ReaxFF Study of Ethanol Oxidation in O₂/N₂ and O₂/CO₂ Environments at High Temperatures

The goal of this study was to investigate the reaction mechanisms linked with the oxy-fuel combustion of ethanol (C₂H₆O). The oxidation of ethanol in O₂/N₂ and O₂/CO₂ environments was examined using reactive molecular dynamics in the temperature range from 2200 to 3000 K at constant density media and O₂/fuel ratio equals to 0.5. The main reactions were examined to supply a description of the ethanol oxidation behavior, the main product distribution, and the corresponding time evolution behavior in the atomic scale. It has been noted that the oxidation of C₂H₆O was initiated mainly from the same routes in both environments generating the same main species. However, the key reaction pathways were different depending on the media. We noticed an increase of CO formation when N₂ was replaced by CO₂ molecules, increasing the net flux of the following reactions: by CO₂ + H → CO + OH and CO₂ + CHO → O═COH + CO. This work also studied the effect of increasing O₂ concentration (O₂/fuel ratio equals to 0.5, 1.0, and 2.0) in O₂/CO₂ combustion. During the simulations, high oxygenated and unstable species were detected such as carbonates and carboxyl radicals. The change of the O₂/fuel ratio from 0.5 to 2.0 lead to an increase of CO₂ formation mainly from O₂ + O═COH → CO₂ + HO₂ and O₂ + CO → CO₂ + O reactions. In addition, the increase of O₂ concentration attenuated the effect of CO₂ and could increase the occurrence of reactions that lead to flame cessation.