Oxidation kinetic analysis of diesel particulate matter using singleand multistage methods

Plenty of diesel particulate matter (PM) is emitted into the atmosphere in the forms of raw PM and partially oxidized PM. Comprehensive investigations of PM oxidation behavior and kinetics contribute to lower PM emission and optimize the PM capture device design. In this paper, diesel PM oxidation behavior was investigated using different temperature control programs, and then the oxidation kinetics was analyzed using the Arrhenius equation. The nanostructure, Fourier transform infrared spectroscopy, and Raman characteristics were adopted to further clarify PM oxidation kinetics. The results indicated that PM oxidation showed multistage reactions, and the reaction rate decreased rapidly in the isothermal process, with the activation energy increasing. Heat transfer limitation significantly decreased the activation energy and also affected the subsequent reactions. In the narrow temperature range (523-537°C), the activation energies of partially oxidized and aging PM were smaller than the values of the initial oxidation stage. The oxidation transformation phase had a huge potential of evolving into heat transfer limitation. The activation energies of partially oxidized and aging PM were smaller than the value of raw PM at the end of oxidation, which was caused by the catalytic reaction of metal ash. The diesel PM nanostructure changed from the onion-like to the core-shell-like structures after partial oxidation.