Efficient Diesel Desulfurization by Novel Amphiphilic Polyoxometalate-Based Hybrid Catalyst at Room Temperature

Amphiphilic hybrid catalysts were prepared by modifying [SMo₁₂O₄₀]^2- with tetrabutylammonium bromide (TBAB), 1-butyl-3-methylimidazole bromide (BMIMBr) and octadecyl trimethyl ammonium bromide (ODAB), respectively. The prepared catalysts were characterized by IR, XRD, SEM, TG and XPS. The desulfurization performance of the catalysts was investigated in model oil and actual diesel using hydrogen peroxide (H₂O₂) as an oxidant and acetonitrile as an extractant. All catalysts exhibited favorable activity for removing sulfur compounds at room temperature. Dibenzothiophene (DBT) can be nearly completely removed using SMo₁₂O₄₀^2--organic catalysts within a short reaction time. For different sulfur compounds, the [TBA]₂SMo₁₂O₄₀ catalyst showed a better removal effect than the [BMIM]₂SMo₁₂O₄₀ and [ODA]₂SMo₁₂O₄₀ catalyst. The [TBA]₂SMo₁₂O₄₀ dissolved in extraction solvent could be reused up to five times in an oxidative desulfurization (ODS) cycle with no significant loss of activity. The [BMIM]₂SMo₁₂O₄₀ performed as a heterogeneous catalyst able to be recycled from the ODS system and maintained excellent catalytic activity. The catalysts showed a positive desulfurization effect in real diesel treatment. Finally, we described the ODS desulfurization mechanism of DBT using SMo₁₂O₄₀^2--organic hybrid catalysts. The amphiphilic hybrid catalyst cation captures DBT, while SMo₁₂O₄₀^2- reacts with the oxidant H₂O₂ to produce peroxy-active species. DBT can be oxidized to its sulfone by the action of peroxy-active species to achieve ODS desulfurization.