A Response Surface Methodology Based Modeling of Temperature Variation in an Ultrasonic-Assisted Biodiesel Production Process

Application of ultrasonic energy at 20 kHz transesterification of vegetable oil is reported. Effects of 5 important variables i.e. pulse on (s), pulse off (s), reaction time (min), power (%) and oil volume (ml) at a constant alcohol to palm oil molar ratio (9:1) and initial reaction temperature of 35°C were studied. A central composite design (CCD) based on response surface technology (RSM) was employed. The system reached its steady state temperature within the first few minutes. Longer pulse on and lower the pulse off at 70% of the maximum power of could bring the reaction to desired temperature for an oil volume of up to 60 ml. A model was proposed based on heat capacity of reactants for conversion of ultrasonic into heat and the steady state temperature of the system could be predicted. This model was tested with 5 types of vegetable oil including used palm oil, canola oil, sunflower oil and corn oil to study the effect of specific heat capacity of the oil. Three different types of catalyst i.e. BaO, SrO and CaO with varying heat capacities were also tested for verification and the model showed good predictions with less than 5% errors.