Direct conversion of starch to hydroxymethylfurfural in the presence of an ionic liquid with metal chloride

Starch can be exploited as an abundant resource for sustainable production of diverse chemical intermediates such as hydroxymethylfurfural (HMF). We present a simple process of producing HMF from starches using an ionic liquid, 1-octyl-3-methylimidazolium chloride ([OMIM]Cl), and CrCl₂ catalyst. The addition of HCl and CrCl₂ significantly affected the yields of HMF on the whole. CrCl₂ increased the yields of HMF by approximately two-folds on average. The synthesis of HMF was most effective between 60 and 90 min reaction time at both concentrations of 0.3 and 0.5 M HCl. Starch concentration had influence on the productivity of HMF. At 20% starch concentration with 0.3 and 0.5 M HCl, its productivity was greatest (2.8 folds high). Eight starch sources (corn, wheat, rice, potato tuber, sweet potato, tapioca, acorn, and kudzu starch) were tested for the synthesis of HMF. The highest yields of HMF (73.0 ± 3.8 wt%) were obtained in tapioca starch dissolved in 0.5 M HCl.