Formation and Acid-Base Surface Properties of Highly Dispersed η-Al2O3 Nanopowders

Highly dispersed eta-Al2O3-based nanopowders have been prepared via glycine-nitrate combustion followed by heat treatment in air. The resultant materials have been characterized by X-ray diffraction, Fourier transform IR spectroscopy, scanning electron microscopy, simultaneous thermal analysis, and other techniques. We have optimized the glycine-to-nitrate ratio (G/N = 0.2) and found heat treatment conditions for combustion products (isothermal holding at a temperature of 700 degrees C for 6 h) that allow one to obtain single-phase nanocrystalline eta-Al2O3 powders with an average particle size of 5 +/- 1 nm and specific surface area of 54 +/- 5 m(2)/g. The acid-base surface properties of the eta-Al2O3 nanopowder have been analyzed using pyridine sorption-desorption processes as an example. The specific concentrations of weak, intermediate, and strong Lewis acid centers on the surface of the eta-Al2O3 nanocrystals have been shown to markedly exceed those on the surface of commercially available gamma-Al2O3 (A-64). The synthesized nanopowders can thus be used as effective supports of acid catalysts.