Process intensification of fatty acid ester production using esterification followed by transesterification of high acid value mahua (lluppai ennai) oil: Comparison of the ultrasonic reactors

Abstract

Sustainable production of biodiesel as second-generation fuel from mahua oil, applied as a green feedstock based on the non-edible nature, was investigated using the two step approach of esterification followed by transesterification reaction with intensification studies using ultrasound. Comparison with the conventional method based on only stirring allowed highlighting the intensification benefits due to ultrasound. Experiments were performed using the ultrasonic horn and ultrasonic bath for comparing the efficacy of the type of ultrasonic reactor for intensification. Effect of various reaction parameters like reaction temperature, the molar ratio of reactants and catalyst loading on the yield has also been analyzed. The results indicated that, maximum intensification was achieved using the ultrasonic horn and optimized parameters established for maximum yield were 45 °C as the temperature, 45 min as the reaction time, 1:9 as the molar ratio of oil to alcohol, 0.5 wt% as the KOH catalyst loading with 120 W as the ultrasonic power and 50% as the duty cycle. Under optimized conditions, the obtained yields for the conventional method was 39%, while the corresponding yield obtained under similar conditions for ultrasonic horn and bath was 93 and 55% respectively. It was clearly demonstrated that ultrasound allowed obtaining higher yields at lower temperature and reaction times directing lower cost of production. Overall, the work clearly demonstrated the process intensification benefits due to the use of ultrasonic horn with better effectiveness compared to the design of ultrasonic bath.