Phase equilibria of oleic, palmitic, stearic, linoleic and linolenic acids in supercritical CO2

Abstract

-The knowledge of the phase equilibrium is one of the most important factors to study the design of separation processes controlled by the equilibrium. Fatty acids are present in high concentration as byproducts in vegetable oils but the equilibrium data involving these components is scarce. The objective of this work is the experimental determination of the liquid-vapor equilibrium of five binary different systems formed by carbon dioxide and palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). The equilibrium experimental data was collected at 40, 60 and 80ºC at 60, 90 and 120 bar, at the extract and raffinate phases, using an experimental apparatus containing an extractor, a gas cylinder and pressure and temperature controllers. The data was modeled using the cubic equation of state of Peng-Robinson with the mixing rule of van der Waals with binary interaction parameters. The model was adequate to treat the experimental data at each temperature and at all the temperatures together. The best model that includes the van der Waals mixing rule with two parameters has maximum deviation of 17%. The distribution coefficients were also analyzed and it was concluded that the fractionation of the fatty acids is possible using supercritical carbon dioxide.

Phase Equilibrium Measurements of Sacha Inchi Oil (Plukenetia volubilis) and CO2 at High Pressures

“…Even though the molar masses of both oils are similar, soybean oil [8] contains more than 175 and 125% of palmitic and oleic acids, respectively. These fatty acids, linolenic and stearic acids showed previously high absorption of CO 2 [20]. Therefore, the high solubility of CO 2 in the soybean oil can be due to the difference in fatty acid composition and its interactions with CO 2 .…”

Phase behavior of (CO2+methanol+lauric acid) system

“…On the other hand, supercritical fluid extraction is an interesting separation process, because the removal of the solvent is accomplished without exposing the triacylglycerols and fatty acids to high temperatures, avoiding the thermal degradation of these compounds [6,7]. In this case, the use of supercritical CO 2 is attractive because it is inexpensive, nontoxic, nonflammable, inert, naturally abundant and has a relatively low critical temperature (304.1 K) [8][9][10][11].…”

“…Knowledge of the phase behavior is of great importance for the modeling, design and optimization of separation processes controlled by equilibrium [9]. However, a lack of experimental data and reliable thermodynamic models which can aid the technicaleconomic evaluation of processes has limited the industrial use of supercritical fluids [10].…”

Molecular dynamics simulation of the interaction between palmitic acid and high pressure CO 2

“…On the whole, the effects of temperature and pressure on oil extraction rate and component selectivity can be largely attributed to the interaction between fatty acids and high-pressure CO 2 , as the composition of oil is the esterification of fatty acids. Although some scholars have studied the solubility data of fatty acids in supercritical carbon dioxide for a long time, the data are relatively limited, and the solubility data of fatty acids in liquid carbon dioxide near the critical region is even more scarce [11,12]. Moreover, studies such as extraction kinetics experiments and solubility experiments only examined the impact of process conditions at the macro level, without explaining the micro dissolution mechanism.…”