Enhancing the oxidative desulfurisation performance of molybdenum-based catalysts by modification of UiO-66 with functional ligands

Abstract

A series of molybdenum-based catalysts were prepared using UiO-66 modified with functional ligands as a carrier. The catalyst structure was characterised using XRD, FT-IR, N₂ adsorption desorption isotherms, TEM and XPS. The introduction of –F atom expanded the pore structure of catalyst and increased the specific surface area, resulting in a greater number of active site and more dispersion. The introduction of functional ligands (-F, –NO₂) enhanced the electron attraction capacity of catalyst, and improved the microenvironment around the active centre of the catalyst, which contributed to enhance the catalytic performance. The effect of catalyst structure on catalytic activity was investigated using the removal of dibenzothiophene (DBT) from simulated oils as a probe reaction. Under the optimum reaction conditions, the catalyst (UiO-66-NO₂-F-MoO₃) was found to be the most effective for the DBT conversion, reached 99.1 %. After 5 desulfurization experiments, the desulfurization activity of the catalyst cound still reach 90.6 %, indicating that the catalyst had good cyclic stability, which was closely connected to the hydrophobicity of the –F atom. The introduction of –F atom improved the hydrophobicity of the catalyst so that the generated sulfone was not easy to be adsorbed on the active site and improved the cyclic stability of the catalyst. Furthermore, the increase in the number of Mo active species was important in improving the cyclic stability of the catalyst.