Solid–Liquid Equilibrium of Binary Mixtures Containing Fatty Acids and Triacylglycerols

Abstract

Solid–liquid phase diagrams of the following systems were measured using differential scanning calorimetry (DSC): tristearin (2,3-di(octadecanoyloxy)propyl octadecanoate) + tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate), tristearin (2,3-di(octadecanoyloxy)propyl octadecanoate) + palmitic acid (n-hexadecanoic acid), tristearin (2,3-di(octadecanoyloxy)propyl octadecanoate) + linoleic acid (cis-9,cis-12-octadecadienoic acid), tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate) + triolein (2,3-bis[[(Z)-octadec-9-enoyl]oxy]propyl (Z)-octadec-9-enoate), and tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate) + commercial oleic acid (commercial (Z)-octadec-9-enoic acid). The eutectic point was observed for two systems, tristearin with tripalmitin or with palmitic acid. Polarized optical microscopy was employed to investigate the solid phase of the systems and confirmed the occurrence of a solid solution at the extreme of the phase diagram rich in the component with a higher melting temperature. Margules-2-suffix, Margules-3-suffix, nonrandom two-liquid (NRTL), and universal quasichemical functional group activity coefficient (UNIFAC) models were employed to describe the liquidus line of the studied systems, except for the system formed by tripalmitin (2,3-di(hexadecanoyloxy)propyl hexadecanoate) + commercial oleic acid (commercial (Z)-octadec-9-enoic acid) which is a pseudobinary system that was well-described by the UNIFAC model. The best results for the other systems were obtained when employing the Margules-3-suffix and NRTL models.