Investigating the Thermodynamic Stabilities of Hydrogen and Methane Binary Gas Hydrates

When hydrogen (H-2) is mixed with small amounts of methane (CH4), the conditions required for clathrate hydrate formation can be significantly reduced when compared to that of simple H-2 hydrate. With growing demand for CH4 as a commercially viable source of energy, H-2 + CH4 binary hydrates may be more appealing than extensively studied H-2 + tetrahydrofuran (THF) hydrates from an energy density standpoint. Using Raman spectroscopic and powder X-ray diffraction measurements, we show that hydrate structure and storage capacities of H-2 + CH4 mixed hydrates are largely dependent on the composition of the initial gas mixture, total system pressure, and formation period. In some cases, H-2 + CH4 hydrate kinetically forms structure I first, even though the thermodynamically stable phase is structure II.