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Effect of Counter Ions on the Silica Oligomerization Reaction


Trinh, T T; Jansen, A P J; van Santen, R A; VandeVondele, J; Meijer, E J (2009). Effect of Counter Ions on the Silica Oligomerization Reaction. ChemPhysChem, 10(11):1775-1782.

Abstract

The silicate oligomerization reaction is key to sol-gel chemistry and zeolite synthesis. Numerous experimental and theoretical studies have addressed the physical chemistry of silicate oligomers in the prenucleation stage of siliceous zeolite formation. Here we report a study of a silica condensation reaction in aqueous solution in the presence of counter ions (Li+ and NH4+). Ab-initio molecular dynamics simulations have been used to construct reaction energy diagrams including transition state free energies. Contact with Li+ as well as NH4+ increases the activat ion energies of the dimerization step compared to the situation in the absence of counterions. The presence of NH4+ has no effect on consecutive oligomerization steps. Hence NH4+ will increase the relative formation rate of larger oligomers.

Abstract

The silicate oligomerization reaction is key to sol-gel chemistry and zeolite synthesis. Numerous experimental and theoretical studies have addressed the physical chemistry of silicate oligomers in the prenucleation stage of siliceous zeolite formation. Here we report a study of a silica condensation reaction in aqueous solution in the presence of counter ions (Li+ and NH4+). Ab-initio molecular dynamics simulations have been used to construct reaction energy diagrams including transition state free energies. Contact with Li+ as well as NH4+ increases the activat ion energies of the dimerization step compared to the situation in the absence of counterions. The presence of NH4+ has no effect on consecutive oligomerization steps. Hence NH4+ will increase the relative formation rate of larger oligomers.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Date:9 June 2009
Deposited On:16 Dec 2009 14:14
Last Modified:05 Apr 2016 13:34
Publisher:Wiley-Blackwell
ISSN:1439-4235
Additional Information:Free access at DOI
Publisher DOI:https://doi.org/10.1002/cphc.200900006

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