Promotion of 5‐hydroxymethylfurfural synthesis from glucose over AlCl₃ catalyst with choline chloride

Efficient production of 5‐hydroxymethylfurfural (HMF) from glucose was achieved in a water‐methyl isobutyl ketone biphasic solvent system over AlCl 3 catalyst, using a green and cheap choline chloride (ChCl) salt as a promoter. An optimized HMF yield of 67% was obtained from 0.6 M glucose over 0.06 M AlCl 3 with 3.8 M ChCl addition at 140°C within 24 min. A comprehensive kinetic model was developed based on the proposed reaction network of glucose conversion to HMF from monophasic experiments, by further incorporating kinetic constants as a function of ChCl concentration. Kinetic modeling results elucidate that ChCl enhanced substantially the reaction rate of fructose dehydration, therefore overcoming the equilibrium limitation of glucose‐fructose isomerization and facilitating HMF synthesis, and suppressed carbon loss from sugar degradation. A reaction mechanism involving the ChCl effect was proposed. The aqueous phase containing ChCl and AlCl 3 could be readily recycled and reused multiple times without an obvious performance loss.