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.

Comparison between theoretical predictions and experimental data for the mixed butane-heptane liquid-vapour phase diagram. The continuum integral equation theory, implemented using a square-well potential, is used to model the intermolecular structure of the pure alkanes; the mixture results are predictions and do not rely on fits to any mixture data.