Abstract: A heat-resistant aluminum hydroxide which is prepared by subjecting a mixture of aluminum hydroxide with a reaction retardant for retarding the conversion aluminum hydroxide to boehmite, as a raw material, to the hydrothermal treatment or to pressurization and heating in a steam atmosphere; and a method for preparing a heat-resistant aluminum hydroxide which comprises subjecting a mixture of aluminum hydroxide with a reaction retardant for retarding the conversion aluminum hydroxide to boehmite as a raw material to the hydrothermal treatment, or to pressurization and heating in a steam atmosphere.

Abstract: A heat-resistant aluminum hydroxide which is prepared by subjecting a mixture of aluminum hydroxide with a reaction retardant for retarding the conversion aluminum hydroxide to boehmite, as a raw material, to the hydrothermal treatment or to pressurization and heating in a steam atmosphere; and a method for preparing a heat-resistant aluminum hydroxide which comprises subjecting a mixture of aluminum hydroxide with a reaction retardant for retarding the conversion aluminum hydroxide to boehmite as a raw material to the hydrothermal treatment, or to pressurization and heating in a steam atmosphere.

Abstract: Method for manufacturing a plate boehmite and a plate alumina having high catalytic activity. The plate boehmite is prepared by subjecting at least one kind of an alkaline earth metal compound, which is selected from calcium, strontium and barium, and aluminum hydroxide to pressurization and heating at 150 to 300° C. in the presence of water. The resulting reaction product is treated with an acid to remove the residual alkaline earth metal compound contained in the product, followed by rinsing with water. The resulting plate boehmite is subjected to calcination at 450 to 1500° C. Thus, a plate alumina comprising a mixture of &thgr;-alumina and &dgr;-alumina as a major component is prepared.