Detailed kinetic analysis of the effect of benzene–acetylene composition on the configuration of carbon nanoparticles

• The nuclei mole fraction increases with additive concentration.
• The nucleation behavior affects the complexity of the aggregate shape.
• The excess addition of additives contributes to the simplification of the shapes.
• The calculated nucleation behavior describes the shapes obtained experimentally.

The reasons why benzene–acetylene composition has an effect on the configuration of carbon black, which is a type of carbon nanoparticle, were investigated using a fixed sectional approach by applying the detailed chemical kinetic reaction for our previous experimental work: the pyrolysis of benzene–acetylene in an inert atmosphere. By comparing the calculated behavior of polycyclic aromatic hydrocarbon formation, nucleation, and the particle size distribution with experimentally observed configurations for carbon black, the impact of the benzene–acetylene composition on the configuration of carbon black is discussed. The nuclei mole fraction increases with additive concentration, which strongly affects the complexity of the aggregate shape. Specifically, when the amount of benzene added to 3.0 vol% acetylene is increased to 5.0 vol% benzene, the particle number concentration of 30–80-nm-sized particles, which are considered as primary particles or spherical aggregates, increases. The increase in the number concentration of 30–80-nm-sized particles contributes to the simplification of the aggregate shapes. When acetylene is added to 1.0 vol% benzene, although the particle size distribution at 200 ms begins to shift to a bimodal shape with the addition of 0.5 vol% acetylene, a log-normal shape clearly appears at 200 ms with the addition of 5.0 vol% acetylene because the nuclei mole fraction reaches equilibrium at 200 ms. Thus, if the reaction is quenched before small particles (<10 nm in size) collide with larger particles with a log-normal shape, the complexity of the aggregate shape increases. The results for both of these cases indicate that the calculated nucleation behavior and the particle size distribution describe the aggregate shapes obtained experimentally.