Review of CO₂-CH₄ clathrate hydrate replacement reaction laboratory studies - Properties and kinetics

Replacement reactions in clathrate hydrates, for which CO₂ is used to replace methane gas trapped in inclusion compounds in the deep sea or permafrost areas, have gained growing attention as a possible method to sequester CO₂ and recover natural gas. This review examines research progress in the replacement reactions and analytical methods with special focus on laboratory studies. Methane hydrate dissociation enthalpies, carbon dioxide hydrate dissociation enthalpies, methane hydrate thermal conductivities and thermal diffusivities are tabulated. Methods used to study the CH₄-CO₂ replacement reaction include material balance (MB), MB with particle size analyzer, MB and Raman, NMR, and magnetic resonance imaging. New analytical methods such as thermo-Raman should be explored in the future to develop a localized picture of the microscopic replacement mechanism including water molecule movement. Combination of these data with molecular simulations will allow new macroscopic models to be developed for use with practical processes for unconventional natural gas.