Phase behavior of carbon dioxide - Low-molecular weight triglycerides binary systems: Measurements and thermodynamic modeling

Abstract

This contribution reports new experimental data on the fluid phase behavior of binary mixtures of carbon dioxide and three saturated, low-molecular weight triglycerides: tributyrin, tricaproin and tricaprylin. The objective of this work is to analyze the effect of the triglyceride molecular weight on the phase behavior of mixtures with carbon dioxide. The experimental work covers a temperature range between 276 and 368 K and pressures up to 15 MPa. All mixtures show liquid-liquid immiscibility near the critical point of pure carbon dioxide. From the analysis of the experimental data, it became apparent that the CO2-systems with tricaproin and tricaprylin have both type-IV fluid phase behavior in the classification of Van Konynenburg and Scott. The fluid phase behavior of these systems was modeled with the group contribution equation of state GC-EoS. The equation was able to describe vapor-liquid, liquid-liquid and vapor-liquid-liquid equilibria, with a single set of group interaction parameters.