Enhanced Resolution of Aluminum and Proton Sites in the Molecular Sieve SAPO-37 by 27Al Multiple Quantum Magic Angle Spinning and 1H Spin Echo Editing NMR

Autor:	Piet J. Grobet, Tie-Hong Chen, and Bart H. Wouters
Rok vydání:	1999
Předmět:	Tetramethylammonium Proton Resolution (electron density) Analytical chemistry Nuclear magnetic resonance spectroscopy Molecular sieve Spectral line Surfaces Coatings and Films chemistry.chemical_compound chemistry Materials Chemistry Magic angle spinning Spin echo Physical and Theoretical Chemistry
Zdroj:	The Journal of Physical Chemistry B. 103:6179-6184
ISSN:	1520-5207 1520-6106
DOI:	10.1021/jp990215z
Popis:	The aluminum coordination state of the molecular sieve SAPO-37 has been studied by 27Al multiple quantum (MQ) magic angle spinning (MAS) NMR spectroscopy. Although the 1D 27Al MAS NMR spectra of the aluminum sites show complex patterns, the 2D 3Q MAS NMR spectra of SAPO-37 samples, submitted to different treatments, lead to the detection of four distinct framework Al species in the as-synthesized sample, i.e., (i) tetrahedral Al sites with four phosphorus atoms, (ii) tetrahedral Al sites with one (or more) Si as nearest neighbors interacting with tetrapropylammonium (TPA), and Al coordinated with (iii) tetramethylammonium (TMA) or (iv) water. Also, the Al environments with or without Si neighbors are distinguished for the first time in calcined, template-free H−SAPO-37. By use of 1H spin echo editing MAS NMR experiments, a new proton signal at 3.4 ppm is observed in the calcined H−SAPO-37. By 1H{27Al} and 1H{31P} spin echo double-resonance experiments, this new signal is assigned to a kind of framework Al...
Databáze:	OpenAIRE
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