Experimental determination and calculation of thermodynamic properties of CO2 + octane to high temperatures and high pressures

The phase behavior and critical points of carbon dioxide + octane are determined from 313 to 393 K, and their molar volumes and densities are measured both in the subcritical and supercritical (SC) regions using a variable-volume autoclave in this study. The critical curve of carbon dioxide + octane has been predicted with an equation of state (EOS) by Heilig and Franck, in which a repulsion term and a square-well potential attraction term for intermolecular interaction has been used. To use the pairwise combination rule for the square-well molecular interaction potential, three adjustable parameters are required. The thermodynamic properties including mole fractions, densities and molar volumes of this system are also calculated using the Heilig–Franck, the Peng–Robison (PR) and the Peng–Robinson–Stryjek–Vera (PRSV) equation of state. Among the equations of state, the Heilig–Franck equation of state has been found to have the best correlation with binary vapor–liquid equilibrium data of the carbon dioxide + octane system.