Alkane mixtures: Comparisons between theory and experiment for the butane–heptane system

In this work we introduce our continuum integral equation methodology to the study of alkane mixtures. The theory is applied to predict liquid–vapour coexistence properties in the mixed butane–heptane system using a model parameterization based only on the pure fluids. These predictions are in strong agreement with corresponding experimental values available for the mixture, including temperature–composition phase envelopes, and temperature–pressure phase diagrams spanning a wide region of the system’s overall coexistence regime. The alkanes are modelled as square-well chains, marking here our first application of the theory to chain mixtures with attractive interactions.