Structure Transition from Semi- to True Clathrate Hydrates Induced by CH4 Enclathration

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• 作者：Woongchul Shin ; Seongmin Park ; Jong-Won Lee ; Yongwon Seo ; Dong-Yeun Koh ; Jiwoong Seol ; Huen Lee
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：August 9, 2012
• 年：2012
• 卷：116
• 期：31
• 页码：16352-16357
• 全文大小：360K
• 年卷期：v.116,no.31(August 9, 2012)
• ISSN：1932-7455

文摘

Diethylamine and n-propylamine, known as semiclathrate hydrate formers, are found to show structural transition when a help gas, CH₄, was introduced. The diethylamine路8.67H₂O semiclathrate hydrates (orthorhombic Pbcn) were changed to sH type (hexagonal P6/mmm) true clathrate hydrates, while the n-propylamine路6.5H₂O semiclathrate hydrates (monoclinic P2₁/n) turned into sII clathrate hydrates (cubic Fd3m). Irregularly distorted voids in the semiclathrate hydrate phases were transformed to conventional ones after changing their structures to gas hydrate phases. The different shape of large voids in the semiclathrate hydrates changed to the typical shape of sH or sII large voids, and pentagonal dodecahedra were formed so as to capture CH₄ molecules. Transition pattern and molecular behavior from semiclathrate hydrate to true clathrate hydrates were analyzed with PXRD, NMR, and Raman methods. In addition, the liquid mixture鈥揅H₄ hydrates鈥揅H₄ vapor (L鈥揌鈥揤) thermodynamic equilibrium conditions were measured.