Issue 11, 2016

Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study

Abstract

The role of resonantly stabilized radicals such as propargyl, cyclopentadienyl and benzyl in the formation of aromatic hydrocarbons such as benzene and naphthalene in the high temperature environments has been long known. In this work, the possibility of benzyl recombination to form three-ring aromatics, phenanthrene and anthracene, is explored. A reaction mechanism for it is developed, where reaction energetics are calculated using density functional theory (B3LYP functional with 6-311++G(d,p) basis set) and CBS-QB3, while temperature-dependent reaction kinetics are evaluated using transition state theory. The mechanism begins with barrierless formation of bibenzyl from two benzyl radicals with the release of 283.2 kJ mol−1 of reaction energy. The further reactions involve H-abstraction by a H atom, H-desorption, H-migration, and ring closure to gain aromaticity. Through mechanism and rate of production analyses, the important reactions leading to phenanthrene and anthracene formation are determined. Phenanthrene is found to be the major product at high temperatures. Premixed laminar flame simulations are carried out by including the proposed reactions for phenanthrene formation from benzyl radicals and compared to experimentally observed species profiles to understand their effects on species concentrations.

Graphical abstract: Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study

Supplementary files

Article information

Article type
Paper
Submitted
23 Oct 2015
Accepted
17 Feb 2016
First published
17 Feb 2016

Phys. Chem. Chem. Phys., 2016,18, 8120-8131

Author version available

Polycyclic aromatic hydrocarbon (PAH) formation from benzyl radicals: a reaction kinetics study

S. Sinha and A. Raj, Phys. Chem. Chem. Phys., 2016, 18, 8120 DOI: 10.1039/C5CP06465A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements