Alumina-based composite oxide and production method for same

A method for producing an alumina-based composite oxide, the method comprising:

• step 1 of obtaining an aqueous solution A consisting of a raw material salt containing two or more metals including an aluminum, and water,
• step 2 of obtaining an aqueous solution B of a soluble carbonate and/or a soluble hydrogen carbonate,
• step 3 of mixing the aqueous solution A and the aqueous solution B to obtain precipitates of an aluminum-based composite hydroxide, and
• step 4 of subjecting the precipitates to heat treatment at 400 to 900° C. to obtain the alumina-based composite oxide,
• wherein the alumina-based composite oxide has an initial crystallite diameter of 10 nm or less and an initial specific surface area of 80 m2/ml or more;
• wherein the alumina-based composite oxide after calcination at 1200° C. for 3 hours in air has a specific surface area of 10 m2/ml or more;
• wherein the alumina-based composite oxide has an initial mean pore size of 10 nm or more and 50 nm or less;
• and
• wherein the alumina-based composite oxide after calcination at 1200° C. for 3 hours in air has a pore volume retention rate of 10% or more, the retention rate being represented by (P1/P0)×100 wherein P0 represents an initial pore volume in ml/g, and P1 represents a pore volume in ml/g after calcination at 1200° C. for 3 hours in air.