Photocatalytic Degradation of Chlorinated Ethanes in the Gas Phase on the Porous TiO2 Pellets: Effect of Surface Acidity

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 114; no. 15; pp. 5092 - 5098
• Main Authors: Yamazaki, Suzuko, Ichikawa, Keiko, Saeki, Atsue, Tanimura, Toshifumi, Adachi, Kenta
• Format: Journal Article
• Language: English
• Published: American Chemical Society 22.04.2010
• Subjects: A: Kinetics, Spectroscopy
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp911842t

The photocatalytic degradation of chlorinated ethanes was studied in a tubular photoreactor packed with TiO2 pellets prepared by sol−gel method. The steady-state condition was not obtained, but the deterioration in the photocatalytic activity was observed during the irradiation. Effects of mole fractions of water vapor, O2, and C2H5Cl or C2H4Cl2 and reaction temperature on the photodegradation of C2H5Cl or C2H4Cl2 were examined, and these data were compared with those obtained by the photodegradation of chlorinated ethylenes. On the basis of the products detected with and without oxygen in the reactant’s gas stream, we proposed the degradation mechanism. Measurement of diffuse reflectance infrared Fourier transform spectroscopy of pyridine adsorbed on the catalysts showed that decrease in the conversion for the photodegradation of C2H5Cl was attributable to the formation of Brønsted acid sites. Comparison of the data obtained with the TiO2 and the sulfated TiO2 (SO4 2−/TiO2) pellets indicated that the photodegradation of C2H5Cl was suppressed by the presence of the Brønsted sites, but that of trichloroethylene was not affected. Such a difference is attributable to the adsorption process of these reactants on the acid sites on the catalyst surface.