Microwave-assisted Conversion of Carbohydrates into 5-Hydroxymethylfurfural Catalyzed by ZnCl2

A convenient system for producing 5-hydroxymethylfurfural (HMF) through dehydration of carbohydrates by microwave heating in the presence of ZnCl2 was studied. The use of ZnCl2 gave higher selectivity than other metal salts in the conversion of glucose. With ZnCl2 as catalyst, sucrose could be utilized effectively. Under the conditions of microwave irradiation (300 W, 8 min), HMF yields were 54.6, 55.1, and 80.6% from glucose, fructose and sucrose, whereas upon conventional oil bath heating (0.11 g mL(-1) sugar solution, weight ratio of ZnCl2 to substrate = 1 : 4, 189 degrees C, 60 min) HMF yields from glucose, fructose and sucrose were only up to 37.7, 42.7, and 57.7 %, respectively.