Second through fifth virial coefficients for model methane–ethane mixtures

Abstract

We report the virial coefficients for model methane–ethane mixtures up to the fifth order from 190K to 320K. United-atom models with modified Buckingham exp-6 sites are used for both methane and ethane. Comparison of computed second- and third-order coefficients to experimental values from the literature reveals some shortcomings in the molecular models, showing differences of order 5–10% for B2, and 20–30% for B3. We use the virial equation of state (VEOS) to obtain spinodal curves and critical points as a function of mole fraction. Despite the inaccuracies in the models’ virial coefficients, we find that the VEOS provides accurate critical points for the methane–ethane mixture, in comparison to experiment.