A photocatalytic membrane reactor for VOC decomposition using Pt-modified titanium oxide porous membranes

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Porous titanium oxide membranes with pore sizes in the range of 2.5-22 nm were prepared by a sol-gel procedure, and were applied for decomposition of methanol and ethanol as model volatile organic compounds (VOCs) in a photocatalytic membrane reactor, where oxidation reaction occurs both on the surface and inside the porous TiO2 membrane while reactants are permeating via one-pass flow. Methanol was completely photo-oxidized by black-light irradiation to CO2 when methanol at a concentration of 100 ppm was used at a feed flow rate of 500 × 10-6 m3/min, but the conversion decreased when the MeOH concentration in the feed was increased. Pt-modification was carried out by photo-deposition, and led to a decrease in pore diameter. Using Pt-modified membranes, a nearly complete oxidation of methanol up to 10,000 ppm at a feed flow rate of 500 × 10-6 m3/min was observed. Thus, such membranes would be effective for purifying a permeate stream after one-pass permeation through the TiO2 membranes. The decomposition of ethanol is also discussed.