Titanium dioxide-modified nanosized TS-1 zeolite-supported phosphotungstic acid as a catalyst for deep catalytic oxidative desulfurization of fuel oil

Abstract

The combustion of sulfur-containing fossil fuels has led to excessive emissions of SOx, and the oxidative deep desulfurization of fuels has rapidly attracted the interest of researchers. The TS-1@TiO₂-x support was fabricated via a simple titanium alkylation method, and the HPW/TS-1@TiO₂-0.05 catalyst was successfully obtained by impregnation of phosphotungstic acid (HPW) on the support. The characterization of the synthesized materials was conducted by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible diffuse reflectance (UV-vis DRS), Raman spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption–desorption. The characterization results showed that the catalyst retained the Keggin structure of HPW and the MFI structure of the support and also proved the interaction between HPW and the support. The catalytic performance of the prepared catalysts was investigated for the oxidative desulfurization of the model oil, including thiophene (TH), benzothiophene (BT), and dibenzothiophene (DBT), with hydrogen peroxide as an oxidant. During the ODS process, the loading amount of TiO₂, reaction temperature, reaction time, catalyst dosage, and molar ratio of O and S were optimal with values of 5%, 60 °C, 90 min, 0.06 g, and 12 : 1, respectively. The conversion rates of three organic sulfides with different sizes (TH, BT, and DBT) over HPW/TS-1@TiO₂-0.05 were 99.9%, 78.8%, and 99.9%, respectively. Furthermore, a possible ODS reaction pathway over HPW/TS-1@TiO₂-0.05 is proposed.