Liquid-phase catalytic activity of sulfated zirconia from sol–gel precursors: the role of the surface features

ZrO2–SO4 powders were prepared through a single step sol–gel reaction by modulating the conditions of the alkoxide hydrolysis and polycondensation steps. Sulfuric acid or (NH4)2SO4 was employed as the sulfating agent. The samples were calcined at 890 K and characterized as to phase composition crystallinity (XRD) and surface area porosity (BET method). Surface functionalities were investigated by TGA/FTIR, FTIR, DRIFTS, and XPS analyses. The liquid-medium catalytic activity was tested in the esterification of benzoic acid to methylbenzoate. The role played by the conditions of the sol–gel reaction, in affecting the surface state and the catalytic properties of the powders, is discussed.