Ultrasound-assisted synthesis of biodiesel from crude cottonseed oil using response surface methodology.

Response surface methodology (RSM) based on central composite rotatable design (CCRD) was used to optimize the three important reaction variables-methanol/oil molar ratio (M), NaOH catalyst concentration (C) and reaction time (T) for transesterification of crude cottonseed oil under ultrasonic irradiation. A quadratic polynomial model was obtained to predict the methyl ester yield. 98 wt% of the methyl ester yield could be reached at the deduced optimal conditions: methanol/oil molar raito of 6.2:1, NaOH catalyst concentration of 1 wt% (by the weight of crude cottonseed oil) and reaction time of 8 min. Validation experiments confirmed the validity of the predicted model. Moreover, ultrasonic irradiation was proved to be an efficient, energy saving and economically feasible way to produce biodiesel.