| 초록 |
Gas hydrates are non-stoichiometric inclusion compounds that formed at high pressure and low-temperature conditions, and gas molecules are encapsulated in the host water cages. The sI, sII, and sH are three different structures of gas hydrates. Quaternary ammonium salts such as TBAC are encapsulated in host water frameworks that are called semi-clathrates. The semi-clathrates have normally higher dissociation temperatures than gas hydrates, and thus they can be utilized for gas separation and storage. However, thermodynamic and structural studies of semi-clathrates containing Xe have not been well conducted. In this study, the phase equilibria of the Xe + TBAC (1.0 and 3.3 mol%) + water systems were measured. The structural transition depending on pressure and temperature was investigated using PXRD and in-situ Raman spectroscopy. The distribution of Xe molecules in gas hydrates or semi-clathrates was observed via 129Xe NMR. The results suggested that the Xe + TBAC + water systems had different thermodynamic stability and crystal structure depending on temperature and pressure. The results are expected to contribute to semi-clathrate-based Xe separation and storage. |
