Optimization of an ultrasonic reactor on a semi-pilot scale for biodiesel production

Abstract Biodiesel has become a very attractive alternative to substitute fossil fuels and therefore, there is an increasing interest in the study and optimization of the transesterification reaction that is used to prepare this fuel. The most popular approach to carry out this reaction employs a homogeneous catalyst in a stirred system and recently, ultrasonic reactors in lab scale studies have shown potential. In this context, an optimization study of the operating conditions of an ultrasonic reactor at a semi-pilot scale is hereby reported. The reaction system includes a 9 L reactor equipped with ultrasonic transducers positioned outside and in contact with the reactor’s walls and connected to a 1500 W ultrasonic generator. The performance was studied using an experimental system working in a continouos process with recirculation. A 33 design of experiment (DOE) and response surface methodology (RSM) were used to evaluate the effect of % weight catalyst, methanol: oil molar ratio and reaction time on biodiesel conversion. The experimental results indicate that while the % catalyst and reaction time have a significant and positive effect on the transesterification conversion yield, the molar ratio is significant only through its interaction with time. According to the empirical equation derived from the statistical analysis, optimal conditions for the operation of the ultrasonic reactor for biodiesel production are 1. 88% of catalyst, 9:1 M ratio and 13 min of reaction to reach a conversion value of 99%.