The Sanchez-Lacombe lattice fluid model for the modeling of solids in supercritical fluids

The Sanchez-Lacombe equation of state is known to describe the thermodynamic properties of molecular fluids of arbitrary size, especially polymer-solvent phase behavior. However, it is rarely used for modeling solid-supercritical fluid equilibria. In this work, it is shown that a proper estimation of the EoS characteristic parameters together with a thermodynamically consistent expression of fugacity coefficients allows a satisfactory correlation of the solubility of solids in the supercritical phase. Binary mixtures containing carbon dioxide, ethane, ethylene and xenon were considered for this purpose. In a first step, the consistency of experimental data was checked using variance analysis. Then, different mixing rules were considered and results compared with those obtained with the Peng-Robinson equation. Finally, the lower and upper boundaries of the solid-liquid-vapor regions (LCEP and UCEP) were also determined and compared with experimental values.