Conversion of dilute nitrous oxide (N(2)O) in N(2) and N(2)–O(2) mixtures by plasma and plasma-catalytic processes

A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma and plasma-catalytic conversion of dilute N(2)O in N(2) and N(2)–O(2) mixtures at both room and high temperature (300 °C). The effects of catalyst introduction, O(2) content and inlet N(2)O concentration on N(2)O conversion and the mechanism involved in the conversion of N(2)O have been investigated. The results show that N(2)O in N(2) could be effectively decomposed to N(2) and O(2) 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 N(2)–O(2) atmosphere, however, N(2)O could be removed only at high temperature, producing not only N(2) and O(2) but also NO and NO(2). Production and conversion of N(2)O occur simultaneously during the plasma and plasma-catalytic processing of N(2)O in a N(2)–O(2) mixture, with production and conversion being the dominant processes at room and high temperature, respectively. N(2)O conversion increases with the increase of discharge power and decreases with the increase of O(2) content. Increasing the inlet N(2)O concentration from 100 to 400 ppm decreases the conversion of N(2)O under an N(2) atmosphere but increases that under an N(2)–O(2) atmosphere. Concentrating N(2)O in the N(2)–O(2) mixture could alleviate the negative influence of O(2) by increasing the involvement of plasma reactive species (e.g., N(2)(A(3)Σ(u)(+)) and O((1)D)) in N(2)O conversion. Packing the discharge zone with a RuO(2)/Al(2)O(3) catalyst significantly enhances the conversion of N(2)O and improves the selectivity of N(2)O decomposition under an N(2)–O(2) atmosphere, revealing the synergy of plasma and catalyst in promoting N(2)O conversion, especially its decomposition to N(2) and O(2).