Phase equilibrium conditions of the CH4, CO2, or N-2 semiclathrate hydrates formed with tetraamylammonium chloride (TAAC: C20H44NCl) aqueous solution at 0.328 mass fraction, corresponding to the stoichiometric composition of TAAC center dot 38H(2)O, were experimentally measured. The experimental data were obtained in the temperature range of (279.9 to 292.8) K and pressure range of (2.11 to 16.40) MPa by employing an isochoric pressure-search method. The results showed that double semiclathrate hydrates of TAAC + CH4, TAAC + CO2, and TAAC + N-2 all had an obvious advantage in thermal stability compared to the corresponding pure CH4, CO2, and N-2 hydrates. In addition, some comparisons were made between our data and experimental equilibrium data from the open literature for semiclathrate hydrates formed with various semiclathrate hydrate formers.