Supported photo sensitizers as new efficient materials for gas-phase photo-oxidation

The photosensitised oxidation of dimethyl sulfide in the gas phase was carried out for the first time on original silica materials in a flow reactor and under visible light irradiation. The photocatalysts were prepared either by physisorption of two different photosensitizers, 9,10-dicyanoanthracene or 9,10-anthraquinone on commercial silica beads, or by incorporation of 9,10-dicyanoanthracene in sol-gel monoliths. Oxidation products are mainly sulfoxide, sulfone and disulfide, and it is assumed that singlet oxygen is the most probable reactive oxygen species. These materials display several advantages as they are activated by visible light, and they act as very efficient traps for partially oxidized products. Accordingly, the gas-flow at the outlet of the photocatalytic device is free of any toxic or nauseous product for several days. As soon as products appear in the gas flow, the catalyst is deactivated, but the silica beads can be easily regenerated by mild thermal treatment under controlled conditions. With regard to the photo-oxidative efficiency, our results point out the influence of the properties of the silica support itself, such as transparency, homogeneity and specific surface area. The adsorption capacity of the material is a crucial parameter, as the most DMS adsorbing material is also the most efficient. (c) 2005 Elsevier B.V. All rights reserved.