Hierarchically Porous Resin-Supported Solid Acid Catalysts: Optimal Sulfonation Strategy and Efficient Biodiesel Production from Oleic Acid via Tailored Esterification

Biodiesel, produced from renewable biomass resources, serves as a viable alternative to fossil fuels. Oleic acid (OA), a predominant component of plant and microbial oils, represents a key feedstock for biodiesel synthesis. Efficient biodiesel production requires both high-performance solid acid catalysts and optimized esterification conditions. In this study, mesoporous resins with different cross-linking degrees were used as carriers, and sulfuric acid served as the Brønsted acid site to prepare the resin-based solid acid catalyst. The effects of various sulfonation conditions (temperature, time, acid dosage, and swelling agent) on the structure of resin-based solid acids and their catalytic performance on biodiesel production from OA were investigated. The optimal sulfonation condition obtained a resin-based catalyst with a specific surface area of 570.92 m2/g, an average pore size of 8.82 nm, and a surface acid content of 1.34 mmol/g. Furthermore, under the optimal esterification conditions (catalyst dosage of 11 wt %, reaction temperature of 65 °C, OA to methanol molar ratio of 1:12, and reaction time of 10 h), the maximum biodiesel yield of 95.67% was achieved. The regeneration experiments demonstrated the high catalytic activity and easy reuse performance of the resin-based solid acid catalyst. In summary, this study elucidates the structure–performance relationship of resin-based catalysts, providing theoretical guidance for the development of novel catalysts and technical support for the further production of biodiesel.