Conversion Of Carbohydrates To5-Hydroxymethylfurfural Catalyzed By Metal-based Ionic Liquids

As one of the ideal substitute of the fossil energy, biomass energy has been investigated from various aspects. Of which, the effective preparation of5-HydroxyMethylfurfural from carbohydrates has became a hotspot. In this reaction system, the applied catalysts and solvents are diverse. Such as inorganic acids, organic acids and solid acids. But ionic liquid has its obvious advantages over those kinds of catalysts, owing to its unique properties.With conventional1-butyl-3-methylimidazolium chloride ([BMIM]C1) and many kinds of metal chloride, multiple new-style metal-based ionic liquids were synthetized. These multiple metal-based ionic liquids were used as catalysts in the conversion of monosaccharide, disaccharide and polysaccharides to5-hydroxymethylfurfural. For fructose,[BMIM][Zn2Cl5] shows the best catalytic activity. The best5-HMF yields96.8%could be reached when the mole ratio of catalyst with substrate was0.1, the reaction temperature was140℃.For glucose,[BMIM][Cr2Cl7] shows the best catalytic activity. The best5-HMF yields68.4%could be got when the mole ratio of catalyst with substrate was0.1, the reaction temperature was160℃. Furthermore, the cyclic utilization performances of catalysts were also evaluated for both fructose and glucose transformation reactions.On the basis of above-mentioned experiments, disaccharide and polysaccharides were further investigated. For sucrose, the best5-HMF yields62.3%could be got when the mole ratio of catalyst with substrate was0.2, the reaction temperature was140℃. For maltose and starch, the best5-HMF yield were41.6%and29.8%under the same conditions, respectively.Finally, mechanisms of reactions were investigated for both dehydrations of glucose and fructose. Glucose is transformed into fructose under effects of metal-based ionic liquids, then fructose is transformed into5-HMF under effects of halide ions.