Theoretical Examination of the Global Fluid Phase Behavior and Critical Phenomena in Carbon Dioxide +n-Alkane Binary Mixtures

Abstract

The phase behavior of carbon dioxide + n-alkane binary mixtures is studied using the statistical associating fluid theory for potentials of variable attractive range. Extensive experimental data is available in the literature concerning the homologous series of carbon dioxide + n-alkane systems; these provide an excellent example of the continuity of fluid phase behavior in binary mixtures. Continuous transitions in the types of phase behavior are observed as the molecular weight of the n-alkane is increased. In our work, the carbon dioxide and n-alkane molecules are treated as attractive spherical segments tangentially bonded together. The attractive interactions are included as square-well potentials of depth e and range λ. The pure component parameters of carbon dioxide are obtained by fitting to experimental vapor pressure and saturated liquid density data from the triple to the critical point, and the optimized molecular parameters of n-alkanes are taken from a set of transferable parameters previous...