Zirconium doped MCM-41 supported WO3 solid acid catalysts for the esterification of oleic acid with methanol Original Research Article

A series of zirconium doped MCM-41 silica supported WOx solid acid catalysts, with WO3 loading ranging from 5 to 25 wt%, has been prepared by impregnation with ammonium metatungstate, and subsequent activation at temperatures between 450 and 800 °C. XRD, Raman and UV–vis spectroscopies have allowed us to establish that at temperatures higher than 700 °C occurs the formation of (WO)x/ZrO2 nanoparticles on the surface of MCM-41 support, which exhibit acidic properties and are active in the esterification of oleic acid with methanol at 65 °C. WO3 loadings of 15–20 wt%, after activation at 700 °C, lead to the most active catalysts, with conversion values close to 100%. The catalyst with 15 wt% WO3 is stable even when the reaction is carried out at 200 °C, reusable at least during four cycles and no leaching of tungsten species in the liquid phase was found.