Nucleation rate of gas hydrates

冰浮在液态水上是因为它的密度比水小。冰的中空结构可以在低温高压条件下将小气体分子作为客人容纳在其空腔中。这些晶体固体中的客体分子被水分子捕获，称为气体水合物。天然气水合物在天然气储存、二氧化碳封存、天然气分离和海水淡化等方面具有潜在的应用前景。天然气水合物也是地球上最大的非常规天然气资源。 天然气水合物的形成是从成核开始的一级相变。成核是指在亚稳母相中形成结晶稳定相，该过程需要克服活化能势垒。这种激活过程本质上是随机的，最好用概率分布来描述。人们希望在希望形成气体水合物时促进成核，而在不希望形成气体水合物时抑制成核。了解成核对化学和石油工业中的许多人都很感兴趣，因为成核虽然在许多化学过程中有好处，但在流动保证方面是一个问题。特别是，有兴趣了解成核过程，以更有效地，成本效益和安全地防止管道中的气体水合物的成核。 研究气体水合物成核的主要困难是研究人员无法比较不同规模和复杂性的各种系统中气体水合物的成核速率，这反过来又限制了研究人员研究成核过程本身的能力。成核速率相当于每单位系统尺寸和每单位时间的成核概率密度，并允许对各种系统之间的成核过程进行科学上有意义的比较。基于我们一直在开发的尖端技术，我们建议建立一种可靠的技术，可以可靠地确定一系列天然气水合物的成核率。我们还建议创建一个广泛条件下气体水合物成核率的数据库，从纯水中单组分气体水合物的最简单情况开始，到涉及混合气体水合物、固体壁和一系列化学品的逐渐复杂的系统。成核速率的系统测定将允许识别对天然气水合物成核具有最大影响的物理化学因素。

Ice floats on liquid water because it is less dense than water. The hollow structure of ice can accommodate small gas molecules as guests in its cavities under low temperature - high pressure conditions. These crystalline solids in which guest molecules are trapped by water molecules are called gas hydrates. Gas hydrates have potential applications in gas storage, carbon dioxide sequestration, gas separation and desalination. Gas hydrates also form the largest unconventional natural gas resources on earth. Formation of gas hydrates is a first-order phase transition that starts with nucleation. Nucleation refers to the formation of a thermodynamically stable phase in the metastable parent phase and the process requires surmounting of an activation energy barrier. This activation process is intrinsically stochastic and is best described in terms of probability distributions. One would wish to facilitate nucleation when the formation of gas hydrate is desirable and suppress nucleation when it is undesirable. Understanding of nucleation is of interest to many in chemical and petroleum industry, as nucleation, while a benefit in many chemical processes, is a concern in flow assurance. In particular, there is interest in understanding the nucleation process to more effectively, cost-efficiently and safely prevent nucleation of gas hydrates in pipelines. A primary difficulty in the investigation of gas hydrate nucleation has been the inability of researchers to compare nucleation rates of gas hydrates across various systems of different scales and complexity, which in turn has been limiting the ability of researchers to study the nucleation process itself. Nucleation rate is equivalent to nucleation probability density per unit system size and per unit time, and allows scientifically meaningful comparisons of nucleation processes between various systems. Based on the cutting-edge technology we have been developing, we propose to establish a robust technology that can reliably determine the nucleation rates of a range of gas hydrates. We also propose to create a database of nucleation rates of gas hydrates under a broad range of conditions that start from the simplest case of single-component gas hydrates in pure water to progressively complex systems that involve mixed gas hydrates, solid walls and a range of chemicals. Systematic determination of nucleation rates will allow identification of physicochemical factors that have the greatest impact on nucleation of gas hydrates.