Transesterification of Vegetable Oils Catalyzed by Immobilized Lipase under Microwave Irradiation

This work investigated the effect of microwave irradiation (MI) on the ethanolysis rate of soybean and sunflower oils catalyzed by supported Novozyme 435 (Candida antarctica). All the experiments were performed at 60 °C.  Conventional heating (CH) transesterification was also conducted using 3.36 % (w/w) of enzyme, evaluating the effects of: tert-butanol and water addition, and oil:ethanol molar ratio. The reactions under CH were monitored up to 24 h to determine the conditions of reaction initial velocity. The investigated variables under MI (50 W) were: reaction time (5.0-180 min) and mode of reactor operation (fixed power, dynamic and cycles) in the absence and presence of tert-butanol (10 % (w/w). The measured response was the reaction conversion in ethyl esters, which was connected to the enzyme catalytic activity. The results indicated that the use of microwave improves the activity at fixed power mode. It was observed a significant effect of the association of tert-butanol and microwave irradiation on the catalytic activity. Compared to CH, the enzymatic reaction rate was increased under microwave heating for soybean and sunflower oils using tert-butanol as a co-solvent. For the MI soybean oil transesterification, the results indicated that it was possible to reach complete conversion (100 %) just after 3 h of reaction, while under CH the conversion was about only 57.23+1.41 % at similar conditions.