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Isothermal phase equilibrium relations of the CO 2 + 1,1,1,2tetrafluoroethane (HFC-134a) and CO 2 + 1,1-difluoroethane (HFC-152a) mixed-gas hydrate systems were measured at 279.15 K. The isothermal phase equilibria of the CO 2 + HFC-134a mixed-gas hydrate system exhibit the heterogeneous azeotropic-like behavior derived from the structural phase transition of the mixed-gas hydrate. The CO 2 + HFC-152a mixedgas hydrate system shows neither a structural phase transition nor azeotropic-like behavior.

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High-pressure phase equilibrium relations of the 1,1-difluoroethane (HFC-152a) + water binary system were investigated in a temperature range of (275.03 to 319.30) K and a pressure range up to 370 MPa. Four three-phase coexisting curves of hydrate + aqueous + gas phases, hydrate + HFC-152a-rich liquid + gas phases, hydrate + aqueous + HFC-152a-rich liquid phases, and aqueous + HFC-152a-rich liquid + gas phases originate from the quadruple point of hydrate + aqueous + HFC-152a-rich liquid HFC-152a + gas phases located at (288.05 ± 0.15) K and (0.44 ± 0.01) MPa. The structure of HFC-152a hydrate remains structure I (s-I) in the pressure range up to 370 MPa. Raman spectra of the HFC-152a molecule in the HFC-152a hydrate indicate that the HFC-152a molecules occupy only large cages of s-I HFC-152a hydrate in the presence of completely vacant small cages at a pressure up to 370 MPa.