PMID: 9550343Apr 29, 1998Paper

1H/27Al TRAPDOR NMR studies on aluminum species in dealuminated zeolites

Solid State Nuclear Magnetic Resonance
Feng DengChaohui Ye

Abstract

Aluminum species in several dealuminated zeolites (ultrastable HY, HZSM-5 and mordenite) were investigated in detail by means of the newly introduced 1H/27Al TRAPDOR method in combination with 27Al MAS NMR, and the quadrupole coupling constants (Q[CC]s) for aluminum atoms associated with these species were obtained. A signal at ca. 6.8 ppm, due to water molecules adsorbed on Lewis acid sites, was observed in the 1H MAS spectra for all the three zeolites. The TRAPDOR NMR provides direct evidence that there is a strong interaction between the adsorbed water molecules and the aluminum atoms of the Lewis-acid sites. The Q(CC) values for this aluminum species of 8.3, 6.7 and 11.3 MHz were determined from the TRAPDOR profiles for the ultrastable HY, HZSM-5 and mordenite zeolites, respectively. The Q(CC)s calculated from the TRAPDOR curves are usually larger than 10 MHz for both Bronsted-acid sites (SiOHAI) and non-framework aluminum species in the three zeolites. Three narrow peaks at 54, 30 and 0 ppm are separately superimposed on a broad hump in the 27Al MAS spectra of the three dehydrated zeolites, while the latter is associated with the 'NMR invisible' Al. The NMR experimental results suggest that the three kinds of aluminum spec...Continue Reading

Citations

Feb 6, 2002·Chemistry : a European Journal·Ding MaSteve C F Au-Yeung
Jul 13, 2018·Chemistry : a European Journal·Ana PalčićValentin Valtchev
Mar 4, 2020·Chemistry : a European Journal·Marjolein E Z VelthoenBert M Weckhuysen
Mar 5, 2021·The Journal of Physical Chemistry Letters·Ke GongGuangjin Hou
Jun 2, 2016·Progress in Nuclear Magnetic Resonance Spectroscopy·Mohamed HaouasCharlotte Martineau
Nov 23, 2021·The Journal of Physical Chemistry Letters·Zichun WangJun Huang

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