Raman spectroscopic studies on methane + tetrafluoromethane mixed-gas hydrate system |
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Authors: | Yuuki Kunita Takashi MakinoTakeshi Sugahara Kazunari Ohgaki |
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Institution: | Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka 560-8531, Japan |
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Abstract: | Raman spectra of intramolecular vibration mode for each guest species in the methane + tetrafluoromethane (CF4) mixed-gas hydrate crystal have been measured at 291.1 K. Both of pure guest species generate the structure-I hydrate in the present pressure ranges. Isothermal phase-equilibrium curve exhibits two discontinuous points around the equilibrium methane compositions (water-free) in the gas phase of 0.3 and 0.8. At the above points, the Raman spectra of both guest molecules have been drastically changed. One of the most important findings is that the crystal of methane + tetrafluoromethane mixed-gas hydrate shows the structural phase-transition (from the structure-I to the structure-II and back to the structure-I) caused by composition changes. |
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Keywords: | Gas hydrate Raman spectroscopy Structural transition Solid&ndash fluid equilibria Mixture |
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