Optimization of ethyl ester production assisted by ultrasonic irradiation

• This study presents optimization of the KOH-catalyzed transesterification reaction.
• The biodiesel was produced by continuous process with ultrasonic assistance.
• Palm oil and ethanol were used as feedstocks.
• The process was optimized by application of factorial design and response surface methodology.
• The products were characterized and compared to the specification of community biodiesel of Thailand.

This study presents the optimization of the continuous flow potassium hydroxide-catalyzed synthesis of ethyl ester from palm oil with ultrasonic assistance. The process was optimized by application of factorial design and response surface methodology. The independent variables considered were ethanol to oil molar ratio, catalyst concentration, reaction temperature and ultrasonic amplitude; and the response was ethyl ester yield. The results show that ethanol to oil molar ratio, catalyst concentration, and ultrasonic amplitude have positive effect on ethyl ester yield, whereas reaction temperature has negative influence on ethyl ester yield. Second-order models were developed to predict the responses analyzed as a function of these three variables, and the developed models predicts the results in the experimental ranges studied adequately. This study shows that ultrasonic irradiation improved the ethyl ester production process to achieve ethyl ester yields above 92%.