Environment

Sulphur is a natural compound of crude oil and it appears in different concentrations depending on the source of the crude oil. It can be as high 6 vol. %. The sulphur is chemically bound to the hydrocarbons of the oil. The binding energy is quite high which makes it so difficult and energy demanding to separate the sulphur from the hydrocarbons. During the combustion process inside the engine the sulphur is oxidized to SO₂ (app. 95 to 98 %) and SO₃ (app. 2 to 5 %).

A fraction of the SO_x reacts to sulfates and turns into particular matter but the major part appears as gaseous SO₂ and SO₃ in the exhaust gas.