Production of 5-hydroxymethylfurfural from mono- and
disaccharides in the presence of ionic liquids
Jincai Shi, Wentao Liu, Ningning Wang, Yan Yang, Haijun Wang*
School of Chemical and Material Engineering, Jiangnan University, Lihu Road, Wuxi 214122,
China
Catalysis Letters
Supplementary data
Contents
1. Synthesis procedure of ILs used in the study
2. Experimental Section
3. References
4. The 1H NMR charts of ILs
5. Supporting figures
6. The optimized geometries for the intermediates and transition states
1. Synthesis Procedure of ILs used in the study
1.1 Preparation of [C3SO3HMIM][HSO4]
N-methylimidazole (0.11 mol) and 1, 3- propane sulfone (0.10 mol) were
dissolved in acetonitrile (20 mL) and stirred for 3 h at 80℃ under a nitrogen
atmosphere. A white precipitate formed which was filtered, washed with diethyl ether
three times, and then dried in avacuum. The resulting white precipitate (0.06 mol) was
added to an aqueous solution of H2SO4 (0.06 mol), and then the mixture was stirred at
room temperature for 2 h. Water was removed in vacuum to give the product. 1H
NMR (400 MHz, D2O): δH (ppm) = 2.29-2.36 (2H, m), 2.91-2.95 (2H, t), 3.91 (3H, s),
4.35-4.39 (2H, t), 7.46 (1H, s), 7.53 (1H, s), 8.75 (1H, s).
Scheme S1. Synthesis of the sulfonic acid ionic liquid [C3SO3HMIM][HSO4].
1.2 Preparation of [NMP][HSO4]
[NMP]HSO4 was obtained by mixing N-methyl-2-pyrrolidone (0.1 mol) with
concentrated sulfuric acid (0.1 mol) at 0-5 °C and stirring for 4 h at room temperature.
The liquid was then washed with ethyl acetate (3×10 mL) and dried at 80 °C in
vacuum. The IL was obtained in quantitative yield. 1H NMR (400 MHz, D2O): δH
(ppm) = 2.01-2.09 (2 H, m), 2.42-2.48 (2 H, t), 2.84 (3H, s), 3.50-3.54 (2H, t).
Scheme S2. Synthesis of the acid ionic liquid [NMP][HSO4].
1.3 Preparation of [AMIM]Cl
[AMIM]Cl is prepared according to the reported procedures1. N-methylimidazole
and allyl chloride at a molar ratio 1:1.25 are added to a round–bottomed flask fitted
with a reflux condenser for 8 h at 50 °C with stirring. The unreacted chemical
reagents and other impurities, such as water, are removed by vacuum distillation, and
the obtained product [AMIM]Cl is further purified using ethyl acetate and ether. After
further evaporation of volatiles, the product is dried in a vacuum oven at 60 °C for 2
days. 1H NMR (400 MHz, D2O): δH (ppm)= 3.82 (3H, s), 4.72 (2H, d), 5.35–5.27 (2H,
m), 5.97 (1H, m), 7.39-7.37 (2H, d), 8.64 (1H, s).
Scheme S3. Synthesis of the ionic liquid solvent [AMIM]Cl.
1.4 Preparation of [BMIM]Cl
The ionic liquids [MIM][HSO4], [BMIM]Cl, [EMIM]Br and [BMIM]Br used in
the study are prepared according to the method described in the literatures2,3, and
obtained with the reasonable yields.
1.5 Hammett acidity of Brønsted-acidic Ils
As the dehydration of carbohydrates is closely associated with the acidity of the
ionic liquid catalyst used in this study, Hammett acidity function of the different ILs
was investigated in methanol solution based on the typical procedure4.
Table S1. Hammett function values of various ionic liquid catalysts
Ionic Liquid
Absorbance
[In] [%]a
[InH+] [%]b
none
1.15
100
0
[EMIM]Ac
1.15
100
0
[MIM][HSO4]
1.09
94.8
5.2
[NMP][HSO4]
0.82
71.3
29.7
[C3SO3HMIM][HSO4]
0.71
61.7
39.3
H0c
2.25
1.37
1.19
a
[In] represents the molar concentration of the 4-nitroaniline indicator. b[InH+] represents the
molar concentration of the protonated 4-nitroa-niline. cH0 = pKa(In)+log([In]/[InH+]), pKa = 0.99;
T=25℃.
Acidic ionic liquids are in the order: [EMIM]Ac < [MIM][HSO4] < [NMP][HSO4] <
[C3SO3HMIM][HSO4].
2. Experimental Section
2.1 General procedure for synthesis of HMF from fructose without catalyst
The reaction is carried out in a stainless steel autoclave with glass liner tube that is
heated in the oil-bath. A mixture of fructose (1.0 mmol) and the solvent IL (2 ml) is
placed in the tube, then heated and stirred at 100 °C for 0.5 h. After reaction, the
resultant mixture is cooled in the ice bath, then diluted with deionized water and
analyzed by HPLC.
2.2 Analytical methods
All reaction products are analyzed by HPLC and quantified using calibration curves
generated with commercially-available standards. Following a typical reaction, the
product mixture is diluted with a known mass of deionized water, centrifuged to
sediment insoluble products, and then analyzed by an HPLC equipped with UV and
refractive index detectors. The concentration of HMF is calculated based on the
standard curve obtained with known concentrations of the standard substance.
2.3 Computational method
DFT calculations are carried out to obtain energy barriers for reactants, transition
states (TSs) and products. All calculations are performed with the framework of the
Gaussian 03 program package, running on a Linux cluster, which are designed to
obtain minima in potential energy surfaces corresponding to stable molecular species
and saddle points that correspond to transition states. The hybrid Becke
3-Lee-Yang-Parr (B3LYP) exchange-correlation functional with the 6-311G (d, p)
basis set is employed for obtaining stable structures and transition states. Vibrational
frequency calculations, from which the zero-point energies (ZPEs) are derived and
have been performed for each optimized structure at the same level to identify the
nature of all the stationary points (local minimum or first-order saddle point).
Reactants and products have no imaginary frequency, whereas transition states have
exactly one imaginary frequency.
2.4 HMF Quantification Procedure
The received reaction mixture (0.1 mL) was diluted with 10 mL of deionized
water and the solution was centrifuged at 10,000 rpm for 10 min. Then 1.0 mL of the
upper clear liquid was pipetted off and diluted with deionized water to 10 mL for
analysis. HMF concentration was measured on a HPLC (Waters Alliance 2695 series
chromatograph equipped with UV detector) at 283 nm using standard curve method
(Figure S2).
MHMF was calculated as follows
MHMF (mg) = HMF concentration (mg/mL) × VRM × DF × 10-3
In which,
VRM is the volume of reaction mixture = 2 mL
DF is the dilution factor in dilution = (10 mL ÷ 0.1 mL) × 10 = 1000
The yield of HMF was calculated from the equation
HMF Yield (%) = [MHMF (mg) ÷ MWHMF] ÷1mmol × 100%
In which,
MHMF is the mass of HMF
MWHMF is the molecular weight of HMF = 126.11
3. References
1.
Zhang, H.; Wu, J.; Zhang, J.; He, J. Macromolecules 2005, 38, 8272.
2. Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am. Chem. Soc.
2002, 124, 4974.
3. Li, Y.-N.; Wang, J.-Q.; He, L.-N.; Yang, Z.-Z.; Liu, A.-H.; Yu, B.; Luan, C.-R.
Green Chem. 2012, 14, 2752.
4.
Tong, X.; Li, Y. ChemSusChem 2010, 3, 350.
4. The 1H NMR charts of ILs
4.1
1-(3-sulfonic
acid)
butyl-3-methylimidazolium
([C4SO3HMIM][HSO4] )
hydrogen
4.2 N-methyl-2-pyrrolidonium hydrogen sulfate ([NMP][HSO4])
4.4 N-methylimidazolium hydrogen sulfate ([MIM][HSO4])
sulfate
4.3 1-allyl-3-methylimidazolium chloride ([AMIM]Cl)
5. Supporting figures
O
HO
O
HMF
Chemical Formula: C6H6O3
Molecular Weight: 126.11
Figure S1. 1H NMR spectra of synthetic HMF.
1
H NMR (400 MHz, D2O) δ 9.44 (1H, s, -CHO), 7.52 (1H, s, =CH-CH=), 6.66 (1H, d,
=CH-CH=), 4.68 (2H, s, -CH2-).
Figure S2. Standard curve of authentic HMF in H2O (HPLC area = 1.81 × 106 × HMF
concentration (mg/mL), R2 = 0.9987).
6. The optimized geometries for the intermediates and transition states
6.1 Solvent
[AMIM]Cl
[BMIM]Cl
6.2 The conversion of fructose to HMF catalyzed by [AMIM]Cl.
1a
TS1a
2a
TS2a
5a
3a
4a
TS3a
6a
6.2 The conversion of fructose to HMF catalyzed by [BMIM]Cl.
1b
2b
TS2b
TS1b
3b
4b
5b
6b
TS3b