Preparation of 5-hydroymethylfurfural by dehydration of fructose in the presence of acidic ionic liquid

In this paper, preparations of 5-hydroymethylfurfural (HMF) by the dehydration of fructose in the presence of the Brønsted acidic ionic liquid, 3-allyl-1-(4-sulfobutyl)imidazolium trifluoromethanesulfonate, as well as its Lewis acid derivative, 3-allyl-1-(4-sulfurylchloride butyl)imidazolium trifluoromethanesulfonate, were investigated. It was concluded that the type of acidic ionic liquid used played a significant role in the reaction, and the Lewis acidic ionic liquid acts more effectively than its Brønsted acidic counterpart. By means of UV–visible spectroscopy, the acidities of both kinds of ionic liquids were characterized, together with an effort to correlate the relationship between acidity and activity. Moreover, it was demonstrated that when these acidic ionic liquids were immobilized on silica gel, they can be used as effective and reusable solid catalysts for the dehydration reaction of fructose to HMF, offering much better performances for the title reaction than sulfuric acid and sulfonylchloride modified silica gels in terms of activity and reusability.