Effect of CaO_K2O heterogeneous catalyst concentration and reaction temperature on trans-esterification of waste cooking oil with ultrasonic wave

Abstract

Cooking oil waste is quite abundant in the community, and this is a threat to the environment. Exploration of biodiesel feedstock is very important to reduce production costs, such as from waste cooking oil. The utilization of heterogeneous catalysts is more environmentally friendly than homogeneous catalysts such as alkaline bases. Ultrasonic wave cavitation will accelerate the reaction rate. The purpose of this study was to determine the optimum conditions for transesterification of used cooking oil with CaO_K2O catalyst using ultrasonic wave, and to characterize and identify the synthesized methyl ester. Several stages in this research are: (1) activation of CaO_K2O catalyst, (2) purification of used cooking oil (3) Transesterification using ultrasonic waves with temperature variations (55, 60, and 65) °C, and the concentration of CaO_K2O catalyst (6, 8 and 10)% w/w, and (4) characterization of the results carried out including density, viscosity, acid number, refractive index, and identification of the results by gas chromatography-mass spectroscopy (GC-MS). The results showed the optimum conditions for methyl ester synthesis using ultrasonic waves at a temperature of 65 °C and a concentration of 8% w/w with a yield of 92.37%. The methyl ester components of cooking oil are 6.37% methyl myristate, 4.34% methyl palmitoleate, 24.62% methyl palmitate, 49.44% methyl oleate, 10.72% methyl stearate, and 4.51% methyl arachidate. The characters of the synthesized methyl ester with density (0.854 ± 0.000) g/mL, viscosity (5.501 ± 0.032) cSt, acid number (0.550 ± 0.000) mg KOH/g, and refractive index 1.447 ± 0.00085 and synthesized methyl ester potential as biodiesel.