Predicting Initial Reactant Miscibility for CO2-Enhanced Transesterification of Triglycerides with Methanol Using a Polar Version of PC-SAFT

The production of biodiesel via the transesterification of triglycerides by low molecular weight alcohols is generally inhibited by the poor mutual miscibility of the polar alcohol and the nonpolar oil. To overcome the hindrance that the initial phase separation imposes on the reactivity of such systems, some research groups have added carbon dioxide as a cosolvent, where this strategy allows for complete conversion of the triglyceride at moderate temperatures and relatively short reaction times. To date, however, it has not been clear what the best conditions for operating such a reaction might be. To explore this, the Polar-PC-SAFT and Group-Contribution-Polar-PC-SAFT were used to predict the phase equilibria of biodiesel related molecules at the very beginnings of the reaction (time t = 0). Depending upon temperature, pressure, and concentration conditions, the CO2 + methanol + triolein system exhibits shifts between LLV, LL, and LV equilibria. It was found that if a particular concentration of CO2 was...