Increasing the utilization of SiBeta support to anchor dual active sites of transition metal and heteropolyacids for efficient oxidative desulfurization of fuel

Abstract

Aiming at improving the activity of supported catalysts toward oxidative desulfurization (ODS) reaction, an increasing support utilization rate strategy is developed by introducing additional phosphotungstic acid (HPW) on V anchored zeolite SiBeta. Both the Keggin HPW on the surface of SiBeta and the tetrahedral V species into the framework of SiBeta possess high intrinsic catalytic activity for the oxidation of sulfides. Grafting V species into the framework of SiBeta can create Lewis acid sites and HPW serves as a typical source of Brønsted acidity, while the synergistic effect between Lewis and Brønsted acids contributes to the formation of numerous peroxometallate complexes with strong oxidizing capacity. The obtained catalyst exhibits outstanding catalytic performance toward ODS reaction and can adsorb ODS products, thus removing them from oil phase. In addition, series of efficient catalysts were prepared by adjusting the types of heteropolyacids and transition metal (V, Ti, Nb and Zr) to control their acidity. It is indicated that the ODS activity is favored by the enhancing the strength and density of Lewis acid sites and the density of Brønsted acid sites. Such concepts of engineering both increasing support utilization and synergistic effect of dual-active sites herald a new paradigm for the construction of supported catalysts.