Isothermal phase equilibria for the (xenon + cyclopropane) mixed-gas hydrate system

Isothermal three-phase equilibria of gas, aqueous, and hydrate phases for the {xenon (Xe) + cyclopropane (c-C3H6)} mixed-gas hydrate system were measured at two different temperatures (279.15 and 289.15) K. The structural phase transitions from structure-I to structure-II and back to structure-I, depending on the mole fraction of guest mixtures, occur in the (Xe + c-C3H6) mixed-gas hydrate system. The isothermal pressure–composition relations have two local pressure minima. The most important characteristic in the (Xe + c-C3H6) mixed-gas hydrate system is that the equilibrium pressure–composition relations exhibit the complex phase behavior involving two structural phase transitions and two homogeneous negative azeotropes. One of two structural phase transitions exhibits the heterogeneous azeotropic-like behavior.

► Isothermal three-phase equilibria for the heading system were measured.
► Two structural phase transitions of the mixed-gas hydrate are detected.
► Two homogeneous and one heterogeneous azeotropes are observed on an isotherm.