Modification of hard-sphere equation of state for thermodynamic properties of light hydrocarbons

Abstract

A modified hard-sphere equation which combines the analytical expression of Ishikawa et al. for the hard sphere repulsive term and the empirical attractive term of the Soave-Redlich-Kwong equation has been applied to the calculation of pure component properties of light hydrocarbons (C₁ - C₆). The two parameters of the modified hard-sphere equation are treated as temperature functions. Molal volumes and vapor pressures of pure saturated liquids were used for evaluating the two parameters of the equation. The calculated results obtained for pure component properties, vapor pressure, saturated liquid and vapor volumes indicate that the new equation performs as well as or better than the Soave-Redlich-Kwong equation and Peng-Robinson equation in all cases treated and shows its greatest advantages in the prediction of liquid phase densities.