Oxidation of dibenzothiophene to dibenzothiophene-sulfone using silica gel

We present a process for oxidizing dibenzothiophene (DBT) to dibenzothiophene-sulfone (DBT-sulfone) using silica gel in the presence of a hydrogen donor solvent where no oxidizing agent was necessary. The oxidation of dibenzothiophene (DBT) to dibenzothiophene-sulfone (DBT-sulfone) has been a topic of particular interest in the past few years, as a possible technique to remove sulfur from crude oil. In this manuscript we show that the oxidation of DBT to DBT-sulfone occurs using silica and does not require the addition of an external oxidizing agent. The effect of the synthesis pH and the calcination temperature on the ability of the silica to oxidize DBT to DBT-sulfone was investigated. The oxidation reactions were performed by refluxing silica with DBT in the following solvents: decahydronaphthalene, tetrahydronaphthalene, dodecane, heptane, and toluene at different temperatures. The reaction was found to work only in hydrogen-donating solvents: tetralin and decalin. HPLC results show that 80% of the original 10,000 ppm DBT was oxidized when the reaction was carried out at 160 °C in decahydronaphthalene. FTIR was used to show that the product of the reaction was DBT-sulfone, which confirmed 80% conversion of the DBT to DBT-sulfone. The product of the oxidation reaction was further identified using powder XRD.