Effect of water vapor and hydrocarbons in removing NOx by using non-thermal plasma and catalyst

The effect of water vapor and hydrocarbons in removing NO/sub x/ was experimentally studied by combining nonthermal plasma with various type of catalyst. Catalysts tested in this paper were copper-coated zeolite, and conventional 3-way catalysts. The combined process of the catalyst and the nonthermal plasma was examined experimentally. Water vapor from 0 to 15% was added in the flue gas to simulate real exhaust gas conditions and compared to dry conditions. With 10% of water vapor, an NO removal rate of about 70% was obtained with a Na-ZSM-5 catalyst at 200-500/spl deg/C where plasma discharge was not applied. Nonthermal plasma improves NO/sub x/ removal rate with 10% water vapor and Na-ZSM-5 at any temperature. Such a high removal rate did not resulted solely in chemical reaction but also absorption by the catalyst. Nonthermal plasma degrades NO/sub x/ removal rate with Cu-ZSM-5 with a gas temperature of 300/spl deg/C or above. With a gas temperature of 100/spl deg/C, the nonthermal plasma process is enhanced by the combination of nonthermal plasma and any type of catalyst. The catalysts investigated in this paper do not work at such low temperature. Absorption characteristics were also investigated and only Na-ZSM-5 showed remarkable absorption characteristics.