Dissociation behaviors of methane hydrate formed from NaCl solutions

The properties of gas hydrates with additives such as electrolytes and surfactants have been studied because their properties are greatly affected by additives. Although sodium chloride is a well known thermodynamic inhibitor of gas hydrate formation and a main component of seawater, little is known about its influence on gas hydrate dissociation. In this study, we formed methane hydrate containing sodium chloride up to 2.7 wt% and conducted a storage test at 253 K under ambient pressure. We used phase contrast X-ray computed tomography, cryo-SEM, and powder X-ray diffraction to investigate the stability of methane hydrate with up to a few percent of sodium chloride. It was revealed that the dissociation rate of methane hydrate containing sodium chloride was faster than that of pure methane hydrate. In addition, smaller particles of methane hydrate exhibited more influence of sodium chloride on dissociation. These experimental results obtained in this study may be caused by occurrences of NaCl solutions even at 253 K.