Measurements of Isothermal Vapor–Liquid Equilibrium and Critical Point-Based Perturbed-Chain Statistical Association Fluid Theory Phase Behavior Modeling of the Propane + Phenol and Tetracosane + Propane/n-Butane Mixtures

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The isothermal vapor–liquid equilibrium (VLE, pressure, temperature, and composition of coexisting vapor and liquid phases, PTxy) was directly determined using a high-pressure optical cell for binary propane + phenol and ternary tetracosane + propane/n-butane systems. Measurements were carried out at three selected isotherms of 383.15, 403.15, and 423.15 K at pressures from 0.94 to 14.5 MPa for propane + phenol and 403.15, 423.15, and 443.15 K at pressures up to 7.5 MPa for tetracosane + propane/n-butane systems. The critical property data (TC and PC) for both mixtures have been derived from the measured VLE data. Based on the initial slopes of the critical lines (shape of the critical lines), the qualitative behavior (pure- and mixture-like behavior) of the isochoric heat capacity (CVx, weak singular property), isobaric heat capacity (CPx), and isothermal compressibility (KTx, strong singular property) of the propane + phenol binary mixture near the critical point has been studied. It is demonstrated that the simplest version of critical point-based perturbed-chain statistical association fluid theory neglecting the complex molecular background of phenol yields reasonably accurate predictions of its pure compound properties. With the value of k12 obtained by fitting the present data of propane + phenol, this model yields reliable predictions for VLE in the systems of other n-alkanes, benzene, carbon monoxide, and nitrogen.