Reducing nitric oxide into nitrogen via a radio-frequency discharge

NO/N2/O2/H2O mixtures are usually converted into HNO3 and/or NO2 using different discharge approaches. In this study, a radio-frequency discharge was successfully used to reduce NO mainly into N2 at a low pressure (4 kPa). The influences of experimental parameters, including carrier gas, inlet concentration of NO, O2, steam, and applied power, are discussed. At least 95.7% of the total N atoms converted from NO into N2. Other traces of byproducts were N2O and HNO2, but neither HNO3 nor NO2 were detected. In addition, conversion of NO apparently increased with elevated applied power or decreased inlet concentration of O2, reaching 92.8% and 74.2% for the NO/N2/O2 (2%) and NO/N2/O2 (6%)/H2O (10%) mixtures, respectively, at 120 W. In addition, from the optical emission spectra, a large amount of N2 (first positive band and second positive band) and NO (γ system) were observed, and the important reactions for NO removal and N2 formation are proposed.