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.甲烷作为天然气的主要成分，是一种至关重要的能源资源，通过氧化反应得到广泛利用。这类反应会根据氧化条件的不同，经由不同的中间反应路径生成多种自由基与分子。本研究采用反应分子动力学（reactive molecular dynamics）模拟方法，探究不同温度以及甲烷/氧气配比条件下甲烷氧化的初期反应机制。分析结果显示，在不同条件下，物种数量、初始反应时间以及主要反应/分子的分布特征均存在显著差异。值得注意的是，所有模拟中均同时观测到甲烷完全氧化（full oxidation of methane, FOM）与甲烷部分氧化（partial oxidation of methane, POM）现象：高温贫燃料条件下更易发生甲烷完全氧化，而低温富燃料环境中则以甲烷部分氧化为主。此外，本研究采用非线性流形学习（nonlinear manifold learning）技术，从反应状态空间中提取出二维流形，并识别出两个控制反应路径的集体变量。本研究系统阐明了不同条件下甲烷氧化的初期反应机制，可为化学科学与燃料工程领域提供有价值的参考见解。