Reaction laws of polycyclic aromatic hydrocarbons and heteroatomic compounds in hydrocracking process

Based on the Structure Oriented Lumping (SOL) method, a molecular-level reaction kinetic model for hydrocracking process was established to investigate the reaction laws of polycyclic aromatic hydrocarbons (PAHs) and heteroatomic compounds in hydrocracking process and calculate the molecular compositions of hydrocracking products. Molecules showed different reaction laws due to the differences of the initial contents, the structural increments and their positions in the reaction network. Since the hydrodenitrogenation reactions of indole and carbazole homologs were more difficult to carry out than the hydrodesulfurization reactions of benzothiophene and dibenzothiophene homologues, the denitrification rate was lower than the desulphurization rate at the outlet of the hydrotreating section. When the reaction temperature of the hydrotreating section was 360 °C, the conversion rates of sulfides and nitrides were 98.4 % and 91.3 %, respectively. The increase of reaction temperature intensified the hydrogenation saturation of aromatics, the ring opening of naphthenes and the cracking of paraffins. As the reaction temperature of the hydrocracking section rose from 370 °C to 410 °C, more isomerized carbon ions were generated due to the β-position cracking of paraffins. The mass ratio of methylbutane to n-pentane in light naphtha increased from 1.29 to 3.08. The increase of reaction temperature accelerated the side chain cracking reactions of naphthenes with 4 or more carbon atoms in the side chains, and generates more naphthenes with 0 to 3 carbon atoms in the side chains. Aromatics mainly underwent the ring-by-ring hydrogenation saturation reactions in the hydrotreating section, and bicyclic aromatic hydrocarbons was significantly easier to be hydrogenated than monocyclic aromatic hydrocarbons.