Biomass-derived SiO₂-supported heterogeneous catalysts for fatty acid methyl ester production: A comprehensive review

The development of sustainable and economically viable heterogeneous catalysts remains a central challenge in fatty acid methyl ester (FAME) production. Biomass-derived SiO₂-based catalysts have emerged as promising alternatives to conventional homogeneous systems due to their renewability, structural tunability, and compatibility with circular bioeconomy principles. This review critically analyzes recent advances in the synthesis, modification, characterization, catalytic performance, and sustainability of biomass-derived SiO₂-supported heterogeneous catalysts for biodiesel production. Various silica-rich agricultural residues, including rice husk, palm kernel shell, corncob, sugarcane bagasse, and arecanut husk, are evaluated as precursor materials. Preparation routes such as thermal treatment, alkaline extraction, impregnation, sol–gel processing, and composite engineering are systematically discussed in relation to their impact on physicochemical properties and catalytic behavior. Comparative analysis demonstrates that catalytic performance is governed by the synergistic interplay between mesoporous structure, surface basicity, active metal dispersion, and strong metal–support interactions. Alkali-modified silicates generally exhibit superior FAME yields (up to ∼99%), whereas mixed oxide systems provide enhanced structural stability and reusability (up to 11 cycles). Sustainability assessment highlights the importance of minimizing energy-intensive calcination, improving resistance to metal leaching, and enhancing catalyst regenerability to ensure long-term environmental viability. Despite these advances, significant challenges remain in translating laboratory-scale systems into industrial applications. Future research must focus on integrating catalyst design with techno-economic analysis, life cycle assessment, and scalable process development to achieve meaningful impacts on biodiesel industries and broader community adoption.