Facile preparation of polyoxometalate nanoparticles via a solid-state chemical reaction for aerobic oxidative desulfurization catalysis

Abstract

Polyoxometalate nanoparticles were synthesized via a concise solid-state reaction method by directly grinding silver nitrate and the polyoxometalate (NH₄)₅H₆PMo₄V₈O₄₀ at room temperature without the assistance of a surfactant. The as-prepared Ag₆(NH₄)₅PMo₄V₈O₄₀ (AgPMo₄V₈) comprised uniform nanoparticles of 50 nm size, which provided significant catalytic oxidative desulfurization (CODS) performance using O₂, N₂ + O₂ or air as an oxidant. The high efficiency of 100% removal was obtained using AgPMo₄V₈ nanoparticles as a catalyst in treating model refractory sulfurs. The coexistence of Ag⁺ and PMo₄V₈O₄₀¹¹⁻ was the main contribution for this CODS procedure, and the Ag⁺ species was employed as the electron transfer mediator (ETM) and the PMo₄V₈O₄₀¹¹⁻ anion was used as the electron donor. The internal electron transfer between Ag⁺/Ag⁰ and V⁵⁺/V⁴⁺ allowed AgPMo₄V₈ to mimic oxygenase to release the activation energy of oxygen. AgPMo₄V₈ nanoparticles also exhibited potential for practical catalytic application in the CODS of diesel and gasoline to produce ultra-clean oils with a S content lower than 10 ppm under mild reaction conditions using a mixture of N₂ and O₂, thus favoring industrial application.