New insights into ultra-deep oxidative desulfurization in the presence of competing molecules over alumina-supported vanadium-promoted tungsten oxide catalyst

Abstract

A series of mesoporous γ-alumina-supported tungsten oxide catalysts, both single-metal (xW/Al) and bimetallic vanadium-promoted (yVxW/Al, where x= 5-40 wt% W and y = 1-7 wt% V), were synthesized via an ultrasonication-assisted incipient wetness impregnation (IWI) and evaluated for the ultra-deep oxidative desulfurization (ODS) of dibenzothiophene (DBT) using tert-butyl hydroperoxide (TBHP) as the oxidant. Catalysts were characterized by the XRD, N2 adsorption-desorption, Raman Spectroscopy, XPS, UV-vis DRS, H2-TPR, NH3-TPD, FTIR, FESEM, HR-TEM. ODS performance was assessed in a batch reactor, systematically investigating the effects of tungstate and vanadium loading, TBHP/DBT molar ratio, catalyst dosage, ultrasonication, calcination temperature, reaction temperature, and the presence of competitive inhibitors. The optimal catalyst, 3V17W/Al (3 wt% V, 17 wt% W), exhibited the highest total acidity (551 μmol NH3/gcat) and achieved complete DBT removal within 2 min, corresponding to a turnover frequency (TOF) of 25 s-1. Notably, 3V17W/Al demonstrated superior performance compared to 20W/Al, particularly in the presence of competitive inhibitors such as cyclohexene (CH), indole (IND), and quinoline (QU). While these inhibitors negatively impacted performance by competing for oxidant and poisoning active sites, p-xylene (PX) enhanced DBT removal by facilitating the solubilization of strongly adsorbed molecules. Density functional theory (DFT) calculations provided further insights into the interactions between reactants, products, and the catalyst surface. Kinetic modeling yielded an apparent activation energy (Ea) of 16.0 kJ/mol. Keywords: Tungsten, Vanadium, Oxidative Desulfurization, Competing Molecules, DFT.