Quantitative studies on the heterogeneous gas-phase photooxidation of CO and simple VOCs by air over TiO2

This paper presents a collection of the authors' recent results concerning the photocatalytic oxidation of gaseous organics and CO over TiO(2) in different kinds of reactors with the accent on providing quantitative information about the photoprocesses studied to enable comparison with results of other authors. A static reactor, an annular flow reactor and a flow-circulating reactor were used. Oxidation of acetone, ethanol and diethyl ether in the static reactor ultimately leads to CO(2), with acetaldehyde, acetaldehyde and ethyl acetate being the intermediate products in the oxidation of ethanol and diethyl ether, respectively. Acetone is completely oxidized to CO(2) during a single pass through the annular flow reactor if the residence time is greater than 1 min. Temperature dependence of the acetone photooxidation rate in the how-circulating reactor has a maximum at 80 degrees C. Four specimens of TiO(2) prepared by principally different methods were tested in oxidation of acetone and CO in the flow-circulating reactor. It has been found that photoplatinization retards the acetone oxidation and prohibits considerably the CO oxidation. These results indicate that the process of heterogeneous photocatalytic oxidation can be substantially improved by optimization of both the catalyst and the conditions of the photocatalytic process. (C) 1997 Elsevier Science B.V.