Augmented stability of hydrogen clathrate hydrates by weakly polar molecules.
Augmented stability of hydrogen clathrate hydrates by weakly polar molecules.
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DOI：
10.1063/1.3271341
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发表时间：
2009-12
期刊：
影响因子：
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通讯作者：
Takato Nakayama;K. Koga;Hideki Tanaka
中科院分区：
文献类型：
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作者：
Takato Nakayama;K. Koga;Hideki Tanaka
在广泛的压力范围内，仅基于所涉及的分子间相互作用，研究了笼合氢水合物的热力学稳定性。我们发现，被称为启动子的第二客体物质（这里是丙酮）确实增强了稳定性，其结果是单独包裹氢的水合物的解离压力显著降低。这一评价是通过范德华-普氏理论的扩展，结合半大规范蒙特卡罗（GCMC）模拟得到的，其中氢分子的数量允许变化，而宿主水和启动子丙酮分子的数量是固定的。然后，GCMC模拟提供了从单笼到四笼的各种类型的氢的笼占率，从中得到笼合物水合物中水的化学势作为丙酮笼占率和压力的函数。这些占有率被用来计算笼形物水合物中水的化学势。通过比较笼形水合物中水的化学势与六方冰中水的化学势来估计其稳定性。我们展示了解离压力随着丙酮占用较大的笼的增加而降低的程度。
Thermodynamic stability of hydrogen clathrate hydrates has been examined in a wide range of pressure based solely on the intermolecular interactions involved. We show that the stability is indeed augmented by a second guest species (here acetone) called a promoter, a consequence of which is notable reduction in the dissociation pressure of the hydrates encaging hydrogen alone. This evaluation is made by extension of the van der Waals-Platteeuw theory combined with semi-grand-canonical Monte Carlo (GCMC) simulations where the number of hydrogen molecules is allowed to vary while those of host water and promoter acetone molecules are fixed. The GCMC simulations then provide various types of cage occupancies of hydrogen from single to quadruple, from which the chemical potential of water in the clathrate hydrate is obtained as a function of the cage occupancy by acetone and the pressure. These occupancies are used to calculate the chemical potential of water in the clathrate hydrate. The stability is estimated by comparison of the chemical potential of water in the clathrate hydrate with that in hexagonal ice. We show the extent to which the dissociation pressure is reduced with increasing the occupancy of the larger cages by acetone.