FLUIDIZED-BED PHOTOCATALYTIC OXIDATION OF TRICHLOROETHYLENE IN CONTAMINATED AIRSTREAMS

Gas-solid heterogeneous photocatalytic oxidation of trichloroethylene (TCE) in humid airstreams is achieved at high conversion levels in a bench-scale flat-plate fluidized-bed photoreactor, which provides efficient continuous contact of near-ultraviolet photons, silica-supported titania photocatalyst, and gaseous reactants. Silica-supported titania catalysts prepared through sol-gel methods require approximately 1 h on stream time to develop their maximum photocatalytic oxidation activity. Steady-state reaction rates as high as 0.8-mu-mol of TCE (g of catalyst)-1 min-1 [2-mu-mol (g of TiO2)-1 min-1] and quantum efficiencies of 13% have been achieved over conditioned catalysts. High conversion of dilute levels (< 10 ppm) of TCE can be sustained for extended periods of operation, although the catalyst reversibly deactivates during conversion of streams containing higher TCE concentrations. Once activated, the fluidized catalyst bed responds rapidly to step changes in feed flow rate, composition, and photon flux.