Abstract: Nitrogen-containing heterocyclic compounds in FCC feedstock, which have strong adsorption capacity and diffusion resistance, are important factors for the poisoning and deactivation of zeolite catalysts. In this paper, two nitrogen-containing heterocyclic compounds, pyridine and piperidine, and two cyclic hydrocarbons with similar structures, benzene and cyclohexane, were selected as model compounds, and the adsorption behaviors of the four compounds on H-FAU zeolite channels and acid sites were investigated by GCMC and DFT methods at 298K. The results showed that the four molecules were mainly distributed in the supercage, and the distribution of two of them was more concentrated. The order of adsorption energy was: piperidine > pyridine > benzene > cyclohexane, and the adsorption of nitrides was chemical adsorption, while benzene and cyclohexane was physically adsorpted. The results of charge density maps revealed that the charge transfer occurs in different degrees between two alkali nitrogen molecules and H protons. The results provide theoretical guidance for the study of nitrogen poisoning mechanism of zeolite catalyst.

Key words: nitride, H-FAU zeolite, GCMC, DFT, adsorption