Computation and modeling of critical phenomena with the perturbed chain-statistical associating fluid theory equation of state

Critical phenomena such as co-solvency, miscibility windows and two-phase holes in the three-phase surfaces can be of great importance in industrial applications of near-critical and supercritical technology, since they occur in a range of temperatures, pressures and compositions where the technological processes are carried out. They are also very important for mapping the transitions between different types of fluid phase behavior. In this work, the perturbed chain-statistical associating fluid theory (PC-SAFT) equation of state was used to model the critical phenomena of various ternary systems and their respective binary subsystems (which include n-alkanes, n-alkanols, aromatic alcohols and carbon dioxide) by fitting binary interaction parameters (kij). The experimental data covered a range of temperatures and pressures of practical interest in engineering. Results were compared with experimental critical data obtained from literature and an excellent agreement was obtained. An algorithm to calculate numerically the double critical endpoints and tricritical points according to their thermodynamic definitions was also developed.