Removal of Thiophenic Sulfurs Using an Extractive Oxidative Desulfurization Process with Three New Phosphotungstate Catalysts

Three Keggin-type phosphotungstates, i.e. [C₅H₅NH]₃PW₁₂O₄₀, [C₄H₆N₂H]₃PW₁₂O₄₀·3C₄H₆N₂ and [(C₄H₉)₄N]₃PW₁₂O₄₀, were synthesized and characterized by elemental analysis, X-ray diffraction, and infrared spectra, meanwhile their catalysis in an extractive catalytic oxidative desulfurization process was studied with ionic liquid (IL) as extractant and H₂O₂ as oxidant. The main factors affecting the desulfurization process were investigated, including temperature, hydrophobicity of IL, and variety of S-compounds, as well as the amount of catalyst, IL, and H₂O₂. Under the optimal conditions, the S-content of DBT oil can be decreased from 1000 to 2 ppm. A new interpretation is proposed for the current process, in which IL is assumed as a reaction phase, and the amount of the extracted S-compound and the peroxidized catalyst wherein greatly affect the desulfurization rate. Besides, the IL with the dissolved catalyst can be reused many times and regenerated easily.