Plasma reactions of methane in nitrogen and nitrogen/oxygen carriers by matrix isolation FTIR spectroscopy

Abstract

The plasma-induced reactions of traces of methane in nitrogen and nitrogen/oxygen carriers have been investigated by freezing the products onto a 10 K CsI substrate and performing FTIR analysis on the product mixture. Isotopic substitution studies have been used to assist in identification of reaction intermediates and final products. A combination of low (10 mTorr) and high (2 Torr) pressure discharges has also been used to help in the identification of these products. Oxygen concentration was increased in a stepwise fashion to determine its effect on the reaction product distribution. In the present work, methyl radical was the principal product in low-pressure N2/CH4 plasmas, and small amounts of HCN and NH3 were also produced. In the higher-pressure plasmas, HCN and NH3 were the principal products. As O2 was added to the plasmas, CO, H2O, CO2, N2O, NO, O3, HONO, and HNO3 were produced in approximately the order shown, i.e., CO was formed in good yield at low oxygen partial pressures, but HNO3 was produced only in slight yield even at the highest oxygen pressures used in this work. These results are discussed in terms of the development of a plasma device having potential application for destruction of environmentally hazardous materials and how trace organic pollutants might react in such a system.