TiO2 microspheres supported polyoxometalate-based ionic liquids induced catalytic oxidative deep-desulfurization

Abstract

A series of TiO₂ microspheres supported polyoxometalate-based ionic liquids (POM-ILs) with different tungsten–titanium molar ratios and different carbon chains ILs were successfully prepared. The supported catalysts were characterized by TG, FT-IR, Raman, Nitrogen adsorption–desorption isotherms, XPS and SEM. It is confirmed that the POM-ILs were indeed immobilized on TiO₂ microspheres and the structures were maintained. The appropriate morphology and loading of the supported catalyst was obtained with [C₁₆mim]₄SiW₁₂O₄₀ (C₁₆SiW) IL and the tungsten–titanium molar ratio was 0.1 (0.1-C₁₆SiW–TiO₂). This heterogeneous catalyst strategy makes the usage of ionic liquid decrease sharply. The supported catalyst 0.1-C₁₆SiW–TiO₂ exhibited high catalytic activity in the extractive coupled catalytic oxidative desulfurization (ECODS) system under mild conditions. The removal of dibenzothiophene (DBT) reached 95.3% with low-dosage oxidant (the molar ratio of H₂O₂ and DBT is only 2), which means high efficiency utilization of H₂O₂ was achieved in this system. Moreover, DBT could be removed completely with a little excess oxidant. Furthermore, the 0.1-C₁₆SiW–TiO₂ catalyst showed excellent reusing ability, the desulfurization efficiency had no obvious decrease after recycling for 8 times, which made it a promising catalyst in oxidative desulfurization process.