INFLUENCE OF STATUS OF Zn SPECIES IN Zn/ZSM-5 ON ITS CATALYTIC PERFORMANCE

Abstract

Abstract: Zn modified ZSM-5 zeolites with various Zn status were prepared by different methods （in situ hydrothermal synthesis，mechanical mixing，incipient wetness impregnation，solid-state ion exchange，and liquid phase ion exchange） and systematically investigated by X-ray diffraction（XRD），transmission electron microscope（TEM），27Al magic-angle spinning（MAS） NMR techniques. The results proved that both the in-situ hydrothermal synthesis and the liquid phase ion exchange methods could facilitate the migration of zinc species into cation site of zeolites in the form of Zn2+. The mechanical mixing and the solid-state ion exchange methods promoted the formation of extra-framework ZnO nanoparticles that were mainly located on the external surface of zeolites. While, the incipient wetness impregnation method promoted part of the Zn species into cation site of zeolites and part of the Zn species on the external surface of zeolites，simultaneously. The synergistic effect between Zn species and zeolites makes ZSM-5 zeolite modified by Zn have outstanding catalytic performance.

Key words: Zn modification, ZSM-5, cation site, ZnO, catalytic cracking

CLC Number:

References

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