Cavitation assisted synthesis of fatty acid methyl esters from sustainable feedstock in presence of heterogeneous catalyst using two step process

•Ultrasound assisted two step synthesis of FAME using heterogeneous catalyst.•A novel approach using sustainable non-edible oil having high FFA content.•Understanding into effect of different operating parameters for both the processes.•Significant intensification obtained due to the use of ultrasound for both steps. The present work reports the intensification aspects for the synthesis of fatty acid methyl esters (FAME) from a non-edible high acid value Nagchampa oil (31mg of KOH/g of oil) using two stage acid esterification (catalyzed by H2SO4) followed by transesterification in the presence of heterogeneous catalyst (CaO). Intensification aspects of both stages have been investigated using sonochemical reactors and the obtained degree of intensification has been established by comparison with the conventional approach based on mechanical agitation. It has been observed that reaction temperature for esterification reduced from 65 to 40°C for the ultrasonic approach whereas there was a significant reduction in the optimum reaction time for transesterification from 4h for the conventional approach to 2.5h for the ultrasound assisted approach. Also the reaction temperature reduced marginally from 65 to 60°C and yield increased from 76% to 79% for the ultrasound assisted approach. Energy requirement and activation energy for both esterification and transesterification was lower for the ultrasound based approach as compared to the conventional approach. The present work has clearly established the intensification obtained due to the use of ultrasound and also illustrated the two step approach for the synthesis of FAME from high acid value feedstock based on the use of heterogeneous catalyst for the transesterification step.