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Effect of Counter Ions on the Silica Oligomerization Reaction
Author(s) -
Trinh Thuat T.,
Jansen Antonius P. J.,
van Santen Rutger A.,
VandeVondele Joost,
Meijer Evert Jan
Publication year - 2009
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200900006
Subject(s) - counterion , chemistry , aqueous solution , ion , zeolite , ab initio , inorganic chemistry , protonation , molecular dynamics , reaction rate , reaction mechanism , silicate , computational chemistry , catalysis , organic chemistry
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 NH 4 + ). Ab‐initio molecular dynamics simulations have been used to construct reaction energy diagrams including transition state free energies. Contact with Li+ as well as NH 4 + increases the activation energies of the dimerization step compared to the situation in the absence of counterions. The presence of NH 4 + has no effect on consecutive oligomerization steps. Hence NH 4 + will increase the relative formation rate of larger oligomers.