Abstract: The chemical transformation of petroleum refining and the proportion of intermediate crude oil supply have a tendency to increase continuously. However, the content of heteroatoms such as sulfur, nitrogen and heavy metals in intermediate base inferior residual oil is high, and there are many hard-to-crack heavy components such as polycyclic aromatic hydrocarbons, resins and asphaltenes, which bring challenges to the way of producing more chemicals and need to be upgraded by pretreatment processes such as hydrotreating. Based on the research of heavy oil molecular level composition, hydrocarbon molecular structure and catalytic cracking reaction chemistry, it is proposed that the best raw material hydrocarbon composition structure for chemicals production is paraffin, cycloalkanes and alkylbenzenes, which needs a good residue hydroupgrading coupling with catalytic cracking. The direction of hydrogenation upgrading of intermediate residue should be super-deep hydrogenation saturation of condensed aromatic hydrocarbons and moderate cracking. The changes of hydrocarbon composition structure of intermediate base residue before and after hydrotreating characterized by molecular level showed that the polycyclic aromatic hydrocarbons, thiophene-type sulfur-containing aromatic hydrocarbons, resins and asphaltenes were directionally converted into the dominant ideal hydrocarbon structure by deep hydrotreating for producing more chemicals, such as paraffins and cycloalkanes, especially monocyclic-tricyclic cycloalkanes. Furthermore, the coupling with highly selective catalytic cracking technology can achieve the goal of producing more chemicals such as light olefins and BTX from inferior intermediate base residue.

Key words: chemicals, propylene, structure-oriented, residue hydotreating, catalytic cracking