Surface reaction and lattice oxygen transfer in chemical looping oxidative coupling of methane: Molecular dynamics simulations

Chemical looping oxidative coupling of methane (CL-OCM) is a promising methodology for ethylene production from methane. This article utilizes molecular dynamic (MD) simulation to assess the performance of eight metal oxide catalytic oxygen carriers in CL-OCM reactions. It also investigates the impact of reaction time and particle size on the efficiency of the most effective Mn2O3 COC. The results indicate that extending the reaction time appropriately enhances C2H4 selectivity and a C/O ratio of 1 is found to be the optimal size for Mn2O3-based CL-OCM. Furthermore, surface reactions and lattice oxygen transfer are analyzed by MD simulation in Mn2O3-based CL-OCM, providing deeply insights into the reaction mechanism. The findings reveal that the gas-phase dimerization of CH3* to form C2H6 serves as the primary carbon coupling pathway in CL-OCM. In addition, there are two other carbon coupling pathways, both initiated by CH2*. Methanol formation through surface combination of CH3* and OH* represents an initial step in CL-OCM side reactions. Therefore, inhibiting methanol formation is crucial for enhancing C2 selectivity in CL-OCM. There exists a transformation of lattice oxygen and surface lattice oxygen plays a key role in methane activation. The quantity of lattice oxygen and difference in bulk lattice oxygen migration resistance are major factors influencing variations CH4 conversion and C2 selectivity. This study provides a new way to reaction mechanism exploration related to CL-OCM catalytic oxygen carriers. © 2024 Science Press. All rights reserved.