Oxidative Desulphurization of Diesel Fuels

Oxidative desulphurization (ODS) enables attainment of ultra-low sulphur content in diesel fuels by oxidation of refractory sulphur compounds that are difficult to remove with hydrodesulphurization when the sulphur content needs to be attained below 10 mg kg(-1). In this work, the effect of the process conditions of ultrasound-assisted ODS (using N,N-dimethylformamide and methanol as extraction solvents) on real diesel fuels was researched. The experiments were conducted in a batch reactor with hydrogen peroxide as oxidant and acetic acid as catalyst. Temperature increase, reaction time extension, and increase in the amount of dibenzothiophene (DBT) in real diesel fuels showed a positive impact on the ODS process efficiency. Comparison of ultrasound-assisted ODS and ODS in a mechanically stirred system revealed a significant reduction in reaction time. The very low sulphur concentrations (3 mg kg(-1)) in the product obtained after 30 minutes of oxidation confirmed high efficiency of the oxidative desulphurization.