Preservation of methane gas in the form of hydrates: Use of mixed hydrates

• Methane gas storage in self-preservation window.
• Mixed hydrates with large amount of CH4 has no self-preservation.
• Mixture of sI & sII hydrates formed in lower mole fractions of 51264 guests.
• Delayed release of CH4 gas in hydrate mixtures is due to melting of sII component.

The release of methane gas was compared in pure CH4 (sI) and mixed (sII) hydrates (with C4H8O – tetrahydrofuran and C3H8 – propane) having methane as dominant constituent. We report absence of the self preservation effect in mixed hydrates, having stiochiometric composition (sII) of larger guest molecules, and they populate the 51264 cages. Their dissociation behaviour is in accordance with the respective phase boundary curve. While a partial methane gas release was observed at 270 K, particularly, in dilute systems. Further, excess gas release was at T > 270 K and complete methane release is governed by the thermodynamic stability of mixed hydrates.

Figure optionsDownload high-quality image (164 K)Download as PowerPoint slide