Investigating the Thermodynamic Stabilities of Hydrogen and Methane Binary Gas Hydrates

When hydrogen (H₂) 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 H₂ hydrate. With growing demand for CH₄ as a commercially viable source of energy, H₂+ CH₄ binary hydrates may be more appealing than extensively studied H₂ + 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 H₂ + CH₄ mixed hydrates are largely dependent on the composition of the initial gas mixture, total system pressure, and formation period. In some cases, H₂ + CH₄ hydrate kinetically forms structure I first, even though the thermodynamically stable phase is structure II