Phase Equilibrium and Critical Phenomena in the n-Pentan–Water and n-Hexane–Water Systems at High Temperatures and Pressures

Abstract

PVTx-properties of the H₂O – n-C₅H₁₂ and H₂O – n-C₆H₁₄ mixtures are measured in the temperature range 303-680 K at pressures up to 60 MPa. The measurements were carried out along 265 liquid and vapor isochors in a density range of 63-713 kg/m³. The measurements were performed for 15 concentrations between 0.110 and 0.987 mole fractions of H₂O for the C₅H₁₂ mixtures and for 11 concentrations between 0.166 and 0.977 mole fractions of H₂O for the C₆H₁₄ mixtures. The temperatures and pressures on the three-phase and two-phase boundary curves were obtained for the mixtures from isochors using the kink or inflection method. The data for the critical parameters of the upper and lower branches of the critical curves were obtained from the boundary curves by the method of rectilinear diameter. The measured three-phase data were used to estimate the value of the upper final critical point.