Acta Phys. -Chim. Sin. ›› 2003, Vol. 19 ›› Issue (09): 805-809.doi: 10.3866/PKU.WHXB20030905

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27Al Multiple Quantum MAS NMR Study on the Distribution of Aluminium in the Zeolite MCM-22

Chen Lei;Deng Feng;Ye Chao-Hui   

  1. State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071
  • Received:2003-02-13 Revised:2003-04-08 Published:2003-09-15
  • Contact: Deng Feng E-mail:dengf@wipm.ac.cn

Abstract: The distribution of aluminum in the zeolite MCM-22 lattice has been investigated by 27Al MQ MAS NMR and quantum chemical calculation. Three different aluminum species in tetrahedral coordination were clearly observed in the 2D 5Q MAS NMR spectrum of zeolite MCM-22. From the spectrum, we can calculate the isotropic chemical shifts(δ 50.5, δ 57.3, δ 62.4 ) and the quadrupolar coupling constant (1.74, 1.68, 1.92 MHz) of the three species. The structure of MCM-22 has the 8 crystallographically distinct T sites. From the simulated 27Al 5Q MAS NMR spectrum, it is evident that 8 T sites can be divided into 3 groups. Sites T2 and T6 correspond to the signals at δ 61, δ 49, respectively; while sites T1, T3, T4, T5, T7, T8 give rise to signal atδ 56. Al is randomly distributed in the framework of MCM-22 zeolite when the Si/Al atom ratio is varied from 10 to 15.

Key words: MCM-22, Distribution of Al, NMR, MQ MAS, Quantum chemical calculation