Equation of state for chain-like molecules using mixing rule based on two-fluid theory

A mixing rule based on two-fluid theory is introduced to consider the non-random mixing of spices in the calculation of the properties of mixtures when an equation of state for chain-like molecules is adopted. The equation is expressed as the sum of a reference term, a perturbation term and an association term. For systems of non-associated spices, the last term is vanished. The mixing rule is used for the second term. The method can be used to correlate vapor–liquid equilibria with only one adjustable parameter. It was found that using two-fluid theory could give better results than that using one-fluid theory for asymmetrical systems or for systems with only self-association.