Acta Phys. -Chim. Sin. ›› 1997, Vol. 13 ›› Issue (08): 693-699.doi: 10.3866/PKU.WHXB19970804

• ARTICLE • Previous Articles     Next Articles

Study Mo/HZSM-5 Catalysts by NMR

Liu Wei-,Xu Yi-De,Li Li-Yun,Hu Hong-Bing   

  1. State Key Laborabory of Catalysis,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023|State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Wuhan Institute of Physics,Chinese Academy of Sciences,Wuhan 430071
  • Received:1996-12-16 Revised:1997-03-12 Published:1997-08-15
  • Contact: Xu Yi-De

Abstract:

By using high-resolution solid state Nuclear Magnetic Resonance spectrometer with 27Al and 29Si probes, the interaction between Mo species and HZSM-5 of Mo/HZSM-5 catalysts has been studied. The results show that there is a strong interaction between Mo species and HZSM-5zeolite. The framework aluminum in the zeolite can be easily extracted by the introduction of Mo species. The extract ability of framework aluminum by Mo species increases with increasing Mo loading and the calcination temperature. The extraction process leads to the formation of non-framework Al at first and then a new crystalline phase of Al2(MoO4)3. The catalyst, therefore, lost its catalytic activity for methane dehydrogenation and aromatization in the absence of oxygen. The MAS NMR results give us an evidence that Al2(MoO4)3 crystallites are much less active for the reaction.

Key words: 27Al and 29Si MAS-NMR, Dealuminum, Mo/HZSM-5, Al2(MoO4)3, Methane activation