Degradation Mechanism of Diesel Particulate Emissions Induced by Non-Thermal Plasma

Abstract

An experimental system for online diesel particulate matter (PM) degradation using non-thermal plasma (NTP) technology was built, and PM oxidation removal tests were carried out under different loads. The micro-nano structure, oxidation activity and element occurrence state of PM before and after NTP were compared by TEM, TGA and XPS. The results show that the degree of PM agglomeration in the original machine increases with the increase of load. After the NTP active substance is introduced, the PM in the agglomerated state begins to break down and transform into a chain structure. The long crystallites in the primary carbon particles are oxidized and decomposed into short crystallites, the crystallite length (La) gradually shortens, and the proportion of large crystallite spacing (Ds>1nm) and large crystallite curvature (Tr>1.3) gradually decreases after the action of NTP. The Ts, Te and Tmax of EC tend to shift to lower temperatures, and the oxidation activity is enhanced. Carbon particle microcrystals contain a large amount of C element. After the microcrystals are cracked, O atoms are continuously inserted into the carbon particles, C-C transforms into C-O, the relative content of C element decreases, and C-O is converted into C=O after NTP oxidation.

Keywords: Particulate Matter, degradation, Non-thermal plasma, Microcrystalline structure, Oxidative activity