Furfural is one of the most essential biomass compounds, which is industrially produced from hemicellulose-derived pen- toses (C5). The development of inexpensive and efficient heterogeneous catalysts for conversion of hexoses (C6), the most abundant resources in the environment, to furfural is critical in biorefineries. In this study, bentonite modified with HCl and H 3 PO 4 was used to convert glucose to furfural in a mono-phasic water–dimethyl sulfoxide (DMSO) system. The effects of acidic properties of the catalysts toward the selective formation of furfural were discussed. Obtained results indicated that the total acidity of bentonite notably decreased after acid treatment, accompanied by increasing surface area. At the same time, the number of weak acid sites increased for H 3 PO 4 -activated bentonite compared to the HCl activation. This endowed H 3 PO 4 -modified bentonite with a lower S/W ratio (strong acid sites to weak acid sites), and lower strong acid density is necessary for selective furfural formation. Because conversion of glucose to furfural is a multistep reaction involving C–C cleavage bond promoted by weak acid sites followed by dehydration catalyzed by strong acid sites. A furfural yield of 69.2% was achieved over H 3 PO 4 -activated bentonite at 170 °C after 60 min.
