The prediction of vapor‐liquid equilibrium constants for binary hydrocarbon systems in the critical region

Abstract

A series of reduced state correlations for the prediction of equilibrium constants for the components of binary hydrocarbon systems have been developed utilizing experimental vapor‐liquid equilibrium data reported by Kay (7, 8, 9) for the enthane‐n‐heptane, ethane‐n‐butane, and n‐butane‐n‐hepane systems. Each correlation applies for a specific values of τ = Tbh/Tbl, the ratio of the normal boiling points of the two components. Plots of β/β° vs. TR covering the complete range of liquid compositions are presented for values of τ = 1.10, 1.20, 1.40, 1.60, 1.80, and 2.00. The term β° represents the reduced vapor pressure of the pure substance, while β is the ratio of the pseudo vapor pressure of this substance in the mixture, Kπ, to the critical pressure of the mixture. The correlations presented in this study reproduce the experimental data used in their development with an average deviation of 2.3% for forty‐eight points, with the experimental critical constants reported by Kay. The reliability of these correlations has been tested with the propane‐isopentane, methane‐ethane, and ethane‐cyclohexane systems which have τ values in the range included in this study and for which experimental critical constants are available. An average deviation of 5.1% was produced for thirty‐six points. In addition the systems methane‐propane, propane‐benzene, nitrogen‐oxygen, and carbon dioxide‐n‐butane were tested with calculated values for their critical constants and produced average deviations of 8.4, 8.2, 9.4, and 20%, respectively.