Catalytic decomposition of chlorodifluoromethane (HCFC-22) over platinum supported on TiO2-ZrO2 mixed oxides

Sulfated and non-sulfated TiO2-ZrO2 were promoted with platinum and the activity and selectivity of the resulting catalysts for the hydrolytic decomposition chlorodifluoromethane in air was investigated. The addition of platinum reduced the specific surface area of the catalyst slightly and lowered the catalytic activity. On the other hand, the selectivity of the catalysts towards CO2 formation was much improved. Metallic platinum was formed by the reduction of the platinum precursor with carbon monoxide produced during the hydrolysis of chlorodifluoromethane over the acidic mixed oxide and promoted the oxidation of CO. At the same time, platinum suppressed completely the formation of the fluorinated byproduct CHF3, possibly by anchoring itself on the active sites responsible for the fluorination reaction. The platinum promoted non-sulfated TiO2-ZrO2 was stable and gave more than 90% of CHClF2 conversion and 95% selectivity to CO2 for over 60 h.