Oxidation of benzothiophene, dibenzothiophene, and methyl-dibenzothiophene by ferrate(VI)

The reduction of sulfur content in liquid fuel is of a high concern environmentally, and oxydesulfurization approaches have shown high efficiency for removing thiophene-containing compounds from the liquid fuels. The present paper investigates the oxidation of benzothiophene (BT), dibenzothiophene (DBT), and 4-methyl-dibenzothiophene (4-MDBT) by ferrate(VI). The effects of reaction conditions such as the reaction medium pH, solvent type, and adsorbent on the reactivity of ferrate(VI) with the thiophene-containing compounds were investigated. The oxidation of DBT in phosphate–acetonitrile medium was found to be highly sensitive toward the reaction pH, and the highest removal efficiency was observed at the pH 8.0. The complete conversion of BT and DBT to their corresponding sulfones by ferrate(VI) was achieved at room temperature and [ferrate(VI)]/[BT/DBT] ∼ 7.5 while this molar ratio was found to be ∼8.5 for 4-MDBT. The addition of silica gel during the reaction was applied to enhance the oxidation of DBT by ferrate(VI).