At present, diesel particulate filter (DPF) is becoming an essential part of the engine exhaust system under the increasingly stringent emission regulations in terms of particulate quality and quantity control. However, the use of DPF also accelerates the increased flow resistance due to particle collection. In order to avoid the formation of high back pressure in the exhaust pipe, the accumulated particles must be removed regularly or continuously. Soot oxidation reactivity is an important property, which directly determines the regeneration process of DPF. A key factor of particle elimination is its oxidation reactivity, which is closely related to its physicochemical properties.

      The main purpose of this study is to study the change of soot oxidation reactivity in diesel exhaust after treatment system, and analyze its quantitative correlation with surface functional groups (SFGS) and graphitization degree. The soot particles of 16-cylinder turbocharged diesel engine before and after doc and CDPF were thoroughly sampled. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman) and thermogravimetric analysis (TGA) were used to characterize the surface functional groups (SFGS), graphitization degree and Oxidation Reactivity of soot particles in exhaust gas after-treatment system. The results showed that under all conditions, the activation energy of soot oxidation increased approximately linearly along the post-treatment system, indicating that soot particles become more and more stable, and the inherent graphitization degree reaches the highest after CDPF. At the same time, the composite characterization results also showed that the amorphous carbon and active light volatiles were removed or oxidized by DOC and CDPF. Therefore, soot particles have lower graphitization degree, higher C-H group concentration and higher oxidation activity. The catalyst components (DOC and CDPF) in the post-treatment system can effectively improve the graphitization degree of tail gas particles, leaving more stable particles, which will require higher activity regeneration energy or more powerful catalyst to clean up the CDPF wall.