Molecular dynamics study of CH4-CO2 mixed hydrate dissociation

Molecular dynamics simulations are performed to study the dissociation process of CH4-CO2 mixed hydrate with different gas composition at P = 5 MPa and T = 275 K, 280 K, and 285 K. Our simulation results show that the concentration of CO2 in 51262 cages greatly influences the structural stability of CH4-CO2 mixed hydrate, and the CH4-CO2 mixed hydrate with theta co2 = 75% is more stable compared to theta co2 = 50%, 25% L, 25% S counterparts. The dissociation rate of CH4-CO2 mixed hydrate strongly depends on the temperature used, with higher dissociation rates at higher temperatures. Moreover, we find that the dissociation of CH4-CO2 mixed hydrate is not strictly layer by layer. The released CH4 and CO2 molecules can reoccupy the incomplete cages near the interface, emphasizing the stochastic nature of the dissociation processes. Structural defects consisted of CH4 and CO2 molecules co-occupied in a cage are also observed. (C) 2015 Curtin University of Technology and John Wiley & Sons, Ltd.