Oxidation behavior of soot generated from the combustion of methyl 2-butenoate in a co-flow diffusion flame

In this study, soots generated from the combustion of methyl 2-butenoate (M2B) and n-pentane (PEN) in laminar co-flow diffusion flames were analyzed via various analytical techniques to investigate the impact of fuel-bound oxygen in fatty acid esters on soot oxidation behavior. Thermogravimetric analysis of the soot samples collected from the diffusion flames showed that M2B soot exhibited only slightly higher oxidative reactivity than PEN soot, indicating that the fuel-bound oxygen in M2B may not enhance soot oxidative reactivity to any significant extent under well-defined diffusion flame tests. Furthermore, structural analysis was performed for both M2B soot and PEN soot by applying X-ray diffraction (XRD), Raman spectroscopy (Raman) and high resolution transmission electron microscopy (HRTEM). Overall, structural analysis via different analytical techniques consistently showed that there is no significant difference in structural arrangement between M2B soot and PEN soot, which is in agreement with the lack of a notable difference in reactivity between M2B soot and PEN soot observed from the temperature-programmed oxidation experiments. In addition, XPS analysis was performed on the unreacted M2B soot and PEN soot. It was observed that both soots have very similar surface O/C ratio (∼0.11), implying that it is unlikely that there are any appreciable amounts of fuel-bound oxygen from M2B present in the M2B-derived soot. Overall, the experimental results obtained from this study suggest that fuel-bound oxygen in the ester moiety of a fatty acid ester has no significant impact on enhancing soot oxidative reactivity.