Publication Details (including relevant citation information):
Citation: In Combustion Generated Fine Carbonaceous Particles; Bockhorn, H., D'Anna, A., Sarofim, A. F., Wang, H., Eds.; Karlsruher Institute for Technology: Karlsruhe, Germany, 2009, p 259-276.
First Author: J. Houston Miller
Institution: Department of Chemistry, The George Washington University, Washington, District of Columbia 20052
In the combustion of fossil or bio-derived fuels under rich conditions, some fraction of the fuel carbon is converted into fine particulate carbon. This carbonization process usually leads to soot, a form of amorphous carbon characterized by small primary particles aggregated into fractal structures. It is our hypothesis that the most critical step in soot inception is the transition from 2-dimensional to 3-dimensional structures and that, for soot formation, this transition is the agglomeration of polynuclear aromatic hydrocarbons of modest molecular size. In the current paper, a review of available literature on experimental observation of PAH in flames as well as computational work that assesses the role of PAH condensation in soot inception is presented. Results of recent atom-pair calculations of intermolecular interactions of ****-molecular and hetero-molecular clusters for many peri-condensed PAH spanning monomer masses ranging from 78-1830 Da are presented. Binding energies of ****-molecular dimers rise rapidly with molecular size and asymptotically approach the experimentally established exfoliation energy for graphite of 5.0 Â± 0.5 kJ (mol)-1(carbon atom)-1. Binding energies of hetero-molecular dimers correlate well with the reduced mass of the pair. From calculations of ****-molecular stacks, binding energies were observed to increase with each added molecule and rise asymptotically, approaching a limit which scales linearly with monomer molecular mass.