Catalytic Oxidation of a Diesel Soot Formed in the Presence of a Cerium Additive. III. Microkinetic-Assisted Method for the Improvement of the Ignition Temperature

In previous studies, it has been shown, using a microkinetic approach of temperature-programmed experiments in a helium flow (denoted as He-TPE), that the surface-oxygenated complexes (SOCs) of a diesel soot, desorbing as CO, are preferentially oxidized in CO2 in the presence of cerium-containing particles that provide reactive oxygen species (Oa) to the soot. The limiting step of the CO2 production during He-TPE is the formation of the Oa species and not the oxidation of the SOCs. The objectives of the present study are (i) to verify this conclusion experimentally, (ii) to use this conclusion to improve the soot oxidation process (the decrease of the ignition temperature), and (iii) to reveal the process imposing the ignition temperature of a diesel soot (denoted as Cec-DS) formed with an engine test bench, using a sulfur-containing fuel with a cerium additive. It is shown that the impregnation of a model diesel soot (Printex U, from Degussa) with two cerium salts of different stabilitycerium nitrate (Ce...