mentioned-above are usually accompanied by a composition-
be regarded as green solvents due to their low vapor pressure, dependent variation of the hydrogen-bond accepting and
good thermal stability and large liquidus temperature range. donating abilities, which will eventually affect its interaction
17,18
Also the physicochemical properties of ILs could be ne-tuned with the dissolved solute.
In general, by changing the type of
by altering the component ions or modifying the substituent ion and/or the ratio of the ions, one could obtain a binary IL
group on the ions, and thus, ILs are also considered as designer mixture with unique properties (e.g., melting point, viscosity,
solvents. As media, ILs could dissolve many inorganic polarity, hydrogen-bond accepting and donating abilities, etc.)
compounds, organic compounds and polymers; e.g., some and tune the chemical reactions in it.
ꢀ
ꢀ
imidazolium-based ILs containing Cl and OAc anions are
5-Hydroxymethylfurfural (HMF) is an important platform
1,2
proved to be good solvents for sugar. In addition, some ILs compound from which various chemicals could be derived. The
have been demonstrated to be catalytically active for some use of sugar as feedstock for the preparation of HMF is one of
3
–5
19,20
chemical reactions via specic solvent–solute interactions.
The physicochemical property of a two-ion IL could also be years, ILs have been tried as catalysts or media for the
tuned via its mixing with molecular solvent or another two-ion production of HMF.
The so-called ‘Double Salt Ionic Liquids’ (DSILs) are functionalized IL, [Bmim]Cl and [HNMP][CH
dened as salts composed of more than two types of ions.
the hotspots in the eld of biomass conversion.
In recent
21–23
As a sugar-dissolving IL and a proton
6–10
IL.
3
SO
3
]
are
6
frequently used for HMF production. However, both ILs are
Usually DSILs are obtained by mixing two simple ILs. Insight solid at room temperature, so the dehydration reaction has to
into the relationship between the composition of DSIL and its be carried out at higher temperature. Higher reaction temper-
physicochemical property has been presented for several binary ature usually results in byproducts (e.g., organic acids and
11–13
24
IL mixtures.
As far as the melting point is concerned, the humin) and also high energy consumption. For the room-
variation of the abundance of each ion could result in an IL temperature conversion of fructose to HMF, some organic
mixture with the melting point or glass-transition temperature molecular solvents are used to formulate deep eutectic solvents
25,26
(DES) with IL to lower the reaction temperature.
Our
previous study has shown that the DES containing alcohol as
hydrogen-bond donor has a negative effect on the HMF
Key Lab for Colloid and Interface Chemistry of the Education Ministry of China,
Shandong University, Jinan 250100, P. R. China. E-mail: xrhuang@sdu.edu.cn
18784 | RSC Adv., 2018, 8, 18784–18791
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
formation. The higher the polarity of the alcohol, the greater the a mixture of acetonitrile and water (15/85, v/v) and the ow rate
25,26
ꢀ1
negative effect.
So, it is of great signicance to formulate was maintained at 0.8 mL min . Under the present HPLC
a room temperature liquidus binary IL mixture, which is conditions, only HMF has a response to the detector with the
capable of dissolving sugar and catalyzing sugar dehydration. In retention time of 6.679 min. The actual concentration of HMF
the present study, the thermal behavior of the mixture of was obtained directly from the calibration curve (correlation
[
Bmim]Cl and [HNMP][CH
interestingly that a liquidus binary mixture of [Bmim]Cl/
HNMP][CH SO ] could be obtained at room temperature and In situ H NMR analysis
3 3
SO ] was investigated. It is found coefficient is 0.999).
1
[
3
3
in this medium fructose can be efficiently converted into HMF.
The HMF yields at a given time in binary mixtures of different
mole fractions are found to be well correlated with the physi-
cochemical properties of the media.
ꢁ
The fructose dehydration at 25 C was monitored on a Bruker
Avance 300 MHz spectrometer. First, 0.35 mmol fructose was
dissolved in 12.6 mmol methanol or DMSO. Then a binary IL
mixture formed by 0.70 mmol [HNMP][CH
Bmim]Cl was added and mixed. The resulting mixture was
transferred into a 5 mm (i.d.) NMR tube (a capillary lled with
O was put into the tube as external standard). Finally, the
3 3
SO ] and 4.2 mmol
[
Experiment
Materials
D
2
NMR tube was subsequently inserted into the chamber of the
spectrometer, followed by recording the H NMR spectra in
N-methyl-2-pyrrolidonium methylsulfonate ([HNMP][CH SO ],
1
3
3
9
9
9%) and 1-butyl-3-methylimidazolium chloride ([Bmim]Cl,
9%) were purchased from Shanghai Chengjie Chemicals Co.,

xed time intervals.
Ltd. N,N-Diethyl-4-nitroaniline (DENA, 97%) and acetonitrile
HPLC grade) were purchased from J&K Chemical Co., Ltd. 4-
Nitroaniline (NA, 98%) was purchased from Aladdin Industrial
Co., Ltd. 1-Ethyl-4-(methoxycarbonyl)pyridinium iodide (EMCPI,
Viscosity measurement
(
The viscosity of the binary IL mixtures was measured on
a Thermo Scientic HAAKE RheoStress 6000 rheometer at 25 C.
Prior to use, the rheometer was calibrated. All data given in the
report were an average of triplicate measurements.
ꢁ
97%) was purchased from TCI Co., Ltd. Fructose (98%), DMSO
(analytical grade) and methanol (analytical grade) were
purchased from Sinopharm Chemical Reagent Co., Ltd. Ultra-
pure water (18.25 MU cm) was used throughout the experiments.
Determination of solvatochromic parameters
Solvatochromic parameters of the probes (NA, DENA and
EMCPI) in binary IL mixtures were determined based on the
wavelength corresponding to the absorption maximum (lmax) of
each probe, which was measured on a UV-2550 UV-Vis spec-
trophotometer (Shimadzu Co., Suzhou, China). The stock
DSC traces of binary ionic liquid mixtures
A mixture of [HNMP][CH
3
SO
3
] and [Bmim]Cl hosted in an
ꢁ
airtight glass vial was kept at 80 C and stirred until it is molten.
The DSC trace of the binary mixture was recorded under the
nitrogen atmosphere on a PerkinElmer DSC8500 differential
scanning calorimeter. In a typical measurement, the sample
ꢀ3
solutions (1 ꢂ 10 M) of the probes were all made in methanol.
The samples for UV-vis measurement were prepared as follows:
First, an aliquot of a probe solution (40 mL) was pipetted into
a vial; aer methanol evaporation, an aliquot of a binary IL
mixture (800 mL) was added and thoroughly mixed for 24 h to
form a nal solution in the binary IL mixture. The nal
concentration of each probe in the solutions was 5 ꢂ 10ꢀ M.
ꢁ
ꢁ
(8.0 mg) was rst heated to 80 C and then kept at 80 C for
ꢁ
5
4
min. Aer that, the sample was cooled to ꢀ70 C at a rate of
ꢁ
ꢀ1
ꢁ
C min and held at ꢀ70 C for 5 min. Finally, the sample
ꢁ
ꢁ
ꢀ1
were reheated to 80 C at a rate of 4 C min
.
5
Typical procedure for fructose conversion into HMF
Results and discussion
All fructose dehydration reactions were carried out in a 5 mL
3 3
airtight glass vial. First, 3.30 mmol [HNMP][CH SO ] was mixed Thermal behavior of the binary IL mixtures
with a given amount of [Bmim]Cl and the mixture was then
heated and stirred until it is molten. The clear mixture was
subsequently cooled down to room temperature. Aer that,
[
3 3
HNMP][CH SO ] and [Bmim]Cl (their structures are shown in
Scheme 1), commonly used respectively as catalyst and solvent
for HMF production, are both solid at ambient temperature,
however, a room-temperature liquidus binary IL mixture could
1
.65 mmol fructose was added and the resulting system was
ꢁ
stirred at 600 rpm for a certain period of time at 25 C. Finally,
the resulting mixture was diluted with ultrapure water and then
analyzed by HPLC. All HMF yields reported in this study were an
average of triplicate experiments.
ꢁ
be obtained by rst heating the solid IL mixture to 80 C and
then cooling down to the room temperature. The resulting
liquid did not crystallize in a week, indicating the much slower
crystallization process. This supercooling phenomenon could
be explored for room-temperature HMF production.
HPLC analysis
For further study, DSC curves of the neat ILs and their
The separation and the detection of HMF were carried out on an mixtures were recorded (see Fig. 1). For neat [HNMP][CH SO ],
3
3
ꢁ
HPLC apparatus equipped with a Shim-pack VP-ODS C18 an exothermal peak at ca. ꢀ8 C and an endothermal peak at ca.
ꢁ
column (250 mm ꢂ 4.6 mm), a Shimadzu LC-20AT pump and 52 C were observed during the cooling and reheating, which
a Shimadzu SPD-20A detector at 283 nm. The mobile phase was correspond to the crystallization and the melting of [HNMP]
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 18784–18791 | 18785

View Article Online
RSC Advances
Paper
a ¼ 0.0485P ꢀ 2.75 ꢀ 0.46p*
b ¼ 0.358 ꢂ (31.10 ꢀ nmax,NA) ꢀ 1.125p*
(3)
(4)
The derived solvatochromic parameters (p*, a and b) as well
as the viscosity (h) of the binary IL mixtures are shown in Fig. 2.
It is seen that, with the increase of the mole fraction of [Bmim]
Cl (x), the absorption maximum of EMCPI moves towards
longer wavelength, which indicates the polarity of the binary IL
mixtures decreases (the ground state of EMCPI is more polar
than its excited state). As for a and b values, Fig. 2A shows that
they are both proportional to the x value; with the increase of
3 3
Scheme 1 Structures of [Bmim]Cl and [HNMP][CH SO ].
[Bmim]Cl content, b increases from 0.46 to 0.91, but a decreases
from 0.81 to 0.44. This is because in the present binary IL
ꢀ
[
CH SO ], respectively. The discrepancy between the melting mixtures, Cl is
a
better hydrogen-bond acceptor than
3
3
27
ꢀ
+
and the freezing temperatures is due to supercooling. As for [CH SO ] , while [HNMP] is a better hydrogen-bond donor
3
3
ꢁ
+
6,11
neat [Bmim]Cl, it melts at 68 C, but aer heated, the molten than [Bmim] . For the viscosity of the binary mixtures, Fig. 2B
Bmim]Cl has no crystallization peak and only glass transition shows that it rises nonlinearly as a function of the x value. This
[
ꢁ
ꢁ
phenomenon (at ca. ꢀ39 C and ꢀ48 C) was observed in the trend could be explained using a similar rationale to that for the
ꢁ
ꢀ1
course of cooling and reheating at the rate of 4 C min (as composition-dependent T , i.e., the ions interaction is the major
g
ꢁ
ꢁ
28
6,32
reported in literature they are at ꢀ41 C and ꢀ48 C). This factor, the larger the force, the larger the viscosity.
phenomenon indicates that the crystallization of [Bmim]Cl is
kinetically much slower than that of [HNMP][CH SO ].
29,30
For
3
3
their mixture, a thermal behaviour similar to the neat [Bmim]Cl Fructose conversion into HMF in binary IL mixtures
was also observed, but the glass-transition temperature (T
g
) was
Fig. 3 shows the time-dependent HMF yield in IL mixtures of
different mole fractions under the reaction conditions of 25 C
ꢁ
shied to lower temperature (ca. ꢀ63 C). The present thermal
ꢁ
behaviours of the binary IL mixture are very similar to those
and 600 rpm. For a given amount of fructose, the HMF yield in
a given time interval increases with the increase of x. Speci-
cally, the HMF yield in 1.0 h varies from the lowest 24.6% to the
highest 73.0%, which indicates that the composition of the
binary IL mixtures affects the formation rate. Based on the
physicochemical properties of the binary mixture (characterized
in the previous section), we speculate that the change may be
related to the viscosity and/or the hydrogen-bond donating/
accepting ability of the medium.
To explore the effect of the viscosity on the formation rate,
a less viscous IL mixture (x ¼ 0.33) and a more viscous IL
mixture (x ¼ 0.86) were selected as media for fructose dehy-
dration, and the HMF yield at a given time in the two media
under different stirring speeds were compared (see Fig. 4). As
shown in Fig. 4, the formation rate of HMF under unstirred
condition is low in both media. The HMF yields in 1.0 h and
2
7,31
reported elsewhere.
Bmim]Cl, the T
It is noteworthy that with the increase of
ꢁ
ꢁ
[
g
of IL mixture rose from ꢀ63 C to ꢀ52 C. This
composition-dependent phenomenon could be rationalized as
ꢀ
follows: on the one hand, more Cl anions, which have smaller
size and higher charge density, result in an enhancement of the
coulombic interaction between ions; on the other hand, the
+
hydrogen-bond donating ability of [HNMP] is stronger than
+
+
that of [Bmim] , so the decrease of [HNMP] content results in
weaker hydrogen bonds and therefore more ordered ionic
32
structure, thereby enhancing ion–ion interaction. However,
the reason why the T values of the binary mixtures in [HNMP]
g
[
CH SO ]-rich region change little is not clear and it need
3 3
further investigation.
Physicochemical properties of the binary IL mixtures
5
.0 h were 10.2% and 23.7% (x ¼ 0.33) and 13.0% and 19.9% (x
The polarity (P), hydrogen-bond donating ability (a) and
¼
0.86), respectively. Relatively speaking, the increment in HMF
hydrogen-bond accepting ability (b) of the binary IL mixtures at
ꢁ
yield in the less viscous mixture is larger than that in the more
viscous mixture. This result indicates that the more viscous the
binary IL mixture is, the greater the mass transfer resistance
and the slower the HMF formation rate. To eliminate the mass
transfer resistance, the reaction system was subjected to agita-
tion. Under the conditions of 600 rpm and 1200 rpm, HMF
yields aer 5.0 h were 45.4% and 48.9% (x ¼ 0.33) and 87.4%
and 88.0% (x ¼ 0.86), respectively. Compared with that under
2
5 C were determined using solvatochromic dyes as probes.
The P parameter is calculated based on eqn (1), where lmax,EMCPI
is the wavelength corresponding to the absorption maximum of
EMCPI in the binary IL mixtures (see Table 1). The a and
b parameters are calculated based on eqn (2)–(4), where
nmax,DENA and nmax,NA are the wavenumbers converted based on
the absorption maxima of DENA and NA in binary IL mixtures
33,34
(see Table 1).
600 rpm, further increase of stirring speed could not enhance
the HMF formation rate signicantly. It follows that without
stirring, the viscosity of the media has signicant negative effect
(2) on the fructose dehydration due to the mass transfer resistance.
P ¼ 28591/lmax,EMCPI
p* ¼ 0.314 ꢂ (27.52 ꢀ nmax,DENA
(1)
)
18786 | RSC Adv., 2018, 8, 18784–18791
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
a
b
Fig. 1 DSC thermograms of pure ILs and their mixtures. x represents the mole fraction of [Bmim]Cl. For pure ILs, the onset temperature is
considered as the melting or freezing temperature; for mixture, the temperature at the peak position was considered as T
g
.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 18784–18791 | 18787

View Article Online
RSC Advances
Paper
Table 1 The wavelength corresponding to the absorption maximum
ꢁ
a
of a probe in the binary IL mixtures at 25 C
c
[Bmim]Cl
0.00 0.33 0.50 0.67 0.80 0.86 0.89 1.00
b
l
l
l
max,EMCPI /nm 345
max,DENA /nm
max,NA /nm
348
415
388
352
413
390
354
414
393
362
415
397
365
416
398
370
417
399
375
416
398
b
411
375
b
a
Pure ILs are solid at RT, therefore, the probe solutions in them were
ꢁ
35
b
prepared at 80 C.
The wavelength corresponding to absorption
maximum of the probe in each solution was determined via the rst-
order derivative transformation.
When the mass transfer resistance was overcome by stirring, the
viscosity is no longer the key factor affecting the formation rate
of HMF.
Fig. 3 Kinetic curves of fructose dehydration into HMF in binary IL
mixtures of different mole fraction.
It is known that the interaction between ILs and reactant/
intermediates/products have effects on chemical reactions in
17,36–39
the ILs as media.
Here, an attempt was made to correlate
3 3
shown that [HNMP][CH SO ] is helpful for the conversion of
the formation rate of HMF with the hydrogen-bond donating/
accepting ability of the binary IL mixtures. To prevent the
interference from the preferential solvation in the [Bmim]Cl-
rich medium and from the negative effect of the high viscosity
fructose into intermediates whether or not [Bmim]Cl is present;
the presence of [Bmim]Cl, however can enhance the trans-
formation of intermediates due to the formation of hydrogen
ꢀ
bond between the Cl and the hydroxyl involved in the
17
on the mass transfer, only data over x ¼ 0.33–0.80 are used for
discussion. In this region, it is found that the HMF yields at
a given time (t ¼ 300 min) in different media are well correlated
with the a and b values (Fig. 5). This indicates that the change of
x not only leads to a change of its physicochemical properties,
but also affects the formation rate of the involved dehydration
reaction.
The dehydration of fructose into HMF goes through the
following basic route (see Scheme 2). Our previous study has
Fig. 4 Effect of the stirring on the formation rate of HMF in two
different binary IL mixtures. Reaction condition: First, 1.65 mmol
fructose was dissolved into the binary IL mixtures, then the resulting
Fig. 2 Variation of solvatochromic parameters (A) and viscosity (B) mixtures were kept stirring at 0 rpm, 600 rpm or 1200 rpm for 5.0 h at
ꢁ
with mole fraction of [Bmim]Cl in the mixture.
25 C.
18788 | RSC Adv., 2018, 8, 18784–18791
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
with DESs formulated by IL/alcohol, the alcohol effect on fruc-
tose dehydration in the present binary IL mixture was investi-
gated. As shown in Fig. 6, the HMF yield at a given time in the
binary mixture with methanol was much lower than that with
DMSO (the latter was very close to that without any additive)
(note: there is a dilution effect in the presence of additives). This
result shows the presence of alcohol has a negative effect on
HMF formation rate.
1
To investigate the effect of additives, in situ H NMR was
used to monitor the fructose dehydration process (see Fig. 7). In
the medium with methanol, the height of signals of interme-
diates 1 and 2 (Scheme 2, marked as I and II, respectively)
increases gradually with time and moreover, they are much
higher at a given time than those of signals of HMF (labelled
with C), indicating that the transformation of intermediates 1
and 2 are very slow. In the medium with DMSO, the formation
and transformation of intermediates 1 and 2 are very fast due to
the absence of the negative effect of methanol, so the signal of
intermediate 1 (peak I) was not detected and the signal of
intermediate 2 (peak II) was observed only at the very beginning
of the reaction (within 5 min); moreover, the signals of HMF
increased with the increase of reaction time. The above result
demonstrates that the binary mixture composed of [HNMP]
Fig. 5 A plot of a (b) versus HMF yield at a given time (t ¼ 300 min) in
different binary IL mixtures.
transformation, which promotes the transfer of proton on
+
25,26
[
HNMP] to the leaving hydroxyl (see Scheme 3).
Since the
amount of [HNMP][CH SO ] as proton donor is much more in
3
3
the present study than that of fructose, the medium effect on
the HMF formation rate should be proportional to the content
of [Bmim]Cl, i.e. the b values.
3 3
[CH SO ] and [Bmim]Cl could effectively catalyse fructose
conversion into HMF, and the presence of methanol has
a marked negative effect. Based on our previous research, we
speculate that the negative effect is exerted mainly via the
hydrogen bond formed between methanol and the ILs. On the
one hand, the hydroxyl on methanol can compete with that of
Comparison with IL/Alcohol medium
[Bmim]Cl could interact with short-chain alcohols to form
DESs, which are liquids at room temperature. The use of these
DESs as media for fructose dehydration into HMF has been
+
26
fructose to form a six-membered ring with [HNMP] , weakening
reported. It has been found that the alcohol as HBD will
compete with both fructose and intermediates to form
hydrogen bonds with ILs, leading to a negative effect on fruc-
tose conversion or intermediates transformation. To compare
+
the interaction between [HNMP] and fructose or intermediates.
On the other hand, methanol can also act as HBD to form
ꢀ
+
hydrogen bond directly with Cl or [HNMP] , destabilizing the
Scheme 2 Route of fructose dehydration into HMF.
Scheme 3 Proposed mechanism for the concerted activation of the intermediates by [HNMP][CH
3 3
SO ] and [Bmim]Cl.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 18784–18791 | 18789

View Article Online
RSC Advances
Paper
Conclusions
For the rst time, a room temperature liquidus binary IL
mixture of [HNMP][CH SO ]/[Bmim]Cl was prepared, the
3
3
composition-dependent physicochemical properties were
characterized, the binary mixture as medium for the room-
temperature fructose dehydration into HMF was tried, and
a correlation between the formation rate of HMF and the
physicochemical parameters were made. It was shown that
a liquidus binary IL mixture could be formed at room temper-
ature when the ILs were subjected to heating and then cooling
down to room temperature. No precipitation was observed in
a week at ambient temperature. The P, a and b values of the
binary IL mixtures vary in a regular way with the change of the
mole fraction of the two ILs. The viscosity of the binary mixtures
Fig. 6 Effect of additives on the fructose dehydration into HMF in the
IL mixture (x ¼ 0.86). Reaction condition: 0.35 mmol fructose was
3 3
added into a binary mixture composed of 0.7 mmol [HNMP][CH SO ]
and 4.2 mmol [Bmim]Cl, followed by adding 12.6 mmol methanol or
ꢁ
DMSO. The resulting mixtures were stirred at 600 rpm for 5 h (25 C). has an impact on the fructose dehydration but it is not the key
factor when an agitation was exerted. The HMF yields at a given
time in different binary IL mixtures are well correlated with the
physicochemical properties (especially a and b). Under speci-
ed conditions, the present IL mixture as medium for fructose
dehydration into HMF is comparable to the medium formed by
ILs and alcohol, where the alcohols have negative effect on the
HMF formation.
transition state and resulting in an accumulation of interme-

diates 1 and 2. DMSO as a hydrogen-bond acceptor can neither
ꢀ
form hydrogen bond with Cl nor a six-membered ring with
+
[
HNMP] , thus, the addition of DMSO has little impact on the
fructose dehydration into HMF.
Conflicts of interest
There are no conicts to declare.
Acknowledgements
We are grateful for the nancial support from the Fundamental
Research Funds of Shandong University (2015CJ005), the
Provincial Key R & D Project of Shandong (2015GSF121035) and
the National Natural Science Foundation of China (21773143).
Notes and references
1
P. Moyer, M. D. Smith, N. Abdoulmoumine, S. C. Chmely,
J. C. Smith, L. Petridis and N. Labbe, Phys. Chem. Chem.
Phys., 2018, 20, 2508–2516.
2
3
4
R. P. Swatloski, S. K. Spear, J. D. Holbrey and R. D. Rogers, J.
Am. Chem. Soc., 2002, 124, 4974–4975.
S. T. Keaveney, R. S. Haines and J. B. Harper, Org. Biomol.
Chem., 2015, 13, 3771–3780.
M. Gazitua, R. A. Tapia, R. Contreras and P. R. Campodonico,
New J. Chem., 2014, 38, 2611–2618.
5
6
X. Kang, X. Sun and B. Han, Adv. Mater., 2016, 28, 1011–1030.
G. Chatel, J. F. B. Pereira, V. Debbeti, H. Wang and
R. D. Rogers, Green Chem., 2014, 16, 2051–2083.
H. Niedermeyer, J. P. Hallett, I. J. Villar-Garcia, P. A. Hunt
and T. Welton, Chem. Soc. Rev., 2012, 41, 7780–7802.
J. Zhu, K. Yu, Y. Zhu, R. Zhu, F. Ye, N. Song and Y. Xu, J. Mol.
Liq., 2017, 232, 182–187.
7
8
9
1
Fig. 7 H NMR spectra collected during fructose dehydration in the IL
Y. Xu, J. Chem. Thermodyn., 2013, 64, 126–133.
mixture (x ¼ 0.86) with (A) methanol or (B) DMSO.
10 Y. Xu, H. Zhu and L. Yang, J. Chem. Eng. Data, 2013, 58, 2260–
2266.
18790 | RSC Adv., 2018, 8, 18784–18791
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
1
1
1
1
1 P. Bharmoria, K. Damarla, T. J. Trivedi, N. I. Malek and 25 J. Zhang, X. Yu, F. Zou, Y. Zhong, N. Du and X. Huang, ACS
A. Kumar, RSC Adv., 2015, 5, 99245–99252. Sustainable Chem. Eng., 2015, 3, 3338–3345.
2 Y. Huang, X. Zhang, Y. Zhao, S. Zeng, H. Dong and S. Zhang, 26 J. Zhang, Y. Xiao, Y. Zhong, N. Du and X. Huang, ACS
Phys. Chem. Chem. Phys., 2015, 17, 26918–26929. Sustainable Chem. Eng., 2016, 4, 3995–4002.
3 F. D'Anna, S. Marullo, P. Vitale and R. Noto, ChemPhysChem, 27 G. Annat, M. Forsyth and D. R. MacFarlane, J. Phys. Chem. B,
012, 13, 1877–1884. 2012, 116, 8251–8258.
4 G. J. Maximo, R. J. B. N. Santos, P. Brandao, 28 M. Kick, K. Philipp and A. K ¨o nig, Fluid Phase Equilib., 2013,
J. M. S. S. Esperanca, M. C. Costa, A. J. A. Meirelles, 338, 172–178.
M. G. Freire and J. A. P. Coutinho, Cryst. Growth Des., 29 O. Yamamuro, Y. Minamimoto, Y. Inamura, S. Hayashi and
014, 14, 4270–4277. H. O. Hamaguchi, Chem. Phys. Lett., 2006, 423, 371–375.
5 D. Y. Song and J. Chen, J. Chem. Eng. Data, 2014, 59, 257–262. 30 K. Nishikawa, S. Wang, H. Katayanagi, S. Hayashi,
2
2
1
1
6 N. Zhao, J. Jacquemin, R. Oozeerally and V. Degirmenci, J.
Chem. Eng. Data, 2016, 61, 2160–2169.
H.-o. Hamaguchi, Y. Koga and K.-i. Tozaki, J. Phys. Chem.
B, 2007, 111, 4894–4900.
1
1
1
2
2
2
2
2
7 E. Priede, S. Brica, E. Bakis, N. Udris and A. Zicmanis, New J. 31 M. Kunze, S. Jeong, E. Paillard, M. Winter and S. Passerini, J.
Chem., 2015, 39, 9132–9142. Phys. Chem. C, 2010, 114, 12364–12369.
8 S. Marullo, F. D'Anna, P. R. Campodonico and R. Noto, RSC 32 K. Fumino, S. Reimann and R. Ludwig, Phys. Chem. Chem.
Adv., 2016, 6, 90165–90171. Phys., 2014, 16, 21903–21929.
9 I. K. M. Yu and D. C. W. Tsang, Bioresour. Technol., 2017, 238, 33 A. Duereh, Y. Sato, R. L. Smith and H. Inomata, J. Phys.
16–732. Chem. B, 2016, 120, 4467–4481.
0 P. Zhou and Z. Zhang, Catal. Sci. Technol., 2016, 6, 3694– 34 Y. Marcus, Chem. Soc. Rev., 1993, 22, 409–416.
7
3
712.
35 Y. Fukaya, A. Sugimoto and H. Ohno, Biomacromolecules,
2006, 7, 3295–3297.
1 Y. Ma, S. Qing, L. Wang, N. Islam, S. Guan, Z. Gao, X. Mamat,
H. Li, W. Eli and T. Wang, RSC Adv., 2015, 5, 47377–47383. 36 S. H. Mushrif, S. Caratzoulas and D. G. Vlachos, Phys. Chem.
2 C. Shi, Y. Zhao, J. Xin, J. Wang, X. Lu, X. Zhang and S. Zhang,
Chem. Commun., 2012, 48, 4103–4105.
3 F. D'Anna, S. Marullo, P. Vitale, C. Rizzo, P. Lo Meo and
R. Noto, Appl. Catal., A, 2014, 482, 287–293.
Chem. Phys., 2012, 14, 2637–2644.
37 C. C. Weber, A. F. Masters and T. Maschmeyer, J. Phys. Chem.
B, 2012, 116, 1858–1864.
38 H. Kimura, M. Nakahara and N. Matubayasi, J. Phys. Chem. A,
2013, 117, 2102–2113.
4 T. Wang, M. W. Nolte and B. H. Shanks, Green Chem., 2014,
16, 548–572.
39 X. Yu, M. Wang and X. Huang, J. Mol. Liq., 2016, 216, 354–
359.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 18784–18791 | 18791