A biobased mixed metal oxide catalyst for biodiesel production from waste cooking oil: reaction conditions modeling, optimization and sensitivity analysis study

This study assessed the utilization of a heterogeneous catalyst derived from waste marble tiles and cow horn for waste cooking oil-derived biodiesel synthesis. The synthesized composite catalyst was prepared from waste marble tiles and cow horn through sequential calcination and wet impregnation. The catalyst and its precursors were characterized to analyze their composition, structural, and surface properties. The biodiesel production process was modeled and optimized via the response surface methodology (RSM) and artificial neural networks (ANN). Characterization of waste cooking oil revealed its suitability in biodiesel production. The catalyst had a surface area of 301.510 m2/g, while the pore volume and pore diameter were 0.165 cm3/g and 2.110 nm respectively, which contributed to the optimum biodiesel yield of 98% at a reaction time of 119.92 min, a catalyst concentration of 5.12 wt%, a reaction temperature of 74.86 °C, and methanol-to-oil ratio of 11.43:1. The catalyst was reusable for up to seven cycles while retaining significant activity. The optimized biodiesel sample had properties that met standards. RSM and ANN demonstrated adequate representation of the biodiesel yield as shown by their high R2 values although ANN was superior since it had higher R2 (0.9993) and adjusted R2 (0.9977) values. Global sensitivity analysis results showed reaction temperature as the most important input variable. This work has provided insights into the valorization of waste cooking oil for sustainable biodiesel production through heterogeneous catalysis.