Theoretical studies on CH4 combustion in O2/H2O atmosphere

Abstract

The hydroxyl radical reactions are of extremely significant in combustion chemistry. Direct dynamics simulations are used to study the atomic-level mechanisms of OH(H2O)n + CH4 (n = 0,1,2) reactions starting from the [(H2O)nOH---H---CH3] central barrier, which is the important step in the combustion of CH4 in an O2/H2O environment. The simulation results show the propensity for the solvated products due to the thermodynamic preference and the stability of water cluster in products. Although there is a deep minimum (H2O)nH2O---CH3 complex in the product exit channel on potential energy surface, the majority of the trajectories avoided this well and instead directly dissociated to products, showing a non-IRC behavior. Significantly, with the addition of two water molecules, the reaction probability, and thus the reaction rate constant increases compared to the one hydrated reaction. This study provides an understanding of CH4 combustion in O2/H2O atmosphere.