The use of statistical associating fluid theory to improve the BACK equation of state: I. Pure fluids

In this paper, statistical associating fluid theory (SAFT) equation of state (EOS) is incorporated into the Boublı́k–Alder–Chen–Kreglewski (BACK) EOS. The adjustable parameters for 16 pure non-associating fluids are compiled from references and those for 25 pure non-associating fluids are regressed with VLE data in this work. A new equation of state called SAFT-BACK equation is proposed by combining the hard convex body term and dispersion term of BACK equation with the associating term of SAFT equation so that it can describe phase equilibrium behavior for pure associating fluids. In this model, an associating molecule is treated as a convex body with associating sites on it. The adjustable parameters for 13 pure associating fluids are regressed. When compared to the original SAFT, the SAFT-BACK EOS can give more accurate description in the near critical region.