Generalization of composition-dependent mixing rules for multicomponent systems: prediction of vapor–liquid and liquid–liquid equilibria

Abstract

A consistent generalization to mixing rules depending on the composition proposed by Adachi and Sugie, Panagiotopoulos and Reid, and Stryjek and Vera for the two-parameter mixing rule and by Schwartzentruber and Renon for the three-parameter mixing rule is presented. The invariance problem and dilution effect shortcomings pointed out by Michelsen and Kistenmacher when the original mixing rules are applied to multicomponent mixtures, are avoided by the generalized mixing rules. The proposed mixing rules involving their respective excess function models associated with a cubic equation of state (PRSV or PRCRP), were used on the representation of binary vapor–liquid (hydrocarbon–hydrocarbon, acetone–alcohol, acetone–water, alcohol–water, and alcohol–hydrocarbon) and liquid–liquid (hydrocarbon–water) equilibrium data. The binary interaction parameters of the model were used to test the performance of the generalization on the prediction of ternary vapor–liquid (acetone–methanol–water, acetone–ethanol–water and hexane–ethanol–benzene) and liquid–liquid (water–methanol–benzene, water–ethanol–hexane and water–1-propanol–benzene) equilibria. In addition, it is shown that a more satisfactory prediction of the ternary vapor–liquid and liquid–liquid equilibria can be obtained by using a limit form of the generalized three-parameter excess function model.