Equation of state for repulsive models of n-alkane pure fluids and mixtures

Theoretically-based equations of state previously developed for hard models of molecular pure fluids and mixtures are extended in this paper to repulsive models of pure n-alkane fluids and mixtures. For pure fluids, the compressibility factor is expressed in terms of a scaling of the excess compressibility factor of a hard-sphere fluid with a packing fraction equal to the effective packing fraction of the true fluid. For mixtures, the excess compressibility factor is expressed as a similar scaling of the excess compressibility factor of a hard-sphere fluid mixture. The theory requires two parameters, namely the scaling factor and the effective (averaged) molecular volume of the fluid (mixture), which can be determined from the molecular geometry. Results are in generally good agreement with available simulation data.