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International Conference on Gas Hydrates (ICGH) (6th : 2008)

IN SITU NMR MEASUREMENT OF CH4 + C2H6 HYDRATE REFORMATION Ohno, Hiroshi; Dec, Steven F.; Sloan, E. Dendy; Koh, Carolyn A.

Abstract

The reformation of methane-ethane hydrate was observed in situ using 13C MAS NMR spectroscopy. In all reformation experiments, structure I (stable state for the reformation conditions) reformed, and the hydrate cage occupancy ratios were found to be almost the same as those predicted by a statistical thermodynamics program CSMGem, suggesting that there is no preferential formation of large or small cages on the relatively long time scale of this NMR experiment. It was also found that the reformation rate of the sample with PVCap is several times faster compared with the pure system, indicating that the presence of PVCap promotes the hydrate reformation at a high subcooling though this chemical is well-known as a good hydrate inhibitor.

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