Low-Temperature Oxidation of Diesel Particulate Matter Using Dielectric Barrier Discharge Plasma

Abstract

The oxidation behavior of actual diesel particulate matter (DPM) prepared from diesel combustion was studied using a dielectric barrier discharge (DBD) reactor. The primary oxidation temperature (T₃₀ at which 30% of DPM was oxidized) was reduced from 524 °C (with non-discharge, NDC) to 409 °C with discharge (DC). It was found that the dry soot (DS) from DPM after dichloromethane extraction was more difficult to be oxidized than DPM due to the loss of soluble organic fraction (SOF) from DPM. The order of activation energies of DPM and DS under conditions of DC and NDC is: DPM–DC < DPM–NDC < DS–DC < DS–NDC. The intermediates of DPM oxidation at different temperatures, pulse peak voltages and reaction gas atmospheres were investigated via operando DRIFTS–MS. It is found that under DC, SOF can be oxidized to oxygen containing compounds (OCC) at low temperatures, and a higher pulse peak voltage is beneficial to DPM oxidation. The main product of 10 vol% O₂/N₂ discharge gas is high valence nitrogen oxides like NO₂, which participates in DPM oxidation. DBD plasma enhances DPM oxidation primarily through two mechanisms: first, by ionizing O₂ to produce strong oxidizing substances, and second, by inhibiting the increasing content of graphitized components. This study provides a comprehensive understanding of DPM oxidation kinetics and intermediates under DBD plasma.