Protonic acid catalysis of sulfonated carbon material: Tunable and selective conversion of fructose in low-boiling point solvent

Catalytic conversion of various carbohydrates into 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) was efficiently conducted by sulfonated carbon material (polyurethane based catalyst, abbreviated as PU-Cat). In the preparation process of catalyst, the tetrahydrofuran was reclaimed. PU-Cat exhibited excellent performance in the synthesis of HMF and EMF from fructose-based carbohydrates. Firstly, the dehydration of fructose into HMF was smoothly carried out in the low-boiling solvent (1, 4-dioxane), which was catalyzed by PU-Cat at 140 °C. The highest yield of HMF was up to 70.1% with full conversion of fructose in 1, 4-dioxane for 2 h. Then, the one-pot conversion of fructose into EMF was also successfully performed in the ethanol/1, 4-dioxane (V/V=70:30) at 140 °C for 2 h, and 66.0% yield of EMF was obtained. Finally, PU-Cat can be recycled five times without significant reduction in catalytic activity.