PREDICTION OF THE CRITICAL LINE OF A BINARY MIXTURE - EVALUATION OF THE INTERACTION PARAMETERS

The critical line of the binary mixture methane-ethane is calculated via the extended corresponding states Van der Waals one fluid theory. The Gibbs free energy criticality criteria are solved numerically. The numerical derivatives are compared with the exact analytical results derived previously for the special case of the shape factors of the extended corresponding states set equal to unity. Binary interaction parameters are adjusted to give a best fit of the critical line to experimental data. These interaction parameters are then used to evaluate vapor liquid equilibrium data away from the critical region. It appears that a fit of the critical line is not sufficient to obtain binary interaction parameters of general applicability. Optimization of the critical point predictions for the pure components is also discussed.