Molecular level investigations and stability analysis of mixed methane-tetrahydrofuran hydrates: Implications to energy storage

The widespread use of methane (CH4) as a bridging fuel to transition into a carbon-constrained world necessitates the need to develop safe, reliable and efficient technology for large-scale CH4 storage. Solidified natural gas (SNG) technology via clathrate hydrates can store large volumes of CH4 at mild storage conditions (atmospheric pressure and moderate temperatures) compared to compressed natural gas (CNG) or adsorbed natural gas (ANG). Slow hydrate growth kinetics and stability of hydrates at moderate temperatures are two challenges that need to be mitigated in order to commercialize SNG technology. In this work, we characterize the mixed (methane-tetrahydrofuran) hydrate formation by analyzing solid hydrate phase highlighting temporal changes of the cage occupancy using in-situ Raman spectroscopy complemented by measuring the CH4 uptake along with visual observations. Powder X-ray diffraction (PXRD) characterization of synthesized hydrates confirms the presence of only sII structure. We also demonstrate the stability of the sII mixed (CH4-THF) hydrates at near atmospheric pressure for a time period of two months.