Multinuclear (27Al, 29Si, 47,49Ti) solid-state NMR of titanium substituted zeolite USY

Multinuclear solid-state NMR spectroscopy, employing Si-29 MAS,Al-27 MAS/3Q-MAS and Ti-47,Ti-49 wide-line experiments, has been used for the structural characterization of titanium substituted ultra-stable zeolite Y (Ti-USY). Al-27 MAS experiments show the presence of aluminum in four (Al-IV), five (Al-V), and six (Al-V) coordination, whereas the multiplicity within Al-IV and Al-VI is revealed by Al-27 3Q-MAS experiments. Two different tetrahedral and octahedral Al environments are resolved and their isotropic chemical shifts (delta(CS)) and second-order quadrupole interaction parameters (P-Q) have been determined by a graphical analysis of the 3Q-MAS spectra. The emergence of signal with higher intensity at -101 ppm in the Si-29 MAS spectrum of Ti-USY samples indicates the possible occurrence of Q(4)(3Si,1Ti) type silicon environments due to titanium substitution in the faujasite framework. High-field (11.74 T) operation, using a probehead specially designed to handle a large sample volume, has enabled the acquisition of Ti-47,Ti-49 static spectra and identification of the titanium environment in the zeolite. The chemical shielding and electric field gradient tensors for the titanium environment in the zeolite have been determined by a computer simulation of the quadrupolar broadened static Ti-47,Ti-49 NMR spectra. (C) 2003 Elsevier Inc. All rights reserved.