The saturation of the aromatic compounds occurred, too, during the hydrogenation step, but for the better efficiency, higher pressures are needed. As it can be seen in Fig. 13, in the case of the lowest applied pressure (20 bar), the aromatic content of the product remained nearly the same as in the feedstock. This was due to the typical aromatic compounds in the feedstock gas oil fraction namely the aromatic sulphur containing molecules (like dibenzothiophenes and its derivatives). In the case of these kinds of compounds, the effective desulphurisation and aromatic saturation requires severe process parameters.