Department of Chemical Engineering, Changwon National University, Gyeongnam 641-773, Republic of Korea.
Langmuir. 2011 Sep 6;27(17):10597-603. doi: 10.1021/la202143t. Epub 2011 Jul 28.
In this study, guest gas enclathration behavior in semiclathrates of tetra-n-butylammonium bromide (TBAB) was closely investigated through phase equilibrium measurement and spectroscopic analysis. The three-phase equilibria of semiclathrate (H), liquid water (L(W)), and vapor (V) for the ternary CH(4) + TBAB + water and CO(2) + TBAB + water mixtures with various TBAB concentrations were experimentally measured to determine the stability conditions of the double TBAB semiclathrates. Equilibrium dissociation temperatures for pure TBAB semiclathrate were also measured at the same concentrations under atmospheric conditions. The dissociation temperature and dissociation enthalpy of pure TBAB semiclathrate were confirmed by differential scanning calorimetry. The experimental results showed that the double CH(4) (or CO(2)) + TBAB semiclathrates yielded greatly enhanced thermal stability when compared with pure CH(4) (or CO(2)) hydrate. The highest stabilization effect was observed at the stoichiometric concentration of pure TBAB semiclathrate, which is 3.7 mol%. From the NMR and Raman spectroscopic studies, it was found that the guest gases (CH(4) and CO(2)) were enclathrated in the double semiclathrates. In particular, from the cage-dependent (13)C NMR chemical shift, it was confirmed that CH(4) molecules were captured in the 5(12) cages of the double semiclathrates.
在这项研究中，通过相平衡测量和光谱分析，深入研究了客体气体在四丁基溴化铵（TBAB）半笼合物中的包合行为。实验测量了三元 CH(4) + TBAB + 水和 CO(2) + TBAB + 水混合物在不同 TBAB 浓度下的三相平衡（H、液态水（L(W)）和蒸气（V）），以确定双 TBAB 半笼合物的稳定条件。还在相同浓度下在大气条件下测量了纯 TBAB 半笼合物的平衡离解温度。通过差示扫描量热法确认了纯 TBAB 半笼合物的离解温度和离解焓。实验结果表明，与纯 CH(4)（或 CO(2))水合物相比，双 CH(4)（或 CO(2)) + TBAB 半笼合物具有大大增强的热稳定性。在纯 TBAB 半笼合物的化学计量浓度下观察到最高的稳定效果，为 3.7 mol%。从 NMR 和拉曼光谱研究中发现，客体气体（CH(4)和 CO(2))被包合在双半笼合物中。特别是，从笼依赖性 (13)C NMR 化学位移证实，CH(4)分子被捕获在双半笼合物的 5(12)笼中。
