Patent ID: 7632776

Claim:
A process for producing an exhaust gas purifying catalyst, comprising: providing a sol containing at least a population of ceria colloid particles and a population of zirconia colloid particles differing in the isoelectric point with each other, the difference between the isoelectric points being at least 3, adjusting the pH of said sol to be closer to the isoelectric point of said population of ceria colloid particles than to the isoelectric point of said population of zirconia colloid particles, thereby aggregating said population of ceria colloid particles, adjusting the pH of said sol to be closer to the isoelectric point of said population of zirconia colloid particles than to the isoelectric point of said population of ceria colloid particles, thereby aggregating said population of zirconia colloid particles onto said aggregated population of ceria colloid particles, drying and firing the obtained aggregate to obtain a metal oxide particle comprising a core part relatively rich in ceria and a surface layer relatively rich in zirconia, and loading rhodium on the obtained metal oxide particle.