Liquid- Vapor and Liquid-Liquid-Vapor Equilibria for systems containing Carbon Dioxide, Propane and Triglycerides

PABLO E. HEGEL; MARTÍN CISMONDI; GUILLERMO D.B. MABE; MARCELO S. ZABALOY; ESTEBAN A. BRIGNOLE

Morelia, Michoacán (México)

Conferencia; EQUIFASE 2006: VII Conferencia Iberoamericana sobre Equilibrio entre Fases para el Diseño de Procesos.; 2006

In previous works we obtained vapor-liquid-liquid experimental data for the system  CO2  +  propane + sunflower oil and vapor-liquid data for the system CO2 + sunflower oil. Liquid CO2 is immiscible and with very low solvent power for vegetable oils. Propane has  good solvent power for vegetable oils but is flammable. By adding  CO2  to propane it is possible to have a vapor phase composition outside the flammability range. In this case, is still possible to avoid the formation of a second liquid phase at suitable extraction conditions, i.e., to have full miscibility between the solvent  mixture and the oil. In the present work, we extend the  database with new experimental data on bubble pressures for the ternary system CO2 + propane + sunflower oil up to the temperature at which the liquid phase becomes unstable. To this end we used a variable volume equilibrium cell. In this work, we also present new experimental phase equilibria data  for the systems n-hexane/ triacetin, propane/triacetin and CO2/triacetin . We model this system using the Group Contribution Equation of State (GC-EOS) coupled to a parameterization strategy based on the observation of the predicted global phase behavior (GPB) for the binary subsystems. We carry out this task with the help of the computer program GPEC.  The GPB is defined by critical and vapor-liquid-liquid lines. In this way revised parameter values for the interactions between the triester group and the alkane and CO2 groups, respectively are obtained.