Center for Hydrate Research, Chemical and Biological Engineering Department, Colorado School of Mines, Golden, Colorado 80401, USA.
J Chem Phys. 2016 Dec 7;145(21):211705. doi: 10.1063/1.4968590.
Molecular level knowledge of nucleation and growth of clathrate hydrates is of importance for advancing fundamental understanding on the nature of water and hydrophobic hydrate formers, and their interactions that result in the formation of ice-like solids at temperatures higher than the ice-point. The stochastic nature and the inability to probe the small length and time scales associated with the nucleation process make it very difficult to experimentally determine the molecular level changes that lead to the nucleation event. Conversely, for this reason, there have been increasing efforts to obtain this information using molecular simulations. Accurate knowledge of how and when hydrate structures nucleate will be tremendously beneficial for the development of sustainable hydrate management strategies in oil and gas flowlines, as well as for their application in energy storage and recovery, gas separation, carbon sequestration, seawater desalination, and refrigeration. This article reviews various aspects of hydrate nucleation. First, properties of supercooled water and ice nucleation are reviewed briefly due to their apparent similarity to hydrates. Hydrate nucleation is then reviewed starting from macroscopic observations as obtained from experiments in laboratories and operations in industries, followed by various hydrate nucleation hypotheses and hydrate nucleation driving force calculations based on the classical nucleation theory. Finally, molecular simulations on hydrate nucleation are discussed in detail followed by potential future research directions.
分子水平上对笼形水合物成核和生长的认识对于深入了解水的本质和疏水性水合物形成物及其相互作用，以及它们在高于冰点的温度下形成类似冰的固体的原因具有重要意义。成核过程的随机性和无法探测与成核过程相关的小长度和时间尺度使得实验确定导致成核事件的分子水平变化变得非常困难。相反，由于这个原因，人们越来越努力地使用分子模拟来获得这些信息。准确了解水合物结构何时以及如何成核将极大地有益于在油气流管中开发可持续的水合物管理策略，以及在能源储存和回收、气体分离、碳封存、海水淡化和制冷等领域的应用。本文综述了水合物成核的各个方面。首先，简要回顾了过冷水和冰成核的性质，因为它们与水合物明显相似。然后，从实验室实验和工业操作中获得的宏观观察开始综述水合物成核，接着是各种水合物成核假说和基于经典成核理论的水合物成核驱动力计算。最后，详细讨论了水合物成核的分子模拟，并探讨了潜在的未来研究方向。
