Synthesis of modified amphiphilic quaternary ammonium silicotungstate and its application in heterogeneous catalytic oxidative desulfurization

A series of novel modified amphiphilic quaternary ammonium phosphotungstate catalysts with a Keggin structure were synthesized. Their physical and chemical properties were characterized by FT-IR, XRD, SEM, and TG-DSC. Heterogeneous catalytic oxidation desulfurization was carried out with dibenzothiophene (DBT) as a typical organic sulfide to be removed in n-octane and H2O2 as the oxidant. The effects of different quaternary ammonium salt structures on the desulfurization effect were studied. By the optimization of experimental conditions, the desulfurization efficiency of the catalyst hexadecyl trimethyl ammonium silicotungstate (HTA)4SiW could reach 98.42% under the following optimal reaction conditions: 50 °C, a H2O2/DBT molar ratio (O/S) of 10 : 1, 0.2 g (HTA)4SiW and 75 min. The catalyst (HTA)4SiW could be recycled 5 times, and the recovered (HTA)4SiW still exhibited a stable chemical structure and achieved the purpose of deep desulfurization. Finally, the possible desulfurization mechanism was proposed.