Preparation of a NiO-Bi2WO6 catalyst and its photocatalytic oxidative desulfurization performance

Abstract In this paper, a hydrangea-like Bi2WO6 material was first synthesized by a hydrothermal method. Then, as a carrier, a NiO-Bi2WO6 composite photocatalyst was successfully synthesized by the hydrothermal method and high-temperature calcination and applied to studying the removal of benzothiophene (BT) from fluid catalytic cracking (FCC) gasoline. The morphology, crystal structure and elemental composition of the catalyst were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS); ultraviolet-visible diffuse reflectance spectroscopy (UV–Vis-DRS) and electronic impedance spectroscopy (EIS) were used to characterize the light absorption and charge transfer ability of the catalyst. The characterization confirmed that the NiO-Bi2WO6 composite photocatalyst was successfully prepared. Moreover, the effects of catalyst dosage, NiO loading and different substrates on the desulfurization rate were investigated by photocatalytic oxidation desulfurization experiments. The experimental results showed that under the conditions of a catalyst dosage of 1.2 g/L and NiO loading of 30%, the highest desulfurization rate of BT was 95.37%. The active species in the reaction process were studied through active radical capture experiments and qualitative analysis of the substances before and after the reaction was carried out via gas chromatography (GC), and the reaction mechanism of the catalyst was explored in depth. The results indicated that the catalyst mainly oxidized BT to benzothiophene sulfone (BTO2) under the oxidation of superoxide radicals to achieve deep desulfurization. Cycling experiments demonstrated that the catalyst still had high stability and catalytic activity after six cycles.