Superheating Clathrate Hydrates for Anomalous Preservation

Tetrahydrofuran (THF)-hydrate crystal conglomerates were kept intact above their melting point by immersing them in cyclopentane (CP), as observed visually, and by diffraction-enhanced X-ray imaging. THF and CP form isostructural sII hydrates with melting points of 277.5 and 280.8 K, respectively. Placing the THF-hydrate crystal in CP converted the outer layer of THF-hydrate to a thin layer of CP-hydrate, which then prevented the THF-hydrate from melting at its usual melting point. The coated THF-hydrate melted at a temperature about 2 K higher than the usual melting temperature for THF-hydrate. Therefore, we can THF-hydrate postulate that superheating less stable clathrate hydrates by equilibrium coating them with hydrates of greater stability may be an approach suitable for the anomalous preservation of less stable clathrate hydrates, for example, fuel gases, for a considerable length of time for transport or storage.