(6by) Synthesis of 5-Hydroxymethylfurfural from Disaccharides Using Niobium-Modified Montmorillonite

Teaching Interests: biomass conversion

Abstract: The technology to converse carbohydrates into 5-hydroxymethylfurfural (5-HMF) effectively is a very significant and potential way. In this work, niobium-modified montmorillonite (Nb-MMT) was synthesized by a one-pot, simple, ion exchange method and used as an efficient catalyst for the direct transformation of disaccharide into 5-HMF, which showed high catalytic activity and selectivity. A 5-HMF yield of 58.82% from cellobiose in a methyl isobutyl ketone (MIBK)/saturated salt water (SSW) biphasic solvent was obtained at 160 °C after 3 h. With sucrose as substrate under the same condition, 5-HMF yields were 50.45%. Moreover, 5-HMF with satisfactory yields were directly achieved from disaccharides in water. Pyridine-FTIR showed Lewis acid sites and Brønsted acid sites existed on Nb-MMT, which might facilitate the hydrolysis of disaccharide and play essential roles in the subsequent isomerization of glucose monomer and the dehydration of fructose monomer. SSW in the inorganic phase can increase the disaccharide conversion and 5-HMF selectivity, which might be attributed that the chloride ion has salting-out effect to increase the distribution coefficient of 5-HMF in the solvent. A catalytic mechanism for conversion of disaccharide to 5-HMF was proposed. In addition, Nb-MMT was recycled at least for four times without a significant decrease in the catalytic activity. This study provides a promising catalytic route for the heterogeneous Nb-containing catalysts used in the effective production of 5-HMF from carbohydrates.