Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

Abstract

A new family of porous inorganic solids based on nanocrystalline metal oxides is discussed. These materials, made up of 4-7 nm MgO, CaO, Al2O3, ZnO, and others, exhibit unparalleled destructive adsorption properties for acid gases, polar organics, and even chemical/biological warfare agents. These unique sorption properties are due to nanocrystal shape, polar surfaces, and high surface areas. Free-flowing powders or consolidated pellets are effective, and pore structure can be controlled by consolidation pressures. Chemical properties can be adjusted by choice of metal oxide as well as by incorporating other oxides as monolayer films.

Synthesis of Derivatives of Organoheterotrimetallic dibutyl-[Al(III), Sn(IV), Ti(IV)]- μ -oxoisopropoxide- μ-oxo n-Propoxide with Salicylates

“…The crystal structures range from simple rock salt to highly complex incommensurately modulated structures and the nature of the metal-oxygen bonding varies from nearly ionic to covalent or metallic 1,2 . Multimetallic oxides cover an always wider range of applications in electronics, optics [3][4][5] , magnetism [6][7][8] , catalysis 9 and environmental issues 10 . High-tech applications rely on materials in high purity and/or in a variety of shapes, formulations or microstructures (nano-particles, coatings, porous matrices, etc.)…”

Chemistry of SO 2 and DeSO x Processes on Oxide Nanoparticles

“…Depending on the exact procedure followed for the preparation, nanoparticles of MgO and CaO with polyhedral or hexagonal shapes can be prepared, but they also contain OH groups (40,49).…”

“…In these morphological shapes, the nanoparticles posses more defects than expected for the typical cubic shape of MgO and CaO (49). Such defects could be of the Frenkel or Schottky type (vacancies), or be manifested as unusual configurations of edges, corners, or crystal planes (40).…”

“…Adsorption data for SO 2 and other molecules are conclusive that the polyhedral or hexagonal nanocrystals of MgO and CaO are more reactive than cubic microcrystals of these oxides (49). This has been mainly attributed to morphological differences, including the concentration of defects.…”

“…However, intrinsic electronic effects due purely to "smallness" (confinement) could not be ruled out (49). (50).…”