Design rules of ionic liquids tasked for highly efficient fuel desulfurization by mild oxidative extraction

- Ionic liquids comprise low basicity/nucleophilicity anions and hydrophilic cations.
- [Choline][Tf2N]-V2O5 system afforded quantitative removal of sulfur compounds.
- [Choline][Tf2N] is a low-cost solvent with potential for large-scale desulfurization.

The deep desulfurization of petroleum-based fuels using oxidative extraction processes has been hampered by the lack of suitable solvent systems and by the poor availability of inexpensive and efficient catalysts. As a strategy to address this limitation, the present study evaluates a number of hydrophilic and hydrophobic ionic liquids (ILs) for the oxidative extraction of dibenzothiophene (DBT) and other aromatic sulfur compounds (e.g., thiophene, TS, benzothiophene, BT, and 4,6-dimethyldibenzothiophene, DMDBT) from n-octane using H2O2 as the oxidant and V2O5 as the catalyst. Our findings are significant for petroleum desulfurization and suggest that ILs for effective sulfur removal will typically comprise low basicity/nucleophilicity anions paired to cations possessing some hydrophilic character. Among a number of suitable ILs identified for this application, [Choline][Tf2N] is particularly promising as a relatively low-cost solvent ideal for use in oxidative extraction to desulfurize fuel. The [Choline][Tf2N]-V2O5 system afforded essentially quantitative removal of DBT, BT, and DMDBT at room temperature, even for initial sulfur levels as high as 3000 ppm. This advance enables a highly efficient and cost-effective desulfurization process that has a promising industrial application for producing ultra-low-sulfur fuel.

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