Conversion of dilute nitrous oxide (N2O) in N2 and N2–O2 mixtures by plasma and plasma-catalytic processes†
Abstract
A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma and plasma-catalytic conversion of dilute N2O in N2 and N2–O2 mixtures at both room and high temperature (300 °C). The effects of catalyst introduction, O2 content and inlet N2O concentration on N2O conversion and the mechanism involved in the conversion of N2O have been investigated. The results show that N2O in N2 could be effectively decomposed to N2 and O2 by plasma and plasma-catalytic processes at both room and high temperature, with much higher decomposition efficiency at 300 °C than at room temperature for the same discharge power. Under an N2–O2 atmosphere, however, N2O could be removed only at high temperature, producing not only N2 and O2 but also NO and NO2. Production and conversion of N2O occur simultaneously during the plasma and plasma-catalytic processing of N2O in a N2–O2 mixture, with production and conversion being the dominant processes at room and high temperature, respectively. N2O conversion increases with the increase of discharge power and decreases with the increase of O2 content. Increasing the inlet N2O concentration from 100 to 400 ppm decreases the conversion of N2O under an N2 atmosphere but increases that under an N2–O2 atmosphere. Concentrating N2O in the N2–O2 mixture could alleviate the negative influence of O2 by increasing the involvement of plasma reactive species (e.g., N2(A3Σu+) and O(1D)) in N2O conversion. Packing the discharge zone with a RuO2/Al2O3 catalyst significantly enhances the conversion of N2O and improves the selectivity of N2O decomposition under an N2–O2 atmosphere, revealing the synergy of plasma and catalyst in promoting N2O conversion, especially its decomposition to N2 and O2.