Phosphorite mining waste as a sustainable silica source for mesoporous SBA-15-supported WO–Zr bifunctional catalysts toward high-efficiency one-pot biodiesel production from waste cooking oil

The development of sustainable heterogeneous catalysts from industrial waste is an effective strategy for reducing catalyst production costs while promoting circular resource utilization for renewable fuel production. However, the use of waste-derived mesoporous silica as a support for bifunctional catalysts capable of simultaneously catalyzing esterification and transesterification remains largely unexplored. In this study, ordered mesoporous SBA-15 silica was successfully synthesized from phosphorite mining waste (PMW) and employed as a sustainable support for a bifunctional WO–Zr catalyst for the one-pot conversion of waste cooking oil into biodiesel. The catalyst was comprehensively characterized using BET, XRD, SEM–EDS, FTIR, TGA, and ICP–OES to establish relationships between its structural properties and catalytic performance. Characterization results confirmed the successful incorporation of tungsten and zirconium oxide species while preserving the mesoporous SBA-15 framework. The catalyst exhibited a specific surface area of 125.3 m 2 g −1 after metal loading while retaining an accessible mesoporous structure, homogeneous metal dispersion, and good thermal stability, thereby providing abundant accessible acidic active sites and facilitating reactant diffusion. Under the optimum reaction conditions of 60 °C, 30 min, a methanol-to-oil molar ratio of 9:1, and a catalyst loading of 1 wt%, the catalyst achieved a biodiesel yield of 97%. Kinetic analysis yielded an apparent activation energy of 35.43 kJ mol −1 under the investigated reaction conditions. The produced biodiesel exhibited several physicochemical properties characteristic of biodiesel, most of them satisfied both ASTM D6751 and EN 14214 specifications, while GC–MS analysis confirmed the predominance of fatty acid methyl esters, indicating near-complete conversion of the feedstock. Compared with previously reported SBA-15-supported catalysts, the developed WO–Zr/SBA-15 catalyst achieved excellent biodiesel yields under substantially milder operating conditions while utilizing PMW as a low-cost silica precursor. These findings demonstrate that waste-derived mesoporous silica is an effective support for bifunctional catalysts and provides a sustainable catalyst-design strategy that integrates industrial waste valorization with high-performance biodiesel production.