Heterogeneous catalysis has been extensively explored for biodiesel production due to its efficiency and reusability. In this study, three basic heterogeneous catalysts were synthesized via the wet impregnation method, using corn husk ash (Zm)—rich in SiO₂—as the support, and calcined sururu shell powder (Mc)—rich in CaCO₃—as the active component. Both Zm and Mc were thermally treated at 800 °C to obtain SiO₂ and CaO, respectively. The resulting catalysts were characterized by BET surface area analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA/DTG), and basic strength using the Hammett indicator method. The characterization confirmed the successful incorporation of CaO into the mesoporous SiO₂-rich support, imparting basic properties, as verified by the basicity tests. BET analysis revealed a mesoporous structure (pore sizes ranging from 19.35 to 35.71 nm), with the Zm-Mc30 sample showing the highest surface area (11.91 m²/g). XRF results indicated increased SiO₂ and CaO contents after calcination, while XRD patterns suggested the partial crystallization of previously amorphous silica. FTIR spectra confirmed the presence of Si–O–Si and Si–O–Ca functional groups. TGA/DTG analysis showed similar thermal stability among Zm-Mc10, Zm-Mc20, and Zm-Mc30, with the most significant mass loss occurring near 760 °C. Overall, the findings demonstrate that low-cost agro-industrial residues can be effectively reused to produce basic heterogeneous catalysts, contributing to the development of more sustainable biodiesel production processes.
