Process Design for Biodiesel Production with Crude Soybean Oils: Methanol Recovery from the Reacting System

Abstract

Biodiesel production has widely spread out throughout the world, with facilities in a wide range of capacities, from a few liters to more than a million liters per day. The process design is strongly related to the size of the production plant and the quality of the raw material. However, each alternative has advantages and disadvantages that have to be carefully evaluated. Methanol elimination by evaporation from the biodiesel phase or from both phases present after the reaction leads to a reversion of the reaction because of the shift of equilibrium toward the reactants. In this work, this process stage is studied, i.e., methanol evaporation before glycerine and biodiesel phase separation, and the effects that different homogeneous catalysts have on this operation. Through a decrease of the methanol concentration in the system, the soaps and other impurities present in the biodiesel are transferred to the glycerine phase because of a decrease in the solubility in the biodiesel phase. The operation time should be short to avoid an increase in the monoglyceride concentration formed by the reverse reaction between methyl ester and glycerine. This process is especially suitable for small installations that use nonneutralized oils as raw materials.