Simultaneous prediction of the critical and sub-critical phase behavior in mixtures using equation of state I. Carbon dioxide-alkanols

A novel EOS that combines van der Waals and Dieterici potentials

“…Whereas in the high-temperature range both models are able to satisfactorily describe the data, the RK-Twu EOS generates completely erroneous phase behavior at low temperatures. This unsatisfactory result is typical of van der Waals-like EOSs (Polishuk et al, 2001). Similarly to the results presented for the other series, the RK-Twu EOS again underestimates the VLE data at temperatures below the CPM and this inaccuracy increases with the increasing asymmetry of homologues.…”

Phase equilibria experiments and calculations for carbon dioxide + methanol binary system

“…A more efficient use of supercritical fluids as media for separations, reactions and material productions requires quantitative prediction of phase equilibria, thermodynamic, and transport properties of supercritical fluid mixtures. Previous works [1,2] have suggested that it is a very difficult and challenging task for equations of state to simultaneously predict the equilibrium properties without preliminary use of experimental data, and to yield accurate results in both the sub-critical and critical regions. The authors have recently undertaken a series of experimental studies of the phase equilibria of binary mixtures composed of carbon dioxide and alcohols [3][4][5][6][7][8][9][10].…”

Prediction of High‐Pressure Phase Equilibria using Cubic EOS: What Can Be Learned?

“…This result is related to the fact that Equation (5) yields a constant critical compressibility value for all compounds (equal to 1/3) and is particularly inaccurate in predicting liquid phase densities. Analysis of the results produced by different cubic EOSs and classical mixing rules indicates that the accuracy in predicting phase compositions in mixtures is directly related to the accuracy of description of the volumetric properties of the pure compounds (Polishuk et al, 2001). Hence, the predictive ability of such models can be substantially increased by improving their volumetric functionality.…”

“…Most of these applications are related with the high-pressure region. However, the experimental data available are still not always reliable (Gurdial et al, 1993;Polishuk et al, 2001) and do not cover the entire PTx range. Hence, the importance of the ability of thermodynamic models to predict accurately the phase behavior of these systems at high pressures, especially at supercritical conditions.…”

“…The tool, which allows fulfil lment of this task, is the quantitative global phase diagram (klGPD) method. It has been also shown (Polishuk et al, 2001) that the values of the adjustable parameters in the classic mixing rules, calculated using the klGPD for a certain member in a homologous series, can be successfully applied to predict the phase behavior of the other members in the series. Although predictive ability can be attached even to classic mixing rules by using klGPD, further improvement can be expected from the implementation of more advanced models.…”