Modelling of Soot Oxidation by NO2in a Diesel Particulate Filter

Two approaches were adopted to study soot oxidation by NO2; firstly microreactor tests were performed on soot produced by a soot generator over a range of NO2concentrations and temperatures. This enabled measurement to be made under well-controlled conditions. Secondly, soot oxidation measurements were made on an engine bench to obtain data under more realistic, if less controlled, conditions. In the microreactor work NO2consumption by soot oxidation and the selectivity of the soot oxidation to CO and CO2were measured. The latter was found to vary only slightly with temperature and to be independent of NO2concentration. By modelling this data using a 1-dimensional model, rate equations for the soot-NO2reaction were determined. These were then tested against the engine data. The soot used in this study was characterised by thermogravimetric analysis, N2physisorption and transmission electron microscopy.