Thermodynamic and spectroscopic analysis for hydrogen gas storage and mixed gas separation using clathrate hydrates

Abstract

Gas hydrates are non-stoichiometric inclusion compounds which are formed by the physically stable interaction between water and relatively small guest molecules occupied in the cavities built by water molecules. Gas hydrates have been applied to many industrial fields such as desalination, food concentration, selective separation of targeted component, carbon dioxide sequestration into the deep ocean and exploitation of natural gas hydrates. In this study, thermodynamic and spectroscopic analysis of pure and mixed gas hydrates was intensively investigated, especially focused on application to recovery, storage and separation of gaseous energy systems. The research scope of this study can be divided into three major fields. The first one is recovery and storage of $H_2$ cluster by using clathrate hydrate and mixed hydrogen hydrates with ethane in sI and propane in sII, the second one is enhancing gas storage capacity of sII double hydrate by using tuning phenomenon, and the last one is spectroscopic analysis of $CO_2$ and $N_2$ mixed gas hydrates for gas separation application. For thermodynamic analysis, hydrate phase behaviors of multi-guest systems were carefully measured. For spectroscopic analysis, the structure, distribution of guest molecules and cage occupancies of mixed hydrate were determined through XRD, NMR, and Raman spectroscopy. First, our results show that promoter guest molecules can be used to store hydrogen a binary clathrate hydrate at low pressures. Although the hydrate lattice appears to be tunable for higher levels of storage, up to ~ 4.0 wt%, the reaction is so slow so as to make the synthetic approach impractical. It is beyond the scope of this thesis to devise an industrial strategy for the efficient synthesis of hydrogen-containing hydrate. However, it is relatively straightforward to demonstrate a promising approach. The reaction of the hydrate/ice mixture with hydrogen is limited by diffusion through a bulk sold phase. So, if the re...