Synergistic conversion of glucose into 5-hydroxymethylfurfural in ionic liquid–water mixtures

A method for converting glucose into 5-hydroxymethylfurfural (5-HMF) without using chromium-containing catalysts was developed. The method uses ionic liquid–water mixtures with a ZrO2 catalyst. Addition of a certain amount of water (10–50 wt.%) into the 1,3-dialkylimidazolium chloride ionic liquid promoted the formation of 5-HMF from glucose compared with that in either pure water or in the pure ionic liquid. A 5-HMF yield of 53% was obtained within 10 min at 200 °C in a 50:50 w/w% 1-hexyl-3-methyl imidazolium chloride–water mixture in the presence of ZrO2. The 1,3-dialkylimidazolium ionic liquids having Cl− or HSO4- anions were effective for promoting 5-HMF formation. Addition of protic solvents such as methanol and ethanol to the ionic liquid had a similar synergistic effect as water and promoted fructose and 5-HMF formation. The results reported in this work can be extended to other fields, where the ratio of ionic liquid and protic solvent can be adjusted to promote the desired reactions.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Efficient process for glucose conversion to 5-HMF without using chromium-analogous catalyst. ► Addition of appropriate amount of water into IL has a synergistic effect on glucose conversion to 5-HMF. ► A 5-HMF yield of 53% was obtained in 10 min at 200 °C in IL–water mixture. ► Neutral ILs with Cl− anion are effective for 5-HMF formation by adding water into the ILs. ► Addition of protic solvents into the ILs favors fructose and 5-HMF formation.