Experimental Study on the Effect of Ammonia on the Phase Behavior of Tetrahydrofuran Clathrates
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- 作者：Tuan Hoang Vu ; Elodie Gloesener ; Mathieu Choukroun ; Ana茂s Ibourichene ; Robert Hodyss
- 刊名：Journal of Physical Chemistry B
- 出版年：2014
- 出版时间：November 26, 2014
- 年：2014
- 卷：118
- 期：47
- 页码：13371-13377
- 全文大小：380K
- ISSN：1520-5207
文摘
Clathrate hydrates, ice-like crystalline compounds in which small guest molecules are enclosed inside cages formed by tetrahedrally hydrogen-bonded water molecules, are naturally abundant on Earth and are generally expected to exist on icy celestial bodies. A prototypical example is Saturn鈥檚 moon Titan, where dissociation of methane clathrates, a major crustal component, could contribute significantly to the replenishment of atmospheric methane. Ammonia is an important clathrate inhibiting agent that may be present (potentially at high concentrations) in Titan鈥檚 interior. In this study, low-temperature Raman experiments are conducted to examine the dissociation point of tetrahydrofuran clathrates, an ambient-pressure analogue of methane clathrates, over a wide range of ammonia concentrations from 0 to 25 wt %. A phase diagram for the H2O鈥揟HF鈥揘H3 system is generated, showing two main results: (i) ammonia lowers the dissociation point of clathrate hydrates to a similar extent compared to the melting of water ice and (ii) THF clathrate exhibits a 鈥渓iquidus-like鈥?behavior in the presence of ammonia, with a eutectic temperature of about 203.6 K. As temperatures higher than this estimated eutectic are anticipated within Titan鈥檚 icy crust, these results imply that partial dissociation of clathrates can occur readily and may contribute to outgassing from the interior.