Destruction of Carbonaceous Material and Nitrogen Oxides in Conditions of Diesel Exhaust

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).