等离子体辅助催化还原NOx的协同特性

Synergy study for plasma-facilitated catalytic reduction of NO_x

以NO/NO2/C2H4/O2/N2为模拟反应气体系,研究了较低催化温度下介质阻挡放电等离子体辅助C2H4在Ag/-γAl2O3催化剂上选择催化还原NOx的协同特性。结果表明,在催化温度为240℃时,等离子体辅助催化脱除NOx方面表现出明显的协同效应;等离子体“预活化”过程产生的协同“媒介”物质包括3类:NO2、醛类(HCHO,CH3CHO)和含氮有机物(CH3ONO2,C2H5ONO2,CH3NO2),放电过程脱除的NOx主要转化为含氮有机物;在等离子体“预活化”过程中,提高放电能量密度或初始C2H4浓度均可促使协同“媒介”NO2向低温催化活性更高的含氮有机物转化和醛类的生成,进一步提高等离子体辅助催化的NOx脱除效率。

The synergistic effect of plasma-facilitated C2H4 selective catalytic reduction （SCR） of NOx over Ag/γ-Al2O3 catalyst at lower catalyst temperature was studied for the NO/NO2/C2H4/O2/N2 gas system, and a dielectric barrier discharge （DBD） reactor was used as plasma reactor. Results showed that plasma-facilitated catalysis system for NOx removal exhibited obvious synergistic effect at 240 ℃. Based on the analysis of the products of plasma pre-activation, the synergistic link products included three kinds of chemical compound like NO2, aldehydes （formaldehyde and acetaldehyde）, nitrogen-contained organic compounds （methyl nitrate, nitro methyl and ethyl nitrate）. The removal of NOx in DBD plasma reactor means that nitrogen-contained organic compounds yield. During the process of plasma preactivation, improving the input energy density of DBD reactor or initial C2 H4 concentration facilitated the conversion of NO2 to nitrogen-contained organic compounds and the formation of aldehydes, further improving the NOx removal efficiency of plasma-facilitated catalysis system.