V and V–P containing Zr-SBA-15 catalysts for dehydration of glycerol to acrolein

Abstract

A series of solid acid catalysts based on vanadium and vanadium–phosphorous supported on a zirconium doped mesoporous SBA-15 silica has been synthesized, characterized by using XRD, N2 sorption, NH3–TPD, FT-IR spectroscopy, X-ray photoelectron spectroscopy and diffuse reflectance UV–vis spectroscopy, and evaluated in the gas-phase dehydration of glycerol. Under the operating conditions used, all materials are active in the glycerol dehydration, being acrolein the main product in all cases. Although higher values of conversion are obtained in the presence of vanadium oxide based catalysts, acrolein yield improves after the treatment with phosphoric acid, attaining a value of 42% after 2h of reaction at 325°C with the 12VP0.2 catalyst, which contains 12wt.% of V2O5 and a V/P molar ratio of 0.2. However, the incorporation of phosphorous to the catalytic system partially destroys the mesoporous structure. Allyl alcohol has been also detected using vanadium based catalysts, due to a partial reduction of V2O5 species during the reaction, increasing its yield with the vanadium oxide loading. All catalysts suffer from deactivation by coke deposition on the catalyst surface, being the carbon content considerably higher for catalysts without phosphorous.