Analysis of low-temperature surface discharge plasma products from gaseous organic compounds

Nonequilibrium low-temperature discharge plasma decomposition products of 1000 ppm gaseous organic compounds contaminated in atmospheric pressure air, nitrogen, or oxygen, such as chlorofluorocarbon (CFC-113), organic chloride (trichloroethylene), and carbon tetrachloride, were studied for a better understanding of the decomposition mechanism of the plasma processing. A gas chromatograph-mass spectrometer was used as a main analyzing equipment. When the decomposition rate is not high (20-80%) for CFC-113, many various halogenated carbons or halogenated hydrocarbons are identified as intermediate products by the plasma processing. As the electric discharge power consumption increases, the decomposition rate of CFC-113 increases and intermediate products decrease. At the decomposition rate of more than 90%, some elemental products of hydrochloric acid, carbon dioxide, and nitrogen suboxide are recognized as final products. On the other hand, if the environmental gas is pure nitrogen without any oxygen and water vapor, the decomposition products are still intermediate with sufficient electric discharge power consumption, suggesting the existence of double decomposition mechanisms of nitrogen radicals and oxygen radicals. In the case of trichloroethylene decomposition, harmful intermediate decomposition products were observed when the decomposition rate was 20-90%.