离子液体中Lewis酸催化葡萄糖和果糖脱水制备5-羟甲基呋喃甲醛

Dehydration of Glucose and Fructose into 5-Hydroxymethylfurfural Catalyzed by Lewis Acid in Ionic Liquids

在离子液体中采用不同的Lewis酸催化葡萄糖和果糖脱水制备5-羟甲基呋喃甲醛(5-HMF).结果表明,CrCln和SnCln均可高效催化葡萄糖转化为5-HMF.另外,Lewis酸的酸性越强,其催化果糖转化为5-HMF的产率越高.镧系金属氯化物在反应中表现出较好的催化活性和产物选择性.同时还研究了离子液体结构对催化反应的影响.结果表明,咪唑型离子液体在葡萄糖转化为5-HMF的反应中表现出明显的奇偶效应,即离子液体支链碳原子数为偶数时,5-HMF产率较高;而在果糖转化为5-HMF的反应中,离子液体的支链烷基长度越短,5-HMF产率越高.在离子液体[C2MIM]Br(溴化1-乙基-3-甲基咪唑)中,SnCl2催化葡萄糖脱水时5-HMF收率为65%,而ErCl3催化果糖得到的5-HMF收率可达92%.

A variety of Lewis acids have been examined for the transformation of glucose and fructose into 5-hydroxymethylfurfural （5-HMF） in ionic liquids （ILs）.SnCln and CrCln are effective catalysts for the isomerization,and Lewis acids with strong acidity can facilitate the dehydration of fructose.The influence of ILs＇ structure,including the length of alkyl side chain and halide anions,on the conversion was also studied.A distinct odd-even carbon-atom-number effect is observed in the conversion of glucose to 5-HMF and the imidazolium bromides with short alkyl side-chains can provide a higher yield of 5-HMF from fructose.In the presence of 1-ethyl-3-methylimidazolium bromide （[C2MIM]Br） and SnCl2,the yields of 5-HMF are 65% and 73% from glucose and fructose,respectively.