Clathrate hydrates for energy storage and transportation

Abstract

Formation pressure of mixed hydrogen + methane, hydrogen + ethane and hydrogen + propane hydrates can be controlled by the gas phase composition allowing these hydrates to be considered as promising hydrogen storage containers. At low methane (ethane) concentration in the gas phase, the hydrate of the cubic structure II is formed, and at the methane concentration exceeding 6 mol.% (1 mol.% for ethane) the cubic structure I is formed. The mass percentage of hydrogen in the hydrate phase depends on the second gas concentration in the gas phase as well as on the thermodynamic conditions of hydrate formation. At a low concentration of methane (ethane) in the gas phase, the mass percentage of hydrogen in the hydrate can reach 2.5 wt% at 250 K. The curves of the monovariant equilibrium "gas-hydrate-ice Ih" for double hydrates are calculated and found to be in agreement with the available experimental data. Thermodynamic properties of mentioned mixed hydrates allow to considering mixed hydrates as appropriate materials for hydrogen storage.