Bimetallic Al/Fe-Modified Mesoporous FDU-12 Nanocatalyst for Ultra-Deep Oxidative Desulfurization of Benzo[ b ]thiophene under Sustainable Conditions

The development of robust and efficient heterogeneous catalysts for oxidative desulfurization (ODS) under mild conditions remains a significant challenge for the production of ultraclean fuel, particularly for less reactive substrates such as benzo[ b ]thiophene. Herein, a bimetallic Al/Fe-impregnated FDU-12 (Fudan University-12) mesoporous silica catalyst was synthesized via a wet impregnation method and evaluated for the oxidation of benzo[ b ]thiophene. Comprehensive characterization using thermogravimetric analysis (TGA), low-angle and high-angle X-ray diffraction studies (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HR-TEM), N 2 adsorption–desorption analysis, and X-ray photoelectron spectroscopy (XPS) confirmed the preservation of the ordered mesoporous framework and the homogeneous dispersion of Al 3+ and Fe 3+ active sites. Under optimized conditions, the Al/Fe–FDU-12 catalyst achieved ∼98.6% conversion with 100% selectivity toward benzo[ b ]thiophene 1,1-dioxide at 60 °C within 3 h using TBHP as the oxidant. The superior performance is attributed to the cooperative action of accessible Lewis acidic Al 3+ and Fe 3+ sites, enabling efficient activation of TBHP and controlled oxygen transfer. The catalyst also exhibited excellent stability and recyclability, demonstrating its potential as a cost-effective and sustainable system for oxidative desulfurization.