Kinetics of the oxidation of diesel soot

The kinetics of the uncatalysed oxidation of a flame soot and diesel soot were studied. Oxidation of the flame soot could be described by an nth-order model, with an order in carbon of 0.7. The order in molecular oxygen concentration was found to be 1 for the flame soot and slightly lower than 1 for the diesel soot. This order in oxygen concentration was also found to be a function of conversion. Water caused a significant increase in oxidation rate of the flame soot, which was accompanied by an increase in reaction order in carbon and a much higher CO2/CO ratio, whereas the activation energy did not change. The oxidation rate of the diesel soot was not significantly influenced by the addition of water. Experimental results were more reproducible for the oxidation of the flame soot than for the oxidation of diesel soot, and the flame soot appeared to be a good model for diesel soot in oxidation studies. Therefore it is recommended to use a model soot in (kinetic) studies of soot oxidation. (C) 1997 Elsevier Science Ltd.