COMPOSITIONS BASED ON CERIUM OXIDE, ZIRCONIUM OXIDE AND, OPTIONALLY, ANOTHER RARE EARTH OXIDE, H

Composition comprising cerium oxide and zirconium oxide in a cerium/zirconium atomic ratio of at least 1 has a surface area of at least 9 m 2>/g after calcination at 1100[deg]C for 4 hours, or contains another rare earth metal oxide and has a surface area of at least 19 m 2>/g after calcination at 1100[deg]C for 4 hours. Independent claims are also included for : (1) a process for producing the composition; (2) a catalyst system comprising the composition; (3) internal combustion engine exhaust gas treatment using the composition as a catalyst.