The catalytic combustion of CH2Cl2 over SO42−–TixSn1−x modified with Ru†
Ru/SO42−–TixSn1−x catalysts were prepared via impregnation with an aqueous solution of RuCl3 on SO42−–TixSn1−x. For the samples with a Ti/Ti + Sn ratio higher or lower than 0.6, TiO2 or SnO2-rutile existed, and both contained the Ti–O–Sn structure. The residual SO42− species as chelating or bridged bidentate complexes with the Ti4+ and Sn4+ ions promoted the acidity significantly. Ru as Ru0 and Ru4+ was highly dispersed on the matrices as a result of the interaction between the Ru and SO42− species. Ti–O–Sn increased the surface oxygen and SO42− complexes, while Ru promoted the redox activity. In CH2Cl2 oxidation, the Ru/SO42−–TixSn1−x catalysts with the Ti–O–Sn structure presented high activity with TOFs at 225 °C of 0.18–0.63 × 10−3 s−1, which could be ascribed to the synergism between SO42−–Ti4+ and the active surface oxygen. At 90% conversion, the selectivity for CO2 and HCl was 90% or higher. Furthermore, the Ru/SO42−–TixSn1−x catalysts maintained stable activity for 50 h in wet or dry feed without significant changes. The in situ FT-IR spectra showed that the –O–CH2–O– organic sulfate was the main intermediate in CH2Cl2 oxidation. The hydroxyl activated by surface oxygen was responsible for high activity and Cl removal.