等离子体在同时去除NOx和碳烟催化反应中的作用

采用程序升温反应(TPR)技术,研究了等离子体辅助同时催化去除富氧柴油机尾气中NO_x和碳烟(soot)的反应特性.研究结果表明,等离子体提高了同时去除NO_x-soot的催化反应活性,降低了碳烟的燃烧温度,使碳烟起燃温度从300 ℃降到280 ℃,燃尽温度从425 ℃降到380 ℃;同时,等离子体辅助提高了NO_x转化为N₂的效率,使催化选择性从1.12％提高到1.53％.本文还分别研究了在NO和O₂的环境中,有或没有等离子体作用下,碳烟在催化作用下的去除特性.等离子体作用使得NO在和O₂共存、只有NO和只有O₂存在的各种条件下,碳烟的催化燃烧活性都有不同程度的提高,促进了N₂的生成.此外,本文也对等离子体辅助同时催化去除NO_x-soot的机理进行了探讨.

The Effects of Plasma on Simultaneously Catalytic Removal of Nox and Soot

The simultaneous removal of NO_x and soot was studied by the temperature program reaction (TPR) technology over La_0.8K_0.2MnO₃ catalyst assisted by plasma. When the experiment was carried out by catalysis process, the results showed that La_0.8K_0.2MnO₃ catalyst had the excellent catalytic performance for the reduction of NO_x by soot in the oxygen rich atmosphere. When the experiment was conducted by catalysis with the assistant of plasma in the same gases condition, the results showed that plasma improved the catalytic activity for simultaneous removal of NO_x and soot, and reduced the combustion temperature of soot. As a consequence, the ignition temperature of soot was reduced from 300 ℃ to 280 ℃, and the burning out temperature was also decreased from 425 ℃ to 380 ℃. The conversion efficiency of NO_x to N₂ was improved by plasma, and the selectivity to N₂ formation was enhanced from 1.12％ to 1.53％. In addition, the catalytic property for soot removal was studied at various gas compositions with or without plasma. The results also showed that plasma improved the catalytic activity for the combustion of soot and the conversion efficiency of NO_x to N₂ whether in the NO＋O₂ or NO atmosphere. Also, the mechanism of plasma-assisted catalysis for simultaneous removal of NO_x and soot was discussed in this paper.