Nanometer-sized gold particles were encapsulated in the micropores
of xerogels and
aerogels. The synthesis involves the sequential reduction of a
gold salt followed by sol−gel
processing in an inverse micelle solution. The inverse micelle
solution solubilizes the metal
salt and provides a microreactor for the nucleation, growth, and
stabilization of the
nanometer-sized clusters. Hydrolysis and condensation of an added
siloxane precursor
produces a wet gel embedding the particles. Characterization of
the particle size and
composition and the particle growth process was completed with
transmission electron
microscopy (TEM), electron diffraction, and UV−visible absorption
spectrometry. Characterization of the gel surface areas was completed with N2
porosimetry. Material properties
determined as a function of the gel precursor (TEOS vs a prehydrolyzed
form of TEOS), the
water to gel precursor reaction stoichiometry, and surfactant
concentration are discussed
in terms of the unique solution chemistry occurring in the
microheterogeneous inverse micelle
solutions.
ABSTIWCTWe report propane dehydrogenation behavior of catalysts prepared using two novel synthesis strategies that combine inverse micelle Pt nanocluster technology with silica and alumina sol-gel processing. Unlike some other sol-gel catalyst preparations. Pt particles in these catalysts are not encapsulated in the support structure and the entire Pt particle surface is accessible for reaction. Turnover frequencies (TOF) for these catalysts are comparable to those obtained over Pt catalysts prepared by traditional techniques such as impregnation, yet the resistance to deactivation by carbon poisoning is much greater in our catalysts. The deactivation behavior is more typical of traditionally prepared PtSn catalysts than of pure Pt catalysts.
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