Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (02): 192-196.doi: 10.3866/PKU.WHXB20050216

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Plasma-induced Conversion of Nitrogen Oxides in a Dielectric Barrier Discharge Reactor

SUN Qi;ZHU Ai-Min;NIU Jin-Hai;XU Yong;SONG Zhi-Min   

  1. Laboratory of Plasma Physical Chemistry, Dalian University of Technology, Dalian 116024
  • Received:2004-06-09 Revised:2004-10-08 Published:2005-02-15
  • Contact: SUN Qi

Abstract: In order to understand the mechanism of NOx removal in non-thermal plasma, the conversion of NO with different reacting gas mixtures under atmospheric pressure has been studied using dielectric barrier discharge plasma at 523 K. Experiments demonstrate that in the NO/N2 system, NO decomposition to N2 and O2 is in the majority. In the NO/O2/N2 system, NO conversion is the lowest for the formation of NO2 and NO. In the NO/C2H4/N2 system, NO is reduced to N2 at the same NO conversion as that in the NO/N2 system. Because the O atoms from NO decomposition are consumed more effectively by reaction of O and C2H4 than reaction of O and NO, NO2 formation is not observed. Dielectric barrier discharge is a very effective means for oxidizing NO to NO2 in the NO/O2/C2H4/N2 system. At the energy density of 125 J•L-1, NO conversion and concentration of NO2 formed in the NO/O2/C2H4/N2 system are the highest, the energy consumption is the lowest, 61 eV per converted NO molecule. C2H4 is mainly oxidized to CO in the dielectric barrier discharge plasma. A small amount of N2O is formed in the four systems. The in-situ optical emission spectra(200~900 nm) have also been investigated under atmospheric pressure at 523 K. The observations of N2 second positive band, NO γ-band and NO β-band with different gas mixtures imply that some excited-state active species from plasma-induced processes can effectively convert NO. Finally, mechanisms for the NO conversion in the four systems were proposed on the basis of experiment and relative literature.

Key words: Dielectric barrier discharge, NOx, C2H4, Plasma chemistry, Optical emission spectroscopy