Efficient selective dehydration of fructose and sucrose into 5-hydroxymethylfurfural (HMF) using dicationic room temperature ionic liquids as a catalyst

Dicationic room temperature ionic liquids (RTILs), with short oligo ethylene glycol linkers have been found to be highly active catalyst for the selective dehydration of fructose and sucrose into 5-hydroxymethylfurfural (HMF). The bis (N-methylimidazolium) cations containing short oligo ethylene glycol linkers and mesylate (CH3SO3−) anions based ILs were employed in catalytic amount for sugar dehydration reactions. As a result, 92.3% of HMF yield was obtained from fructose in 40 min with one equivalent of [TetraEG(mim)2][OMs]2 at 120 °C. While, 67.2% of HMF was achieved from dehydration of sucrose at 120 °C in 150 min using two equivalents of [TetraEG(mim)2][OMs]2. Among those dicationic RTILs, [TetraEG(mim)2][OMs]2 RTIL was observed to be the most efficient catalyst, demonstrated by its ability to achieve 100% conversion and highest yield of HMF. In addition, effect of reaction time, molar ratio, temperature, and co-catalyst effect were discussed. The use of dicationic RTILs as a catalyst in sugar dehydration greatly reduces the equimolar ratio of catalyst and reaction time required for conversion of sugar into HMF.

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► Dicationic RTILs found as efficient catalysts for dehydration of sugars into HMF.
► Oligo ether linked imidazolium cations and CH3SO3− anions based RTILs employed.
► 92.3 % and 67.2 % HMF yields obtained from fructose and sucrose, respectively.