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Title: 27 Al MAS NMR Studies of HBEA Zeolite at Low to High Magnetic Fields

Abstract

27Al single pulse (SP) MAS NMR spectra of HBEA zeolites with high Si/Al ratios of 71 and 75 were obtained at three magnetic field strengths of 7.05, 11.75 and 19.97 T. High field 27Al MAS NMR spectra acquired at 19.97 T show significantly improved spectral resolution, resulting in at least two well-resolved tetrahedral-Al NMR peaks. Based on the results obtained from 27Al MAS and MQMAS NMR acquired at 19.97 T, four different quadrupole peaks are used to deconvolute the 27Al SP MAS spectra acquired at vari-ous fields by using the same set of quadrupole coupling constants, asymmetric parameters and relative integrated peak intensities for the tetrahedral Al peaks. The line shapes of individual peaks change from typical quadrupole line shape at low field to essentially symmetrical line shapes at high field. We demonstrate that for fully hydrated HBEA zeolites the effect of second order quadrupole interaction can be ignored and quantitative spectral analysis can be performed by directly fitting the high field spectra using mixed Gaussian/Lorentzian line shapes. Also, the analytical steps described in our work allow direct assignment of spectral intensity to individual Al tetrahedral sites (T-sites) of zeolite HBEA. Finally, the proposed concept is suggested generally applicable tomore » other zeo-lite framework types, thus, allowing a direct probing of Al distributions by NMR spectroscopic methods in zeolites with high confi-dence.« less

Authors:
ORCiD logo; ORCiD logo; ; ORCiD logo; ; ; ORCiD logo; ORCiD logo
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1368112
Report Number(s):
PNNL-SA-125685
Journal ID: ISSN 1932-7447; 48810; KC0302010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry. C; Journal Volume: 121; Journal Issue: 23
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Environmental Molecular Sciences Laboratory

Citation Formats

Hu, Jian Zhi, Wan, Chuan, Vjunov, Aleksei, Wang, Meng, Zhao, Zhenchao, Hu, Mary Y., Camaioni, Donald M., and Lercher, Johannes A.. 27 Al MAS NMR Studies of HBEA Zeolite at Low to High Magnetic Fields. United States: N. p., 2017. Web. doi:10.1021/acs.jpcc.7b03517.
Hu, Jian Zhi, Wan, Chuan, Vjunov, Aleksei, Wang, Meng, Zhao, Zhenchao, Hu, Mary Y., Camaioni, Donald M., & Lercher, Johannes A.. 27 Al MAS NMR Studies of HBEA Zeolite at Low to High Magnetic Fields. United States. doi:10.1021/acs.jpcc.7b03517.
Hu, Jian Zhi, Wan, Chuan, Vjunov, Aleksei, Wang, Meng, Zhao, Zhenchao, Hu, Mary Y., Camaioni, Donald M., and Lercher, Johannes A.. Thu . "27 Al MAS NMR Studies of HBEA Zeolite at Low to High Magnetic Fields". United States. doi:10.1021/acs.jpcc.7b03517.
@article{osti_1368112,
title = {27 Al MAS NMR Studies of HBEA Zeolite at Low to High Magnetic Fields},
author = {Hu, Jian Zhi and Wan, Chuan and Vjunov, Aleksei and Wang, Meng and Zhao, Zhenchao and Hu, Mary Y. and Camaioni, Donald M. and Lercher, Johannes A.},
abstractNote = {27Al single pulse (SP) MAS NMR spectra of HBEA zeolites with high Si/Al ratios of 71 and 75 were obtained at three magnetic field strengths of 7.05, 11.75 and 19.97 T. High field 27Al MAS NMR spectra acquired at 19.97 T show significantly improved spectral resolution, resulting in at least two well-resolved tetrahedral-Al NMR peaks. Based on the results obtained from 27Al MAS and MQMAS NMR acquired at 19.97 T, four different quadrupole peaks are used to deconvolute the 27Al SP MAS spectra acquired at vari-ous fields by using the same set of quadrupole coupling constants, asymmetric parameters and relative integrated peak intensities for the tetrahedral Al peaks. The line shapes of individual peaks change from typical quadrupole line shape at low field to essentially symmetrical line shapes at high field. We demonstrate that for fully hydrated HBEA zeolites the effect of second order quadrupole interaction can be ignored and quantitative spectral analysis can be performed by directly fitting the high field spectra using mixed Gaussian/Lorentzian line shapes. Also, the analytical steps described in our work allow direct assignment of spectral intensity to individual Al tetrahedral sites (T-sites) of zeolite HBEA. Finally, the proposed concept is suggested generally applicable to other zeo-lite framework types, thus, allowing a direct probing of Al distributions by NMR spectroscopic methods in zeolites with high confi-dence.},
doi = {10.1021/acs.jpcc.7b03517},
journal = {Journal of Physical Chemistry. C},
number = 23,
volume = 121,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}