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Particulates (soot) were sampled from the regenerative trap of an automotive diesel engine run under three speed/load conditions. The fuel was doped with a cerium-based catalyst to promote oxidation of the soot bed. The soots were subjected to combustion testing in a DTG under both temperature ramping and isothermal conditions, and under temperature ramping in a small fixed bed. The combustion gas was 10% oxygen in nitrogen, which was supplemented in the case of the fixed bed with other gases found in diesel exhausts. The temperatures of initiation of combustion Tin were measured in the DTG and in the fixed bed. The kinetic rates of oxidation were calculated from the DTG results taking into account the influence of oxygen transport. The effect of gas composition on ignition and burnout in the fixed bed was determined. Ignition did not occur in the DTG, but rather burning progressed steadily.

Post-treatment of diesel exhaust was studied on a laboratory scale, using a reactor to simulate the post-combustion of soot collected inside a monolithic particulate trap. A parametric study of the trap regeneration was carried out. A periodic hydrocarbon injection system was developed to assist the catalyzed trap regeneration. This technique led to the trap regeneration with a temperature of the entering gas of 150°C, which is very low. An optimization of the injection process allowed one to minimize the injected amount of hydrocarbons and to have good control of the trap temperature. Another advantage of the hydrocarbon injection is to provide good conditions for reducing NO in an oxidizing atmosphere (10% O2). The importance of the hydrocarbon content was pointed out by a parametric study of NO conversion under a wide range of hydrocarbon concentrations (1000 ppm to 2.5% in CH4 equivalents).