Guest gas enclathration in tetra-n-butyl ammonium chloride (TBAC) semiclathrates: Potential application to natural gas storage and CO_2 capture

摘要

The enclathration of guest gases such as CH_4 and CO_2 in tetra-n-butyl ammonium chloride (TBAC) semiclathrates and their potential application to natural gas storage and CO_2 capture were examined with a primary focus on stability condition measurements and cage filling characteristics. The phase behaviors clearly demonstrated that the double CH_4 (or CO_2) + TBAC semiclathrates yielded a significantly enhanced thermodynamic stability. In particular, the highest stabilization occurred at 3.3 mol%, the stoi-chiometric concentration of TBAC·29.7H_2O. The cage-dependent ~(13)C NMR chemical shift identified CH_4 molecules enclathrated in the small 5~(12) cages of the double TBAC semiclathrates. CO_2 inclusion in the double TBAC semiclathrate was also confirmed using Raman spectroscopy. In addition, the dissociation enthalpy and the dissociation temperature of the TBAC semiclathrate under atmospheric pressure were measured to be 204.8 ± 1.7 J/g and 288.0 K, respectively, by a differential scanning calorimeter. The experimental results demonstrate that TBAC semiclathrates can potentially be used for gas storage and CO_2 capture due to their high thermodynamic stability and favorable enclathration characteristics of guest gases.