Catalytic Conversion of Carbohydrates into 5-Hydroxymethylfurfural by Germanium(IV) Chloride in Ionic Liquids

Direct conversion of carbohydrates into 5-hydroxymethylfurfural (HMF) catalyzed by germanium(IV) chloride in ionic liquids has been investigated in search of an efficient and environmentally friendly process. Monosaccharides D-fructose and D-glucose, disaccharides sucrose and maltose, and even the polysaccharide cellulose were successfully converted into HMF with good yields under mild conditions (yield up to 92% in 5 min in the case of fructose). The structure of ionic liquids, catalyst loading, reaction temperature and water content had noticeable effects on this catalytic system. Addition of 5 angstrom molecular sieves during the dehydration of glucose resulted in an increase in HMF yield from 38.4% to 48.4%. A mechanism for glucose conversion to HMF catalyzed by germanium(IV) chloride was proposed according to C-13 NMR spectra obtained in situ under different conditions using D-glucose-2-C-13 as the substrate.