X-ray absorption spectroscopic study on the structure and crystallization of Ga-containing MFI-type zeolites

Research output: Contribution to journalArticleResearchpeer review

Authors

  • Peter Behrens
  • Hendrik Kosslick
  • Anh Tuan Vu Anh Tuan
  • Michael Fröba
  • Frank Neissendorfer

External Research Organisations

  • University of Konstanz
  • Leibniz Institute for Catalysis at the University of Rostock (LIKAT)
  • Universität Hamburg
  • University of Potsdam
View graph of relations

Details

Original languageEnglish
Pages (from-to)433-441
Number of pages9
JournalMicroporous Materials
Volume3
Issue number4-5
Publication statusPublished - Jan 1995
Externally publishedYes

Abstract

The local environment of the Ga atoms in a series of gallosilicates with MFI structure as well as in the dried synthesis gel has been investigated by GaK XANES and EXAFS. In fully crystallized gallosilicate MFI samples, Ga is tetrahedrally coordinated by oxygen atoms with a GaO bond distance of 1.83 Å. Lack of order beyond the first coordination shell is in agreement with Ga located in several different crystallographic sites of the zeolite-type framework. For the gel, the same oxygen coordination is observed for the first coordination shell. As expected for the amorphous gel, no order beyond the first coordination shell is detected. Thus, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) cannot differentiate between tetrahedrally coordinated Ga atoms in a gel phase and Ga atoms incorporated into the framework. Inspection of a series of samples prepared with different crystallization times and with Si Ga ratios>40 show that during crystallization framework and extra-framework Ga remain in tetrahedral coordination. A sample with a low Si Ga ratio of 19 in the gel, a value far below the so far observed maximum Ga framework content of Si Ga≈40, contains also octahedral Ga after prolonged hydrothermal treatment. A quantitative evaluation shows that extra-framework Ga in gallosilicate MFI samples occurs in both tetrahedral and octahedral coordination. This result on the nature of extra-framework Ga is of importance, since these Ga species are believed to play a decisive role in catalytic processes on gallosilicate MFI-type solids.

Keywords

    Extended X-ray absorption fine structure, Extra-framework gallium, Gallosilicate, MFI, X-ray absorption near edge structure

ASJC Scopus subject areas

Cite this

X-ray absorption spectroscopic study on the structure and crystallization of Ga-containing MFI-type zeolites. / Behrens, Peter; Kosslick, Hendrik; Vu Anh Tuan, Anh Tuan et al.
In: Microporous Materials, Vol. 3, No. 4-5, 01.1995, p. 433-441.

Research output: Contribution to journalArticleResearchpeer review

Behrens P, Kosslick H, Vu Anh Tuan AT, Fröba M, Neissendorfer F. X-ray absorption spectroscopic study on the structure and crystallization of Ga-containing MFI-type zeolites. Microporous Materials. 1995 Jan;3(4-5):433-441. doi: 10.1016/0927-6513(94)00054-Y
Behrens, Peter ; Kosslick, Hendrik ; Vu Anh Tuan, Anh Tuan et al. / X-ray absorption spectroscopic study on the structure and crystallization of Ga-containing MFI-type zeolites. In: Microporous Materials. 1995 ; Vol. 3, No. 4-5. pp. 433-441.
Download
@article{b6c98ce624774aaeb3f95b81baf60ff8,
title = "X-ray absorption spectroscopic study on the structure and crystallization of Ga-containing MFI-type zeolites",
abstract = "The local environment of the Ga atoms in a series of gallosilicates with MFI structure as well as in the dried synthesis gel has been investigated by GaK XANES and EXAFS. In fully crystallized gallosilicate MFI samples, Ga is tetrahedrally coordinated by oxygen atoms with a GaO bond distance of 1.83 {\AA}. Lack of order beyond the first coordination shell is in agreement with Ga located in several different crystallographic sites of the zeolite-type framework. For the gel, the same oxygen coordination is observed for the first coordination shell. As expected for the amorphous gel, no order beyond the first coordination shell is detected. Thus, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) cannot differentiate between tetrahedrally coordinated Ga atoms in a gel phase and Ga atoms incorporated into the framework. Inspection of a series of samples prepared with different crystallization times and with Si Ga ratios>40 show that during crystallization framework and extra-framework Ga remain in tetrahedral coordination. A sample with a low Si Ga ratio of 19 in the gel, a value far below the so far observed maximum Ga framework content of Si Ga≈40, contains also octahedral Ga after prolonged hydrothermal treatment. A quantitative evaluation shows that extra-framework Ga in gallosilicate MFI samples occurs in both tetrahedral and octahedral coordination. This result on the nature of extra-framework Ga is of importance, since these Ga species are believed to play a decisive role in catalytic processes on gallosilicate MFI-type solids.",
keywords = "Extended X-ray absorption fine structure, Extra-framework gallium, Gallosilicate, MFI, X-ray absorption near edge structure",
author = "Peter Behrens and Hendrik Kosslick and {Vu Anh Tuan}, {Anh Tuan} and Michael Fr{\"o}ba and Frank Neissendorfer",
note = "Funding information: We thank Hasylab Desy (Hamburg, Germany) for allocating beamtime and the Hasylab staff for technical assistance. Help during the measurements from Stefanie Assmann (Universit~t Konstanz) and Karin Lochte (Universitfit Hamburg) is gratefully acknowledged. M.F. thanks the Alexander von Humboldt Foundation for a Feodor Lynen Research Fellowship.",
year = "1995",
month = jan,
doi = "10.1016/0927-6513(94)00054-Y",
language = "English",
volume = "3",
pages = "433--441",
journal = "Microporous Materials",
issn = "0927-6513",
publisher = "Elsevier",
number = "4-5",

}

Download

TY - JOUR

T1 - X-ray absorption spectroscopic study on the structure and crystallization of Ga-containing MFI-type zeolites

AU - Behrens, Peter

AU - Kosslick, Hendrik

AU - Vu Anh Tuan, Anh Tuan

AU - Fröba, Michael

AU - Neissendorfer, Frank

N1 - Funding information: We thank Hasylab Desy (Hamburg, Germany) for allocating beamtime and the Hasylab staff for technical assistance. Help during the measurements from Stefanie Assmann (Universit~t Konstanz) and Karin Lochte (Universitfit Hamburg) is gratefully acknowledged. M.F. thanks the Alexander von Humboldt Foundation for a Feodor Lynen Research Fellowship.

PY - 1995/1

Y1 - 1995/1

N2 - The local environment of the Ga atoms in a series of gallosilicates with MFI structure as well as in the dried synthesis gel has been investigated by GaK XANES and EXAFS. In fully crystallized gallosilicate MFI samples, Ga is tetrahedrally coordinated by oxygen atoms with a GaO bond distance of 1.83 Å. Lack of order beyond the first coordination shell is in agreement with Ga located in several different crystallographic sites of the zeolite-type framework. For the gel, the same oxygen coordination is observed for the first coordination shell. As expected for the amorphous gel, no order beyond the first coordination shell is detected. Thus, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) cannot differentiate between tetrahedrally coordinated Ga atoms in a gel phase and Ga atoms incorporated into the framework. Inspection of a series of samples prepared with different crystallization times and with Si Ga ratios>40 show that during crystallization framework and extra-framework Ga remain in tetrahedral coordination. A sample with a low Si Ga ratio of 19 in the gel, a value far below the so far observed maximum Ga framework content of Si Ga≈40, contains also octahedral Ga after prolonged hydrothermal treatment. A quantitative evaluation shows that extra-framework Ga in gallosilicate MFI samples occurs in both tetrahedral and octahedral coordination. This result on the nature of extra-framework Ga is of importance, since these Ga species are believed to play a decisive role in catalytic processes on gallosilicate MFI-type solids.

AB - The local environment of the Ga atoms in a series of gallosilicates with MFI structure as well as in the dried synthesis gel has been investigated by GaK XANES and EXAFS. In fully crystallized gallosilicate MFI samples, Ga is tetrahedrally coordinated by oxygen atoms with a GaO bond distance of 1.83 Å. Lack of order beyond the first coordination shell is in agreement with Ga located in several different crystallographic sites of the zeolite-type framework. For the gel, the same oxygen coordination is observed for the first coordination shell. As expected for the amorphous gel, no order beyond the first coordination shell is detected. Thus, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) cannot differentiate between tetrahedrally coordinated Ga atoms in a gel phase and Ga atoms incorporated into the framework. Inspection of a series of samples prepared with different crystallization times and with Si Ga ratios>40 show that during crystallization framework and extra-framework Ga remain in tetrahedral coordination. A sample with a low Si Ga ratio of 19 in the gel, a value far below the so far observed maximum Ga framework content of Si Ga≈40, contains also octahedral Ga after prolonged hydrothermal treatment. A quantitative evaluation shows that extra-framework Ga in gallosilicate MFI samples occurs in both tetrahedral and octahedral coordination. This result on the nature of extra-framework Ga is of importance, since these Ga species are believed to play a decisive role in catalytic processes on gallosilicate MFI-type solids.

KW - Extended X-ray absorption fine structure

KW - Extra-framework gallium

KW - Gallosilicate

KW - MFI

KW - X-ray absorption near edge structure

UR - http://www.scopus.com/inward/record.url?scp=0000897430&partnerID=8YFLogxK

U2 - 10.1016/0927-6513(94)00054-Y

DO - 10.1016/0927-6513(94)00054-Y

M3 - Article

AN - SCOPUS:0000897430

VL - 3

SP - 433

EP - 441

JO - Microporous Materials

JF - Microporous Materials

SN - 0927-6513

IS - 4-5

ER -