Thermodynamic and Spectroscopic Identification of Guest Gas Enclathration in the Double Tetra-n-butylammonium Fluoride Semiclathrates

详细信息    查看全文

• 作者：Seungmin Lee ; Youngjun Lee ; Sungwon Park ; Yunju Kim ; Ju Dong Lee ; Yongwon Seo
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：August 2, 2012
• 年：2012
• 卷：116
• 期：30
• 页码：9075-9081
• 全文大小：320K
• 年卷期：v.116,no.30(August 2, 2012)
• ISSN：1520-5207

文摘

The precise nature and unique pattern of the double tetra-n-butylammonium fluoride (TBAF) semiclathrates with a guest gas (CH₄ or CO₂) was closely investigated through thermodynamic and spectroscopic analyses. The three-phase equilibria of semiclathrate (H), liquid water (L_W), and vapor (V) for the ternary CH₄ + TBAF + water and CO₂ + TBAF + water mixtures with various TBAF concentrations were experimentally measured in order to determine the stability conditions of the double TBAF semiclathrates. The double CH₄ (or CO₂) + TBAF semiclathrates showed remarkably enhanced thermal stability when compared with pure CH₄ (or CO₂) hydrate. The highest stabilization effect was observed at the stoichiometric concentration of pure TBAF semiclathrate, which is 3.3 mol %. Gas uptake measurements were undertaken in order to estimate the amount of gas consumed during double semiclathrate formation. CH₄ was found to be a relatively more favorable guest for the 5¹² cages of the double TBAF semiclathrate than CO₂. From the results of the NMR and Raman spectroscopic analyses it was identified that the guest gas molecules (CH₄ or CO₂) were enclathrated in the 5¹² cages of the double TBAF semiclathrates. The overall results given in this study are useful for understanding the fundamental guest gas enclathration behavior in the double semiclathrates.