CH2Cl2 catalytic oxidation over Ce-Ti-Zr mixed oxide catalysts

Ce-Ti-Zr mixed oxide catalysts prepared by sol-gel method were used in catalytic combustion of CH2Cl2. The characterization reveals that the incorporation of Ce and Zr into TiO2 anatase or Ti and Zr into CeO2 fluorite promotes hydroxyl groups, Lewis acidity and surface oxygen through the formation of Ti-O-Zr, Ti-O-Ce and Ce-OZr species. Ce-Ti-Zr catalysts show high activity for CH2Cl2 oxidation with the rate of 5.66 x 10-3-6.45 x 10-3 mu mol s(-1) m(-2) at 250 degrees C and high stability for 50 h. The substitution of surface oxygen for Cl maintains the availability of Ti-OH and thus promotes Cl removal as HCl, which is verified by a great increase in the stable activity of physically closely contacted mixture of separated CeO2 and TiO2 or Ti9Zr1 particles. In situ FT-IR shows that CH2Cl2 interacts with Ti-OH to form -O-CH2-O-, which is quickly rearranged into formate. Finally, formate is oxidized with surface oxygen into CO or CO2.

Automated summary

Ce-Ti-Zr mixed oxide catalysts prepared by sol-gel method exhibit high activity and stability for CH2Cl2 oxidation. The incorporation of Ce and Zr promotes the formation of hydroxyl groups, Lewis acidity and surface oxygen, leading to efficient CH2Cl2 removal.