Development of intermolecular potentials for predicting transport properties of hydrocarbons.

We explore the ability of a modified form of an n-6 potential to represent transport property data of n-paraffins over a range of temperatures, pressures, and chain lengths. General features of the relationship between the potential form and resulting properties are investigated for methane, where it is shown that the tunable softness of the potential function allows for adjustment of transport properties, through modulation of the magnitude of the density fluctuations, while leaving thermodynamic properties such as liquid density and vapor-liquid coexistence properties essentially unchanged. We tune potential parameters of a united atom model for n-paraffins to viscosity and density data of low molecular weight (C4-C10) species and demonstrate the robust predictive capability of viscosity-temperature-pressure relationships for species up to n-C36.