Formation of Polycyclic Aromatic Hydrocarbon Structures and their Role in Soot Formation

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

This is a detailed computational analysis of the elementary reaction steps leading to the growth of planar and curved polycyclic aromatic hydrocarbons (PAHs) and subsequently to carbon particles. Thermodynamic properties are computed by means of density functional theory (DFT) using BLYP and B3LYP functionals. Vibrational analysis is performed on the optimized geometries followed by determination of entropies and heat capacities. Uncertainties are assessed by comparing the results with higher-level computations using the complete basis set (CBS) method. Kinetic parameters at the high-pressure limit are determined by transition-state theory, while pressure dependence of chemically activated reactions is analyzed with quantum Rice-Ramsperger-Kassel (QRRK) theory. Competitive reactions of PAH radicals with acetylene, hydrogen, oxygen, and hydroxyl are assessed. The data predictions are incorporated into an existing kinetic model and tested for benzene, acetylene, and ethylene flames using data previously generated on flame structures in these systems including mole-fraction profiles of planar and curved PAHs and fullerenes.