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050008: Nano-layered Silicates with High Chemical Reactivity

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The smectite family of layered silicate minerals the so-called \"swelling clays\"" have theoretical surface areas of 700 meters per gram or larger. However accessing this surface area for important materials applications such as catalysis adsorption and polymer-clay nanocomposite formation is not readily achievable; the elementary one-nanometer thick nanolayers stack to form tactoids thus reducing the effective surface area for useful chemical reactions. The tactoids can be swelled by a swelling solvent to access interlayer regions. However this approach is inconvenient and limits applications to only swelling solvents. Other approaches e.g. pillared clays result in limited gains in effective surface area of the clays. It would be desirable to have a more effective approach that avoids the formation of tactoids. Description The invention provides reactive layered silicate materials with a novel nano-layered structure and reactive silanol groups. The invention prevents the stacking of nanolayers and resulting formation of tactoids. The silicate layers of this invention contain silanol groups in tetrahedral sheets. The compositions of the invention differ from existing alternatives in that a substantial fraction of silicon atoms in the tetrahedral sheets are bonded to hydroxyl groups. The dimensions of the nanolayers vary from one to 200 nanometers and the nanolayers are aggregated into particles less than 2 microns in size. The preparation of the silicate uses a reaction mixture containing a silica source a divalent metal oxide source and water forming a paste or slurry (optionally with a base) with a molar ratio of silica to divalent metal oxide source between 1.33 and 1.60 allowing the mixture to react at a temperature between 60° C and 225° C to form the product."

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