Hledat publikace

The consumption of diesel fuel is increasing and the quality requirements (i.e. content of sulfur and aromatics) are becoming stricter. The secondary processes for deeper conversion of crude oil produce wide spectra of middle distillates. These fractions do not reach quality of the primary (straight-run) products from crude oil distillation. They contain higher levels of sulfur, nitrogen and aromatic compounds with lower activity in hydrorefining. The possibility of using the secondary distillates in the production of high quality diesel fuel (EN-590) on the existing hydrodesulfurization (HDS) catalysts is limited. The investigation was focused on the possibility of deep removal of sulfur and aromatics from secondary middle distillates using hydrocracking (HCK) process. The process was tested on continuous pilot plant unit with commercial HCK catalyst. The feedstock was a mixture of straight-run distillate having 25 wt. % secondary middle distillates (light cycle oil from FCC (LCO), gas oil from thermal cracking (GO-VBU) and C9 fraction from steam cracking). The effect of pressure on hydrodesulfurization (HDS) and hydrodearomatization (HDA) was studied. The experiments were carried out at temperature 360 °C and pressure of 18 - 14 - 10 - 6 and 4.5 MPa. The yield of the diesel fraction 200-360 °C and its quality were the main objectives. The diesel fractions were evaluated in terms of their use for diesel blending. The efficiency of HDS using the HCK catalyst was higher than 99.9 wt. %. Conversely, the efficiency of HDA really depends on the reaction pressure. The removal of aromatics was about 30 wt. % at the pressure 4.5 MPa. At the pressure 10 MPa aromatic hydrocarbons were removed with efficiency around 80 wt. %. A further increase in the reaction pressure did not influence the degree of aromatics removal.