Microwave radiation improves biodiesel yields from waste cooking oil in the presence of modified coal fly ash

This paper studied the effects of using modified coal fly ash as a catalyst to convert waste cooking oil (WCO) into biodiesel under microwave-strengthened action. Coal fly ash was modified with sodium sulphate and sodium hydroxide, and the obtained catalyst was characterized using FT-IR and X-ray diffraction (XRD). The experimental results showed that the modified coal fly ash catalyst improved biodiesel yields under the microwave-assisted system, and the maximum biodiesel yield from waste cooking oil reached 94.91% at a molar ratio of methanol to WCO of 9.67:1 with 3.99% wt% of modified coal fly ash catalyst (based on oil weight) at a 66.20 °C reaction temperature. The reusability of the modified coal fly ash catalyst was excellent, and the conversion yield remained greater than 90% after the catalyst was reused 8 times. The produced biodiesel met the main parameters of the ASTM D-6751 and EN14214 standards.