Photocatalytic oxidative Degradation of vapors of some organic compounds over TiO2

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Abstract
Rates and diffuse reflectance FTIR spectra have been measured for the photocatalytic reactions of a number of vaporized organic compounds with O2 over Degussa P-25 TiO2 irradiated at wavelengths in the vicinity of 360 nm. Trichloroethylene (TCE) has been investigated extensively. Other compounds investigated in some depth include perchloroethylene (PCE), i-octane, methanol, acetone and acetonitrile. Rates of consumption of components and intermediates have been determined for several binary mixtures. Photoefficiencies (Ep) of their consumption have been evaluated for 17 compounds. Principal findings include the following: Ep of consumption significantly greater than unity has been observed for TCE, PCE methanol and ethanol, with values up to 90 observed with TCE. For the 17 compounds, Ep varies over a factor of more than 108. TCE substantially promotes the consumption of i-octane, CH2Cl2 and CHCl3 and inhibits the consumption of acetone and acetonitrile. These effects last after the TCE is completely consumed. Promotion and inhibition by added Cl2 has been observed. Mechanistic rationalizations are proposed.