Ultrasound-Assisted Oxidative Desulfurization/Denitrification of Liquid Fuels with Solid Oxidants

The restrictions placed on ultralow sulfur content in diesel fuels by stringent legislation have led to the search for alternative cost-effective and complementary methods for the deep desulfurization of fossil-fuel-derived oil. Current technology for oxidative fuel desulfurization/denitrification is hampered by mass-transfer efficiency, post-treatment purification, and process costs. Owing to their mild operative conditions, ultrasonic-assisted oxidative desulfurization (UAOD) processes are currently a hot investigation topic. In this piece of work, we have applied UAOD to two model compounds, dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT), as well as a mild hydrotreated diesel feedstock, using a number of different solid oxidants, including Oxone, sodium persulfate, and potassium superoxide. The oxidized organic sulfur compounds (sulfones) have been extracted using a suitable polar solvent or adsorbent. Oxone was the most efficient of all of the solid oxidants tested under a high-intensity ultrasound. After 30 min of sonication, this protocol enabled the consistent reduction of S and N contents in treated diesel to less than 10 and 2 ppm, respectively.