The investigation on the vapor + liquid equilibrium for the ternary mixture isobutene (R600a) + 1,1-difluoroethane (R152a) + 1,1,2,2-tetrafluoroethane (R134) at temperatures from 253.150 to 273.150 K

• The VLE for the ternary system isobutane + 1,1-difluoroethane + 1,1,2,2-tetrafluoroethane was measured.
• The experiment was carried out using an apparatus based on the recirculation method.
• Correlation of VLE data was made using PR-VDW and PR-MHV2-NRTL models.
• A saddle point azeotropic behavior was found.

In this work, the vapor + liquid phase equilibrium for the ternary system isobutane + 1,1-difluoroethane + 1,1,2,2-tetrafluoroethane was measured using an apparatus based on the recirculation method at temperatures range from 253.150 to 273.150 K. The uncertainties of the temperature, pressure and composition were less than ±5 mK, ±0.0005 MPa and ±0.005, respectively. PR-VDW and PR-MHV2-NRTL models were employed to describe the VLE properties of system concerned. Both models can give satisfied results, and PR-MHV2-NRTL model exhibited better performance than PR-VDW model on the VLE description. A saddle point azeotropic behavior was found, and the azeotropic compositions were calculated by both methods. With the regressed binary interaction parameters from ternary VLE data, the binary VLE were predicted, and the results agree well with the experimental data.