Boosting oxidative desulfurization of model fuel by POM-grafting ZIF-8 as a novel and efficient catalyst

Abstract

In this article, a water-soluble Keplerate-type polyoxometalate (POM), known as {Mo132} nanoballs, was supported over the zeolitic imidazolate framework-8 (ZIF-8) to achieve a highly efficient heterogeneous nano-structure catalyst (ZIF-8@{Mo132}) evaluated in oxidative desulfurization (ODS) of dibenzothiophene (DBT) presenting in model fuel. The ZIF-8@{Mo132} nano-structured catalyst was characterized using various methodologies including FT-IR, XRD, SEM, TGA, UV–Vis spectra of solid state and N2 adsorption–desorption confirming the incorporation of the {Mo132} nanoballs over the ZIF-8. The catalytic ODS performances of the as-synthesized catalyst revealed that high DBT removal efficiency around 87% and 92% after 6 and 12 h of reaction, respectively, in the presence of tert-butyl hydroperoxide (TBHP) as an oxidant, while they were only around 40% and 55% for pristine ZIF-8 at the same condition. The reaction mechanism suggested that the presence of Mo atoms enhances the formation of metal-peroxide formed by nucleophilic attack of TBHP and consequently enhancing DBT removal from a model fuel. Thin-layer chromatography (TLC) and gas chromatography (GC) were implemented for DBT concentration determination. In addition, the operating variables, including catalyst dosage, temperature, initial concentration of DBT, and oxidant to sulfur (O/S) ratio affecting the ODS efficiency were investigated to find the optimum condition. Finally, the remarkable heterogeneous catalyst indicated recyclability for various catalytic cycles.