Deep oxidative desulfurization of dibenzothiophene with {Mo132} nanoballs supported on activated carbon as an efficient catalyst at room temperature

Abstract

In this paper, the Keplerate nanoball iso-polyoxomolybdate {Mo₁₃₂} supported on activated carbon (AC) has been synthesized and evaluated as a new, green and cost-effective catalyst for the oxidative desulfurization of a model fuel containing dibenzothiophene (DBT). The {Mo₁₃₂}/AC catalysts, which were prepared with various {Mo₁₃₂} contents, were characterized using FT-IR, XRD, SEM, EDX, ICP-OES, H₂-TPR and nitrogen adsorption/desorption isotherms. Experimental evaluations showed that the catalyst was highly efficient in the removal of DBT using hydrogen peroxide (H₂O₂) as the oxidant, which could result in a sulfur removal of up to 99.5% (or even more than that) under optimum reaction conditions. The factors affecting the process including catalyst dosage, temperature, O/S molar ratio, reaction time and initial sulfur content were evaluated, and the optimum operating conditions were determined. In addition, the new catalyst was recoverable and the recovered {Mo₁₃₂}/AC demonstrated a relatively similar catalytic activity to the fresh one. According to the results of GC-MS analysis, a sulfone species was found to be the only product of DBT oxidation by H₂O₂ over {Mo₁₃₂}/AC. Moreover, a mechanism for the oxidative desulfurization of DBT by the new catalyst was proposed. The present study suggested that the {Mo₁₃₂}/AC composite could be used as an efficient catalyst for the deep oxidative desulfurization and removal of refractory sulfur compounds in fossil fuels.