Optimization of the Acid Value Reduction in High Free Fatty Acid Crude Palm Oil via Esterification with Different Grades of Ethanol for Batch and Circulation Processes

This research focuses on the acid value reduction in crude palm oil (CPO) achieved through an esterification process with different types of ethanol in batch and circulation processes. The esterification process was optimized by varying three independent variables, the ethanol content, sulfuric acid (H2SO4) concentration, and reaction time, using a response surface methodology to determine the optimal conditions for the acid value reduction in the esterified oil. Three grades of ethanol—95% hydrous ethanol, 99% anhydrous ethanol, and 99% analytical reagent (AR) ethanol—were used to study the batch esterification process. The optimal conditions for hydrous ethanol were 82.7 vol.% ethanol content, 10.6 vol.% H2SO4 concentration, and 25.4 min reaction time; for anhydrous ethanol, the optimal conditions were 78.1 vol.% ethanol content, 10.2 vol.% H2SO4 concentration, and 26.3 min reaction time; for AR-grade ethanol, the conditions were 77.7 vol.% ethanol content, 10.5 vol.% H2SO4 concentration, and 28.6 min reaction time. The experimental results indicate that the acid value of esterified oil could be reduced under optimal conditions using hydrous ethanol, anhydrous ethanol, and AR-grade ethanol at concentrations of 1.85 mg KOH/g, 0.97 mg KOH/g, and 0.95 mg KOH/g, respectively. Anhydrous ethanol had the most cost-effective production. Therefore, anhydrous ethanol was selected to study acid value reduction in esterified oil in a circulation esterification process to increase process efficiency. The results showed an acid value of 1.42 mg KOH/g under optimal conditions of 66.9 vol.% anhydrous ethanol content, 7.3 vol.% H2SO4 concentration, and 27.7 min circulation time, with a production cost of 0.460 USD/batch. The circulation esterification process can reduce ethanol content, H2SO4 concentration, and production costs by 14.34%, 28.43%, and 16.21%, respectively, compared to the batch esterification process, resulting in significant reductions in chemical and production costs.