Decomposition of Benzene and Toluene in Air Streams in Fixed-Film Photoreactors Coated with TiO₂ Catalyst

Abstract

The decomposition of benzene and toluene in air streams by UV/TiO₂ process was studied in different annular photoreactors under various operating conditions. The shells of reactors used in this research are made of stainless steel, Pyrex glass, or titanium. The TiO₂ film was coated to the inner surface of the reactors by either rotating coating or sol-gel techniques. The TiO₂ films coated by sol-gel technique were found to be smoother and more uniform than those coated by rotating coating. However, experimental results indicated that the photocatalysis of benzene or toluene in a glass reactor with rotating-coated TiO₂ film delivered higher decompositions in air streams than that with sol-gel coated reactors. Benzene and toluene were decomposed more effectively in a coated glass reactor than in a coated stainless steel reactor under the same operating conditions. The presence of water vapor in air-stream plays an important role in the decomposition of benzene and toluene, and a relative humidity of ∼5–6% was found to be adequate. The presence of excessive amounts of humidity retarded the decomposition to certain extents possibly results from the competitive adsorption of water molecules on the active sites of TiO₂.