Title: Combined in situ Si-29 NMR and small-angle X-ray scattering study of precursors in MFI zeolite formation from silicic acid in TPAOH solutions
Authors: Houssin, Christophe ×
Kirschhock, Christine
Magusin, Pieter
Mojet, BL
Grobet, Pierre
Jacobs, Pierre
Martens, Johan
van Santen, RA #
Issue Date: 2003
Series Title: Physical Chemistry Chemical Physics vol:5 issue:16 pages:3518-3524
Conference: date:Eindhoven Univ Technol, Schuit Inst Catalysis, NL-5600 MB Eindhoven, Netherlands; Katholieke Univ Leuven, Ctr Oppervlaktechem & Katalyse, B-3001 Louvain, Belgium
Abstract: Silicic acid powder was dissolved and polymerized in a concentrated aqueous tetrapropylammonium (TPA) hydroxide solution at room temperature. Two complementary techniques were employed to follow this process leading to silicalite-1 zeolite upon heating. The formation of small silicates and specific oligomers involved in the assembly of silicalite-1 nanoprecursors was investigated using Si-29 NMR. Small-angle X-ray scattering (SAXS) was used to follow processes at a colloidal level. Dissolution and polymerization of silicic acid could then be related to events occurring at both molecular and colloidal scales. The appearance of very well-defined colloidal particles was linked to a specific intermediate already observed in systems using an organic and monomeric silica source. In situ time-resolved ultra-small-angle X-ray scattering (USAXS) using synchrotron radiation showed a linear growth of the average crystal diameter, which was slower than of that encountered in Na+ containing synthesis mixtures. Using the results presented here, we propose a mechanism describing the TPA-mediated self-assembly of silicalite-1 from silicic acid powder as silica source. This model is in agreement with rising evidence of a common mechanism involving nanoblock aggregation for organic mediated crystallization of high-silica zeolites.
ISSN: 1463-9076
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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