Nucleation of the CO2 Hydrate from Three-Phase Contact Lines

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• 作者：Dongsheng Bai ; Guangjin Chen ; Xianren Zhang ; Wenchuan Wang
• 刊名：Langmuir
• 出版年：2012
• 出版时间：May 22, 2012
• 年：2012
• 卷：28
• 期：20
• 页码：7730-7736
• 全文大小：467K
• 年卷期：v.28,no.20(May 22, 2012)
• ISSN：1520-5827

文摘

Using molecular dynamics simulations on the microsecond time scale, we investigate the nucleation and growth mechanisms of CO₂ hydrates in a water/CO₂/silica three-phase system. Our simulation results indicate that the CO₂ hydrate nucleates near the three-phase contact line rather than at the two-phase interfaces and then grows along the contact line to form an amorphous crystal. In the nucleation stage, the hydroxylated silica surface can be understand as a stabilizer to prolong the lifetime of adsorbed hydrate cages that interact with the silica surface by hydrogen bonding, and the adsorbed cages behave as the nucleation sites for the formation of an amorphous CO₂ hydrate. After nucleation, the nucleus grows along the three-phase contact line and prefers to develop toward the CO₂ phase as a result of the hydrophilic nature of the modified solid surface and the easy availability of CO₂ molecules. During the growth process, the population of sI cages in the formed amorphous crystal is found to increase much faster than that of sII cages, being in agreement with the fact that only the sI hydrate can be formed in nature for CO₂ molecules.