Citric acid and temperature programming assisted synthesized Vanadium Silicate-1 for oxidative desulfurization of dibenzothiophene

Abstract

Vanadium-MFI zeolites possess phenomenal potential for catalytic oxidation, while their application is constrained by vanadium content and species distribution. Here, we constructed Vanadium Silicate-1 (VS-1) with enhanced content and preferable distribution by the addition of citric acid in tandem with a temperature-program strategy. Citric acid could modulate the pH in the initial gel and coordinate with vanadium, inhibiting the hydrolysis of vanadium and promoting vanadium incorporation. Moreover, a temperature program was employed to generate unsaturated silicon species, overcoming the tendency of aggregation in vanadium precursor and further promoting vanadium insertion. Furthermore, the effects of the first-stage crystallization temperature and time on the properties of zeolite have been investigated in detail. The sample synthesized through the optimal temperature program achieved 99.9 % dibenzothiophene conversion in 2 h, 10.4 times that of conventional synthesis. To explain the excellent reaction activity, the relationship between different vanadium species and reaction results was investigated. Through linear fitting, V=O(OSi)2(OH) was considered as the dominant active species in oxidative desulfurization (ODS) reaction. Notably, the recycled zeolite proved good reusability, further enhancing its promising application prospect.