(671a) The Phase Behavior Effect On the Reaction Engineering of Transesterification Reactions for Biodiesel Production

The phase behavior effect on the reaction engineering of transesterification reactions is investigated in this study. First, the partition coefficient of the catalyst, KOH, was determined. It was found that the vast majority of the catalyst resides in the methanol phase; thus this phase is taken as the primary reaction volume. Mass transfer studies of soybean oil triglycerides show that triglycerides are in fact soluble in methanol. Additionally, it is shown that the rate of mass transfer and the equilibrium concentration of triglycerides in methanol increase with increasing methyl ester concentration. Establishing the methanol phase as the primary reaction volume facilitated the thorough investigation of the rate-limiting step. First, the terms mass transfer control and reaction control are defined for transesterification reactions. Once properly defined, it is shown that the sigmoidal, or s-shaped, methyl ester production curve that is so often observed is not necessarily caused by a transition from a mass transfer controlled regime to a reaction controlled regime, as is so often speculated in the literature. Rather, it is shown that the cause of the acceleration, regardless of the rate-limiting step, is a phase transition from a two-phase system to a single-phase system.