Formation and Growth of Tetrahydrofuran Hydrate at the Ice/Hexane Interface

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The formation and growth of the tetrahydrofuran (THF) clathrate hydrate (CH) are studied at the interface between ice and hexane containing THF by a confocal Raman microscopy. Raman spectroscopic measurements across the ice/hexane interface have clearly detected the formation of the THF CH under an appropriate condition. The ring breathing mode of THF found around 915 cm–1 is the most efficient probe for a change in the molecular environment of THF; we can distinguish the THF CH, THF in hexane, and THF in water on the basis of the band shift of this mode. The temperature is a critical parameter governing the formation of the THF CH. The THF CH is formed at −2.0 °C, and its layer thickness increases with time; a layer thickness of ca. 30 μm is reached 160 min after the contact of ice with THF/hexane. This has been supported by the analysis of the Raman spectra in the higher wavenumber range as well. In contrast, an induction time longer than 100 min is necessary for the THF CH formation at −2.5 and −5.0 °C...