Two diesel soots formed in a engine/exhaust line by using a fuel that contained 350 ppm (by weight) of sulfur with and without a cerium-based additive (diesel soots denoted Cec-DS and nc-DS, respectively) are studied (i) via temperature-programmed experiments in the temperature range of 300-1300 K and (ii) adsorption of O 2 , CO, and CO 2 at several adsorption temperatures (T a ). It is shown that, during the linear increase of temperature in a helium flow (a procedure denoted as the He-Temperature Programmed Experiment, He-TPE), the "as-prepared" Cec-DS soot leads to the detection of a high CO 2 peak, with a maximum at T m ) 905 K, which is not observed on nc-DS. After the treatment of Cec-DS at 1200 K in helium, the adsorption of O 2 at T a < 660 K leads, during the successive He-TPE, to observations similar to that on the freshly prepared soot, showing that the characteristic CO 2 peak is not linked to the formation of a particular surface-oxygenated complex (SOC), because of the experimental conditions of the engine/ exhaust line. This CO 2 peak is ascribed to the oxidation of SOCs by oxygen species coming from the cerium-containing particles. A kinetic modeling of the observations during He-TPE is presented as a first step of a microkinetic approach of the soot oxidation. Three main surface elementary steps are considered: (i) decomposition of the cerium-containing particles (identified as cerium sulfate, Ce 2 (SO 4 ) 3 , in the as-prepared soot), which provides oxygen species O s to the soot; (ii) the oxidation of the SOCs into CO 2 by the O s species; and (iii) the desorption of the SOCs as CO. The kinetic model gives theoretical CO 2 and CO productions that are consistent with the experimental observations for a set of activation energies that leads to the conclusion that it is the decomposition of the cerium-containing particles that controls the formation of the CO 2 peak during the He-TPE. This kinetic model is (i) compared to literature data on the calciumcatalyzed gasification of carbon materials and (ii) used to suggest an orientation for the oxidation of diesel soots at lower temperatures.
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