Solubility of solids in supercritical solvents. IV. Mean-field lattice gas description for the p- T- x space diagram of the system ethylene—naphthalene

Abstract

The mean-field lattice gas (MFLG) model is a simple molecular model for the description of thermodynamic behaviour of small-molecule mixtures and polymer systems. The model contains several empirical parameters for the pure substance and for the mixture. The adjustment of parameters for the mixture in a binary system is discussed here, based on liquid/vapour (L/V) equilibrium data and L ≡ V critical data. The latter option turns out as favourite, provided relevant expressions for the critical conditions in the MFLG model are used. The predictive power of the model is then tested by calculating the p- T- x space diagram, including spinodals, L/V equilibria, solid/liquid (S/L) equilibria and the S/L/V equilibrium. Comparison with extensive experimental data on p- T- x phase behaviour of ethylene-naphthalene has been made. A final stringent test on the model is the prediction of excess molar volumes, which compared not unfavourably with literature data.