Abstract: Based on the molecular structure of diesel components, the relationship of compositions of various diesel raw materials with hydrogenation products was analyzed; the dearomatization reaction rules in the hydrotreating process of diesel components and the impacts of different hydrogenation depths on LCO recycle conversion were discussed; the different processing routes of LCO from the economic point of view were compared. The results showed that the H2 consumption of hydrogenation saturation reaction accounted for about 50% of the total hydrogen consumption of the reaction in the hydrotreating process for producing China VI standard vehicle diesel fuel. Due to high density and high content of polycyclic aromatic hydrocarbons of raw material LCO, deep dearomatization is required for the production of China VI standard diesel fuel, resulting in large hydrogen comsumption and the poor economy. The combined process of selective hydrotreating and catalytic cracking (LTAG) can reduce the hydrogenation depth and greatly decrease the hydrogen cost. The technologies such as hydroconversion to produce gasoline, hydroconversion to produce aromatics, hydrocracking mixed blending feedstock, and combined process of residue hydrocracking and catalytic cracking reycling to realize efficient utilization of LCO resources rich in aromatics.

Key words: diesel fraction processing, molecular level, catalytic cracking, hydrogenation dearomatization