Exhaust gas purifying catalyst and method for producing the same

Abstract

Provided is an exhaust gas purifying catalyst with an excellent effect of suppressing deterioration due to aggregation of a noble metal catalyst that would occur during endurance at a high temperature. The exhaust gas purifying catalyst includes a porous support and a noble metal catalyst carried on the porous support. The porous support contains particles of an alumina-ceria-zirconia composite oxide, and the porous support has the following physical property values after subjected to baking at 900° C. for 5 hours: a pore diameter of the particles in the range of 2 to 20 nm, a specific surface area of the particles in the range of 75 to 115 m 2 /g, a crystallite size of a ceria-zirconia composite oxide that is contained in the particles in the range of 4 to 6 nm, and a bulk density of the particles in the range of 0.5 to 0.9 cm 3 /g.

What is claimed is: 
     
         1 . An exhaust gas purifying catalyst comprising:
 a porous support; and   a noble metal catalyst carried on the porous support, wherein   the porous support contains particles of an alumina-ceria-zirconia composite oxide, and   the porous support has the following physical property values after subjected to baking at 900° C. for 5 hours: a pore diameter of the particles in a range of 2 to 20 nm, a specific surface area of the particles in a range of 75 to 115 m 2 /g, a crystallite size of a ceria-zirconia composite oxide that is contained in the particles in a range of 4 to 6 nm, and a bulk density of the particles in a range of 0.5 to 0.9 cm 3 /g.   
     
     
         2 . A method for producing an exhaust gas purifying catalyst, comprising:
 producing an alumina-ceria-zirconia composite oxide by preparing an aqueous solution by dissolving a cerium salt compound and a zirconium salt compound in an aqueous solvent, adding an aluminum isopropoxide into the aqueous solution to produce a precursor solution, removing moisture from the precursor solution, and drying and baking a residue; and   producing an exhaust gas purifying catalyst from the alumina-ceria-zirconia composite oxide.