Influence of temperature on gas-phase photo-assisted mineralization of TCE using tubular and monolithic catalysts

The influence of temperature on the photocatalytic oxidation of a model volatile organic compound, trichloroethylene, in gas streams using UV-Vis radiation is analyzed. Two different photoreactors have been tested at different temperatures from 60 degrees C to 250 degrees C. A solar simulator consisting of a Xe lamp with filters to remove IR radiation was used as the source of illumination for the first monolithic photoreactor, but for the second, a tubular catalyst in a Pyrex tube is concentric to a fluorescent UV lamp. The experimental setup was prepared to discriminate the thermal effect from the purely photocatalytic process at wavelengths below 400 nm. From the results, it may be concluded that the oxidation mechanism has two different phases. The first phase of TCE oxidation, in which the active species are chlorine radicals, is not improved by an increase in temperature. The second phase, corresponding to dechlorination of first-phase by-products, seems to follow a thermal-catalytic mechanism. A good balance between temperature and residence time is necessary to obtain the best cost/benefit relationship. (C) 1999 Elsevier Science B.V. All rights reserved.