Optimization of Glycerolysis of Free Fatty Acids from Cocoa Bean with MgO Catalyst Using Response Surface Methodology

Diacylglycerol (DAG) is one of the oil derivatives that have relatively high economic value. It has considerable prospects in the global market, which can be synthesized chemically by glycerolysis of oil/fat containing triacylglycerols. The process uses an alkaline catalyst such as sodium hydroxide (NaOH) at the temperature of 210-260 °C. The present study utilized a free fatty acid compound from cocoa bean processing waste as alternative raw material for producing DAG. The reaction system using a MgO catalyst and tert-butanol as solvent was known to be more favorable. The solvent can increase the solubility of oil in glycerol so that the reaction temperature can be lowered to 70-90 °C. This study aims to determine the effect of temperature and the ratio of glycerol/FFA on the glycerolysis process and to determine the optimized variables that result in a maximum conversion. The glycolysis reaction was optimized with two factors using a central composite design, i.e., reaction temperature and glycerol/FFA ratio. The selected fixed variables were catalyst loading (3.5 wt%), the mass of FFA (10 grams), stirring speed (400 rpm), reaction time (4 hours), and volume of solvent (20 mL). The optimization process was evaluated using the response surface method, which shows that the optimum condition was achieved at a glycerol/FFA ratio of 5 g/ml and a reaction temperature of 90 °C. The experiment carried out under these optimum conditions resulted in 97.5% conversion, while the two-order polynomial model developed using RSM was able to predict the conversion of 96.7% under the same condition.