O3和C2H4在介质阻挡放电转化NO中的作用

Effects of Ozone and Ethylene on NO Conversion in DBD Plasma

放电等离子体结合选择催化还原脱除NOx是一项很有前景的贫燃尾气治理技术,其预处理过程中,尾气中NO会向NO2转化。为了解重要的活性中间产物O3的作用和生成特性以及常见的烃类添加剂C2H4的作用,在介质阻挡放电等离子体反应器内进行了相关实验研究。监测N2/O2,N2/O2/NO,N2/O2/C2H4,N2/O2/NO/C2H4共4个体系下的O3产生特性,并通过N2/O2/NO和N2/O2/NO/C2H4体系的比较考察C2H4对NO转化影响的结果表明:除N2/O2体系外,其它体系中都不会产生大量的O3;C2H4不但提高了NO的转化率,还明显地抑制放电过程NO的生成。可以推断,O3作为氧化剂能促进NO向NO2的转化,C2H4添加剂可以提高NO的转化率。

Plasma-facilitated selective catalytic reduction of NOx is one of promising after-treatment methods for lean-burn exhaust, which could overcome the disadvantages of the conventional three way catalyst method in rich oxygen condition at low temperature（〈300℃）. This method could be divided into plasma process and catalysis process. It has been reported that ozone is a key intermediate among the products of plasma, and hydrocarbon is a common additive for this process. So in this experiment, characteristics of ozone produced and C2 H4 effects were necessary to study in N2/O2, N2/O2/NO, N2/O2/C2H4 , and N2/O2/NO/C2 H4 systems, for the sake of discussing the related chemical reactions mechanism. Results showed that in N2/O2 mixture a large amount of ozone produced was observed, but in other gas systems, no more than 20×10^-6 ozone was generated. NO oxidation took place with the plasma applied, and the addition of ethylene increased the oxidation up to 35 % in the experimental range. And in N2/O2 and N2/O2/C2 H4 systems, it was found that ethylene additive could greatly restrict the formation of nitrogen oxides in the discharge. Finally two conclusions were made： ozone served as an important oxidizer in NO to NO2 conversion, and ethylene could enhance the conversion of NO to NO2.