Catalytical conversion of fructose and glucose into 5-hydroxymethylfurfural in hot compressed water by microwave heating

Production of 5-hydroxymethylfurfural (5-HMF) from glucose and fructose catalyzed by TiO₂ and ZrO₂ under microwave irradiation was studied. For the case of TiO₂ used in the fructose reaction, 5-HMF yield was 38.1% for a fructose conversion of 83.6% for 5 min reaction time. A 5-HMF yield of 30.5% for a fructose conversion of 65% was obtained for 5 min reaction time in the presence of ZrO₂. The ZrO₂ was found to promote isomerization of glucose to fructose, in which the selectivity of fructose from glucose became higher than 60% for about 50% glucose conversion for a reaction time of 1 min. Under the conditions (5 ml of 2 wt% fructose solution, 0.05 g of TiO₂, 200 °C, and 3 min), fructose conversion and HMF yields by microwave heating (73% and 35%, respectively) were higher than those by sand bath heating (27% and 12%, respectively).