Zinc Tungstate Supported on Graphitic Carbon Nitride for Efficient Oxidative Desulfurization of Oil

Abstract

Binary metal oxides hold immense potential in catalysis; however, their efficient utilization remains a significant challenge. Zinc tungstate (ZnWO₄) was loaded onto graphitic carbon nitride (g-C₃N₄) via a highly efficient and energy-saving room-temperature stirring method to prepare a ZnWO₄/g-C₃N₄ (ZnWO/CN) composite with a sandwich structure for oxidative desulfurization. The appearance, structure, and stability of ZnWO/CN were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and some other characterization tests. Results demonstrate the successful incorporation of ZnWO₄ nanoparticles within the layered porous structure of g-C₃N₄, achieving a highly dispersed state. In addition, ZnWO/CN exhibits a significantly higher specific surface area and enhanced stability compared to pure ZnWO₄ and effectively mitigates the propensity of ZnWO₄ towards agglomeration. The catalytic performance evaluation indicates that ZnWO/CN (30 wt%) achieves exceptional desulfurization efficiency at a lower preparation cost. A near-complete sulfur removal rate of 99.89% was achieved within 180 min under optimized conditions (m(catalyst) of 20.00 mg, V(ILs)/V(Oil) of 1/20, and V(H₂O₂) of 0.2 mL, 80°C). Furthermore, the catalyst retained high desulfurization efficiency even after eight consecutive cycles. Notably, the adsorption affinity of ZnWO/CN towards reactants enabled a significant reduction in ionic liquid dosages. By combining catalytic characterization testing, quenching experiment, and EPR test, the catalytic reaction mechanism of the oxidation desulfurization was ultimately obtained. The preparation of this sandwich catalyst provides research ideas for the preparation of new supported catalysts.