Growth Kinetics and Gas Diffusion in Formation of Gas Hydrates from Ice

Abstract

Clathrate hydrates are ubiquitous in deep-sea sediments and the permafrost on earth, as well as abundant in interstellar environments. Despite many potential applications of gas hydrates for gas storage/transportation, carbon sequestration, and water treatment, the fundamental mechanism for gas hydrate nucleation and growth are still poorly understood due to the difficulty in spatial and temporal measurements that can probe specific structural properties. Here, high resolution measurements for xenon hydrate formation from ice spheres by X-ray computed tomography are reported. For the first time, the nucleation and growth of hydrates can be accurately and directly quantified from microscale measurements, resulting in new estimates for the intrinsic reaction rate constant of xenon hydrate formation, and the effective diffusion coefficient of xenon in the hydrate. The measured activation energy of hydrate formation is 71.11 kJ/mol and the diffusivity of xenon in hydrate ranges from 2.8 × 10–15 to 4.3 × 10–14 m2/s. These results are of fundamental value in developing a comprehensive understanding on the mechanism of gas hydrate formation, which is essential in their application for energy solutions and increasingly important in astrophysical science.