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 illumination (CPI) was investigated. The oxidation of trichloroethylene (TCE) was studied in a versatile reactor designed to provide periodic illumination of the TiO2 films. The reactor was operated in two different geometric configurations, tubular and annular. Multiple flow regimes were investigated: kinetic- and diffusion-limited. No enhancement on the rate or the selectivity of TCE oxidation was observed at any of the CPI conditions investigated in the kinetically limited flow regime. The ratio of TCE oxidized to dichloroacetyl chloride (DCAC) produced was 0.59 at all light and dark times investigated for kinetically limited operation. In diffusion-limited regimes, CPI increased the rate of oxidation and decreased the relative amount of DCAC in the product stream. In the kinetic-limited regimes the apparent quantum yield was constant at around 150%; however, in the diffusion-limited regimes the apparent quantum yield almost doubled with CPI.