Deep Oxidative Desulfurization of Model Fuels Catalyzed by Subnanosized Ti Oxoclusters

Oxidative desulfurization is a highly effective approach to decrease the sulfur content in transportation fuel and has become an attractive research topic in recent years. Herewith, we have developed a new kind of carboxylic acid-functionalized imidazolium-based ionic liquid-stabilized Ti oxoclusters via a solvothermal method. The as-synthesized Ti oxoclusters were investigated by elemental analysis, Fourier transform infrared spectroscopy, diffuse reflectance UV–vis, X-ray diffraction, thermogravimetric analysis, high-resolution transmission electron microscopy (HRTEM), and high-angle annular dark field–scanning TEM. Characterization indicated that Ti oxoclusters existed in the form of subnanosized structure and uniformly dispersed with an average particle size of ca . 1 nm due to the protection role of the ionic liquids (ILs). Especially, Ti oxo–HSO 4 afforded a superior catalytic activity in the extraction and catalytic oxidative desulfurization process with MeOH as an extractant and H 2 O 2 as an oxidant. The full removal of dibenzothiophene in model fuels was achieved within 30 min at 60 °C. Besides, the Ti oxoclusters were robust and exhibited high stability in consecutive catalytic recycles. The parent Ti oxoclusters treated with H 2 O 2 can afford Ti–OOH species, which was catalytically active species. The anion HSO 4 – in IL played a crucial role in the activation of Ti–hydroperoxo species by forming hydrogen bonds. This may provide a new insight into the construction of metal oxoclusters for oxidative desulfurization.