(113c) Pore Structure Dynamics of Carbonaceous Particles By Surface and Internal Oxidation

The dynamics and impact of internal and surface oxidation on carbon particle (CP) pore structure are elucidated by lattice Monte Carlo (LMC) simulations and compared to experimental data from the literature (Kelesidis et al., 2022). The fractal-like pore structure or network of unoxidized or as-prepared CPs is determined by diffusion limited aggregation and validated with those measured for carbon blacks and soot. At high temperatures (i.e. 800 ^oC and above), surface oxidation reduces the CP diameter, d_p, without affecting its internal structure. So, the evolution of CP mass, d_p and specific surface area, SSA, closely follows the classic shrinking particle model (Kelesidis & Pratsinis, 2019). At low temperatures (550 ^oC), internal oxidation dominates, compacting the CP fractal-like pore network. This triples the CP SSA up at 75 % conversion. In the presence of a non-reactive graphitic shell though, internal oxidation stops after the reactive and largely amorphous CP core is consumed (Fig. 1) leveling off its SSA at large conversions (> 50 %). Accounting for the realistic core-shell pore structure of CPs during internal and surface oxidation nicely explains several measurements of soot and carbon black SSA, for the first time to the best of our knowledge. So the LMC-derived oxidation dynamics of CPs presented here can be used to assist the design of highly porous carbon black grades from first principles, as well as the mitigation of soot emissions by enhancing their oxidation in the exhaust of combustion engines.

References:

Kelesidis, G. A., and Pratsinis, S. E. 2019. Estimating the internal and surface oxidation of soot agglomerates. Combust. Flame 209: 493-499, doi.org/10.1016/j.combustflame.2019.08.001.

Kelesidis, G. A., Rossi, N., and Pratsinis, S. E. 2022. Porosity and crystallinity dynamics of carbon black during internal and surface oxidation. Carbon 197:334-340, doi.org/10.1016/j.carbon.2022.06.020.

Figure 1. Cross-sections of CPs derived by LMC for internal and surface oxidation and mass conversions of 0, 25, 50 and 75 %, along with microscopy images of Printex 95 (Kelesidis et al., 2022).