Innovative catalytic approaches for optimizing biodiesel production: A review of homogeneous, heterogeneous, enzymatic, and nanostructured catalysts

This review examines the advancements in catalysts for biodiesel production, highlighting the benefits of innovative approaches such as homogeneous and heterogeneous catalysts, enzyme catalysis, and nanoparticles. It uniquely synthesizes insights into catalytic methods, evaluating their effectiveness and challenges, particularly in the context of high free fatty acid feedstocks. Alkaline catalysts, while efficient, face limitations due to saponification; however, recent developments in catalyst doping with metal oxides have significantly improved reactivity and mitigated side reactions. Homogeneous acid catalysts are effective for high FFA feedstocks but present challenges such as corrosiveness and high alcohol consumption. In contrast, heterogeneous catalysts, including solid materials like zeolites and metal oxides, offer enhanced separation, stability, and reusability. This review also highlights the role of enzyme catalysts, particularly lipases, emphasizing immobilization techniques and enzyme engineering for improved stability and reusability. A distinctive aspect of this work is its in-depth exploration of nanocatalysts, such as nanoparticles and Metal–Organic Frameworks, which enhance catalytic efficiency and stability due to their high surface area to volume properties. Additionally, the review critically assesses various preparation methods, including sol–gel and impregnation techniques, providing guidelines for future work. By identifying research gaps and future directions, this study contributes to the advancement of sustainable biodiesel production technologies.