EPR investigation and reactivity of diesel soot activated (or not) with cerium compounds

Parameters influencing the diesel soot reactivity versus the combustion rea ction are studied on two diesel soot samples. The presence of cerium additi ves favours the reactivity of the doped soot and shifts the combustion reac tion towards low temperatures. However, these additives do not affect the C O-CO2 selectivity. Oxygenated and non-oxygenated radicals adsorbed on the c arbon particulate are evidenced whatever the composition of the soot sample . After a vacuum treatment, the adsorbed hydrocarbons content drastically d ecreases and the reactivity of both soot samples is attenuated. However, th e cerium-doped sample reveals higher radical contents and also higher react ivity than the non-activated soot. The presence of cerium additives stabili ses and strengthens radical-carbon interactions and these hydrocarbon radic al species play an important role in the activation of the diesel soot comb ustion.