Journal of Sol-Gel Science and Technology

, Volume 21, Issue 3, pp 157–165

Modification of Non-Hydrolytic Sol-Gel Derived Alumina by Solvent Treatments

  • G.S. Grader
  • G.E. Shter
  • D. Avnir
  • H. Frenkel
  • D. Sclar
  • A. Dolev
Article

Abstract

The effect of wetting non-hydrolytic derived alumina xerogels with water and organic solvents in the 20–70°C range on the alumina's properties was investigated. Wetting with organic solvents does not affect the alumina. However, contact with water was found to change the sharp crystallization at ∼800°C to a continuous crystallization starting at ∼450°C. Water treatment for a day at room temperature (RT) followed by second calcination decreased the surface area by 10%. This decrease in surface area is less pronounced with increasing wetting periods. On the other hand water treatment at 50–70°C followed by a second calcination resulted in a surface area increase of up to 15%. Upon water treatment the total pore volume has decreased from 0.65 (cm3/gr) to 0.48 (cm3/gr) and the average pore size decreased from 6.8 nm to 4.1 nm. The Cl content was found to be uneffected by the water treatment, remaining at ∼2.5% wt. Wetting with water at elevated temperature (70°C) accelerated the morphological changes, eliminating the crystallization peak at 800°C in one hour. A dissolution-reprecipitation mechanism is suggested to explain the results. In addition, Mass-Spectroscopy of the effluent gas during heat treatment revealed the emission of CO2 and water upon phase transition into α-Al2O3, at 1150–1300°C.

non-hydrolytic sol-gel alumina solvent modification calcination 

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Copyright information

© Kluwer Academic Publishers 2001

Authors and Affiliations

  • G.S. Grader
    • 1
  • G.E. Shter
    • 1
  • D. Avnir
    • 2
  • H. Frenkel
    • 2
  • D. Sclar
    • 1
  • A. Dolev
    • 1
  1. 1.Chemical Engineering DepartmentTechnionHaifaIsrael
  2. 2.Institute of ChemistryThe Hebrew University of JerusalemJerusalemIsrael

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