Atomic insights into the mechanism of ammonia inhibiting soot formation during pyrolysis of new bio-oxygenated fuels

Along with the implementation of carbon peaking and carbon neutrality, higher requirements have been put forward for decarbonization of fuels in the energy sector. This study selected new bio-oxygenated fuels (dimethyl ether, 2,5-dimethylfuran, anisole) and carbon-free ammonia co-pyrolysis to explore the reaction mechanism and the soot formation, in order to the large-scale use of carbon neutral and carbon-free fuels. This study adopted reactive force field molecular dynamics (ReaxFF MD) to investigate the characteristics of soot formation and pollutant generation during the pyrolysis of new bio-oxygenated fuels and ammonia from atomic perspective. The research showed that with the increase of ammonia blending ratio, the amount of products generated increased, and the higher the carbon content of bio-oxygenated fuels, the more products were generated. As the blending ratio of ammonia increased, nitrogen atoms occupied more active sites that originally belonged to hydrogen atoms, further inhibiting the growth of polycyclic aromatic hydrocarbons (PAHs) and initial soot. Meanwhile, an increase in the blending ratio of ammonia reduced carbon number and increased H/C ratio of the largest molecules, thereby reducing the degree of soot graphitization. During the graphitization process of soot, nitrogen atoms occupied the edges of the soot to form nitrogen containing side chains or ternary rings. With the increase of ammonia blending ratio, the soot particle size of formed by new bio-oxygenated fuels reduced.