Intensification of esterification of karanja oil for production of biodiesel using ultrasound assisted approach with optimization using response surface methodology

Intensification of acid catalyzed esterification of karanja oil using an ultrasound assisted approach was investigated with the use of sulphuric acid as catalyst in the esterification. Pretreated oil was also utilized further for biodiesel production via alkali catalyzed transesterification reaction. Response Surface Methodology (RSM) was employed to optimize the operating parameters in the case of ultrasonic (US) horn and US flow cell. The optimum conditions established for US horn were molar ratio of 1:6, catalyst loading of 1.5 wt% with duty cycle of 70% in addition to reaction time of 90 min. In the case of US flow cell, optimized parameters were molar ratio of 1:6, catalyst loading of 1.5 wt% with an amplitude of 70% and flow rate as 0.33 Lpm for a total reaction time of 45 min. Highest conversion obtained for esterification using optimum conditions for US horn and US flow cell was 77% and 74% respectively. Biodiesel yield of 83% and 80% was obtained in the transesterification of from one step esterified oil using US horn and US flow cell respectively. Enhanced yield of biodiesel as 92% and 88% was observed when esterification reaction was performed in two steps followed by transesterification, confirming the degree of improvement due to the use of two stages. The present work has clearly demonstrated an effective way for utilization of non-edible oil for biodiesel production with process intensification benefits at different stages of processing based on the use of ultrasound and optimization of operating conditions.