Microwave assisted conversion of carbohydrates and biopolymers to 5-hydroxymethylfurfural with aluminium chloride catalyst in water

Abstract

The common Lewis acid AlCl₃ has efficiently produced 5-hydroxymethylfurfural (HMF) from carbohydrate and biopolymer substrates in water, DMSO, and water–methylisobutylketone biphasic solvents under microwave irradiation. The yield of HMF in different solvents follows an increasing order from water to water–MIBK biphasic solvent to DMSO. The yield of HMF increased with an increase in catalyst loading whereas it remains unchanged upon increase of the carbohydrate concentration. In most reactions, the maximum yield of HMF is recorded within 2 min of reaction time. The mechanism of the AlCl₃ catalyzed glucose dehydration reaction is proposed to proceed through the isomerization of glucopyranose to fructofuranose, followed by a proton assisted transformation of fructofuranose to HMF.