2-3-4 構造II型クラスレートハイドレートへのガス吸収

抄録

The migration of the hydrogen molecules (H₂) in structure-II (sII) hydrates has relatively low-energy barrier, while the barrier in the case of other guest molecules is so large that the guest molecules barely migrate into the sII hydrate crystals. Tetrahydrofuran (THF) hydrate, which also attracts attention as an H₂ storage medium, is stable at a temperature below 277.4 K and atmospheric pressure. In the present study, we have regarded the enclathration of H₂ as the absorption into the hydrate crystal formed in advance. The dissociation temperature and enthalpy of THF+H₂ mixed hydrates have been measured under various pressure conditions. From the difference of enthalpies between simple THF hydrate and THF+H₂ mixed hydrate with consideration of temperature differences, the absorption enthalpy of H₂ into the sII THF hydrate was estimated as 13.0±3.4 kJ/mol (THF). The pressure swing method for the H₂ storage in (and release from) THF hydrates is superior (approximately 1/10 for the energy requirement) to the decomposition/reformation of THF+H₂ mixed hydrates.