The influence of ethene on the conversion of NOx in a dielectric barrier discharge

The possibility of removing toxic impurities from gaseous streams by electrical gas discharges has been investigated for almost a decade. Cold discharges, i.e. plasmas in which the electrons are not in thermal equilibrium with ions and molecules, seem to be a potential method for the conversion of NOx (=NO, NO2) in exhaust gases of cars or in flue gases of incineration plants. In this work we present a model for the temporal evolution of the plasma chemical processes in a dielectric barrier discharge in a mixture containing N-2, O-2, H2O and small amounts of NO, NO2 and optionally C2H4 (ethene). The results of the calculations are compared with our experimental data. Quantitative analysis of the reaction turnovers allows the identification of the main chemical pathways. Most of the conversion of NOx is due to oxidation and only a small fraction is caused by chemical reduction. The complete removal of NO can be achieved at an energy expense of 5 to 10 eV per NO molecule if 2000 ppmv C2H4 are present in the gas stream. If C2H4 is not present 60 eV/NO are needed.