Efficient production of 5-hydroxymethylfurfural through the dehydration of sugars with caprolactam hydrogen sulfate ([CPL]HSO4) ionic liquid catalyst in a water/proprylene glycol monomethyl ether mixed solvent

Efficient production of 5-hydroxymethylfurfural (HMF) through the dehydration of sugars was achieved by developing a new catalyst caprolactam hydrogen sulfate ([CPL]HSO 4 ) ionic liquid or using metal halide as the co-catalyst in a new water/proprylene glycol monomethyl ether solvent system. With an optimum synthesis condition, the yield of HMF derived from fructose dehydration at 105 °C for 90 min is as high as 80.5 % in the presence of [CPL]HSO 4 . The nature behind the attractive results was revealed by proposing the catalysis mechanism of the fructose dehydration. The yield of HMF is about 70 % using [CPL]HSO 4 as the catalyst for fructose dehydration after being reused five times. The catalyst system [CPL]HSO 4 /metal halide was used for the dehydration of sucrose, and the optimum yield is as high as 64–68 %.