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27Al&{1H} cross-polarization and ultrahigh-speed 27Al MAS NMR spectroscopy in the characterization of USY zeolites

✍ Scribed by Lars Kellberg; Magnus Linsten; Hans J. Jakobsen

Publisher
Elsevier Science
Year
1991
Tongue
English
Weight
545 KB
Volume
182
Category
Article
ISSN
0009-2614

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✦ Synopsis

41 MAS NMR spectroscopy with 'H cross-polarization is shown to be an efficient technique for distinguishing non-framework from framework Al in USY zeolites and has revealed the presence of non-framework tetrahedral Al. Field-dependent measurements and simulations show that the non-framework 30 ppm 27A1 resonance observed for USY zeolites must be considered an individual signal and not part of a second-order quadrupole lineshape as recently suggested. Ultrahigh-speed spinning (I!,= 18-20 kHz) is demonstrated to be a prerequisite for obtaining quantitative results for these systems by 2'Al MAS NMR. Finally, experimental evidence for the similarity between the non-framework Al phases in USY zeolites and steamed silica-alumina is presented.

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