| 초록 |
One of the way to separate F-gases, which are widely used in semiconductor industries and refrigeration systems while being greenhouse gases, is gas hydrate formation. In this study, c-C4F8 (GWP: 8,700, lifetime: 3,200 years) was selected to form gas hydrate in presence of CH4, since c-C4F8 is too large to form gas hydrate by itself (7.66Å). The three-phase (H-LW-V) equilibrium curve of c-C4F8 (5%) + CH4 (95%) hydrate was moved toward thermodynamically more stable regions compared to that of pure CH4 hydrate, implying the enclathration of c-C4F8 and thereby possible structural transformation. Then, PXRD and 13C NNR spectroscopy revealed that both sI (Pm3n) hydrate formed by pure CH4 and sH (P6/mmm) hydrate formed by c-C4F8 and CH4 are coexisting. From these results, it was verified that c-C4F8 molecule acted as an sH hydrate former. Also, it was confirmed from the equilibrium curve shift depending on c-C4F8 concentrations (c-C4F8 2.0% and 5.0%) that c-C4F8 is clearly a gaseous guest of sH hydrates. The gaseous sH hydrate former has never been discovered before, and since it is one of F-gases, these results will give a significant impact on gas hydrate application studies. |
