Interaction between soot particles and NOx during dielectric barrier discharge plasma remediation of simulated diesel exhaust

Plasma remediation is being investigated as a means to remove NOx from comb ustion effluent and from diesel exhausts in particular. Soot particles are inevitably present in actual exhausts and may, through heterogeneous chemis try, affect the remediation process. In this article, a computational inves tigation of the effect of soot on the plasma chemistry of NOx removal in a simulated diesel exhaust processed in a dielectric barrier discharge reacto r is presented using a zero-dimensional global-kinetics simulation. A surfa ce chemistry model is employed to describe soot oxidation by O and OH radic als, and soot-NOx interactions. The NOx chemistry may be substantially affe cted by the reactions at the soot surface. In particular, for soot particle s having densities of 10(8) cm(-3) and diameters of 100 nm, significant inc reases of NO are obtained when taking into account NO2--> NO conversion on the soot surface. Heterogeneous reaction of NO2 also results in an increase in the gas-phase OH density which results in the increased formation of HN O2, thereby adding to the NOx remediation. NO2--> NO heterogeneous conversi on also results in an increase of CO and a subsequent reduction of the soot mass. The mechanism for soot-NOx interactions depends on the deactivation of active hydrocarbon radicals on the soot. (C) 2000 American Institute of Physics. [S0021-8979(00)03023-1].