CP-CH4二元水合物的结构、形成机制和表面形貌研究,Energy & Fuels

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CP-CH4二元水合物的结构、形成机制和表面形貌研究
Energy & Fuels ( IF 5.2 ) Pub Date : 2023-01-24 , DOI: 10.1021/acs.energyfuels.2c03849
Qiu-Nan Lv _{1,

2,

3} , Kai Zhang _{1,

2,

3} , Xiao-Sen Li _{1,

2,

3} , Gang Li _{1,

2,

3}

Affiliation

环戊烷(CP)常被用作水合物形成剂，在水合物法脱盐中表现出优异的促进作用。为了阐明水合物形成过程中客体分子的分布和微观机制，对 CP-甲烷二元水合物进行了原位拉曼光谱分析。主体和客体分子的分子内振动模式的拉曼光谱表明，sII CP-甲烷水合物是在 CP 和 CH ₄分别包裹在大笼和小笼中形成的。但小笼并没有完全填满。由于CP具有五元环结构，氢键水分子排列在CP周围形成亚稳态结构，从而加快了水合物的成核速率。O-H 伸缩振动峰 ( R _OH-H =I ₃₁₇₀ / I ₃₄₀₀ ) 在水合物相中是氢键有序的指示。在 3.5 MPa 时，小笼中的 CH ₄占有率为 0.9978，小笼中的 CP 占有率为 0.1751。根据网箱占有率和基于范德瓦尔斯-普拉图的热力学模型，计算出的水合数为 12.6。应用冷冻扫描电子显微镜观察水合物的表面形态。能量色散光谱用于通过识别元素 C 来区分水合物和冰。

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Investigation on the Structure, Formation Mechanism, and Surface Morphology of CP–CH4 Binary Hydrate

Cyclopentane (CP) is often used as a hydrate former, which shows an excellent promotion effect in hydrate-based desalination. To elucidate the guest molecule distribution and microcosmic mechanism during hydrate formation, the in situ Raman spectroscopy of CP–methane binary hydrates is performed. The Raman spectra for the intramolecular vibration mode of host and guest molecules reveal that sII CP–methane hydrate formed with CP and CH₄ encaged in large and small cages, respectively. But the small cages were not completely filling in. Because of the structure of CP with a five-membered ring, hydrogen-bonded water molecules arranged around CP forming a metastable structure, which accelerates the nucleation rate of hydrate. The peak O–H stretching vibration (R_OH–H = I₃₁₇₀/I₃₄₀₀) in hydrate phase is an indication of hydrogen-bond ordering. At 3.5 MPa, the CH₄ occupancy in the small cages was 0.9978 and the CP occupancy in the small cages was 0.1751. According to cage occupancies and the thermodynamic model based on van der Waals–Platteeuw, the calculated hydration number was 12.6. Cryo-scanning electron microscopy was applied to observe the surface morphology of hydrate. Energy-dispersive spectroscopy was used to distinguish hydrate from ice by identifying element C.

更新日期：2023-01-24

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