Reconstruction of the molecular model of CO2 in the statistical associated fluid theory with Mie potential of various range based on the PρT correlation and critical properties

The accurate prediction of fluid thermodynamic properties using equations of state (EOS) relies heavily on experimental reference data. To enhance the thermodynamic prediction accuracy of the statistical associating fluid theory with Mie potentials of variable range (SAFT-VR-Mie EOS) in the critical region, this study developed a molecular parameterization method incorporating fluid PρT data and critical properties. Carbon dioxide (CO2) was selected as the reference fluid to evaluate the extrapolation capabilities of the EOS for thermodynamic property calculations. Key thermodynamic properties—including density, saturation properties, isobaric heat capacity, speed of sound, and specific entropy—were systematically calculated and compared. The analysis addressed two critical aspects: (1) the impact of repulsive–dispersive Mie potential pairs on SAFT EOS performance and (2) limitations of CO2 molecular models parameterized using saturated properties and speed of sound data. Notably, fluid PρT data are readily accessible, and establishing precise PρT relationships represents a fundamental prerequisite for reliable thermodynamic property extrapolation. The integration of critical point constraints ensures alignment between the numerical critical point and the fluid's true critical point. This composite parameterization methodology demonstrates applicability to complex fluid systems, offering potential for advancing calculations in thermodynamic cycle systems, petrochemical processes, and carbon capture and sequestration technologies.