Soap formation in biodiesel production: effect of water content on saponification reaction

In biodiesel production, soap formation creates phase separation problem during purification process resulting in low the biodiesel yield and ester content. This research evaluates the effect of water contents (0.05-1 wt%) on the saponification reaction of refined palm oil (RPO). In comparison, saponification of fatty acid methyl ester (FAME) with varying water contents (0.05-1wt%) are determined. From a microscopic point view, soap should act as a mass-diffusion barrier affecting a lower reactant mass flux to the reaction zone. Regarding soap formation in biodiesel production, the high-water content leads to soap formation in FAME and RPO due to hydrolysis, neutralization and saponification reaction. This work suggests that the soap formation behaviour in biodiesel production should be addressed; and thus, the optimal water content in raw material oils should be determined.