Feasibility of biodiesel production in a continuous flow microwave reactor with static mixing

Biodiesel, a renewable and biodegradable fuel have been recently considered a suitable biofuel for blends with jet fuel in aviation applications. Biodiesel is traditionally produced by batch transesterification reactions of vegetal oils, carried out with short-chain alcohols in the presence of homogeneous basic catalysts. Microwave irradiation has been presented as a potential method to accelerate the transesterification reaction, with significant reduction in energy and reactants consumption. Large scale operation of microwave-irradiated reactors requires the study of a continuous process. In the present work, an innovative continuous flow microwave-irradiated reactor with static mixing and capacity of 42.5 L/hour was developed to produce biodiesel. Transesterification reactions with soybean oil, ethanol and NaOH as catalyst were carried out. To optimize reaction conditions, the effects of process variables on biodiesel ester content were evaluated by a Box-Behnken experimental plan. The conditions that provided the highest ester content (84%) were ethanol-to-oil molar ratio of 9:1, catalyst loading of 1% (m/m oil), reaction time of 33 seconds and product temperature of 56.4 o C at microwave power of 1000 W. The developed reactor was deemed suitable for scale- u p.