Boosting transformation of glucose and fructose to 5-hydroxymethylfurfural by a strategy of dual catalyst in biphasic solvent system with salt

5-Hydroxymethylfurfural (HMF) derived from biomass can be converted to a variety of high-value chemicals. Transformation of glucose and fructose to HMF is the typical reactions involved in transformation of raw biomass to HMF. However, poor stability of heterogeneous solid acid and the side reactions of HMF consumption still is a challenge for the entitled reaction. In the present work, a strategy of catalyst with dual acid of Lewis acid and Brønsted acid combined with the biphasic solvent system of organic-aqueous salt is employed to design the effective catalytic system for the transformation of glucose and fructose to HMF. An SiO2-Zr-P heterogeneous solid acid with the dual acid sites was prepared by grafting of zirconium dioxide on silica followed by its phosphation. The surface grafted zirconium dioxide was transformed to the zirconium phosphate with the formula of Zr(HPO4)2·H2O. Both the Lewis acid and Brønsted acid of the SiO2-Zr-P are enhanced and their influences for the entitled reaction was investigated. The prepared catalyst was employed to catalyse the entitled reaction in the biphasic solvent of tetrahydrofuran-aqueous NaCl solvent, giving 99.9% yield of HMF for fructose and 75.2% yield of HMF for glucose. The catalyst showed good stability and can be applied for the catalytic transformation of various sugars to corresponding HMF and fufural with satisfied yield.