Title: New evidence for precursor species in the formation of MFI zeolite in the tetrapropylammonium hydroxide-tetraethyl orthosilicate-water system
Authors: Kirschhock, Christine ×
Kremer, Sebastien
Grobet, Pierre
Jacobs, Pierre
Martens, Johan #
Issue Date: 2002
Series Title: The journal of physical chemistry. B, Condensed matter, materials, surfaces, interfaces & biophysical vol:106 issue:19 pages:4897-4900
Conference: date:Katholieke Univ Leuven, Ctr Oppervlaktechem Katalyse, B-3001 Louvain, Belgium
Abstract: Tetraethyl orthosilicate was hydrolyzed and polymerized in concentrated aqueous tetrapropylammonium (TPA) hydroxide solution at 0 and 10 degreesC and room temperature. The formation of silicate oligomers involved in the TPA-mediated self-assembly process of colloidal Silicalite-1 was investigated using Si-29 NMR. A pentacyclic dodecamer with four edge-sharing five-rings on a four-ring was detected as a new intermediate in the formation of Silicalite-1 zeolite. The formation of this pentacyclic dodecamer with a curved inner hydrophobic silicon dioxide surface is a new example of the structure-directing action of TPA. The temperature was found to be a key parameter with respect to the transformation of the intermediates with 11 and 12 Si atoms. At 0 and 10 degreesC, the tetracyclic undecamer having three five-rings on a four-ring was converted into the pentacyclic dodecamer by insertion of one additional silicate unit. At these low temperatures, it slowly underwent an intramolecular condensation and formation of capped double five-ring not leading to Silicalite-1 formation. At room temperature, three pentacyclic dodecamers rapidly condensed into the Silicalite-1 precursor. The involvement of the pentacyclic dodecamer in the self-assembly process offers an explanation for the absence of systematically missing T-sites in colloidal Silicalite-1.
ISSN: 1520-6106
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
× corresponding author
# (joint) last author

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