Biodiesel from an alkaline transesterification reaction of soybean oil using ultrasonic mixing

The feasibility of using ultrasonic mixing to obtain biodiesel from soybean oil was established. The alkaline transesterification reaction was studied at three levels of temperature and four alcohol-to-oil ratios. Excellent yields were obtained for all conditions. For example, at 40 degrees C with ultrasonic agitation and a molar ratio of 6:1 methanol/oil, the conversion to FAME was greater than 99.4% after about 15 min. For a 6:1 methanol/oil ratio and a 25 to 60 degrees C temperature range, a pseudo second-order kinetic model was confirmed for the hydrolysis of DG and TG. Reaction rate constants were three to five times higher than those reported in the literature for mechanical agitation. We suspect that the observed mass transfer and kinetic rate enhancements were due to the increase in interfacial area and activity of the microscopic and macroscopic bubbles formed when ultrasonic waves of 20 kHz were applied to a two-phase reaction system.