Spectroscopic identifications and phase equilibria of THF + 3-OH THF + CH4 clathrate hydrates

Abstract

In this study, the inclusion phenomena of tetrahydrofuran + 3-hydroxytetrahydrofuran + CH4 clathrate hydrates were explored via thermodynamic and spectroscopic approaches. The phase equilibria of the double hydrates - THF + CH4 and 3-OH THF + CH4 clathrate hydrates - were determined by pressure-temperature trace during hydrate formation and dissociation, and the result revealed that the equilibrium pressures were shifted to lower pressure region compared to pure CH4 hydrate. The powder X-ray diffraction patterns revealed that the double hydrates of THF + 3-OH THF formed structure II type clathrate hydrates with CH4. The dispersive Raman spectra of the double clathrate hydrates also exhibited that CH4 can be trapped in both 51264 and 512 cages whereas THF and 3-OH THF were encaged in 51264 cage.