Molecular coupling and enhancement in pyrolysis pretreatment and catalytic cracking process of vacuum residue: based on resins analysis

The effective coupling of decarbonization pretreatment of raw materials and catalytic cracking process can enhance the yield of light olefins. However, it still faces some problems such as mismatch between pyrolysis gas-oil molecules and pore structure of catalysts, which leads to the rapid reduction of catalyst activity. To solve these problems, it is important to realize the relay between pyrolysis and catalytic cracking at the molecular scale. Thus, this research first visually drew the molecular structure diagram of the raw materials (resin sub-fractions) based on the structural parameters. Then, the effect of reaction conditions on the product distribution from resins pyrolysis was investigated. The results showed that the production of light gas-oil can be maximized when the reaction temperature and heating rate are 650 oC and 1000 oC/s, respectively. There are long alkyl side chains and low degree of condensation aromatic rings in the light resin (LR) molecular structure, resulting in more light olefins, C5-C23 alkenes, and monocyclic aromatic hydrocarbons produced by LR pyrolysis. Finally, by comparing the catalytic cracking products distribution of pyrolysis gas-oil on FCC catalyst, Cat-40, Cat-80, Cat-200, and calcium aluminate catalyst, it was found that Cat-40 catalyst is beneficial for the production of light olefins and BTX due to its high surface area, acid strength and density.