Desulfurization of Benzothiophene Derivatives by Solvent Extraction Coupled With Oxidation Using Oxomolybdenum(VI) Bis(pyrazolyl)methane Catalysts

An organic–inorganic hybrid material of the MoO 3 /organonitrogen ligand class, formulated as [MoO 3 (bpm)] ( 2 ) (bpm = bis(pyrazolyl)methane), has been prepared under mild conditions by the hydrolysis of the complex [MoO 2 Cl 2 (bpm)] ( 1 ). Polymeric 2 was used in the extractive and catalytic oxidative desulfurization (ECODS) of a model diesel under sustainable conditions, with H 2 O 2 as oxidant and ethanol as extraction solvent, achieving near‐quantitative elimination of 1‐benzothiophene, dibenzothiophene, 4‐methyldibenzothiophene, and 4,6‐dimethyldibenzothiophene after 2 h. The activity was largely retained for several desulfurization cycles. Characterization of species isolated from the treatment of 2 with H 2 O 2 in ethanol indicated a catalytic process involving the in situ formation of the homogeneous catalyst [MoO(O 2 ) 2 (bpm)] which is retained in the extraction phase. Application of the ECODS system to a real diesel (1335 ppm S) led to a sulfur removal of 54%. When the ionic liquid [BMIM][PF 6 ] was employed as the extraction solvent (BMIM = 1‐butyl‐3‐methylimidazolium), the quantitative elimination of S compounds from the model fuel was achieved within 2 h. In recycling experiments, loss of activity due to the accumulation and precipitation of sulfones could be nullified by their removal between cycles, allowing the catalyst/[BMIM][PF 6 ] phase to be used for at least five cycles without loss of desulfurization efficiency.