Synergistic PW₁₂O₄₀³⁻ oxidation and TiAl–SBA–15 photocatalysis in PW₁₂O₄₀³⁻@NH₃⁺–TiAl–SBA–15 for highly efficient dibenzothiophene desulfurization

In this study, a novel composite catalyst, PW₁₂O₄₀³⁻@NH₃⁺–TiAl–SBA–15 (denoted as PW@TiAl–SBA–15), was successfully synthesized by immobilizing phosphotungstic acid (HPW) through 3-aminopropyltriethoxysilane (APTES) and integrating it with a TiAl–SBA–15 photocatalyst for the oxidative desulfurization of dibenzothiophene in diesel fuel. The incorporation of HPW introduces a reversible W⁶⁺/W⁵⁺ redox cycle, which significantly promotes the efficient utilization and activation of hydrogen peroxide. The synergistic interaction among the multiple catalytic components enhances H₂O₂ activation, facilitating the formation of reactive peroxotungstate species and oxygen-derived radicals (·OOH/·O₂⁻). These effects were systematically confirmed by H₂–TPR, XPS, UV–Vis diffuse reflectance spectroscopy, and radical scavenging experiments. As a result, the PW@TiAl–SBA–15 catalyst exhibits outstanding photocatalytic oxidative desulfurization performance under mild conditions (50 °C), achieving nearly complete DBT removal within 100 min under visible-light irradiation. Furthermore, the catalyst demonstrates excellent stability and reusability, maintaining over 98.83% desulfurization efficiency after five successive regeneration cycles. The photocatalytic oxidation process over the PW@TiAl–SBA–15 catalyst follows pseudo-first-order kinetics, with an apparent activation energy of 28.143 kJ·mol⁻¹. This work provides valuable insights into the rational design of efficient, stable, and environmentally benign photocatalysts for sulfur removal from fuels, contributing to global efforts toward cleaner and more sustainable energy systems.