Abstract: The study of reaction kinetics can provide decision-making basis for the production of “Safe, Stable, Long cycle, Full load, High quality” of the industrial catalytic cracking unit, promote the progress of catalytic cracking technology, and help deepen the understanding of reaction mechanism and reaction network. In this paper, based on the guidance of molecular refining, the digital reconstruction of molecular composition of feed oil is realized based on the structure-oriented lumping(SOL) method and advanced analytical instruments. Based on the reaction mechanism, a molecular level catalytic cracking reaction kinetics model is constructed. Combined with the reactor structure characteristics of catalytic cracking unit (MIP-CGP process), a molecular level catalytic cracking reaction process model is constructed. The effects of reaction conditions on product distribution are studied at molecular level and the optimization of catalytic cracking process is carried out by the calculation of the model. As the reaction temperature increase from 500℃ to 560℃, the content of pentene, isopentene and methyl thiophene molecules in gasoline increase, the content of methyl hexene in gasoline first increase and then decrease, and the content of butyl naphthalene, methyl phenanthrene and dimethyl benzothiophene molecules in diesel increase. It elucidates from the molecular level that low temperature contributes to the reduction of the olefins and sulfur content in gasoline and the polycyclic aromatic hydrocarbons and sulfur content in diesel. If the gasoline yield is not less than 40% and the olefin content in gasoline is not more than 18%, the reaction temperature range is 515―525℃ and the ratio of catalyst to oil range is 8.0―10.0. The catalytic cracking reactor model based on the SOL method can provide the theoretical guidance at the molecular level for the process optimization of heavy oil lightering in refineries.

Key words: molecular refining, structure-oriented lumping, catalytic cracking, reaction kinetics