On the mechanism of soot nucleation

• Published in: Physical chemistry chemical physics : PCCP Vol. 22; no. 9; pp. 5314 - 5331
• Main Authors: Frenklach, Michael, Mebel, Alexander M.
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 04.03.2020; Royal Society of Chemistry (RSC)
• Subjects: Carbon; Dimers; Nucleation; Soot
• ISSN: 1463-9076; 1463-9084; 1463-9084
• DOI: 10.1039/D0CP00116C

The mechanism of carbon particulate (soot) inception has been a subject of numerous studies and debates. The article begins with a critical review of prior proposals, proceeds to the analysis of factors enabling the development of a meaningful nucleation flux, and then introduces new ideas that lead to the fulfillment of these requirements. In the new proposal, a rotationally-activated dimer is formed in the collision of an aromatic molecule and an aromatic radical; the two react during the lifetime of the dimer to form a stable, doubly-bonded bridge between them, with the reaction rooted in a five-member ring present on the molecule edge. Several such reactions were examined theoretically and the most promising one generated a measurable nucleation flux. The consistency of the proposed model with known aspects of soot particle nanostructure is discussed. The foundation of the new model is fundamentally the H-Abstraction-Carbon-Addition (HACA) mechanism with the reaction affinity enhanced by rotational excitation.