Decomposition Mechanism of Fluorinated Compounds in Water Plasmas Generated Under Atmospheric Pressure

Decomposition mechanism of HFC-134a, HFC-32, and CF4 in water plasmas at atmospheric pressure has been investigated. The decomposition efficiency of 99.9% can be obtained up to 3.17 mol kWh(-1) of the ratio of hydrofluorocarbon (HFC) feed rate to the arc power and 1.89 mol kWh(-1) of the ratio of perfluorocarbon (PFC) feed rate to the arc power. The species such as H-2, CO, CO2, CH4, and CF4 were detected from the effluent gas of both PFC and HFC decomposition. However, CH2F2 and CHF3 were observed only in the case of HFC decomposition. The HFC and PFC decomposition generate CH2F, CHFx (x:1-2), and CFy (y:1-3) radicals, then those radicals were subsequently oxidized by oxygen, leading to CO and CO2 generation in the excess oxygen condition. However, when there is insufficient oxygen available, those radicals were easily recombined with fluorine to form by-product such as CH2F2, CHF3, and CF4.