Thermodynamic stability of structure-H hydrates of methylcyclopentane and cyclooctane helped by methane

The four-phase equilibria were measured for the methylcyclopentane+methane+H2O hydrate system (274.28–287.40 K, 1.75–9.34 MPa) and the cyclooctane+methane+H2O hydrate system (274.08–288.57 K, 1.60–9.33 MPa). Each structure-H hydrate has the lower equilibrium pressure than the pure methane structure-I hydrate in the temperature range of the present work. The isothermal equilibrium pressures of both methylcyclopentane and cyclooctane hydrates are slightly higher than that of methylcyclohexane hydrate.