Catalytic performance of amorphous Fe78Nb14B8 powder in biodiesel production

The conversion of waste cooking oils into biodiesel is hindered by high free fatty acid (FFA) content, which conventional catalysts cannot efficiently process. We herein report a trifunctional amorphous Fe₇₈Nb₁₄B₈ powder, synthesized via mechanical alloying, to overcome this bottleneck. The material exhibits a mesoporous texture ( 4.8\ m²/g ) and soft ferromagnetism ( Mₛ ≈ 16.17\ emu\,g⁻¹ ), enabling easy magnetic recovery. For refined soybean oil, it achieves a $$68.76%$$ biodiesel yield via transesterification. Notably, with waste cooking oil, it attains a $$63.9%$$ yield and $$60.31%$$ conversion by simultaneously esterifying FFAs and cracking long-chain compounds into light olefins (ethylene/propylene). This performance stems from the synergistic interplay of Nb-OH Brønsted acid sites, Fe/Nb Lewis acid sites, and boron-driven electronic modulation, which stabilizes transition states and cleaves C–C bonds. The catalyst’s remarkable tolerance to impurities and magnetic separability underscore its promise for integrated, sustainable biorefineries.