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–HSO4 afforded a superior catalytic activity in the extraction and catalytic
oxidative desulfurization process with MeOH as an extractant and H2O2 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 H2O2 can afford Ti–OOH species, which was catalytically
active species. The anion HSO4
– 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.