VLE measurements of biphenyl in supercritical binary mixture of (0.527propane/0.473n-butane)

• VLE properties of biphenyl in supercritical binary solvent (propane + n -butane). • Critical curve data of (propane/ n -butane) + biphenyl mixture. • PTxy phase diagram of (propane/ n -butane) + biphenyl mixture. In the present work, new VLE data of biphenyl in supercritical binary mixture (solvent) of (0.527propane/0.473 n -butane) are reported for three selected isotherms of (403, 423, and 443) K for pressures up to 6.65 MPa. The VLE property ( PTxy ) measurements were performed using a new recently developed high-pressure and high-temperature optical cell with a volume of 117 cm 3 . The concentrations of the liquid and gas equilibrium phases were measured independently without breaking the phase equilibrium ( PT ) conditions during the sampling procedure from each phase. This allows considerable increase the accuracy of the concentration determination of the equilibrium phases using gravimetric method, especially for vapor phase. The values of the critical parameters T C = 403 ± 0.2 K , P C = 4.25 ± 0.03 MPa, x = 0.051 ± 0.006 mole fraction of biphenyl; T C = 423 ± 0.2 K, P C = 5.55 ± 0.03 MPa, x = 0.06 ± 0.006 mole fraction of biphenyl; and T C = 443 ± 0.2 K, P C = 6.80 ± 0.03 MPa, x = 0.09 ± 0.006 mole fraction of biphenyl for the mixture (0.527 propane / 0.473 n -butane) + biphenyl have been estimated from the experimental VLE data near the critical point. The measured VLE properties ( PTxy relationship) of (0.527 propane / 0.473 n -butane) + biphenyl mixture was presented in various projections P - x for different isotherms, T - x for various isobars, and P - T projection. The combined expanded uncertainty of the temperature, pressure, and concentration measurements at 0.95 confidence level with a coverage factor of k = 2 is estimated to be 0.15 K, 0.22 % (or 0.0022 P ), and 0.03, respectively.