Modeling the properties of methane + ethane (Propane) binary hydrates, depending on the composition of gas phase state in equilibrium with hydrate
Modeling the properties of methane + ethane (Propane) binary hydrates, depending on the composition of gas phase state in equilibrium with hydrate
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根据与水合物平衡的气相状态的组成，对甲烷乙烷（丙烷）二元水合物的性质进行建模
DOI：
10.1134/s1810232810040041
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发表时间：
2010
影响因子：
2.4
通讯作者：
V. Nakoryakov
中科院分区：
文献类型：
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作者：
R. Zhdanov;T. P. Adamova;O. Subbotin;A. A. Pomeranskii;V. Belosludov;V. R. Dontsov;V. Nakoryakov
从理论上研究了立方结构Si和SiI的甲烷+乙烷水合物和甲烷+丙烷水合物的性质。结果表明，形成的二元水合物的组成强烈地依赖于气相中较重的客体的百分比。例如，气相中乙烷摩尔浓度为1%时，即使在低压下，乙烷也占据水合物SiI中60%的大空穴，当压力增加到100atm时，乙烷在低温下占据80%的大空穴。在高于冰融点的温度下，这一趋势保持不变，但水合物中的甲烷浓度下降到30%。在结构硅中，混合气体的组成对形成的水合物的组成的影响不明显。然而，在这种情况下，计算还表明，对于气相中摩尔乙烷浓度为1%的乙烷，根据压力的不同，乙烷分子占据了8%到10%的大型水合物空腔。考虑到客体分子不完全占据水合物中的空穴，模拟了甲烷+乙烷二元水合物立方结构Si和SiI之间的相变。当混合气体中乙烷浓度低于2%时，结构SiI的热力学稳定性比结构Si更稳定。然而，随着平衡冰-气-水合物中乙烷浓度增加到20%和水-气-水合物中乙烷浓度增加到40%，结构Si的热力学稳定性变得更高。因此，对于气体混合物中的低乙烷浓度，结构硅只能形成为亚稳定相。考虑了甲烷水合物Si和混合甲烷+丙烷水合物SIi的相平衡，这取决于气相组成。对于这一平衡也得到了类似的结果；这可以证明在低丙烷浓度下同时形成水合物Si和SiI。
The properties of methane + ethane and methane + propane hydrates of cubic structures sI and sII are theoretically investigated. It is shown that the composition of the formed binary hydrate strongly depends on the percentage of a heavier guest in gas phase. For instance, for a 1% molar ethane concentration in gas phase, even at a low pressure, ethane occupies 60% large cavities in the hydrate sII, and as the pressure grows to 100 atm, it occupies 80% large cavities at a low temperature. The tendency remains the same at a temperature of higher than the ice melting point, but the methane concentration in the hydrate decreases to 30%. In the structure sI, the influence of the component composition of the gas mixture on that of the formed hydrate is less evident. However, in this case, calculation showed also that for a 1% molar ethane concentration in gas phase, ethane molecules occupy from 8 to 10% large hydrate cavities, depending on the pressure. This work is concerned with modeling phase transitions between cubic structures sI and sII of methane + ethane binary hydrates in view of incomplete occupation of cavities in the hydrate by guest molecules. For an ethane concentration under 2% in the gas mixture, the structure sII becomes more thermodynamically stable than the structure sI. However, as the ethane concentration grows to 20% in the equilibrium ice-gas-hydrate and to 40% in the equilibrium water-gas-hydrate, the structure sI becomes more thermodynamically stable. Hence, for low ethane concentrations in a gas mixture, the structure sI can be formed only as a metastable phase. Phase equilibria of methane hydrate sI and mixed methane + propane hydrate sII are considered, depending on the gas phase composition. Similar results are obtained for this equilibrium; this can evidence simultaneous formation of hydrates sI and sII at low propane concentrations.
影响因子：
--
作者：
BERENDSEN, HJC;GRIGERA, JR;STRAATSMA, TP
通讯作者：
STRAATSMA, TP