Kinetic Study of Biodiesel Production by Enzymatic Transesterification of Vegetable Oils

Although acid and alkaline catalysts are mostly used commercially for the synthesis of biodiesel, the difficulties related with the glycerol recovery, catalyst removal and the purification steps stimulate several studies of the enzymatic transesterification of oils since through this rout such problems are inexistent. Even though the high cost of the enzyme is still a drawback for the use of this process in industrial scale, the positive aspects of this technology motivate the researches in this field so that better operation conditions and competitiveness of the process are achieved. The Ping Pong Bi-Bi mechanism taking into account the competitive inhibition of the alcohol has been proposed to represent the kinetics of the enzymatic transesterification in many references in the literature, but the kinetic modeling of the enzymatic ethanolysis for the production of biodiesel has not been widely studied. In this work a kinetic modeling of the ethanolysis of sunflower oil catalyzed by lipase Novozym (R) 435 was carried out with kinetic parameters fitted to experimental data retrieved from the literature. The model was successful in predicting the experimental data with the reactor operating in a batch model. A semibatch reactor with continuous feed of ethanol was also investigated with respect to the influence of the ethanol flow rate on the inhibition of the enzyme.