HETEROGENEOUS PHOTOCATALYSIS - INSITU PHOTOCONDUCTIVITY STUDY OF TIO2 DURING OXIDATION OF ISOBUTANE INTO ACETONE

Using a special flow-reactor, the electrical photoconductivity σ of TiO2 and the photocatalytic activity for isobutane oxidation at room temperature over this catalyst have been simultaneously measured. The formation rates in acetone (partial oxidation) and CO2 (partial and total oxidation) as well as σ are proportional to light intensity, provided the photon energy is greater than the band gap of anatase. Kinetic orders have been determined. A reaction mechanism is suggested. In the pressure range from 100 to 500 Torr for O2 and i-C4H10 and under steady-state conditions, the electron-hole recombination is considered negligible; the dependence of σ upon PO-1 is explained by the capture of photoproduced electrons by O2ads, species in equilibrium with gaseous O2, whereas the independence of the formation rate in acetone upon PO is interpreted by the neutralization and activation of Oads- species (adsorbed at saturation) by photoproduced holes; isobutane reacts in a neutral adsorbed state with the activated oxygen species thus obtained. © 1979.