(230c) Process Design for Carbon Black Size and Morphology

The structure (size and morphology) of carbon black (CB) largely determines its performance in tires, inks, batteries etc. (Kelesidis & Pratsinis, 2021). Here, the impact of CB process synthesis variables, i.e. temperature, T, precursor (i.e. acetylene) flow rate, Q, and volume fraction, φ, on CB structure (size and morphology) is elucidated by discrete element modeling (DEM; Kelesidis et al., 2017) and compared to experimental data in the literature. The CB structure is quantified by the mobility, d_m, and primary particle, d_p, diameters, effective density, ρ_eff, and fractal dimension, D_f. Decreasing Q or T enhances the CB yield, surface growth and agglomeration. This increases the mean d_m and d_p, consistent with experimental data from laminar flow ethylene pyrolysis reactors. The CB made at high Q or T is less compact than that made at low Q and T, having up to 50% smaller ρ_eff and 30% smaller D_f, in excellent agreement with experimental data also. Increasing the φ (e.g. by increasing the precursor flow rate), results in CB aggregates (covalently-bonded CB spherules) and increases the mean d_m and d_p, explaining commercial furnace black data. These CB aggregates are quite compact having up to 45% larger D_f and larger ρ_eff than those of ethylene black. So process design diagrams (Fig. 1) generated by the present DEM simulations can be used to guide design and optimization of CB for various applications (e.g. batteries, Kelesidis et al., 2022) from first principles.

References:

Kelesidis, G. A., and Pratsinis, S. E. 2021 A perspective on gas-phase synthesis of nanomaterials: Process design, impact and outlook. Chem. Eng. J. 421:129884, doi.org/10.1016/j.cej.2021.129884.

Kelesidis, G.A., Goudeli, E., and Pratsinis, S.E. 2017. Morphology and mobility diameter of carbonaceous aerosols during agglomeration and surface growth. Carbon 121:527–535, doi.org/10.1016/j.carbon. 2017.06.004.

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. Design diagram of CB structure by varying the volume fraction, T and residence time.