A Study of the Methane Oxidation Mechanism and Reaction Pathways Using Reactive Molecular Simulation and Nonlinear Manifold Learning.

Methane, as the primary component of natural gas, is a vital energy resource extensively utilized through oxidation reactions. These reactions yield diverse radicals and molecules via varying intermediate reaction routes, contingent upon the oxidation conditions. In this study, we employ reactive molecular dynamics simulations to investigate the early-stage mechanism of methane oxidation across different temperatures and methane/oxygen conditions. Our analysis reveals distinct variations in species count, initial reaction times, and the spectrum of the main reactions/molecules under diverse conditions. Notably, both full oxidation of methane (FOM) and partial oxidation of methane (POM) are observed in all simulations, with FOM favored under high-temperature and fuel-lean conditions, while POM prevails in low-temperature and fuel-rich environments. Furthermore, we utilize nonlinear manifold learning techniques to extract a 2D manifold from the reaction state space, identifying two collective variables governing the reaction pathways. This research provides a systematic understanding of the initial stage mechanisms of methane oxidation under varying conditions, offering useful insights into chemical science and fuel engineering.