| Summary: | Two quaternary ammonium catalysts based on the monovacant polyoxotungstate ([PW<sub>11</sub>O<sub>39</sub>]<sup>7−</sup>, abbreviated as PW<sub>11</sub>) were prepared and characterized. The desulfurization performances of the PW<sub>11</sub>-based hybrids (of tetrabutylammonium and trimethyloctadecylammonium, abbreviated as TBA[PW<sub>11</sub>] and ODA[PW<sub>11</sub>], respectively), the corresponding potassium salt (K<sub>7</sub>PW<sub>11</sub>O<sub>39</sub>, abbreviated as KPW<sub>11</sub>) and the peroxo-compound (TBA-PO<sub>4</sub>[WO(O<sub>2</sub>)<sub>2</sub>], abbreviated as TBA[PW<sub>4</sub>]) were compared as catalysts for the oxidative desulfurization of a multicomponent model diesel (2000 ppm S). The oxidative desulfurization studies (ODS) were performed using solvent-free systems and aqueous H<sub>2</sub>O<sub>2</sub> as oxidant. The nature of the cation in the PW<sub>11</sub> catalyst showed to have an important influence on the catalytic performance. In fact, the PW<sub>11</sub>-hybrid catalysts showed higher catalytic efficiency than the peroxo-compound TBA[PW<sub>4</sub>], known as Venturello compound. TBA[PW<sub>11</sub>] revealed a remarkable desulfurization performance with 96.5% of sulfur compounds removed in the first 130 min. The reusability and stability of the catalyst were also investigated for ten consecutive ODS cycles without loss of activity. A treated clean diesel could be recovered without sulfur compounds by performing a final liquid/liquid extraction diesel/EtOH:H<sub>2</sub>O mixture (1:1) after the catalytic oxidative step.
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