Thermal characterization of the metal-silicalites obtained from aqueous nonalkaline fluoride gels
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Thermal analysis of crystalline Metallosilicalite-1 precursors with various heteroatoms was carried out in a nitrogen atmosphere. Different interactions between tetrapropylammonium species and the zeolitic environment were evidenced, depending on the type of metallic complexes in the reaction medium. The results support the mechanism of Metallosilicalite-1 formation through a condensation process from the liquid phase.
Isomorphous substitution of T element in a molecular sieve material is very interesting in order to modify its acidity or redox catalytic properties [1–6].
Normally zeolites are synthesized in hydrothermal mixtures. Alkaline hydroxides, TPABr, silica and water are typically required to obtain Silicalite-1. Recently, MFI zeolitic structures have been obtained from near-neutral nonalkaline reaction mixtures containing fluoride ions [7–8].
Using tetrapropylammonium bromide (TPABr) as a template, molecular sieve Bi-, Ce-, Cu-, Cr-, Mo-, Pb-, Sb-, Ti-, V- and W-Silicalite-1 was the only phase obtained in the presence of fluoride ions.
In this paper, it is investigated how the thermal decomposition of TPA ions is influenced by the presence of heteroatoms in the framework of crystals.
Keywordsfluoride containing gels isomorphous substitution Silicalite-1
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