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Si-29 NMR and UV-raman investigation of initial oligomerization reaction pathways in acid-catalyzed silica sol-gel chemistry

Anouschka Depla, David Lesthaeghe UGent, Titus S van Erp, Alexander Aerts, Kristof Houthoofd, Fengtao T Fan, Can Li, Veronique Van Speybroeck UGent, Michel Waroquier UGent and Christine EA Kirschhock, et al. (2011) JOURNAL OF PHYSICAL CHEMISTRY C. 115(9). p.3562-3571
abstract
The initial molecular steps of the acid-catalyzed silica sol-gel process departing from tetraethylorthosilicate (TEOS) were investigated by in situ Si-29 NMR and UV-Raman spectroscopy. The use of a substoichiometric H2O:TEOS molar ratio (r-value 0.2-1.2) slowed the silicate oligomerization reaction and allowed unraveling the initial steps of silica condensation. Molecular modeling confirmed Raman signal and Si-29 NMR shift assignment. A comprehensive listing of all Raman and Si-29 NMR assignments is provided, including unique Raman assignments of cyclosilicates and the linear tetramer. The combination of experiment and modeling allowed an analysis of the reaction kinetics. The derived kinetic model and the experimental observation both revealed that the H2O:TEOS molar ratio had a strong influence on the reaction kinetics but not on the reaction pathways. The multianalytical approach led to development of an oligomerization scheme. As dominant oligomerizations, chain growth, cyclodimerization, and branching were identified. Under the investigated conditions, chains did not grow longer than pentamer, and ring sizes were limited to 6-rings. Chains of 4 Si atoms and 4-rings were abundant species. Branched rings and chains were formed by attachment of dimers and trimers. Gelation proceeded from branched 4-rings and branched chains with limited hydroxyl functionalities.
Please use this url to cite or link to this publication:
author
organization
year
type
journalArticle (original)
publication status
published
subject
keyword
VIBRATIONAL-SPECTRA, CONTROLLED-RELEASE, AMORPHOUS MICROPOROUS SILICA, FAUJASITIC ZEOLITES, HYDROLYSIS REACTION, SYNTHESIS MECHANISM, SI/AL RATIO, SPECTROSCOPY, FRAMEWORK, POLYMERIZATION
journal title
JOURNAL OF PHYSICAL CHEMISTRY C
J. Phys. Chem. C
volume
115
issue
9
pages
3562 - 3571
Web of Science type
Article
Web of Science id
000287833200008
JCR category
MATERIALS SCIENCE, MULTIDISCIPLINARY
JCR impact factor
4.805 (2011)
JCR rank
23/229 (2011)
JCR quartile
1 (2011)
ISSN
1932-7447
DOI
10.1021/jp109901v
language
English
UGent publication?
yes
classification
A1
copyright statement
I have transferred the copyright for this publication to the publisher
id
1192006
handle
http://hdl.handle.net/1854/LU-1192006
date created
2011-03-21 10:04:59
date last changed
2011-04-18 14:25:47
@article{1192006,
  abstract     = {The initial molecular steps of the acid-catalyzed silica sol-gel process departing from tetraethylorthosilicate (TEOS) were investigated by in situ Si-29 NMR and UV-Raman spectroscopy. The use of a substoichiometric H2O:TEOS molar ratio (r-value 0.2-1.2) slowed the silicate oligomerization reaction and allowed unraveling the initial steps of silica condensation. Molecular modeling confirmed Raman signal and Si-29 NMR shift assignment. A comprehensive listing of all Raman and Si-29 NMR assignments is provided, including unique Raman assignments of cyclosilicates and the linear tetramer. The combination of experiment and modeling allowed an analysis of the reaction kinetics. The derived kinetic model and the experimental observation both revealed that the H2O:TEOS molar ratio had a strong influence on the reaction kinetics but not on the reaction pathways. The multianalytical approach led to development of an oligomerization scheme. As dominant oligomerizations, chain growth, cyclodimerization, and branching were identified. Under the investigated conditions, chains did not grow longer than pentamer, and ring sizes were limited to 6-rings. Chains of 4 Si atoms and 4-rings were abundant species. Branched rings and chains were formed by attachment of dimers and trimers. Gelation proceeded from branched 4-rings and branched chains with limited hydroxyl functionalities.},
  author       = {Depla, Anouschka and Lesthaeghe, David and van Erp, Titus S and Aerts, Alexander and Houthoofd, Kristof and Fan, Fengtao T and Li, Can and Van Speybroeck, Veronique and Waroquier, Michel and Kirschhock, Christine EA and Martens, Johan A},
  issn         = {1932-7447},
  journal      = {JOURNAL OF PHYSICAL CHEMISTRY C},
  keyword      = {VIBRATIONAL-SPECTRA,CONTROLLED-RELEASE,AMORPHOUS MICROPOROUS SILICA,FAUJASITIC ZEOLITES,HYDROLYSIS REACTION,SYNTHESIS MECHANISM,SI/AL RATIO,SPECTROSCOPY,FRAMEWORK,POLYMERIZATION},
  language     = {eng},
  number       = {9},
  pages        = {3562--3571},
  title        = {Si-29 NMR and UV-raman investigation of initial oligomerization reaction pathways in acid-catalyzed silica sol-gel chemistry},
  url          = {http://dx.doi.org/10.1021/jp109901v},
  volume       = {115},
  year         = {2011},
}

Chicago
Depla, Anouschka, David Lesthaeghe, Titus S van Erp, Alexander Aerts, Kristof Houthoofd, Fengtao T Fan, Can Li, et al. 2011. “Si-29 NMR and UV-raman Investigation of Initial Oligomerization Reaction Pathways in Acid-catalyzed Silica Sol-gel Chemistry.” Journal of Physical Chemistry C 115 (9): 3562–3571.
APA
Depla, A., Lesthaeghe, D., van Erp, T. S., Aerts, A., Houthoofd, K., Fan, F. T., Li, C., et al. (2011). Si-29 NMR and UV-raman investigation of initial oligomerization reaction pathways in acid-catalyzed silica sol-gel chemistry. JOURNAL OF PHYSICAL CHEMISTRY C, 115(9), 3562–3571.
Vancouver
1.
Depla A, Lesthaeghe D, van Erp TS, Aerts A, Houthoofd K, Fan FT, et al. Si-29 NMR and UV-raman investigation of initial oligomerization reaction pathways in acid-catalyzed silica sol-gel chemistry. JOURNAL OF PHYSICAL CHEMISTRY C. 2011;115(9):3562–71.
MLA
Depla, Anouschka, David Lesthaeghe, Titus S van Erp, et al. “Si-29 NMR and UV-raman Investigation of Initial Oligomerization Reaction Pathways in Acid-catalyzed Silica Sol-gel Chemistry.” JOURNAL OF PHYSICAL CHEMISTRY C 115.9 (2011): 3562–3571. Print.