TRAPDOR double-resonance and high-resolution MAS NMR for structural and template studies in zeolite ZSM-5

A combination of Al-27 magic-angle spinning (MAS)/multiple-quantum (MQ) MAS, and Al-27-{N-14} TRAnsfer of Population in DOuble-Resonance (TRAPDOR) nuclear magnetic resonance (NMR) was used to study aluminium environments in zeolite ZSM-5. Al-27-{N-14} TRAPDOR experiments. in combination with N-14 NMR were employed to show that the two tetrahedral peaks observed in the Al-27 MAS/3Q-MAS spectra of as-synthesized ZSM-5 are due to aluminium atoms occupying crystallographically inequivalent T-sites. A C-13-{Al-27} TRAPDOR experiment was used to study the template, tetrapropyl ammonium bromide (TPABr), in the three-dimensional pore system of ZSM-5. The inequivalency of the methyl groups of TPA was observed in the C-13-{Al-27) TRAPDOR spectra of as-synthesized ZSM-5 and the motion of the methyl end of the propyl chain appeared to be more restricted in the sinusoidal channel than in the straight channel. (C) 2009 Elsevier Inc. All rights reserved.