Rapid oxidation of dibenzothiophene in model fuel under ultrasound irradiation

Abstract

An experimental investigation was conducted on the ultrasound-assisted oxidative desulfurization (UAOD) of a model sulfur compound (i.e., dibenzothiophene) in toluene as a model light fuel oil. Hydrogen peroxide–formic acid was used as the oxidation system. The main aim of the present work was to reduce the required reaction time of this oxidation system using ultrasound irradiation. Response surface methodology, Box–Behnken design, has been applied to find the optimum conditions of the UAOD process and also to study the influences of various operating parameters. A reasonable mathematical model was obtained for the prediction of sulfur conversion. More than 97 % sulfur conversion was achieved under the optimum conditions (i.e., oxidant to sulfur molar ratio of 26.7, acid to sulfur molar ratio of 74.6, ultrasound power per fuel oil volume of 7 W/cm3, and temperature of 50 °C). It should be noted that 95 % sulfur conversion was achieved in only 80 s sonication under the optimum reaction conditions through generation of very fine emulsion between the aqueous and organic phases. This low reaction time improves the performance of the present oxidation system in industrial applications.