Gas phase oxidation of n-decane and PCE by photocatalysis using an annular photoreactor packed with a monolithic catalytic bed coated with P25 and PC500

Abstract

Perchloroethylene (PCE) and n-decane are persistently present in the indoor air of several industrial/corporate facilities and households. The present paper reports studies on the photocatalytic oxidation (PCO) of n-decane and PCE using an annular photoreactor equipped with a compound parabolic collector (CPC) and packed with transparent cellulose acetate monolithic structures coated with two commercially available TiO2, namely PC500 and P25, under simulated solar light. Such configuration allowed the illumination of the whole tubular reactor perimeter and catalytic bed, enhancing therefore the photonic efficiency and to take advantage of the low pressure drop and the high surface-area-to-volume ratio, typical of honeycomb reactors. The influence of the type of TiO2, feed flow rate, pollutant concentration, relative humidity, gas-phase molecular oxygen and irradiance on the pollutants PCO was assessed. PC500 film showed higher conversion of both pollutants in comparison with P25 despite the lower mass of catalyst used for film coating. n-Decane (Cdec,feed=71ppm) and PCE (CPCE,feed=1095ppm) conversions close to 100% were obtained operating at Qfeed=150cm3min-1 (τ=88s), I=38.4WUVm-2 and RH=40%. The mineralization's of PCE over both photocatalytic films were similar. However, n-decane was 100% and 69% mineralized respectively over PC500 and P25 films, under the same operating conditions. In addition, competitive adsorption between the pollutants and water molecules on the TiO2 film surface was observed above 20% of RH. Results obtained at low RH suggest that Cl radical chain propagation reactions may be included in the PCO mechanism of PCE. Finally, the absence of oxygen drastically impairs the photoreaction.