A novel approach for improved in-situ biodiesel production process from gamma-irradiated castor seeds using synergistic ultrasound and microwave irradiation: Process optimization and kinetic study

In the present work, first time, the process optimization of in-situ biodiesel production from gamma-irradiated castor seeds using the synergistic application of ultrasound and microwave irradiation has been studied and compared with the performance of normal castor seeds reported earlier. The optimum reaction conditions determined for gamma-irradiated in-situ biodiesel production process employing response surface methodology coupled with Box-Behnken Design are gamma radiation dosage of 9 kGy, methanol to oil molar ratio of 288:1, catalyst amount of 1.33%, reaction temperature of 52.5 degrees C, and reaction time 30 min. A maximum biodiesel yield of 96.04 +/- 0.53% is obtained using gamma-irradiated castor seeds, which is higher by 2.54% compared to that of normal castor seeds. The gamma irradiation caused a significant reduction in methanol to oil molar ratio, catalyst loading, and energy consumption by 17.7%, 22.22%, and 12.5%, respectively, for in-situ transesterification of castor seeds. The reaction rate of the in-situ process has been improved by 30-40%, and activation energy has been decreased by 50% (14 kJ/mol) compared to normal castor seeds. Physico-chemical properties of biodiesel were compared with biodiesel standards (ASTM D6751 and EN 14214) and found satisfactory.