Vapor–liquid equilibria of the 1,1-difluoroethane (HFC-152a) + isobutene system

Isothermal vapor–liquid equilibrium (VLE) data were measured for the 1,1-difluoroethane (HFC-152a) + isobutene system in the temperature range from 273.15 K to 348.15 K at 15 K intervals. The experiments were carried out with circulating-type apparatus with on-line gas chromatography. The VLE data were well correlated by the Peng–Robinson–Stryjek–Vera equation of state with the Wong–Sandler mixing rules involving NRTL model, and the results show a positive azeotrope at each temperature.