Catalytic Decomposition of Chlorofluorocarbons in the Presence of Alcohols -Decomposition of Various Chlorofluorocarbons-

Abstract

The catalytic decomposition of various chlorofluorocarbons (CFCs) in the presence of alcohols over FeX₃/CuCl₂ supported on active charcoal was carried out in order to investigate the relationship between their molecular structure and reactivity.
It was found that ethyl chloroforma te was an intermediate in the catalytic decomposition of carbon tetrachloride in the presence of ethanol. Therefore, the catalytic decomposition of CCl₄ is initiated with the dissociation of CCl₄ into CCl₃⁺ and Cl^- in the presence of FeX₃. The nucleophilic attack of alcohol to CCl₃⁺ may give alkyl trihalomethyl ether. It is considered that this intermediate played an important role in the postulated step, The catalytic decomposition of CFC-11 took place even at a temperature below 200°C. Decrease in the conversion of CFC-11 could be prevented by keeping the reaction tempera ture at 250°C or above.
As the reaction system was under a reductive atmosphere, iron (III) halide was reduced into low-valency iron. However, the low-valency iron was oxidized with copper (II) chloride into iron (III) chloride. Thus, the copper-assisted catalytic decomposition of CFC-12 could be continued for a long time at 330°C. The more fluorine atoms CFCs had, the harder the catalytic decomposition of them became, owing to the increase in the bond dissociation energy.