High-pressure phase behaviour of the carbon dioxide + n-heptane system: a model system with experiments, modelling, and critical literature assessment

• Isothermal vapour-liquid equilibrium in the temperature range 313.15–383.15 K for carbon dioxide + n -heptane binary system • Vapour – liquid critical curve • Literature critical analysis • Modelling using the Peng–Robinson (PR), Soave–Redlich–Kwong (SRK), and General Equation of State (GEOS) • Semi-predictive modelling approach using both constant binary interaction parameters ( k 12 , l 12 ) and temperature-dependent k 12 with constant l 12 New isothermal vapour – liquid equilibrium data in the temperature range 313.15–383.15 K and vapour – liquid critical points are reported for the carbon dioxide + n -heptane system. All available experimental data for this mixture were also collected and critically reviewed, showing that previous modelling efforts reported in the literature were largely limited to reproducing the specific isothermal data measured in each study, while only two works addressed the vapour – liquid critical behaviour in the pressure–temperature projection. The phase behaviour of the system was modelled using the Peng–Robinson (PR), Soave–Redlich–Kwong (SRK), and General Equation of State (GEOS), employing both constant binary interaction parameters and temperature-dependent k 12 with constant l 12 . The interaction parameters were transferred from the carbon dioxide + n -hexane system without further optimisation. The models reproduce the critical behaviour with reasonable accuracy, although deviations remain in phase compositions and upper critical endpoint predictions. The combined experimental, literature, and modelling results provide a consistent description of the phase behaviour of the carbon dioxide + n -heptane system.