Efficient biodiesel production from waste cooking oil using a bifunctional Ce/Mn/γ-Al₂O₃ catalysts

As the demand for sustainable energy sources intensifies, biodiesel emerges as a compelling renewable alternative to petroleum-based fuels. Leveraging waste cooking oil (WCO) as a feedstock not only offers an environmentally friendly fuel source but also addresses waste disposal issues. However, biodiesel production from WCO faces challenges, particularly due to its high free fatty acid (FFA) content, which can hinder efficient conversion and lead to soap formation in traditional alkaline-catalysed processes. This study seeks to overcome these challenges by developing and optimizing a bifunctional Ce/Mn(10:90)/γ-Al₂O₃ catalyst via the incipient wetness impregnation (IWI) method. The catalyst's dual acidic and basic active sites enable simultaneous esterification and transesterification, enhancing biodiesel production efficiency from high-FFA feedstocks. Various parameters were optimized, including calcination temperatures, catalyst loadings, and reaction conditions such as methanol-to-oil ratio, catalyst loading, reaction temperature, and time for the transesterification process. The Ce/Mn(10:90)/γ-Al₂O₃ catalyst, calcined at 800 °C, achieved a maximum triglyceride (TG) conversion of 97% under optimal conditions. These conditions were determined to be 10 wt% catalyst loading, a 1:24 methanol-to-oil ratio, a reaction temperature of 65 °C, and a reaction time of 3 h. The catalyst's high efficiency is attributed to its high basicity (1.543 mmol/g), large surface area (143 m²/g), and small particle size (22 nm), which collectively enhance its catalytic performance. This bifunctional catalyst design thus offers a robust solution for the efficient conversion of high-FFA WCO into biodiesel, maximizing performance and sustainability.