Catalytic conversion of sugar into hydroxymethylfurfural in ionic liquids

Triisobutyl(methyl)phosphonium tosylate is discovered as a highly active and selective ionic liquid solvent for conversion of fructose into HMF without any catalyst addition under moderate reaction conditions (80–110 °C). This ionic liquid provides high solubility for sugar and hydroxymethylfurfural (HMF), does not produce heavy or insoluble by-products, is available at a reasonable cost in large quantities, and thus, is promising for development of a practical HMF production process. This ionic liquid is also effective for conversion of glucose into HMF in presence of CrCl2 catalyst. Formation of some unknown compounds during the sugar conversion is reported first time in the field. In this work, a number of ionic liquid + catalyst combinations are screened using a combinatorial experimental technique with fructose, high fructose corn syrup, and glucose as a feed. Reaction kinetics of sugars in the new ionic liquid is tested in a batch reactor under various reaction conditions, in comparison to [EMIM]Cl – an ionic liquid extensively studied in the previous work. It is found that the catalytic activity of an ionic liquid is determined by choice of both cation and anion, and can also be affected by its production source significantly. Reaction pathways are proposed based on the experimental results.