Ionic liquid-functionalized halloysite as an efficient catalyst for the production of 5-hydroxymethylfurfural

Three different acidic ionic liquids were covalently grafted on halloysite to give heterogeneous catalysts. The acidity of the catalysts was higher than halloysite and differed based on the nature of ionic liquid. Investigation of the catalytic activity of the catalysts for the synthesis of 5-hydroxymethylfurfural indicates that imidazolium-based ionic liquid showed the highest activity. Using this catalyst (30 wt%), 5-hydroxymethylfurfural was achieved from dehydration of fructose in 88% yield at 85 °C in 73 min. Furthermore, the catalyst was recyclable up to six runs with slight loss of activity. Comparison of the performance of the catalyst with halloysite-free counterpart confirmed the role of halloysite in improvement of the catalytic activity and recyclability.