2
54
J. Shi et al.
Chemical Company and dried prior to use. Others are
prepared according to the published reports [23–26]. Sul-
furic acid (98 %) and other chemicals (AR) are commer-
cially available and used without further purification unless
otherwise stated.
3.2 Degradation of Sucrose to HMF
We initially attempt to prepare HMF from sucrose directly
and characterize the reactivity of sucrose with different
conditions. It was found that the degradation of sucrose
was performed well in [AMIM]Cl and [BMIM]Cl
2
.2 Typical Procedure for Synthesis of Ionic Liquids
(Table 2). In the absence of H
declined at 120 °C. For example, the addition of 0.1 mL
O enabled HMF yields of 87.0 % (entry 3) in [AMIM]Cl
for 1 h catalyzed by [NMP][HSO ], but it was only 82.2 %
2
O, the yield of HMF
The preparation procedures of the ILs used in this study
and characterization data were presented in supplementary
data file.
H
2
4
(entry 1) at the same conditions without addition of water.
It is not difficult to understand, because sucrose is a typical
disaccharide and a small amount of water can improve the
hydrolysis process in the early stages of the degradation
reaction. The kind of solvent seem to have a great impact
on the yield of HMF, higher HMF yields were obtained in
either [AMIM]Cl or [BMIM]Cl when compared to 1-alkyl-
3-methylimidazolium bromide solvents (entries 5–6). In
addition, when it came to test about the reactivity of
[EMIM]Ac (entry 7), we further discovered that there was
no HMF formed and nearly all sucrose changed to a kind of
intractable gel. When reactions were carried out with dif-
ferent catalysts, HMF yields obtained from the same sol-
vent did not change too much. It indicated that both the two
catalysts used in this work were appropriate for the present
reaction system.
2
.3 Representative Procedure for Synthesis of HMF
from Carbohydrates
The catalytic conversion of sucrose to HMF is carried out in a
stainless steel autoclave with glass liner tube that is heated in
the oil-bath. Typically, 0.1712 g sucrose (0.5 mmol) is
added into 2 mL [AMIM]Cl solvent, followed by the addi-
tion of the desired catalyst and H O at the reaction temper-
2
ature. After the appointed reaction time, 0.1 mL samples are
pipetted, quenched immediately with NaOH solution and
diluted with deionized water (9100). The solution is cen-
trifuged at 10,000 rpm for 10 min and the upper clear liquid
is pipetted off and diluted with deionized water (910). Any
humins are removed prior to HPLC analysis. Only low levels
of colored products, other than HMF, are detected by HPLC.
More experimental sections are presented in supple-
mentary data file.
3.3 Degradation of Maltose and Lactose to HMF
Maltose is another important disaccharide, we found the
transformation of it into HMF to be challenging (Table 3).
Only [AMIM]Cl acted as an efficient solvent resulting in the
yield of HMF about 30 % (entry 6), which was far higher than
3
Results and Discussion
3
.1 Examine Various Catalysts
that obtained in other solvents catalyzed by [NMP][HSO ]
4
with the additive of CoCl at 140 °C for 1 h. Maltose almost
2
The activity of various catalysts for the sucrose conversion in
AMIM]Cl was investigated and the results were presented
can not convert into HMF in [BMIM]Cl (entry 2) according to
[
our study. Slightly higher yields of HMF were obtained in
in Table 1. From the results, we can see that [NMP][HSO4]
and [C SO HMIM][HSO ] exhibited excellent activity in
[AMIM]ClwiththeadditiveofMnCl
enabled the better yields, the highest yield was 55.7 % (entry
12) catalyzed by [C SO HMIM][HSO
] at 140 °C for 0.5 h,
indicating that [C SO HMIM][HSO ] performed better
compared to [NMP][HSO ] catalyst, which revealed only
2 2
(entries4,9), butCoCl
3
3
4
[
AMIM]Cl, with the HMF yields of 82.3 % (entry 5) and
3
3
4
7
8.5 % (entry 6) at 120 °C for 1 h, respectively. These
3
3
4
results were more competitive when compared to GeCl [27]
4
4
and Amberlyst-15 [28], which the solvent was [BMIM]Cl
and TEAB, respectively. Moreover, the Brønsted-acidic ILs
commonly had more efficient activity than mineral acids and
30.4 % (entry 6) yield of HMF in the same reaction
conditions.
For further study of lactose in Table 3, this disaccharide
showed a lower activity compared to sucrose and maltose.
heteropolyacids, except [MIM][HSO ], which presented
4
much lower acidity among these IL catalysts (Supplemen-
tary data, Table S1), only 36.6 % (entry 4) of HMF was
obtained. The different yields of HMF revealed that both
catalyst and solvent had great influence on sucrose conver-
sion, especially the acidity and structure of catalyst, obvi-
It was hard to use the catalyst of [NMP][HSO ] to promote
4
the conversion of lactose into HMF, with a maximum yield
of 19.5 % (entry 15) achieved at 140 °C. However,
[C
SO HMIM][HSO ] was more suitable (entries 18–21)
3 4
3
for the present system according to Table 3, the highest
ously, the catalytic system of [NMP][HSO ]–[AMIM]Cl
4
yield of HMF was 36.1 % (entry 21) with adding CoCl as
2
met the requirements.
a co-catalyst in [AMIM]Cl at 140 °C.
1
23
Shi, Jincai
