Conversion of Carbohydrates into Platform Chemicals Catalyzed by Alkaline Ionic Liquids

A series of alkaline ionic liquids (ILs) including 1-butyl-3-methylimidazolium benzoate ([BMIM] PHCOO), 1-butyl-3-methylimidazolium carbonate ([ BMIM] 2CO(3)), 1-butyl-3methylimidazolium acetate ([BMIM] OAc), 1-butyl-3-methylimidazolium hydroxide ([ BMIM] OH), ethanolamine tetrafluoroborate ([MEA] BF4), and 1,1,3,3-tetramethylguanidine (TMG)-based ILs, etc., were synthesized and utilized as catalysts for the conversion of carbohydrates into 5-HMF. 1,1,3,3-tetramethylguanidine tetrafluoroborate ([TMG] BF4) was confirmed to exhibit excellent catalytic activity, and was much cheaper than other ILs such as 1-butyl-3-methylimidazolium chloride ([ BMIM] Cl) for use as a solvent in the conversion of C-6 carbohydrates into 5-HMF. The 5-HMF yields from fructose, glucose, cellobiose, and microcrystalline cellulose (MCC) were 74.19%, 27.33%, 20.20%, and 17.73%, respectively. In addition, the possible pathway of carbohydrates (MCC, cellobiose, glucose, etc.) conversion into 5-HMF with [TMG] BF4 as a catalyst was speculated, and the conversion of glucose into 5-HMF was determined to likely be the committed step in the transformation of MCC catalyzed by [TMG] BF4.