Phase equilibria of the system methane-ethane from temperature scaling Gibbs Ensemble Monte Carlo simulation

A new technique of temperature scaling method combined with the conventional Gibbs Ensemble Monte Carlo simulation was used to study liquid-vapor phase equilibria of the methane-ethane (CH₄-C₂H₆) system. With this efficient method, a new set of united-atom Lennard-Jones potential parameters for pure C₂H₆ was found to be more accurate than those of previous models in the prediction of phase equilibria. Using the optimized potentials for liquid simulations (OPLS) potential for CH₄ and the potential of this study for C₂H₆, together with a simple mixing rule, we simulated the equilibrium compositions and densities of the CH₄-C₂H₆ mixtures with accuracy close to experiments. The simulated data are supplements to experiments, and may cover a larger temperature-pressure-composition space than experiments. Compared with some well-established equations of state such as Peng-Robinson equation of state (PR-EQS), the simulated results are found to be closer to experiments, at least in some temperature and pressure ranges.