Diesel Fuel Desulfurization. Sulfur is a common component in crude oil, where it can be present both in elementary form and in the form hydrogen sulfide and organic substances, such as disulfides, mercaptan etc. Generally, the influence of sulfur and its compounds on oil products is negative, due to its corrosive properties. That is why it is recommended to eliminate sulfur and hydrogen sulfide and limit the content of mercaptan. The content of other sulfur compounds is regulated by such parameter as “sulfur content by weight”.
The strict the requirements on sulfur content in fuel, the deeper the purification and the cost of the process. This is the reason that this chemical element is present in practically all fuels in the market.
Nevertheless, the weight part of sulfur in oil products is limited by regulations for environmental reasons. Sulfur compounds increase toxicity of exhaust gases and are under close scrutiny of environmental protection agencies.
Desulfurization begins at the stage of crude oil refining. This is achieved in the processes of catalytic hydrotreatment, biodesulfurization, oxidation of sulfur compounds by hydroperoxides etc. The content of sulfur in finished product is also one of the criteria of grading it. Euro-2 diesel fuel contains no more than 500 mg/kg of sulfur compounds, Euro-3 – 350 mg/kg, Euro-4 – 50 mg/kg and Euro-5 -10 mg/kg.