Precursor spherical bodies of a porous alumina ceramic were prepared by forming, hydrating and calcining a powder mixed amorphous alumina, obtained by flash calcination of Al(OH)(3), with a pore generating agent. To prepare the porous alumina ceramic from precursor bodies, they were immersed in an aqueous solution of a mixture of dilute nitric and acetic acids, and then they were hydrothermally treated and calcined. Acicular platelet crystals were transformed into acicular crystals of boehmite through the hydrothermal process. In this change, it was found that a reversible phase transformation due to the hydrothermal reaction took place between boehmite and gamma-alumina. In comparison to the precursor before the hydrothermal treatment, the N-2 adsorption capacity was increased from 450 ml/g to 670 ml/g, and the pore volume which a diameter between 100 angstrom and 1,000 angstrom was increased from 0.15 ml/g to 0.77 ml/g, and the mechanical strength was increased from 1.4 MPa to 2.2 MPa after the hydrothermal treatment. Also, the product showed a remarkable thermal resistance which sustained the alumina crystal structure and pores between 100 A and 1,000 A even though the porous alumina ceramic was heated for 24 h at 1,000 degrees C in 40 vol% steam.

Keywords: amorphous alumina; boehmite; porous alumina; nano pore; catalyst