Conversion of dilute nitrous oxide (N2O) in N-2 and N-2-O-2 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 N2O in N-2 and N-2-O-2 mixtures at both room and high temperature (300 degrees C). The effects of catalyst introduction, O-2 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 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 degrees C than at room temperature for the same discharge power. Under an N-2-O-2 atmosphere, however, N2O could be removed only at high temperature, producing not only N-2 and O-2 but also NO and NO2. Production and conversion of N2O occur simultaneously during the plasma and plasma-catalytic processing of N2O in a N-2-O-2 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 O-2 content. Increasing the inlet N2O concentration from 100 to 400 ppm decreases the conversion of N2O under an N-2 atmosphere but increases that under an N-2-O-2 atmosphere. Concentrating N2O 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)Sigma(+)(u)) and O(D-1)) 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 N-2-O-2 atmosphere, revealing the synergy of plasma and catalyst in promoting N2O conversion, especially its decomposition to N-2 and O-2.