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.