Abstract
High surface area pillared-clays were prepared from naturally occurring montmorillonite by exchanging interlayer ions with polyoxocations containing: (i) iron, (ii) aluminum, (iii) discrete mixtures of (i) and (ii), or (iv) iron and aluminum located within the same complex. The valence state, solid-state properties and stability of these pillars were determined following reduction and oxidation using: Mossbauer spectroscopy, X-ray diffraction and BET surface area measurements. Mossbauer data suggested interlayer-formation of metallic iron domains following reduction of type (i) and (iii) pillared systems. The magnetic properties and the oxidation behavior deduced from Mossbauer, XRD and BET measurements indicated that these crystallites were in the form of thin-film/pancake-shape islands. Reduced domains remained accessible to the gas phase and resisted sintering during redox cycles. The expanded structure of the type (iii) pillared system was found to be stable following reduction up to 673K due to the irreducible nature of discrete aluminum pillars at these conditions. Based on these findings inteccalation of clays with mixtures of chemically distinct pillars appears to provide a unique method for preparing highly dispersed metallic or bimetallic systems possessing two-dimensional sieve-like behavior and high surface area.
Original language | English |
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Pages (from-to) | 661-664 |
Number of pages | 4 |
Journal | Hyperfine Interactions |
Volume | 41 |
Issue number | 1 |
DOIs | |
State | Published - Dec 1988 |