| 초록 |
This study investigated the influence of CO2 injection into CH4 (90%) + C3H8 (10%) hydrate on structural transition and cage-dependent distribution of guest molecules. The compositions of the vapor and hydrate phases after replacement were measured using a gas chromatograph. The extent of the replacement was increased as the CO2 injection pressure was increased. To monitor the replacement behavior and to observe possible structural transition during the replacement, in-situ Raman spectroscopy was adopted. The powder X-ray diffraction (PXRD) patterns were also analyzed to identify the crystalline hydrate structure and to examine the cage-dependent distribution of guest molecules in the initial and replaced hydrates. The experimental results indicated that the injection of CO2 caused a structural transition of initial sII hydrate into sI hydrate and thus, coexistence of both sI and sII was observed after replacement. Most of CH4 molecules remained in the small 512 cages of sII hydrate, whereas most of CO2 molecules were enclathrated in the large 51262 cages of sI hydrate after replacement. |
