Application of the full factorial design to optimization of base-catalyzed sunflower oil ethanolysis

In the present work, the sodium hydroxide-catalyzed synthesis of fatty acid ethyl esters (FAEE) from sunflower oil and ethanol was optimized using a 33 full factorial design of experiments with two replications and the response surface methodology (RSM). The effects of temperature, ethanol-to-oil molar ratio and catalyst loading on the FAEE were studied. The ANOVA results shows that at the 95% confidence level all three factors and the 2-way interactions of reaction temperature with ethanol-to-oil molar ratio and catalyst loading significantly affect the FAEE formation. A second-order polynomial equation is developed to relate the FAEE purity and the operational variables (temperature, ethanol-to-oil molar ratio and catalyst loading). The fitted model shows a good agreement between predicted and actual FAEE purities (R2 = 0.937; mean relative percentage deviation ±1%), demonstrating the validity of the regression analysis in the process optimization. The optimal process conditions were: ethanol-to-oil molar ratio of 12:1, reaction temperature of 75 °C and catalysts loading of 1.25%. The RSM is proved to be suitable method for optimizing the operating conditions in order to maximize the FAEE purity.