Vanadium Containing Metal-organic Frameworks as Highly Efficient Catalysts for the Oxidation of Refractory Aromatic Sulfur Compounds

The wet impregnation method was applied to prepare vanadium species on the chromium(III) terephthalate metal-organic framework (MIL-101) and on the aluminum fumarate metal-organic framework (A520), two highly efficient catalysts, as well as vanadium species on the zinc terephthalate metal-organic framework (MOF-5), using vanadium(V) oxytributoxide as a precursor. The prepared catalysts were characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), N(2)sorption measurement (BET), thermal analysis (TGA-DTA), and X-ray photoelectron spectroscopy (XPS). The prepared materials were utilized as catalysts for the oxidation of the refractory aromatic sulfur compound, dibenzothiophene (DBT), in a model diesel fuel. The catalytic oxidation of DBT to DBT-sulfone was performed in the presence oftert-butyl hydroperoxide (TBHP) under mild operating conditions. The heterogeneous catalysts, OV((OBu)-Bu-t)(3-x)(OH)(x)@MIL-101(Cr), OV((OBu)-Bu-t)(3-x)(OH)(x)@A520, and OV((OBu)-Bu-t)(3-x)(OH)(x)@MOF-5 demonstrated activities of 98, 98, and 10 %, respectively, in the oxidative desulfurization (ODS) process at 60 degrees C. The catalysts were recycled easily and reused without a significant decrease in their activity. The oxidation of DBT to DBT-sulfone was investigated using gas chromatography, and the formation of DBT-sulfone was confirmed by FT-IR and(1)H NMR spectroscopies.