Ultrasound-assisted transesterification of crude Jatropha oil using cesium doped heteropolyacid catalyst: Interactions between process variables

Transesterification of crude Jatropha oil in the presence of cesium doped heteropolyacid catalyst and assisted by ultrasonic irradiation was investigated. Different Cs heteropolyacid catalysts with different levels of cesium exchange were synthesized and characterized for physical and chemical properties. They were subsequently tested in pre-elementary reaction conditions to identify the most active catalyst. Cs1.5H1.5PW12O40 catalyst showed the highest FAME (fatty acid methyl ester) yield of 81.3% in 60 min while higher Cs levels resulted in poorer activity. Four reaction variables i.e. reaction time (10–50 min), methanol to oil molar ratio (5:1–25:1), ultrasonic amplitude (30–90% of the maximum sonifier power) and catalyst amount (2.5–4.5 w/w oil) were optimized to generate mathematical representation of FAME yield. The highest yield of 90.5% was achieved in just 34 min under the optimum reaction conditions i.e. at an ultrasonic amplitude of ∼60%, and a molar ratio of 25:1. The catalyst was also investigated for possible reusability and leaching under ultrasonic conditions. The reaction was mostly heterogeneous in nature and the catalyst also showed minimal reduction in the activity after three successive reaction runs under the optimum reaction conditions.