Consequences of propene and propane on plasma remediation of NOx

Dielectric barrier discharge (DBD) reactors are being investigated for plasma remediation of NOx from the exhaust of internal combustion engines and diesel emissions, in particular. In earlier works, it was found that unburned hydrocarbons (UHCs), inevitably present in exhausts, play a significant role in altering NOx remediation pathways and increasing the oxidation of NO. In this study, the DBD processing of NOx in simulated diesel exhausts with hydrocarbons [propane (C3H8) and propene (C3H6)] has been investigated. In general, the presence of UHCs improved the energy efficiency of remediation. For example, at 56 J/L, NOx remediation improved from 12% without UHCs to 32% in the presence of 175 ppm propene. The W-values for NO remediation at 56 J/L decreased from 160 eV/molecule in the absence of UHCs to 96 eV/molecule with 175 ppm propene, though the majority of this improvement is a result of conversion to NO2. Temperature dependencies of NOx remediation were investigated and it was found that higher temperatures improve NO remediation whereas the effect on total NOx remediation is not significant, implying that NO remediation at higher temperatures results from increased NO2 formation.