Prediction of the critical locus in binary mixtures using equation of state: I. Cubic equations of state, classical mixing rules, mixtures of methane-alkanes

This work compares the critical lines predicted by six cubic equations of state (EOS) and classical mixing rules with the experimental data available for the mixtures of methane-alkanes up to and including octane. A simple method for calculating the critical line is proposed. The influence of the values of the unlike pair parameter k₁₂ is followed and analyzed from the point of view of the global phase diagram. It is shown that different cubic EOS can yield similar semi-quantitative and even quantitative predictions with the optimized values of this parameter. The results are compared with the information available in the literature.