Prospects of novel heterogeneous base catalysts and nanocatalysts in achieving sustainable biodiesel production

The present review primarily focuses on the perspectives and state-of-the-art of heterogeneous catalysts, nanocatalysts, biocatalysts, bifunctional catalysts, metal-organic frameworks (MOF), and covalent organic frameworks (COF) for biodiesel production. The environmental concern associated with nonrenewable fossil fuels has led to finding alternative energy sources that can be used to meet global energy demands. Biofuels such as biodiesel are one of the energy sources that could replace fossil fuels. The homogeneous acid and base catalysts are generally used for commercial biodiesel production. However, homogeneous catalysts have downsides such as toxicity, corrosion, soap formation, high wastewater output, and non-reusability. Consequently, heterogeneous acid and base catalysts have been introduced that are less sensitive to moisture and free fatty acids (FFAs), easily separated and recovered, and reusable. Recently, novel catalysts such as waste biomass-derived mesoporous heterogeneous catalysts, chemically synthesized heterogeneous catalysts, metal ion-doped heterogeneous catalysts, bifunctional acid-base catalysts, and carbonaceous char-supported hetero catalysts, nanocatalysts, MOF and COF catalysts have potential to replace homogeneous base catalysts, aid in sustainable and cost-effective biodiesel production. This review provides insights into the recent advancement of various catalysts, catalyst preparation and operations, type of catalysts and suitability, catalyst efficiency, life cycle assessment, catalyst-associated challenges, and prospects for sustainable biodiesel production.