III Iberoamerican Conference on Supercritical Fluids Cartagena de Indias (Colombia), 2013 1 FRACTIONATION OF FATTY ESTERS AND ACYLGLYCEROLS BY CO 2 LIQUID-LIQUID EXTRACTION G. Soto, G. Mabe, P. Hegel, S. Pereda* and E.A. Brignole Department of Chemical Engineering PLAPIQUI - Universidad Nacional de Sur - CONICET Camino La Carrindanga km. 7, Bahia Blanca, Argentina Email: spereda@plapiqui.edu.ar Abstract. Oleochemistry is gaining importance due to its wide range of applications in the energy, food and pharmaceutical industries. The production of biodiesel or fatty acid methyl esters (FAMEs) is of great interest due to their use in diesel engines, blended with petroleum fuels. Also, acylglycerols (ACs) are employed in the food and pharmaceutical industries as emulsifiers. Alternative technologies have been proposed in the last decade to improve the conventional process of biodiesel production from unrefined oils and fats. One process of high interest is non-catalytic continuous supercritical methanolysis (scMeOH), which can process raw materials with high free fatty acids (FFA) and water contents. The vegetable oil is treated with an excess of alcohol (40:1 methanol to oil molar ratio) at 593 K and 150 bar to achieve complete conversion. However, working under milder conditions, ACs could also be obtained (543 K to 573 K). In this work, a method for the fractionation of FAMEs + ACs mixtures with liquid CO 2 was studied. A CO 2 liquid-liquid extraction technique was implemented to fractionate the products obtained in a scMeOH process. Working at 298 K and 64 bars, a 98 wt% of FAMEs was obtained in the extract phase and almost pure acylglycerols in the raffinate phase. Keywords: Fatty esters, acylglycerols, CO 2 , liquid-liquid extraction 1. Introduction Biodiesel is produced by transesterification of vegetable oils with methanol to obtain glycerol (a byproduct) and the biofuel, which is a mixture of fatty acid methyl esters (FAMEs). The global price of crude grade glycerol is going down due to an oversupply from the biodiesel industry. However, new applications are being developed for this byproduct in the food/beverage as well as pharmaceutical sector [1,2]. Acylglycerols (ACs) and mixtures of mono and diglycerides (MG and DG) are glycerol derivatives that are also produced as intermediate products in the transesterification of vegetable oils. MG and DG have applications as emulsifiers in the food industry and, because of the excellent skin compatibility of monoglycerides sulfates, ACs are relevant in the elaboration of personal care products [1]. Alternative technologies have been proposed to improve the conventional process of biodiesel production from unrefined oils and fats [3]. One of the most studied is non-catalytic supercritical methanolysis (scMeOH), which can process raw materials with high free fatty acids (FFA) and water contents [4]. The scMeOH process is carried out at temperatures higher than 325 ºC and pressures higher than 150 bar, using a 40:1 molar ratio of methanol to oil (MeOH/Oil). Under these conditions, it is possible to produce biodiesel in specification (96.5 wt.% FAMEs) in 30 min. of reaction time [5]. Nevertheless, it is also possible to obtain ACs if the process is carried out at milder operating conditions. It was determined that, working with a lower molar ratio of 20:1 MeOH/Oil at 300 ºC and 130 bar, a complete conversion of triglycerides was obtained in 20 min. of reaction time, but the reaction product contains a high concentration of MGs and DGs [6]. These reaction products can be separated in order to obtain FAMEs, MGs and DGs of higher added value. Supercritical CO 2 extraction and fractionation is a green technology that has been widely studied, and some applications, like the extraction of specialty lipids and the fractionation of tocopherols from deodorizer distillate, have reached commercial scale [7]. In a previous work [6] it was shown that FAMEs and ACs can