Abstract: The coordination status of Al atom in MFI type shape selective zeolites used in FCC catalysts and the relationship of Al atom coordination with the acidity of zeolite were investigated in this paper. Results showed that with the increase of Fe, P and RE contents in zeolite samples, the framework tetracoordinated Al atoms increase, as well as the non-framework pentacoordinated and hexacoordinated Al atoms increase, thus the acid density of the zeolite increases. However, the total amount of Br?nsted acid increases and the total amount of Lewis acid decreases, which indicates that the framework tetracoordinated Al atoms relate with the formation of weak Br?nsted acid sites, the non-framework pentacoordinated and hexacoordinated Al atoms associate with the formation of strong Br?nsted acid sites, and the non-framework low coordinated Al atoms effect the formation of Lewis acid sites.

Key words: FCC Catalysts, Shape-selecting Zeolites, Acidity, coordination