PHOTOCATALYTIC OXIDATIVE-DEGRADATION OF VAPORS OF SOME ORGANIC-COMPOUNDS OVER TIO2

Rates and diffuse reflectance FTIR spectra have been measured for the photocatalytic reactions of a number of vaporized organic compounds wi th 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 consumpt ion of components and intermediates have been determined for several b inary mixtures. Photoefficiencies (E(p)) of their consumption have bee n evaluated for 17 compounds. Principal findings include the following : E(p) of consumption significantly greater than unity has been observ ed for TCE, PCE methanol and ethanol, with values up to 90 observed wi th TCE. For the 17 compounds, E(p) varies over a factor of more than 1 0(8). TCE substantially promotes the consumption of i-octane, CH2Cl2 a nd CHCl3 and inhibits the consumption of acetone and acetonitrile. The se effects last after the TCE is completely consumed. Promotion and in hibition by added Cl2 has been observed. Mechanistic rationalizations are proposed.