Oxidative desulfurization of benzothiophene and thiophene with WO _x/ZrO ₂ catalysts: Effect of calcination temperature of catalysts

Oxidative desulfurization (ODS) of model fuel containing benzothiophene (BT) or thiophene (Th) has been carried out with WO _x/ZrO ₂ catalyst, which was calcined at various temperatures. Based on the conversion of BT in the model fuel, it can be shown that the optimum calcination temperature of WO _x/ZrO ₂ catalyst is around 700°C. The most active catalyst is composed of tetragonal zirconia (ZrO ₂) with well dispersed polyoxotungstate species and it is necessary to minimize the contents of the crystalline WO ₃ and monoclinic ZrO ₂ for a high BT conversion. The oxidation rate was interpreted with the first-order kinetics, and it demonstrated the importance of electron density since the kinetic constant for BT was higher than that for Th even though the BT is larger than Th in size. A WO _x/ZrO ₂ catalyst, treated suitably, can be used as a reusable active catalyst in the ODS.