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 Ru-0 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 degrees C of 0.18-0.63 x 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.