Patent ID: 8741799

Claim:
An exhaust gas-purifying catalyst comprising: a substrate; and a catalytic layer facing the substrate and including a precious metal, alumina, an oxygen storage material, and a sulfate of an alkaline-earth metal having an average particle diameter falling within a range of 0.01 to 0.70 μm, the average particle diameter being obtained by observation using a scanning electron microscope, wherein the oxygen storage material is a composite oxide containing cerium and zirconium; and the catalytic layer having a correlation coefficient ρ PM,AE of 0.60 or more, the coefficient ρ PM,AE being expressed by the following formula (7): ρ PM , AE = C PM , AE σ PM ⁢ σ AE ( 7 ) wherein C PM,AE , σ PM and σ AE in the formula (7) are represented by the following formulae (8), (9) and (10), respectively: C PM , AE = 1 350 ⁢ ∑ i = 1 350 ⁢ ( I PM , i - I PM , av ) ⁢ ( I AE , i - I AE , av ) ( 8 ) σ PM = 1 350 ⁢ ∑ i = 1 350 ⁢ ⁢ ( I PM , i - I PM , av ) 2 ( 9 ) σ AE = 1 350 ⁢ ∑ i = 1 350 ⁢ ⁢ ( I AE , i - I AE , av ) 2 ( 10 ) in the formulae (8) to (10), i is a natural number of 1 to 350, I PM,i is intensity of characteristic X-ray emitted by the precious metal measured using an electron beam microanalyzer on the i-th intersection point among 350 intersection points of faces that are obtained by dividing the catalytic layer into 350 equal parts arranged in the thickness direction with a line that is perpendicular to a main surface of the catalytic layer, I PM,av is an arithmetic average value of the I PM,i given by the following formula (11): I PM , av = 1 350 ⁢ ∑ i = 1 350 ⁢ I PM , i ( 11 ) I AE,i is intensity of characteristic X-ray emitted the alkaline-earth metal element that is measured using the electron beam microanalyzer at the i-th intersection point, and I AE,av is an arithmetic average value of the I AE,i given by the following formula (12): I AE , av = 1 350 ⁢ ∑ i = 1 350 ⁢ I AE , i . ( 12 )