Process for preparing an alumina composition

A process for preparing an alumina composition, comprising:

• adding water and one of a monobasic acid or its salt and a pore structure controlling agent selected from the group consisting of an oxygen-containing organic compound and an inorganic polybasic acid to alumina having a ρ-crystal structure to prepare a reaction mixture having a k value adjusted to be in the following range, said k value being represented by the following formula:
• 0.0001≦K≦0.20
• k=(b/a)×(b/c)
• wherein a is a number of moles of alumina in the reaction mixture in terms of Al2O3, b is a number of moles of acid or its salt, and c is a number of moles of water,
• then subjecting the reaction mixture to ○-forming reaction at a temperature of not higher than 250° C. to obtain one or both of an aqueous alumina sol and an aqueous alumina gel,
• optionally subjecting one or both of the aqueous alumina sol and the aqueous alumina gel to neutralization with an alkali and hydrothermal treatment at a temperature of not higher than 250° C.;
• and
• subjecting one or both of the aqueous alumina sol and the aqueous alumina gel to molding, then drying and calcining.

A process for preparing an alumina composition, comprising:

• adding water, one of a monobasic acid or its salt and a pore structure controlling agent selected from the group consisting of an oxygen-containing organic compound and inorganic polybasic acid to at least one aluminum source selected from the group consisting of pseudoboehmite and a thermal decomposition product of an aluminum salt to prepare a reaction mixture having a k value adjusted to be in the following range, said k value being represented by the following formula:
• 0.0001≦k≦0.20
• k=(b/a)×(b/c)
• wherein a is a number of moles of alumina in the reaction mixture in terms of Al2O3, b is a number of moles of acid or its salt, and c is a number of moles of water,
• then subjecting the reaction mixture to sol-forming reaction at a temperature of not higher than 250° C. to obtain one or both of an aqueous alumina sol and an aqueous alumina gel,
• optionally subjecting one or both of the aqueous alumina sol and the aqueous alumina gel to neutralization with an alkali and hydrothermal treatment at a temperature of not higher than 250° C.;
• and
• subjecting one or both of the aqueous alumina sol and the aqueous alumina gel to molding, then drying and calcining.