Mechanisms for formation of inorganic byproducts in plasma chemical processing of hazardous air pollutants

Plasma chemical behavior of hazardous air pollutants (HAP's) (Cl2C=CCl2, Cl2C=CHCl, Cl3C-CH3, Cl2CH-CH2Cl, CH3Cl, CH3Br, and benzene), their molecular probes (CH4 CH3-CH3, and CH2=CH2), and carbon oxides (COx) was investigated with a ferroelectric packed-bed plasma reactor to obtain information on the formation of COx and N2O. It has been shown that the oxidation of CO to CO2 is a slow reaction in plasma, and that CO and CO2 mainly result from different precursors. Simultaneous achievement of complete oxidative decomposition of HAP's in plasma and recovery of CO as a chemical feedstock could be favorable. The process of N2O formation is affected by HAP structures and oxygen concentration. In the decomposition of olefinic HAP's, such as Cl2C=CCl2 and Cl2C=CHCl, high-power short-residence-time operations are effective in suppressing N2O formation. In the cases of CH3Cl and CH3Br, low specific energy density operations could be necessary to reduce NaO concentrations. The yields and selectivities of CO, CO2, and N2O change drastically by adding only 2% of oxygen to N-2, and oxygen concentration is not a good factor to control these inorganic oxides.