Tribological investigations into modern diesel fuels and lubricity additives

Sulphur dioxide emissions from combustion engines and industry furnaces had to be reduced in order to reduce environmental damage by acid rain which is mainly caused by sulphuric acid. This was achieved by the introduction of flue gas desulphurization in industrial applications and by hydrodesulphurization of automotive fuels. For the combustion engine this had three main beneficial effects. At first, corrosion of cylinder liners caused by the formation of corrosive sulphuric acid in the combustion chamber could be alleviated. Secondly, this allowed the development of more enhanced exhaust gas aftertreatment systems, especially nitrogen oxides storage catalysts which are being deactivated by sulphur. Thirdly, the emission of particulate matter could be reduced because it is directly proportional to the fuel sulphur content. Organic sulphur compounds in crude oil are removed in refineries by hydrodesulphurization. In this process the distillation fractions are treated with hydrogen gas at pressures of 30…200 bar, with cobalt-molybdenum or nickel-molybdenum-based catalysts and temperatures of 250…400 °C. The optimization of this process in order to reduce process costs and lower sulphur contents in the product is still the objective of research and development. Apart from this conventional process new technologies like sulphur extraction by ionic liquids are the subject of investigations and assessments for industrial application.