| Dwindling petroleum resources and deteriorating environmental conditions have an increasing effect on the sustainable development of economy and society. An urgent solution is to develop the renewable resources, biomass, for alleviating pressure from environment and traditional fossil resources. 5-hydroxymethylfurfural(5-HMF) has received significant attention as an important platform chemical for synthesizing a broad range of chemicals and liquid transportation fuels. The utilization of glucose to generate the compound effectively is a very important topic.In combination with non-corrosive and low-toxic boric acid, AlCl3·6H2O was effective for the synthesis of 5-HMF from glucose. In this work, a 5-HMF yield of ~60% was obtained at 170 ℃ for 40 min in a H2O/THF biphasic solvent mixture. Addition of KCl not only improved partition coefficients but also inhibited by-product formation. Low concentration of ZnCl2, CoCl2·6H2O, MnCl2·4H2O, NiCl2·6H2O, FeCl3·6H2O were unsuitable for the catalyst system. ZrOCl2·8H2O, InCl3·4H2O had high activity for the reaction. The addition of Boric acid could enhance the isomerization of glucose to fructose. The mechanism of dehydration reaction was proposed to proceed through the isomerization of glucose to fructose followed by transformation from fructose to 5-HMF. Compared with other homogeneous catalysts(Cr/ionic liquid systems, H2SO4 and HCl), the described AlCl3-B(OH)3-NaCl-H2O/THF biphasic medium was a very attractive catalyst system.The catalyst(SO42-/WO3-γ-Al2O3) with WO3 load of 15 wt% prepared by the impregnation method, and subsequent calcinated at 650℃ for 4 h, was used in the catalytic conversion of glucose to 5-HMF. An 5-HMF yield of 30.4% was obtained in a biphasic medium of H2O/THF. The optimal reaction conditions were as follows: the amount of glucose was 0.04 g, V(THF):V(H2O)=3.2:1, oil bath heating temperature was 175℃, reaction time was 40 min, the amount of KCl and catalyst was 2.8 g and 0.24 g, respectively. |
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