Synthesis of biodiesel from waste cooking oil using a pulsed high-intensity ultrasound method

Biodiesel is widely recognized as an environmentally friendly biofuel. The key to the industrial production of biodiesel is the cost of components, especially that of the feedstock. In this study, a green pulsed ultrasound-assisted synthesis method for biodiesel production is reported. The biodiesel was prepared from waste cooking oil by transesterification in the presence of KOH, a homogeneous catalyst, under pulsed high-intensity ultrasonic treatment. The effects of various experimental parameters such as catalyst type, catalyst dosage, molar ratio of oil to methanol, temperature, ultrasonic power, and ultrasonic pulse mode were investigated. The results demonstrated that KOH had high catalytic performance compared to a heterogeneous K3PO4 catalyst for the transesterification of waste cooking oil. The yield of biodiesel reached up to 91.5% in 120 min of reaction time under the most optimal reaction conditions. The reaction conditions included a catalyst dose of 3% KOH, oil to methanol molar ratio of 1:6, temperature of 55 degrees C, ultrasonic intensity of 260 W, and pulse mode of 9 s on/1 s off. Kinetic studies were conducted to obtain the rate constants at various reaction temperatures. The kinetic rate constant was observed to increase with increasing temperatures, and the activation energy for the ultrasonic method was calculated to be 35.9 kJ/mol. Hence, this green method shows great potential for applications in biodiesel production.