Determination of Critical Properties Using a Dynamic-Synthetic Apparatus: Experimental Work and Modeling

Critical point data of mixtures are essential for the optimization of petroleum and supercritical extraction processes. These data supply information on fluid behavior at extreme conditions of equilibrium. Due to strong fluctuations of densities at near-critical conditions, it is difficult for most equations of state to satisfactorily predict the phase behavior near the critical region. In addition, the empirical trend of the binary parameters changes after reaching the critical point of the low boiling component, making model predictions less obvious.

In this communication we propose a “dynamic-synthetic” method with an apparatus designed for the visual detection of critical temperatures and pressures. The apparatus is capable of pure component and mixture measurements with the compositions being synthesized for the mixtures. Critical points are reported herein for several pure components and binary mixtures, correlated using various models ranging from polynomial expression to equation of states. Results show that, in the absence of interaction parameters, general disagreements still exist when modeling more complex systems with equation of states.