Phase Behavior and Thermophysical Properties of Propane–Bitumen Mixtures Near Saturation Pressure: Implications for Solvent-Aided Recovery

Solvent-assisted recovery methods offer a promising alternative to conventional thermal techniques, particularly in reducing environmental impacts and energy intensity. This study investigates the liquid–liquid equilibrium behavior and thermophysical properties of propane–bitumen mixtures under conditions near the saturation pressure of propane. Experimental measurements were conducted across a temperature range of 323.15 to 353.15 K, pressures from 2.00 to 3.43 MPa, and propane feed concentrations between 30 and 50 wt %. Measured properties include the density and viscosity of both liquid phases (except heavy phase viscosity at lower temperatures), propane concentration in each phase, bubble point pressures, and yield. Phase separation and bubble point data were used to construct a Px envelope identifying homogeneous, vapor–liquid, and liquid–liquid regions. Furthermore, gel permeation chromatography was used to analyze the molecular weight distribution of both light and heavy cuts. A thermodynamic model based on the Cubic Plus Association equation of state was developed and tuned using experimental data, and its predictive capability was evaluated against the measured data. The results provide valuable insights into the behavior of propane–bitumen systems under conditions relevant to solvent-assisted in situ recovery.