Photocatalytic performance of sulfated TiO2 and Degussa P-25TiO2 during oxidation of organics

Photocatalytic oxidations (PCOs) of heptane, trichloroethylene (TCE), ethanol, acetaldehyde, and toluene were carried out on sulfated TiO2 (SO42-/TiO2) and Degussa P-25. Coverages of all organics on SO42-/TiO2 were significantly higher than on P-25. but P-25 was more active for PCO at room temperature. Pulse PCO at room temperature suggests that steady-state PCO rates of acetaldehyde on the two catalysts may be similar, however. During PCO of heptane at room temperature, SO42-/TiO2 deactivated slower than P-25 so that the CO2 formation rate on P-25 was only 11% greater than that on SO42-/TiO2 after five 110 mu mol/g catalyst pulses of heptane. Both pulse and steady-state PCO of TCE showed that although P-25 was more active than SO42-/TiP2, the CO2 production rate decreased with time on P-25 but not on SO42-/TiO2. Furthermore, CO2 selectivity increased with time as PCO of TCE approached steady-state on SO42-/TiO2, whereas it decreased on P-25. Selectivity to phosgene formation on P-25 was twice that on SO42-/TiO2. Sulfated TiO2 was more active and deactivated more slowly than P-25 during PCO of acetaldehyde above 373 K. Since acetaldehyde is an intermediate for PCO of several organics, SO42-/TiO2 may be preferable to Degussa P-25 for PCO at elevated temperatures. (C) 2001 Elsevier Science B.V. All rights reserved.