| Issue |
Korean Chemical Engineering Research,
Vol.49, No.3, 367-371, 2011
Vol.49, No.3, 367-371, 2011
TBAB를 포함하는 혼합 하이드레이트의 상평형 및 13C NMR 분석
Phase Equilibria and 13C NMR Analysis of the Double Semi-Clathrates Containing TBAB
TBAB(tetra-n-butyl ammonium bromide)는 상온/상압 조건에서 semi- clathrate를 형성하는 물질로서 최근 가스 하이드레이트 형성법을 이용한 천연가스 수송 및 저장, 기체분리 공정 등에서 열역학적 촉진제로 주목받고 있다. 본 연구에서는 TBAB의 열역학적 촉진제로서의 특성을 알아보기 위해 CH4+TBAB와 CO2+TBAB 혼합 하이드레이트계에 대하여 TBAB 농도(5, 32 wt%)에 따른 가스 하이드레이트 3상(하이드레이트(H)-물(Lw)-기상(V)) 평형 조건을 측정하였다. 혼합 하이드레이트의 경우 TBAB의 농도가 5 wt%일 때에 비해 32 wt%일 경우에 열역학적 촉진 효과가 훨씬 크게 나타나는 것을 알 수 있었으며, 이는 순수 TBAB semi-clathrate의 농도별 상압 해리 온도 경향과 유사하였다. 또한,
13C NMR 분석을 통하여 CH4 + TBAB 혼합 하이드레이트의 동공에 CH4 기체가 포집되어 있음을 확인하였고 이 동공의 특성이 순수 CH4 하이드레이트(구조-I)의 작은 동공(512)과 동일함을 확인할 수 있었다.
TBAB (tetra-n-butyl ammonium bromide) forms a semi-clathrate with water under atmospheric pressure conditions and recently has attracted great attention due to its usage as a thermodynamic promoter in gas storage and separation process using gas hydrate formation. In this study, we measured the three-phase (hydrate (H) - liquid water (Lw)-vapor (V)) equilibria of the ternary CH4+TBAB+water and CO2+TBAB+water mixtures at the TBAB concentrations of 5 and 32 wt% to investigate promoting characteristics of TBAB. The greater promotion effect of TBAB was observed at 32 wt% than at 5 wt%. This result was in good agreement with that from pure TBAB semi-clathrate phase diagram under atmospheric pressure conditions. Through 13C NMR analysis of the CH4+TBAB semi-clathrate, it was found that CH4 molecules are enclathrated in the cages of the double semi-clathrate and the position of resonance peak from encaged CH4 molocules in the double semi-clathrate is the same as that from encaged CH4 molocules in the pure CH4 hydrate of structure I.
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