Characterization of the gel phases on AlPO4-11 molecular sieve synthesis by solid-state NMR

Article Abstract:

Several solid-state NMR techniques are used in conjunction with powder X-ray diffraction (XRD) and FT-Raman spectroscopy to characterize the structures of the intermediate phases of AlPO4-11 molecular sieve synthesis. The evolution of the gel phases as a function of crystallization time was followed by (super 31)P and (super 27)Al magic angle spinning NMR to obtain information on the local environments of Al and P atoms and by powder-XRD to detect the long range ordering of the gel samples.

Methods, X-ray diffraction, Crystallization

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Distribution of aluminum in different periodical building units of MOR and BEA zeolites

Article Abstract:

Commercial, homemade, and dealuminated mordenites (MOR), beta (BEA) zeolites and cobalt modified BEAs are characterized by (super 29)Si and (super 27)Al solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. A detailed theoretical structure analysis enabled a deeper understanding of the origin of defect sites, the mechanism of dealumination and ion exchange through the (super 29)Si and (super 27) Al NMR analysis of Si and Al site contribution.

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Effects of adsorbate molecules on the quadrupolar interaction of framework aluminum atoms in dehydrated zeolite H,Na-Y

Article Abstract:

The effect of adsorbate molecules on the quadrupolar interaction of framework aluminum atoms with the electric field gradient in dehydrated zeolite H,Na-Y is analyzed by using [.sup.27Al] MAS NMR and [.sup.27Al] MQMAS NMR spectroscopy. The results reveal that the proton transfer is accompanied by a strong improvement of the tetrahedral symmetry of zeolite framework AlO4 tetrahedra and a decrease of the electric field gradient.

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