(251d) A New Volume Translated Peng-Robinson Equation of State for Saturated and Single-Phase Liquid Densities

A new volume translation method is presented for the Peng-Robinson equation-of-state. In a departure for earlier studies in the literature, the volume translation function in this study was developed for both saturated and single-phase liquid density predictions. The method includes only one fluid-specific parameter, which has been generalized in terms of molecular properties such as critical compressibility factor, acentric factor and dipole moment. The method was tested with a large database of highly accurate data for liquid densities. The database contained 65 pure fluids involving several classes of chemical compounds that varied strongly in terms of their molecular size, shape, chain-length, asymmetry and polarity. The model was developed based on these 65 fluids and an additional 20 fluids were used for validating the generalized model.

Results indicate that the volume translation method is capable of precise representations of the saturated liquid densities, yielding an overall average absolute percentage deviation (%AAD) of 0.6 for 65 fluids involving more than 12,000 data points. Generalization of the model was also performed, which provided predictions with %AAD of 0.8 for the same database. Further, the validation of the model was also conducted by utilizing data for liquid densities of 20 fluids not used in the model development. The generalized method yielded liquid densities with a %AAD of 0.96, which is comparable to the deviations obtained for the fluids used in model development.

The volume translation approach was extended to predict compressed liquid densities in the single-phase region. Of the fluids tested, the generalized model provided predictions with a %AAD of 1.8. Thus, the volume translation approach developed in this study appears capable of reliable and accurate predictions of both saturated and compressed liquid densities for diverse classes of molecules.