Photocatalytic performance of sulfated TiO_2 and Degussa P-25 TiO_2 during oxidation of organics

摘要

Photocatalytic oxidations (PCOs) ofheptane, trichloroethylene (TCE), ethanol, acetaldehyde, and toluene were carried out on sulfated TiO2 (SO4 2- rriO2) and Degussa P-25. Coverages of all organics on SO4 2- rrio2 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, SO4 2- rrio2 deactivated slower than P-25 so that the CO2 formation rate on P-25 was only 11% greater than that on SO4 2- rrio2 after five 110 IJ.mo1/g catalyst pulses of heptane. Both pulse and steady-state PCO ofTCE showed that although P-25 was more active than SO42- rrio2, the CO2 production rate decreased with time on P-25 but not on SO42- rrio2. Furthermore, CO2 selectivity increased with time as PCO of TCE approached steady-state onSO42- rrio2, whereas it decreased on P-25. Selectivity to phosgene formation on P-25 was twice that on so42-rrio2. 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-rrio2 may be preferable to Degussa P-25 for PCO at elevated temperatures.