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... [ view full abstract ]

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.