Modelling phase behavior of biodiesel related systems with CO2 using a polar version of PC-SAFT

Abstract In previous work, Soh et al., 2014 [1] obtained >98% conversion of triolein to biodiesel (a fatty acid methyl ester) using temperatures of 95 °C, a methanol to triglyceride ratio of 5:1, and carbon dioxide as a co-solvent that enhanced the miscibility of the oil and methanol reactants. To try to determine the most advantageous conditions to operate such reactions where CO 2 is employed as a benign co-solvent, the PC-SAFT theory has been employed to model the phase behavior of the associated mixtures (including alcohols, CO 2 , fatty esters, and glycerol) that one would encounter throughout the reaction. Modelling results achieved accurate phase behavior representations for pure components, plus binary and ternary mixtures that include carbon dioxide by using a polar version of PC-SAFT. Group contribution methods were employed to predict pure component parameters for a range of fatty acid methyl- and ethyl-esters, simplifying the modelling while minimizing the number of parameters. Small errors were obtained using very low values of binary interaction coefficients (below 0.07) for the binary mixtures. Successful modelling for liquid-liquid and vapor-liquid regimes of binary and ternary systems suggest the possibility to determine process conditions for transesterification performed in multiphasic reactors in presence of CO 2 .