Conversion of dilute nitrous oxide (N2O) in N2 and N2–O2 mixtures by plasma and plasma-catalytic processes

摘要

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) .