CHLORINATED BY-PRODUCTS FROM THE PHOTOASSISTED CATALYTIC-OXIDATION OFTRICHLOROETHYLENE AND TETRACHLOROETHYLENE IN THE GAS-PHASE USING POROUS TIO2 PELLETS

The photocatalytic degradation of trichloroethylene and tetrachloroeth ylene in the gas phase, when porous TiO2 pellets were used, produced s uch undesirable chlorinated byproducts as chloroform (CHCI3) and carbo n tetrachloride (CCI4). The formation of byproducts was reduced by inc reasing oxygen mole fractions in the feed gas stream and/or using the TiO2 pellets fired at a lower temperature. Theoretical calculations in dicate that the Cl-radical-initiated reaction produces these byproduct s. On the basis of the experimental and the theoretical results, a met hod to prevent the formation of the chlorinated byproducts is discusse d.