The chemical association lattice-gas model

Recently the chemical association lattice model (CALM) was introduced and applied to the calculation of excess functions and phase equilibria of binary and ternary systems with one associating component. In this paper CALM is extended to the chemical association lattice-gas model (CALG). Here a compressible lattice with occupied and vacant sites (holes) is considered. So, the model is able to describe high pressure phase equilibria. Currently, the model is restricted to binary systems consisting of an associating and a non-polar component. Most of the model parameters may be fitted to pure-component data as vapor pressures, critical point and liquid densities. There are only two binary mixing parameters. To test the model the phase equilibria of the systems n-hexane + methanol, n-heptane + methanol, n-hexane + ethanol and n-heptane + ethanol at elevated pressures were predicted fitting the two binary mixing parameters to experimental data at moderate pressures. The predicted curves agree reasonably well with the experimental data.