Potential of Fatty Acid Methyl Ester as Diesel Blends Produced from Free Fatty Acid in Waste Cooking Oil Catalyzed by Montmorillonite-Sulfonated Carbon

Abstract

This research, biodiesel production from waste cooking oil (WCO), was conducted using a montmorillonite-sulfonated carbon catalyst from molasses. The biodiesel product would be blended with diesel fuel with various volume variations to see its fuel properties. The catalyst was assessed by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), N2 adsorption-desorption isotherm, and acidity analysis using the titration method. The effect of the weight ratio of montmorillonite to sulfonated carbon was also evaluated. The process of esterification reaction was optimized using the response surface methodology with a central composite design (RSM-CCD). The study showed that the weight ratio of montmorillonite to sulfonated carbon of 1:3 generated the highest acidity of 9.79 mmol/g with a prominent enhanced surface area and was further employed to optimize the esterification reaction. The optimum condition was obtained at a reaction temperature of 78.12°C, catalyst weight of 2.98 g, and reaction time of 118.27 with an FFA conversion of 74.101%. The optimum condition for the mixture of FAME and diesel fuel was achieved at the composition of the B20 blend, which met the FAME standard. The reusability study revealed that the catalyst had adequate stability at three consecutive runs, with a reduced performance was 18.60%. The reduction of FFA conversion was due to the leaching of the catalyst’s active site. This study disclosed that the FAME generated from the esterification of FFA on WCO-catalyzed montmorillonite-sulfonated carbon had a promising option as biodiesel blends for increasing the quality of commercial diesel.