Thermokinetic modeling of the combustion of carbonaceous particulate matter

The scope of this study was to determine the kinetics (conversion model, preexponential factor and activation energy) of the combustion of two diesel sootlike materials (Printex XE-2B and Flammruss 101) in the presence of an excess of oxygen by dynamic thermogravimetry. A composite kinetic analysis procedure was applied to evaluate the full kinetic triplet from nonisothermal kinetic data. First, the activation energy values were obtained from the Kissinger–Akahira–Sunose isoconversional method. The values were 129 kJ mol−1 (Printex XE-2B) and 144 kJ mol−1 (Flammruss 101). The higher reactivity of Printex XE-2B material was attributed to its markedly greater surface area. The activation energy was found to depend slightly on conversion, suggesting that the combustion was a single-step process for both materials. Second, a comparison of the theoretical masterplots deduced by assuming various conversion models with the experimental masterplots obtained from the kinetic data allowed the selection of the appropriate conversion model of the process. Both materials were found to follow a mechanism based on surface nucleation with subsequent movement of the resulting surface, which was consistent with the penetration of oxygen through the porous structure of the solid samples. Also, the preexponential factors and exact kinetic exponents were evaluated on the basis of predetermined activation energies and conversion models. The adequate consistency of the kinetic triplet was assessed by comparing both experimental and calculated thermoanalytical curves at constant heating rate.