Phosgene formation from the decomposition of 1,1-C2H2Cl2 contained gas in an RF plasma reactor

In this study, a radio-frequency (RF) plasma system was used to decompose the 1,1-dichloroethylene (DCE) contained gas. The reactants and final products were analyzed by using an FTIR (Fourier Transform Infrared Spectroscopy). The effect of plasma operational-parameters for DCE decomposition was evaluated. In addition, the possible reaction pathways for DCE decomposition and phosgene (COCl2) formation were built up and discussed. Both DCE decomposition efficiency and the fraction of total carbon mass converted into CO2 and CO were decreased by the increasing DCE feeding concentration. The DCE decomposition efficiency at varied equivalence ratios, phi (stoichiometric O-2/actual O-2), was controlled by both oxidation and energy transfer efficiency. At lower equivalence ratios having an excess of oxygen, a larger amount of COCl2 was formed due to a higher oxygen-feeding concentration. Higher input power wattage can increase both the DCE decomposition efficiency and the fraction of total-carbon mass converted into CO2 and CO, resulting in the reduction of the COCl2 effluent concentration. However, more soot was found in the plasma reactor when the input power wattage was higher than 60 W. Because high concentrations of C2Cl4, CHCl3 and CCl4 were detected and because copper inner-electrode might act as catalyst, the most possible pathways for the COCl2 formation were C2Cl4 + OH, C2Cl(3) + O-2, CHCl3 + O, CHCl2 + O, CCl3 + O and CO + Cl-2.