Bifunctional Imidazole-Benzenesulfonic Acid Deep Eutectic Solvent for Fructose Dehydration to 5-Hydroxymethylfurfural

Imidazole (Im) and benzenesulfonic acid (BSA) formed deep eutectic solvents (DESs) were used as acidic catalyst and solvent for the dehydration of fructose to 5-hydroxymethylfurfural (5-HMF). The DES formation involved an acid-base neutralization to produce equimolar salt from BSA and Im, and subsequent interaction between equimolar salt as hydrogen bond acceptor and excessive BSA as hydrogen bond donor. The BSA-rich DES [Im:1.5BSA] with a 1:1.5 molar ratio of Im:BSA and 10% dosage exhibited high catalytic activity for fructose dehydration with a 5-HMF yield of 90.1% at 100 degrees C after a very short reaction time (3 min). The bifunctionality of [Im:1.5BSA] for promoting reaction rates and catalytic activity of fructose dehydration has been identified by tuned acidity of DESs and hydrogen bond interaction among fructose, 5-HMF, and DESs demonstrated by conductor-like screening model for real solvents (COSMO-RS) theory. [GRAPHICS] .