Initiation mechanisms and kinetics of the combustion of cyclopentane and cyclopentene from ReaxFF molecular dynamics

Abstract

The detailed understanding of the combustion process differences between saturated and unsaturated hydrocarbons is of paramount importance for the rational design of more efficient fuel blends. In this work, extensive ReaxFF molecular dynamics simulations have been employed to characterize and differentiate the initial combustion profiles of cyclopentane and cyclopentene. The main goal is the comprehensive identification of the main intermediates and reaction channels. The results show that, while homolytic carbon-carbon bond cleavage constitute the main initiation pathway, the rate of such type of elementary reaction depends highly on the internal energy content of the system. Thus, towards lower temperatures, hydrogen abstraction by dioxygen and other radicals become more prominent. The presence of a single unsaturation leads to a greater number of distinct points of attack on cyclopentene, but such feature does not implicate in a faster decay of the olefin during combustion. A pool of radicals, especially HO·and HO2·, was found to be present over the entirety of both processes, contributing to chain propagation and branching. Therefore, a cogent picture of the similarities and differences between the combustion process of an unsaturated and a saturated hydrocarbon is presented and discussed.