Ionic liquid immobilized on magnetic mesoporous microspheres with rough surface: Application as recyclable amphiphilic catalysts for oxidative desulfurization

The wettability of catalysts is of importance to biphasic reaction of oil and water. Magnetic mesoporous microspheres with different surface morphology were prepared as carriers to support polyoxometalates based ionic liquids. The as-prepared catalysts were characterized by SEM, TEM, XRD, FT-IR, N₂ adsorption-desorption and superconducting quantum interference device (SQUID). The contact angle test verified that the wettability of catalysts was significantly controlled by their surface morphology and further influenced the desulfurization efficiency. It was found the magnetic mesoporous silica catalyst with appropriate rough surface ([(C₄H₉)₃NCH₃]₃PMo₁₂O₄₀/RS-MMS) showed the highest catalytic activity on oxidation of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and the sulfur content in model oil could be decreased to 3.4 mg kg⁻¹. In contrast, the catalysts with smooth surface or superhydrophobic rough surface showed strong hydrophilicity or hydrophobicity had low catalytic activity. After reaction, the catalyst could be regenerated and recycled for at least five times.