Catalytic oxidation of chlorinated VOCs over Ru/TixSn1-x catalysts

Ru/TixSn1-x catalysts, prepared by incipient-wetness with aqueous solution of RuCl3 were applied in the catalytic oxidation of dichloromethane (DCM) and chlorobenzene (CB). In mixed oxides of TixSn1-x, Sn4+ entered into TiO2-rutile and Ti4+, into SnO2-rutile, forming Ti-O-Sn species, which disordered rutile lattice and increased strong Lewis acid. Ru was identified as Ru-O-Ti and Ru-O-Sn, as a result of the interaction between TiO2 or SnO2 and Ru. Ru-O-Sn increased surface oxygen, while Ru-O-Ti promoted the basicity of surface lattice oxygen. In oxidation of DCM at 240 degrees C and CB at 275 degrees C, Ru/TixSn1-x catalysts presented high activity with the rates of 0.084-0.201 and 0.046-0.719 umol min(-1)m(-2), respectively, which was ascribed to the synergism between Ru-OTi and Ru-O-Sn. At 90% conversion, CO2 was almost only the carbon-containing product. Ru/TixSn1-x catalysts maintained stable activity for at least 50 h without substantial changes. High activity for Deacon was responsible for quick removal of Cl species, which was a slow step in the reaction. In the presence of water, the temperature needed for 100% conversion maintained constant. In situ FT-IR showed that chloromethoxyl and phenolate were the adsorbed species of DCM and CB, respectively, which were sequentially converted by surface oxygen into carboxylates and CO2.