Effect of minor components on chemical composition, thermal behavior, and morphology of biodiesel precipitate

Investigating the effect of minor components on chemical composition, thermal behavior, and morphology of biodiesel precipitate was the main objective of this study. Blends of distilled palm oil biodiesel (DPOB) spiked with the minor components were prepared and held at 20 °C for 16 h to promote the formation of precipitate. The precipitate was then isolated and analyzed using FTIR, DSC, and SEM/EDS. In contrast to monopalmitin, free steryl glucosides (FSG) were found to induce the formation of multicomponent precipitate. DSC measurements demonstrated the formation of a hydrated phase, called α-gel, when monopalmitin crystallized at high levels of moisture. The α-gel was found to have a lower crystallization temperature than the α form and to be more soluble. Precipitate possessing a flake-like morphology was observed as a result of monopalmitin crystallization whereas a layered structure resulting from extensive sticking of fibrillar aggregates was observed for the precipitate isolated from biodiesel spiked with FSG. Flakes resulting from monopalmitin crystallization were smaller as moisture content increased whereas follicle-like structures were observed for a mass ratio of moisture to FSG exceeding a critical value (>18), in addition to the fibrillar aggregates. Thus, interaction among biodiesel minor components was confirmed to result in precipitate of different sizes shapes, and properties.