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

• Replacement reaction studies on CO2–CH4 gas hydrates are reviewed.
• Dissociation enthalpies, thermal conductivities and thermal diffusivities are tabulated for CO2 hydrate and CH4 hydrate.
• Experimental methods for measuring the kinetics are reviewed.
• New analytical methods such as thermo-Raman should be explored to develop a localized picture.

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.