Comparison of four different PC- SAFT versions to predict liquid-liquid equilibria of polymer and asphaltene systems at low temperatures

Abstract

In this work, a simple temperature- and density-effective diameter expression recently published in the literature was combined with a new set of universal constants for the perturbed chain-statistical association fluid theory equation of state (PC- SAFT EoS). Then, the resulting PC- SAFT version was used to perform thermodynamic calculations of Brown's first- order ideal curves, phase behavior for simple hydrocarbon binary mixtures (critical loci), cloud-points (CP) for ternary polymeric mixtures, and asphaltene onset pressures (AOPs) for ill- and well-defined hydrocarbon mixtures prone to precipitate asphaltenes. In addition, the new PC- SAFT version was used to predict the crossover temperatures of one of the ill-defined petroleum mixtures under the injection of different amounts of CO2. This modified PC- SAFT model predicted both AOPs and CPs lower than those found by using the original universal constants by Gross and Sadowski (GS). The predictive calculations with both GS and Liang- Kontogeorgis (LK) universal constants produced as a result that a temperature- and density-dependent effective diameter significantly modifies the predictions for dense and complex systems, while does not generate an important impact on the calculation of properties of systems made-up by simple molecules under ordinary conditions.