Reaction mechanisms in both a CCl₂F₂/O₂/Ar and a CCl₂F₂/H₂/Ar RF plasma environment

Decomposition of dichlorodifluoromethane (CCl₂F₂ or CFC-12) in a radio-frequency (RF) plasma system is demonstrated. The CCl₂F₂ decomposition fractions (η_CCl2F2) and mole fractions of detected products in the effluent gas stream of CCl₂F/O₂/Ar and CCl₂F₂/H₂/Ar plasma, respectively, have been determined. The experimental parameters including input power wattage, O₂/CCl₂F₂ or H₂/ CCl₂F₂ ratio, operational pressure, and CCl₂F₂ feeding concentration were investigated. The main carbonaceous product in the CCl₂F₂//O₂/Ar plasma system was CO₂, while that in the CCl₂F₂/H₂/Ar plasma system was CH₄ and C₂H₂. Furthermore, the possible reaction pathways were built-up and elucidated in this study. The results of the experiments showed that the highly electronegative chlorine and fluorine would easily separate from the CCl₂F₂ molecule and combine with the added reaction gas. This led to the reactions terminated with the CO₂, CH₄, and C₂H₂ formation, because of their high bonding strength. The addition of hydrogen would form a preferential pathway for the HCl and HF formations, which were thermodynamically stable diatomic species that would limit the production of CCl₃F, CClF₃, CF₄, and CCl₄. In addition, the HCl and HF could be removed by neutral or scrubber method. Hence, a hydrogen-based RFplasma system provided a better alternative to decompose CCl₂F₂.