Supercritical production and fractionation of fatty acid esters and acylglycerols

• Fatty acid esters/monoglycerides (MG) fractionation using CO2 under mild conditions.
• Phase equilibria experimental measurements to assess the separation process.
• GCA-EoS (Group Contribution with Association) modeling of the experimental data.
• Mathematical simulation of the process based on GCA-EoS predictions.
• High purity MG can be recovered without raw material losses by thermal degradation.

The production of biodiesel or fatty acid esters (FAE) from lipids with supercritical methanol (scMeOH) has gained interest in the last decade because it allows the direct transesterification of crude oils and fats. The reaction should be carried out above 593 K in order to achieve complete conversion. When milder conditions are set, also monoglycerides (MG) and diglycerides (DG), together with glycerol, are obtained as byproducts of the transesterification process. Acylglycerols are common food emulsifiers and surface active agents in many industrial cleaning products.The main goal of this work is to study the fractionation of FAE and acylglycerols by using CO2 as a green solvent. Mixtures of FAE, MG and DG were produced by partial transesterification of sunflower oil with scMeOH in a temperature range of 556–605 K and using different methanol to oil molar ratios (between 20 and 50). Then, experimental data on phase equilibria of reaction products + CO2 were measured at 298 K and 313 K in a variable volume cell with windows. The measured data were used to test the predictive capability of the Group Contribution with Association Equation of State (GCA-EoS). The acylglycerols can be purified by near critical extraction of the FAE with CO2. The simulation of the extraction process working with CO2, in liquid or supercritical state, gives a concentration of acylglycerols higher than 99.8 wt.% in the raffinate phase with a concentration of FAE above 97 wt.% in the extract phase.

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