High-pressure phase equilibria measurements of eugenol + paraffins + CO2 mixtures

PABLO E. HEGEL; MONTOYA, MARIANA FORTUNATTI; SELVA PEREDA

Conferencia; WCCE11; 2023

AAIQ

Supercritical fluid extraction is a green technology that allows obtaining high quality products, free of any trace of organic solvent, feature that is of high interest for the manufacture of food, cosmetics, and bioactive natural products in general. In this regard, a single supercritical CO2 extraction of a vegetable matter not only extracts the aromas or bioactive principles but produces the co-extraction of other no-volatile compounds. For instance, in many cases, the supercritical CO2 also co-extracts cuticular waxes that are located on the surface of the solid matrix [1]. Depending on the vegetable specie, these waxes comprise long chain paraffins and or fatty esters. In many cases, these compounds impair the product quality due to the appearance of precipitates that cause opacity of the natural extract. Therefore, their removal post-extraction is of interest, which is conventionally carried out by cooling the extract below -7ºC, a costly and inefficient process. In this work, we investigate alternative processes, taking advantage of the presence of CO2 in the extract, to remove waxes by means of high-pressure separators or fractionation columns under feasible selective conditions. To select adequate operating conditions, which promote the precipitation of non-desired co-extracted solutes, a thorough understanding of phase behavior of the extract with CO2 is essential. As a first approach, we assess the behavior of a simplified synthetic system comprising an allyl chain-substituted guaiacol (eugenol), paraffins (chain length between C28 and C32) and CO2. In particular, we measure phase equilibria of the binary system CO2 + eugenol and the solubility of synthetic mixtures of eugenol + paraffins in liquid and supercritical CO2.The equilibrium measurements of the binary and ternary systems are carried out in a high-pressure variable volume equilibrium cell using a synthetic/analytic and visual method (windowed cell). In addition, the solubility of eugenol in supercritical CO2 is measured using an isothermal-isobaric continuous flow method. To accurately assess the selectivity in the near-critical region, which is known to depict highly non-ideal multiphase behavior, we test a wide range of conditions (263K ? 333K and 64bar ? 250 bar). The binary eugenol+CO2 system shows liquid-liquid-vapor equilibria at temperatures between 298 K and 308 K. Moreover, the multicomponent system formed by paraffins + eugenol + CO2 shows solid-liquid-vapor equilibria at 298 K and 64 bar. In this work, we also model the new experimental data using the Group Contribution equation of state (GCA-EOS), which have already shown robustness for modeling phase behavior of biobased products and CO2 [2]. A good agreement between modeling and experimental solubility data shows GCA-EOS can be used to design operating windows and perform a proper engineering of supercritical fractionation units.