Influence of Soot Surface Changes on DPF Regeneration

Soot oxidation has been a critical issue for regeneration of diesel particulate filters (DPFs). The design of the regeneration strategy and the durability requirement for DPFs depend on an understanding of soot burning. Raman and thermal analysis have been used to monitor surface configuration changes. Under thermal aging, engine soot undergoes a transformation from a mostly amorphous carbon structure into more orderly polyaromatic structures which exhibit resistance towards oxidation. Certain neutralization products, such as thio-phosphorous and phosphorous derivatives, can also alter the thermal behavior of soot through interactions between ash and soot adsorbed species. The incomplete regeneration can be attributed to a buildup of a physical barrier that prevents oxygen or NO₂ from diffusing effectively onto the carbon surface.