Reactive localized sr-radicals on rim-based pentagonal rings: Properties and concentration in flames

The impact of localized sr-radicals on soot formation is explored by considering their electronic structure and computing their relative concentrations in flame conditions. Electronic structure calculations reveal that the presence of localized sr-radicals on rim-based pentagonal rings is due to aromaticity. We further calculated a complete mechanism for the formation and elimination of the site from hydrogen additions and abstractions. A batch reactor with flame concentrations of H center dot and H 2 was used to determine the time-dependent concentration of localized sr-radicals. Low temperatures ( < 1000 K) favored the fully saturated rim-based pentagonal ring. Soot nucleation temperatures (1000-1500 K) give way to unsaturated rim-based pentagons being favored. Localized sr-radicals on rim-based pentagonal rings are found to be in higher concentration than the aryl-type a-radical on the rim-based pentagon (mole fractions of 10 & minus;6 & minus; 10 & minus;7 ) in below < 1500 K, consistent with recent experimental observations. Higher temperatures favor the a-radical and the concentration of the localized sr-radical on rim-based pentagons becomes negligible. A kinetic Monte Carlo treatment of multiple sites indicates that multiple localized sr-radicals are possible on a single molecule. These results reveal the importance of localized sr-radicals on rim-based pentagonal rings for PAH chemistry leading to formation of soot nanoparticles in flames involving aromatic rim-linked hydrocarbons (ARLH). (c) 2020 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The impact of localized sr-radicals on soot formation was explored based on their electronic structure and relative concentrations in flame conditions. It was found that different temperatures favor different structures on rim-based pentagonal rings. Localized sr-radicals were more concentrated at lower temperatures but became negligible at higher temperatures.