Phase equilibria of tetra-iso-amyl ammonium bromide (TiAAB) semiclathrates with CO2, N-2, or CO2 + N-2

Abstract

This study examined the thermodynamic stability and guest gas inclusion of tetra-iso-amyl ammonium bromide (TiAAB) semiclathrates with CO2, N-2, or CO2 (20%) + N-2 (80%), with a primary focus on semi-clathrate phase equilibria and Raman spectra. The three-phase (H-L-W-V) equilibria of TiAAB semi-clathrates with CO2, N-2, or CO2 (20%) + N-2 (80%) were measured at a stoichiometric concentration (TiAAB 3.7 mol%) using both a conventional isochoric method and a stepwise differential scanning calorimeter (DSC) method. The phase equilibria demonstrated that TiAAB (3.7 mol%) semiclathrates with CO2, N-2, or CO2 (20%) + N-2 (80%) were significantly stabilized compared with the corresponding CO2, N-2, or CO2 (20%) + N-2 (80%) gas hydrates. The enclathration of CO2 and N-2 molecules in the cages of TiAAB semiclathrates was clearly confirmed via Raman spectroscopy. The experimental results indicate that TiAAB semiclathrates can incorporate CO2 and N-2 into the cage lattices at elevated temperatures and lowered pressures and are potential materials for CO2 capture.