物理化学学报 >> 1997, Vol. 13 >> Issue (08): 693-699.doi: 10.3866/PKU.WHXB19970804

研究论文 上一篇    下一篇

27Al和29Si MAS-NMR对Mo/HZSM-5催化剂的研究

刘薇,徐奕德,李丽云,胡红兵   

  1. 中国科学院大连化学物理研究所催化国家重点实验室,大连 116023|中国科学院武汉物理研究所波谱与原子分子国家重点实验室,武汉 430071
  • 收稿日期:1996-12-16 修回日期:1997-03-12 发布日期:1997-08-15
  • 通讯作者: 徐奕德

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

摘要:

使用29Si和27Al固体高分辨核磁技术对甲烷无氧芳构化催化剂Mo/HZSM-5分子筛进行了研究,发现HZSM-5分子筛本体中仅含有少量非骨架Al,Mo物种与分子筛骨架Al及骨架外Al的相互作用随Mo担载量以及焙烧温度的升高而增加,在高温焙烧下,Mo物种会使分子筛骨架严重脱铝,并且生成Al2(MoO4)3新相,最终导致分子筛骨架塌陷,催化性能下降.

关键词: Mo/HZSM-5, NMR, 脱铝, Al2(MoO4)3, 甲烷无氧活化

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