PHASE-EQUILIBRIA PREDICTION OF HYDROGEN-FLUORIDE SYSTEMS FROM AN ASSOCIATING MODEL

Thermodynamic properties of hydrogen fluoride are strongly affected by the tendency of its molecules to form oligomers through hydrogen bonding in both the vapor and liquid phases. In this work, the associated perturbed anisotropic chain theory (APACT) is applied to correlate the vapor pressure and the saturated liquid and saturated vapor densities of pure hydrogen fluoride from the triple point up to the critical point with very good accuracy. An equilibrium model is used to account for hydrogen bonding that assumes the formation of dimer, trimer, hexamer, and nonamer species. The model is used to predict the phase behavior of binary hydrogen fluoride mixtures with CFCs and HCl and accurately describes the azeotrope formation of these systems. Liquid-liquid equilibria are predicted for several hydrogen fluoride-fluorocarbon mixtures that have not been experimentally detected in the past.