Methane storage in water frameworks: Self-preservation of methane hydrate pellets formed from NaCl solutions

The use of methane (CH4) hydrate as a CH4 or natural gas storage medium offers an efficient and green source of energy. In this study, we produced CH4 hydrate pellets containing NaCl at up to 2.7 wt%, and storage tests were performed to investigate the stability of CH4 hydrates with NaCI at 253 or 248 K under ambient pressure. Based on assessing mass variations and powder X-ray diffraction analyses, it was determined that the dissociation rate of the hydrate greatly depends on the storage temperature. Below the eutectic point of the water-NaCl system, the hydrate exhibited self-preservation, while specimens readily dissociated at 253 K. The experimental results obtained in this study elucidate the effects of the NaCl solution on the self-preservation of CH4 hydrates, and allow a kinetic model for this self-preservation phenomenon to be proposed. The results indicate that CH4 hydrate pellets formed from sea water are a viable CH4 storage and transportation media below the eutectic temperature.