Sandwich structured Zn–W–Bi–O catalysts with low activation energy for highly effective oxidative desulfurization of oil

Abstract

In this study, Zn–W–Bi–O catalysts with a sandwich structure were prepared by mixing zinc tungstate and bismuth nitrate to form bismuth tungstate at the interface. The catalyst was composed of bismuth nitrate as the upper layer, zinc tungstate as the lower layer, and phase interface (bismuth tungstate) as the core. The generation of phase interfaces provides a new reaction mechanism for catalytic processes. Based on the different intermediate state changes in the reaction process, the Zn–W–Bi–O catalysis system can be divided into H-S Mechanism, B-R Mechanism, and P-G Mechanism. These reaction mechanisms will simultaneously react with H₂O₂ to generate various transition states, which will cooperatively oxidize sulfur atoms to remove them. The structural characteristics and stability of Zn–W–Bi–O catalysts were determined. There are strong stability and catalytic efficiency for Zn–W–Bi–O catalysts. The desulfurization rate can be close to 100% under optimal conditions (Catalyst of 0.02 g, ionic liquids of 0.5 mL, H₂O₂ of 0.2 mL, model oil of 5 mL, 80 °C). Zn-W-Bi-O-2 catalysts lead to 3 times improvement in ODS activity for the upper layer and 1.25 times improvement in ODS activity for the lower layer. The catalytic reaction mechanism was obtained by the structure-activity relationship.