Phase equilibria (LLE and VLE) of refining operations for enzymatic biodiesel production via quantum mechanical COSMO-RS method



Phase equilibria, both liquid–liquid equilibria (LLE) and vapor-liquid equilibria (VLE), are equally important in the refining operations of biodiesel production. Equilibrium distributions of components at the down-processing of enzymatic ethanolysis reaction were investigated through quantum mechanical COnductor-like Screening MOdel-Real Solvent method with implemented vapor pressure equations. Due to the composite nature of fatty acid ethyl ester (FAEE) components as the biodiesel fuel, multicomponent predictive phase equilibria approach was applied for a model reaction system of refined soybean oil with 30% molar excess amount of ethanol. Simulation results for the LLE at 303 K were in significant agreement with reported experimental data. Minimum boiling azeotropes were found for FAEE-glycerol binaries at isothermal (at 423 and 473K) and isobaric (at reduced pressures) VLE simulations. Similar results were also found at the VLE of glycerol purification operations for multicomponent real case simulations. The feasibilities of simple and rigorous unit operations were also pointed up in this study. © 2012 American Institute of Chemical Engineers AIChE J, 2012