Ultrasound-assisted production of biodiesel from oils with saturated and unsaturated fatty acids

Abstract

The reaction of biodiesel or FAME (Fatty Acid Methyl Esters) production can become especially slow because of the mass transfer between the non-polar phase (oil) and polar (alcohol) is one of the critical factors. Thus, different technologies have been developed to reduce the reaction time . One of them is ultrasound. Ultrasound is an acoustic wave with a frequency greater than the upper limit of human hearing. In the present work biodiesel from oils rich in unsaturated fatty acids (rapeseed and soybean) and saturated (coconut and palm) has been synthesized using ultrasound as auxiliary energy. For this, an ultrasonic probe at a fixed frequency of 20 kHz and 450 W of power was used. Moreover, it attempted to determine if the chemical composition affects the ultrasound assisted biodiesel synthesis... FAME yields were evaluated in the different oils. The rapeseed, soybean and palm yields achieved above 90 % wt., close to meet with European standard UNE EN 14003, but coconut oil was just over 80% wt. conversion. Thus, it was observed that the differences between the oil yields are determined by chain length of the fatty acids that form part of the triglyceride. Coconut oil has mainly short chain fatty acids opposed to rapeseed, soy and palm fatty acids having 16 carbons or higher. Regarding the reaction time, it was reduced significantly compared to conventional transesterification.