Ionic liquid binary mixtures: Promising reaction media forcarbohydrate conversion into 5-hydroxymethylfurfural

Abstract

The conversion of carbohydrates into 5-hydroxymethylfurfural (5-HMF) has been studied in binary mixtures of ionic liquids (ILs), using strongly acidic resin Amberlyst 15 as the catalyst. In particular, both mono- and disaccharides, such as fructose, glucose and sucrose have been investigated. Considering the favorable effect exerted by chloride-based ionic liquids in the dissolution of carbohydrates, we used binary mixtures of 1-butyl-3-methylimidazolium chloride ([bmim][Cl]) with [bmim+] based ionic liquids differing in size, shape and coordination ability of the anion ([bmim][BF4], [bmim][N(CF3SO2)2], [bmim][N(CN)2], [bmim][SbF6] and [bmim][CF3SO3]). Carbohydrate conversion in [bmim][BF4]/[bmim][Cl] binary mixtures, has been studied under both magnetic stirring and ultrasound (US) activation. The catalytic system used led to the formation of 5-hydroxymethylfurfural in good yield under mild conditions. A significant influence of IL binary mixture composition on the outcome of the target processes was evidenced. Improvements in both reaction time and temperature have been observed, under US activation.