Sustainable production of 5-hydroxymethylfurfural from fructose and inulin using active and stable acidic ionic liquids as homogeneous and heterogeneous catalysts

Abstract

Two Brønsted acidic ionic liquids (IL) were synthesized by quaternization of an organic base (imi-dazole and triethylammonium) with 1,4-butane sultone and its successive protonation with sulfu-ric acid. After a deep characterization, they were tested, as catalyst and solvent, in the 5-hydroxymethylfurfural production from D-fructose. IL1, [C4SO3Hmim][HSO4], showed the bestcatalytic activity in the dehydration of fructose, obtaining 58% of 5-HMF. This IL could be recy-cled and reused without appreciable loss of catalytic activity in four catalytic cycles (58%, 57%,56%, and 53%, respectively). It was used with other carbohydrates (monosaccharides, disaccha-rides, and polysaccharides) showing that all substrates containing fructose units were efficientlyconverted to 5-HMF. Furthermore, a heterogeneous system was prepared with IL1 supported onsilica gel, and this system exhibited high activity in the fructose dehydration reaction and a yieldof 70% of isolated and purified 5-HMF was achieved.