Investigation of Critical Properties and Surface Tensions for n-Alkanes by Perturbed-Chain Statistical Associating Fluid Theory Combined with Density-Gradient Theory and Renormalization-Group Theory

Abstract

The perturbed-chain statistical associating fluid theory (PC−SAFT) and density-gradient theory (DGT) are used to construct an equation of state (EOS) applicable for nonuniform fluids. In the bulk phases, the nonuniform EOS reduces to PC−SAFT and the phase equilibria inside the critical region are calculated by combining the renormalization-group theory (RGT). In the vapor−liquid surface, the density profile, surface thickness, and surface tension are calculated by using the nonuniform EOS with the equilibrium bulk properties as input. Investigation shows that PC−SAFT is able to provide accurate critical properties by combining the RGT and correlating the surface tensions for both the light and heavy n-alkanes satisfactorily by combining the DGT.