Catalytic Hydrolysis of CFC-12 over MoO₃/ZrO₂-TiO₂

Abstract

Solid acid MoO₃/ZrO₂-TiO₂ catalysts were prepared by impregnation method, and catalytic hydrolysis of difluorodichloromethane(CFC-12) over the catalyst was studied. The presence of MoO₃/ZrO₂-TiO₂ catalyst in polycrystalline state could be clearly observed by transmission electron microscopy (TEM). Mesopores were detected by N₂ adsorption-desorption isotherms which further confirmed the MoO₃/ZrO₂-TiO₂ structural characteristics of catalyst. The results of NH₃-TPD showed that the calcination temperatures had a great influence on the acidity of the catalyst, and the weak acidic site had a strong catalytic activity for the catalytic hydrolysis of CFC-12. Moreover, ZrO₂-TiO₂ was highly dispersed in the MoO₃ framework, suggested by powder X-ray diffraction (XRD) and N₂ adsorption-desorption results. The effects of the catalyst calcination temperatures on the conversion rate of CFC-12 were studied. The effects of catalytic hydrolysis temperatures and water vapor concentration on the catalytic hydrolysis rate of CFC-12 were also studied. The solid acid MoO₃/ZrO₂-TiO₂ was calcined at 500 °C for 3 h at a catalytic hydrolysis temperature of 400 °C and water vapor concentration of 83.18%, and catalytic hydrolysis rate of CFC-12 reached 98.65 %. The hydrolysis rate of CFC-12 remained above 65.34% after 30 hours continuous reaction.

Keywords

catalytic hydrolysis / difluorodichloromethane(CFC-12) / MoO₃/ZrO₂-TiO₂ / solid acid catalyst