Investigation of the physicochemical properties of soot subjected to non-catalytic and CeO₂-catalytic aging under sequential aerobic and anaerobic exhaust-like conditions simulating the transition from engine operation to cessation

Understanding the physicochemical properties of aged soot particles is crucial for enhancing diesel particulate filter (DPF) regeneration strategies. This study examines the physicochemical properties of such soot subjected to both non-catalytic and CeO₂-catalytic aging, utilizing a fixed bed test bench where soot samples are aerobically aged at 300–500 °C for 30–90 min before being cooled to ambient temperature under anaerobic conditions. The results indicate that sequential aging at 300–400 °C has minimal impact on soot oxidation activity, with a slight reduction in ignition temperature compared to nascent soot. Concurrently, there is a notable decrease in soot agglomeration, resulting in reduced macropore sizes ranging from 100 nm to 210 nm. The effects of non-catalytic and catalytic aging on soot oxidation activity diverge significantly at 500 °C. The crystallite arrangement in the soot particles takes precedence over oxidation activity, despite the formation of numerous pores post aging above 400 °C. Graphitization in non-catalytically aged soot increases, whereas it decreases following catalytic sequential aging. Post sequential aging at temperatures ranging from 300 to 500 °C, a noticeable shift occurs in soot particles, characterized by the depletion of C[dbnd]O functional groups and concurrent emergence of C[sbnd]O functional groups. Moreover, the presence of catalysts during this aging process markedly enhances the reduction of C[dbnd]O functional groups.