Investigating catalytic oxidative desulfurization of model fuel using hollow PW₁₂/TiO₂@MgCO₃ and performance optimization via box-behnken design

A facile and eco-friendly synthesis of PW₁₂/TiO₂@MgCO₃ hollow tubes (PW₁₂ ·∼· H₃[PW₁₂O₄₀] = polyoxometalate) using a soluble and reusable MgCO₃·3H₂O micro-rods template was reported for the first time. The resultant hollow tubes were characterized by Fourier transform infrared spectroscopy (FT-IR), UV–visible spectroscopy, powder X-ray diffraction (PXRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM), which indicated that the [PW₁₂O₄₀]^3- structure remained intact within the hollow tubes. Furthermore, the specific surface area (88.982 m²/g) and average pore size (2.6 nm) of the PW₁₂/TiO₂@MgCO₃ hollow tubes were calculated using the Brunauer-Emmett-Teller (BET) analysis. This study explored the catalytic performance of PW₁₂/TiO₂@MgCO₃ hollow tubes using a three-level Box-Behnken design (BBD), through which optimization curves were designed. The desulfurization of model fuel using hollow tubes was optimally performed when the catalyst dose, time, temperature, and oxidant/sulfur (O/S) were 20–80 gm, 80–120 min, 25–80 °C and 3–8 molar ratio, respectively. These results were further processed, and the experiments were replicated twenty-nine times using a model based on two quadratic polynomials to create a response surface methodology (RSM). This permits a mathematical correlation linking the desulfurization and experimental parameters. The optimal performance of reaction mixture was evaluated to be 80 mg for catalyst concentration, 25 °C of temperature, reaction time of 100 min, and 5.5 for oxidant/sulfur molar ratio from 20 mL of octane simulation oil containing 350 ppm dibenzothiophene (DBT). The predicted desulfurization rate of the model fuel under these optimal conditions was 95.3%. The correspondence between the experimental results and predicted values was verified based on regression analysis, with an R² value greater than 0.99. These hollow tubes could be used for their desulfurization properties ten times a row without significantly reducing catalytic activity.