CATALYTIC DESTRUCTION OF CHLOROFLUOROCARBONS AND TOXIC CHLORINATED HYDROCARBONS

The problem of the destruction of the ozone layer by chlorofluorocarbons (CFCs) has led to the proposed phase-out of their production by 1995. A number of chlorinated hydrocarbons which are toxic to man have also been found to destroy the ozone layer. A series of catalysts were tested for their ability to destroy CFC113 and trichloroethylene. CFC113 destruction over alumina-based catalysts led to severe catalyst deactivation due to fluorination of the alumina. However, zirconia-based catalysts were found to have some tolerance against fluorine species. A Pt/ZrO2-(PO4) catalyst was developed which could maintain more than 99% conversion of CFC113 over a 300 hour trial period at 500-degrees-C. The major product was CO2 with a yield above 93%. A significant side reaction (selectivity 5%) was observed due to the fluorination of incoming CFC113 feed to form CFC114. A reaction mechanism was hypothesized for CFC113 destruction over zirconia-based catalysts. Trichloroethylene destruction was more easily achieved than CFC113. Over Pt/ZrO2, more than 99.9% conversion was possible at 500-degrees-C over a 100 hour trial period. A side reaction associated with the chlorination of the feed to tetrachloroethylene had a selectivity below 0.05% indicating that the reactivity of the fluorine species was far higher than the chlorine species.