Quantum mechanical study of molecular weight growth process by combination of aromatic molecules

• Published in: Combustion and flame Vol. 126; no. 1; pp. 1506 - 1515
• Main Authors: Violi, A, Sarofim, A.F, Truong, T.N
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01-07-2001; Elsevier Science
• Subjects: Air pollution caused by fuel industries; Applied sciences; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Metering. Control; Quantum mechanics; Soot; Air pollution; Combustion; Polycyclic aromatic compound; Molecular mass; Modeling; Formation mechanism; Unburned product
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/S0010-2180(01)00268-1

Formation pathways for high-molecular-mass compound growth are presented, showing why reactions between aromatic moieties are needed to explain recent experimental findings. These reactions are then analyzed by using quantum mechanical density functional methods. A sequence of chemical reactions between aromatic compounds (e.g., phenyl) and compounds containing conjugated double bonds (e.g., acenaphthylene) was studied in detail. The sequence begins with the H-abstraction from acenaphthylene to produce the corresponding radical, which then furnishes higher aromatics through either a two-step radical-molecule reaction or a direct radical-radical addition to another aromatic radical. Iteration of this mechanism followed by rearrangement of the carbon framework ultimately leads to high-molecular-mass compounds. This sequence can be repeated for the formation of high-molecular-mass compounds. The distinguishing features of the proposed model lie in the chemical specificity of the routes considered. The aromatic radical attacks the double bond of five-membered-ring polycyclic aromatic hydrocarbons. This involves specific compounds that are exceptional soot precursors as they form resonantly stabilized radical intermediates, relieving part of the large strain in the five-membered rings by formation of linear aggregates.