Catalytic Conversion Of Saccharide To5-methoxymethylfurfural With Ionic Liquids

In recent years, with increasing fossil resources consumption, many countriespay more and more attention to the biomass resources research anddevelopment.Carbohydrates are abundant and renewable biomass. It is one of themost attractive topics that high value-added chemicals, such as furan derivatives,can be prepared from saccharides. Due to its high energy density,5-methylfurfural（MMF） is becoming a good fuel or fuel additive. This paper investigated one-potcatalytic conversion of various saccharides, especially monosaccharide, into5-methoxymethylfurfural （MMF） in the ionic liquid-methanol system.Firstly, a series of ionic liquids, such as EMIMSO₄, DMIMHSO₄, DMIMSO₄and MIMBF4, etc., were synthesized.Then different acidic metal salts-ionic liquidscatalysts for dehydration and etherification of glucose were studied.Some factors, such as catalyst loading, reaction temperature, reaction time,feed ratio, water content, were studied. Under the optimal condition: m（AlCl₃.6H₂O）:m（glucose）: m（EMIMSO₄）:m（methanol）=0.5:1:1:3.95, the yield of MMF was17.8%at140℃for1.5h. Under the same optimal reaction condition, the yields of MMFwere33.5%and19.8%respectively for fructose and sucrose.Secondly, the one-pot catalytic dehydration and esterification of fructose wasstudied. We concentrated on how metal chlorides, ionic liquids, reactiontemperature, reaction time, influenced dehydration and etherification. The optimalcondition was obtained by orthogonal experiment L9（33）. The results showed that1,3-Dimethylimidazolium hydrogen sulfate （DMIMHSO₄） acted as solvent, as wellas catalyst. Under the optimal condition, the yield of MMF and methyl-levulinatecan achieve57.2%and19.3%after1h under130℃.We tried to apply DMIMHSO₄to catalyze other carbohydrates. The MMF yield of19.5%was obtained for sucrose.At last, ammonium bisulfate was found to be cheap catalyst for fructose, replace ofDMIMHSO₄, the yield of MMF and methyl-levulinate can achieve31.5%and13.7%.