Photocatalytic oxidative desulfurization of dibenzothiophene catalyzed by amorphous TiO₂ in ionic liquid

Three types of TiO₂ were synthesized by a hydrolysis and calcination method. The catalysts were characterized by X-ray powder diffraction (XRD), diffuse reflectance spectrum (DRS), Raman spectra, and X-ray photoelectron spectroscopy (XPS). The XRD and Raman spectra indicated that amorphous TiO₂ was successfully obtained at 100 .deg. C. The results indicated that amorphous TiO₂ achieved the highest efficiency of desulfurization. The photocatalytic oxidation of dibenzothiophene (DBT), benzothiophene (BT), 4,6-dimethyldibenzothiophene (4,6-DMDBT) and dodecanethiol (RSH) in model oil was studied at room temperature (30 .deg. C) with three catalysts. The system contained amorphous TiO₂, H₂O₂, and [Bmim]BF₄ ionic liquid, ultraviolet (UV), which played vitally important roles in the photocatalytic oxidative desulfurization. Especially, the molar ratio of H₂O₂ and sulfur (O/S) was only 2 : 1, which corresponded to the stoichiometric reaction. The sulfur removal of DBT-containing model oil with amorphous TiO₂ could reach 96.6%, which was apparently superior to a system with anatase TiO₂ (23.6%) or with anatase - rutile TiO₂ (18.2%). The system could be recycled seven times without a signicant decrease in photocatalytic activity