DEEP DESULFURIZATION AND AROMATICS SATURATION FOR AUTOMOTIVE GAS-OIL MANUFACTURING

The strive towards a cleaner environment has lead to low sulphur speci fications for middle distillate fuels. In addition compositional speci fications are presently debated, Thus, to meet future emission standar ds regarding, specifically, particulates emissions, the motor industry calls for improved automotive gasoil (AGO) quality. Although this gas oil quality clearly effects diesel engine emissions it must be conside red that it is less influential then engine design and maintenance. Su lphur, density and cetane number are the fuel properties having the gr eatest influence on diesel engine emissions while also aromatics and e ndpoint specifications have been defined in environmentally adopted go vernmental initiatives. This paper reviews the options which are avail able to tackle these new requirements. The high severity single stage concept (using conventional mixed sulphides catalysts) will be discuss ed in its potential to meet more severe product requirements as well a s in terms of its limitations, especially at the point of aromatics sa turation and cetane upgrading. In addition newly developed technologie s for aromatics saturation in AGO manufacturing will be reviewed and t heir potential to break the limitations of the single stage concept di scussed. As the first example of commercial scale aromatics saturation for AGO production the new Shell Middle Distillate Hydrogenation (SMD H) technology, applying a (semi) two-stage approach based on the Shell proprietary hydrogenation catalyst S-704, is described. The new S-704 catalyst is crucial in this process and allows a highly integrated mo de of operation. It is characterised by a high tolerance to S and N an d a high stability. A number of applications of this novel process are discussed, especially the production of environmentally adapted AGO f rom straight run light gasoil (SR-LGO) in Sweden, and the upgrading of cycle oils in premium quality middle distillates.