Molecular Dynamics Simulations of the CO2-CH4 mixed hydrates

Gas hydrates are crystalline, nonstoichiometric inclusion compounds formed under high pressure and at moderately low temperatures. Their structure consists of a three dimensional framework of hydrogen-bonded water molecules which can incorporate a number of relatively small 'guest' molecules, such as CH4, CO2, H2S. The interest on CO2-CH4 mixed hydrates characterization has increased remarkably over the last few years due to the possibility of using them for waste CO2 recovery, capture and storage. Nevertheless, the modelling of CO2 and CH4 mixed hydrates has received less attention so far, and the theoretical estimation of their phase equilibria and thermophysical and transport properties still needs further contributions. In this case, rigid non polarizable molecular models have been used to describe H2O, CO2 and CH4, and the three phase CO2 Hydrate-Liquid H2O-Liquid CO2 equilibrium line has been determined using Molecular Dynamics by direct coexistence technique. Finally, CO2-CH4 separation was evaluated at different pressure and temperatures conditions and compared with experimental results