Efficient conversion of cellulose into 5-hydroxymethylfurfural by inexpensive SO42-/HfO2 catalyst in a green water-tetrahydrofuran monophasic system

Efficient and green catalysis of cellulose to 5-hydroxymethylfurfural (HMF) is currently a challenge that needs a breakthrough. In this study, a series of inexpensive (x)SO42-/HfO2 heterogeneous catalysts were prepared and exhibited superior catalytic performance for conversion of cellulose into HMF in the green water-tetrahydrofuran monophasic system (H2O-THF). An optimal HMF yield of 54% was acquired through detailed evaluation of reaction conditions. Various analyzes including ICP-OES, XRD, SEM, TEM, FTIR, N2 adsorption–desorption isotherm, XPS, TG, NH3-TPD and Py-FTIR were applied to inspected the physicochemical characteristics of the (x)SO42-/HfO2 catalysts. Meanwhile, the recyclability of the catalyst and the by-products generated during the reaction process were studied and captured, respectively. The results presented herein show that the catalytic system of (30%)SO42-/HfO2 catalyst combined with H2O-THF monophasic solvent is advanced, and it can be both green and efficient without the presence of other additives and promoters, and has great potential in the future.