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Title: Quantitatively Probing the Al Distribution in Zeolites

Abstract

The degree of substitution of Si4+ by Al3+ in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. As the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and 27Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al-distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in the HBEA150 sample has been determined from a combination of these methods. This work was supported by the U. S. Department of Energy (DOE), Office ofmore » Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1149231
Report Number(s):
PNNL-SA-100687
47841; KC0302010
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society, 136(23):8296-8306
Country of Publication:
United States
Language:
English
Subject:
aluminum; extended X-ray absorption fine structure spectroscopy; MD-EXAFS; HBEA structure; zeolite T-sites; Environmental Molecular Sciences Laboratory

Citation Formats

Vjunov, Aleksei, Fulton, John L., Huthwelker, Thomas, Pin, Sonia, Mei, Donghai, Schenter, Gregory K., Govind, Niranjan, Camaioni, Donald M., Hu, Jian Z., and Lercher, Johannes A. Quantitatively Probing the Al Distribution in Zeolites. United States: N. p., 2014. Web. doi:10.1021/ja501361v.
Vjunov, Aleksei, Fulton, John L., Huthwelker, Thomas, Pin, Sonia, Mei, Donghai, Schenter, Gregory K., Govind, Niranjan, Camaioni, Donald M., Hu, Jian Z., & Lercher, Johannes A. Quantitatively Probing the Al Distribution in Zeolites. United States. doi:10.1021/ja501361v.
Vjunov, Aleksei, Fulton, John L., Huthwelker, Thomas, Pin, Sonia, Mei, Donghai, Schenter, Gregory K., Govind, Niranjan, Camaioni, Donald M., Hu, Jian Z., and Lercher, Johannes A. Wed . "Quantitatively Probing the Al Distribution in Zeolites". United States. doi:10.1021/ja501361v.
@article{osti_1149231,
title = {Quantitatively Probing the Al Distribution in Zeolites},
author = {Vjunov, Aleksei and Fulton, John L. and Huthwelker, Thomas and Pin, Sonia and Mei, Donghai and Schenter, Gregory K. and Govind, Niranjan and Camaioni, Donald M. and Hu, Jian Z. and Lercher, Johannes A.},
abstractNote = {The degree of substitution of Si4+ by Al3+ in the oxygen-terminated tetrahedra (Al T-sites) of zeolites determines the concentration of ion-exchange and Brønsted acid sites. As the location of the tetrahedra and the associated subtle variations in bond angles influence the acid strength, quantitative information about Al T-sites in the framework is critical to rationalize catalytic properties and to design new catalysts. A quantitative analysis is reported that uses a combination of extended X-ray absorption fine structure (EXAFS) analysis and 27Al MAS NMR spectroscopy supported by DFT-based molecular dynamics simulations. To discriminate individual Al atoms, sets of ab initio EXAFS spectra for various T-sites are generated from DFT-based molecular dynamics simulations allowing quantitative treatment of the EXAFS single- and multiple-photoelectron scattering processes out to 3-4 atom shells surrounding the Al absorption center. It is observed that identical zeolite types show dramatically different Al-distributions. A preference of Al for T-sites that are part of one or more 4-member rings in the framework over those T-sites that are part of only 5- and 6-member rings in the HBEA150 sample has been determined from a combination of these methods. This work was supported by the U. S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences.},
doi = {10.1021/ja501361v},
journal = {Journal of the American Chemical Society, 136(23):8296-8306},
number = ,
volume = ,
place = {United States},
year = {Wed Jun 11 00:00:00 EDT 2014},
month = {Wed Jun 11 00:00:00 EDT 2014}
}