Abstract: TiO₂/SiO₂ is employed as the representative semiconductor catalyst to investigate the effects of initial concentration of reactant, oxygen content, water vapor content and light intensity on the photocatalytic reaction. The reaction rate increases when increasing the initial concentration of toluene, maintained constant eventually, increases when increasing oxygen content, and then decreases after higher than 25%. When water vapor content is 0.4%, the reaction rate reaches its maximum level. The more is the light intensity, the more is the reaction rate. When reached 3.0 mW/cm², the reaction rate is invariable. The degradation of toluene is promoted in the presence of SO₂, but the degradation of intermediate products is inhibited. Meanwhile, the degradation of SO₂ is also inhibited by the presence of toluene.

Key words: toluene, sulfur dioxide, photocatalysis, titaniasilica