Products, Intermediates, Mass Balances, and Reaction Pathways for the Oxidation of Trichloroethylene in Air via Heterogeneous Photocatalysis

Studies of the photocatalytic reaction of a solution of trichloroethylene in the air and in contact with UV-irradiated titanium dioxide have produced conflicting reports in regard to the composition of the product mixture. This paper resolves these discrepancies by reporting the results of experiments designed to identify and quantify intermediates, products, and reaction pathways. Mass balances are closed in differential and integral modes to ascertain the effects of factors such as the extent of conversion, feed composition, and photon energy on the composition of the product stream. Dichloroacetyl chloride, phosgene, carbon dioxide, carbon monoxide, and hydrogen chloride were observed in the effluent of photocatalytic reactors featuring thin films of titanium dioxide catalyst. These observations were made with a gas-phase Fourier transform infrared spectrometer. The instrument directly samples the effluent from the reactor without splitting or dilution. A direct sampling molecular beam mass spectrometer used in a parallel study has also identified molecular chlorine as a component of the effluent.