Effects of reaction temperature and water vapor content on the heterogeneous photocatalytic oxidation of ethylene

The photocatalytic degradation of ethylene in airstreams has been studied over the temperature range 30-110 degrees C using a packed bed reactor containing sol-gel-derived TiO2 or platinized TiO2 particulates. Results of this study indicate that the reactivity of ethylene is greatly enhanced at increased temperatures and that the fraction of ethylene that reacts is stoichiometrically oxidized to CO2 under all operating conditions. The effect of raising the temperature has been ascribed to decreasing adsorption of water for both types of catalysts, as well as an increase in conventional heterogeneous catalytic reactions occurring on the Pt/TiO2 catalyst. In addition, platinizing the TiO2 photocatalyst and increasing the content of water vapor in the gaseous feed streams both decrease the rate of photocatalytic oxidation of ethylene. The activation energies for the photocatalytic and heterogenous catalytic oxidation of ethylene were determined to be 13.9-16.0 kJ mol(-1) and 82.8 kJ mol(-1) respectively.