Anatase–rutile transformation in TiO2–V2O5 catalyst coatings for ceramic foams

The aim of this investigation was to study the thermal stability of TiO2–V2O5 catalysts prepared from aqueous powder suspensions based on pigment grade anatase and sub-micron vanadia particles. Such catalysts are proposed for dip coating of ceramic foams for application in a new reactor design for the synthesis of phthalic anhydride. Catalyst mixtures with vanadia contents up to 10% were annealed in air in the temperature range from 400 to 1200 °C. The influence of temperature and vanadia content on the anatase to rutile transformation and the specific surface were monitored, employing XRD, SEM and BET measurements. Results show that the addition of V2O5 strongly affects the temperature of phase transformation. This process is accompanied by a large decrease of surface area. The structural changes can produce a pronounced effect on catalytic performance for the oxidation reaction of o-xylene. Possible mechanisms and the consequences for catalytic performance are discussed.