Dichloromethane oxidation over FexZr1-x oxide catalysts

FexZr1-x-S mixed oxide catalysts were prepared by precipitation of FeSO4 and ZrOCl2, and used in catalytic oxidation of dichloromethane (DCM). Analyses by a series of characterization technologies reveal that Fe-O-Zr solid solution with tetragonal ZrO2 or alpha-Fe2O3 structure can be formed, dependent on Fe/Fe + Zr ratio. Residual SO42- species obtained from FeSO4 precursor exist in a form of bridged bidentate complex with Zr4+ or Fe3+ ion, which increases acidity significantly. FexZr1-x-S catalysts with Fe/Fe + Zr of 0.2-0.5 possess high contents of both SO42- and surface oxygen, and are highly active in catalytic combustion of DCM with T-90 below 320 degrees C and TOFs at 200 degrees C of 0.98-1.89 mu mol/(m(2)min). Another test shows that the activity for the other CVOVs oxidation over Fe0.5Zr0.5-S is 1,2-dichloroethane > dichloromethane > trichloroethylene > 1,2-di chlorobenzene. Because the substitution of Cl species for surface oxygen is retarded, high stable activity maintains within reaction temperatures for at least 80 h. In situ FT-IR indicates that DCM is adsorbed and activated mainly through the formation of chloromethyl sulfate, which is oxidized quickly into formate ion. The synergism between SO42- complex anchoring on Zr-O-Fe solid solution and surface oxygen obtained from Fe2O3 cluster or nano-particles promotes the oxidation of formate.