Investigation of 27Al‐NMR chemical shifts in zeolites of the faujasite type
Investigation of 27Al‐NMR chemical shifts in zeolites of the faujasite type
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八面沸石型沸石的 27Al-NMR 化学位移研究
DOI：
10.1002/crat.19810160322
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发表时间：
1981
期刊：
影响因子：
--
通讯作者：
H. Behrens
中科院分区：
文献类型：
--
作者：
D. Freude;H. Behrens
铝硅酸盐中铝的化学键与这些固体的结构有关，特别是对于沸石，它影响它们的催化性能。为了解释固体的27 Al-NMR谱，必须考虑核四极矩与核位置处的电场梯度之间的四极相互作用、由于电子壳层对外部磁场的屏蔽而引起的共振的化学位移以及核之间的偶极-偶极相互作用。在我们的工作中，我们希望通过测量共振位移的平均值来获得有关A型沸石中铝分布的一些信息，如果四极相互作用和偶极-偶极相互作用对线宽的贡献可以减少到足够低的值，那么这是可能的。关于沸石的结构，参见例如BARRER（特别是关于八面沸石PFELFER）。沸石粉末样品中的11 Al-NMR（关于四极相互作用对沸石中的NMR谱线形状的影响，参见LECHERT）的特征在于对应于具有磁量子数+1/2和-1/2的能级之间的跃迁的单条谱线，并且该谱线被四极相互作用强烈地加宽到二级。线宽θ v1，θ v2（半高处的宽度）由下式给出：
The chemical bond of aluminum in aluminosilicates is related to the structure of these solids and particularly, for zeolites it affects their catalytic properties. In order to interpret the 27Al-NMR-spectra of solids one has to consider the quadrupole interaction between the nuclear quadrupole moment and the electric field gradient at the nucleus site, the chemical shift of the resonance due to the shielding of the external magnetic field by the electron shell and the dipole-dipole interaction between the nuclei. In our work we want to get some information about the aluminium distribution in A-zeolites by measuring the mean value of the resonance shift which is possible if the contribution of the quadrupole interaction and of the dipole-dipole interaction to the line width can be reduced to a sufficiently low value. Concerning the structure of zeolites see e.g. BARRER (especially about faujasites PFELFER). The ,'Al-NMR in zeolite powder samples (regarding influence of the quadrupole interaction on the NMR- line shape in zeolites see LECHERT) is characterized by a single line which corresponds to the transitions between the energy levels with magnetic quantum numbers + 1/2 and -1/2 and which is strongly broadened by the quadrupole interaction to second order. The line width 6v1,, (width at half heigh) is given by