Enhancing tungsten oxide/SBA-15 catalysts for hydrolysis of cellobiose through doping ZrO2

Abstract

The number of strong acid sites on a hydrolysis catalyst accessible by the bulky cellulose limits its efficiency in the conversion and utilization of biomass-based resources. In this work, high surface area WZr/SBA-15 catalysts (>400m2/g) were prepared by hydrothermal method and characterized using XRD, N2 adsorption, TEM, Raman, UV–vis, XPS and FTIR of pyridine adsorption. The results showed that doping a moderate amount of ZrO2 into the WO3/SBA-15 catalyst stabilized the tungstate species in the form of a polytungstate species as a result of the strong ZrOx-WOx interaction as well as increased the surface area of the catalyst. The resulting polytungstate species provided strong Brønsted acid sites for hydrolysis. Consequently, the cellobiose conversion was maximized at 5% ZrO2 loading, corresponding to a maximized surface area and density of Brønsted acid sites. This catalytic activity is significantly higher than that of a WO3/ZrO2 catalyst prepared using the conventional impregnation method, indicating the importance of mesoporous structure to the dispersion of active species and to the accessibility of the active sites by the bulky reactant. This result indicates that the density of the strong Brønsted acid sites with improved accessibility by the bulky reactant is essential to achieve a high hydrolysis activity.