Complete oxidation of benzene in gas phase by platinized titania photocatalysts

Photocatalytic oxidation of benzene in gas phase was carried out with a flow reactor at room temperature. In a humidified airstream ([H₂ O] = 2.2%), benzene was quantitatively decomposed to CO₂ over UV-irradiated 1.0 wt %-Pt/TiO₂ catalyst. When the benzene conversion was decreased, the selectivity to CO₂ was decreased, while that to CO was increased. As the amount of Pt loaded on the TiO₂ catalyst was increased, the rate of the CO photooxidation was increased, while that of benzene photooxidation was almost unchanged. These findings showed that the photooxidation of benzene to CO₂ over Pt/ TiO₂ catalyst proceeded by the two sequential steps: (i) benzene was decomposed to CO₂ and CO with the selectivities of 94% and 6%, respectively, and (ii) CO was subsequently oxidized to CO₂. The rate of CO photooxidation over Pt/ TiO₂ catalyst was greatly decreased by the presence of benzene in the reaction gas stream. The complete oxidation of benzene to CO₂ could be also achieved by using the hybrid catalysts comprising pure TiO₂ and platinized TiO₂.