Decomposition of chlorofluorocarbons on TiO2ZrO2

Abstract The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. The TiO 2 ZrO 2 catalyst was found to have the highest activity and longest life among the catalysts examined. The activity of the TiO 2 ZrO 2 catalysts depended upon the content of TiO 2 . At the contents of TiO 2 from 58 to 90 mole%, the TiO 2 ZrO 2 catalysts exhibited high activity, and these catalysts were proven to contain TiZrO 4 crystal. From the study of the XRD peak intensity of the TiZrO 4 crystal, it was highest on the TZ-58 which contained 58 mole% of TiO 2 , and decreased with increasing the content of TiO 2 . Furthermore, the conversion of CFC113 measured at 673 K was highest at TZ-58, and decreased gradually with increasing TiO 2 content. Therefore, the TiZrO 4 crystal influences the activity of decomposition of CFC113. However, the TiO 2 ZrO 2 catalyst was gradually deactivated during the reaction due to the elimination of titanium atoms. A good relationship was found between the activity on TiO 2 ZrO 2 catalyst and bond energy of C Cl in the compounds of chlorofluorocarbons and hydrochlorocarbons, suggesting that the rate controlling step was the cleavage of C Cl bond.