Phase Equilibria of Double Semiclathrate Hydrates Formed with Tetraamylammonium Bromide Plus CH4, CO2, or N-2

Dissociation data for the semiclathrate hydrates formed with tetraamylammonium bromide (TAAB: C20H44NBr) + CH4, + CO2, or + N-2 were measured in the pressure range of (1.33 to 20.37) MPa and temperature range of (279.8 to 291.9) K at (0.050 and 0.100) mass fraction of TAAB. The experimental data were obtained by employing an isochoric pressure-search method. The results showed that at a given pressure, the temperature required to form double TAAB + CH4, + CO2 or + N-2 hydrates was higher than that required for the corresponding pure CH4, CO2, or N-2 hydrates, and as the TAAB concentration increased, its effect of enlarging the hydrate stability zone was strengthened. However, the experimental dissociation temperatures for double semiclathrate hydrates were lower than those for TAAB hydrates formed without guest gases. In addition, the data for double semiclathrate hydrates formed from TAAB generated in this work were compared with those formed from some other semiclathrate hydrate formers (such as tetrabutylammonium bromide, tetrabutylammonium chloride, and tetrabutylammonium fluoride) reported in literature