Investigation of the effects of controlled periodic illumination on the oxidation of gaseous trichloroethylene using a thin film of TiO2

Enhancement of gas-phase photocatalytic oxidation by controlled periodic il lumination (CPI) was investigated. The oxidation of trichloroethylene (TCE) was studied in a versatile reactor designed to provide periodic illuminati on of the TiO2 films. The reactor was operated in two different geometric c onfigurations, tubular and annular. Multiple flow regimes were investigated : kinetic- and diffusion-limited. No enhancement on the rate or the selecti vity of TCE oxidation was observed at any of the CPI conditions investigate d in the kinetically limited flow regime. The ratio of TCE oxidized to dich loroacetyl chloride (DCAC) produced was 0.59 at all light and dark times in vestigated for kinetically limited operation. In diffusion-limited regimes, CPI increased the rate of oxidation and decreased the relative amount of D CAC in the product stream. In the kinetic-limited regimes the apparent quan tum yield was constant at around 150%; however, in the diffusion-limited re gimes the apparent quantum yield almost doubled with CPI.