Catalyst system to be used in automobile exhaust gas purification apparatus, exhaust gas purification apparatus using the same and exhaust gas purification method

A catalyst system to be used in an automobile exhaust gas purification apparatus, comprised of using two or more exhaust gas purification catalysts comprising a first catalyst supported on a honeycomb structure (D), and a second catalyst other than the first catalyst, characterized in that:

• the first catalyst is supported on a part of the honeycomb structure (D) positioned at an upstream side when arranged in an exhaust gas passage;
• the first catalyst comprises a cerium-zirconium-type composite oxide (A′) with a structure of a cubic crystal and/or a tetragonal structure, not comprising a pyrochlore phase;
• the second catalyst is supported on a part of the honeycomb structure (D) positioned at a downstream side when arranged in an exhaust gas passage;
• the second catalyst comprises a cerium-zirconium-type composite oxide (A) having a pyrochlore phase in the crystal structure and the cerium-zirconium-type composite oxide (A′);
• the second catalyst is covered as at least two layers on the honeycomb structure (D) and the cerium-zirconium-type composite oxide (A) and the cerium-zirconium-type composite oxide (A′) are supported on the lower layer;
• and
• the second catalyst further comprises one or more kinds of active metal species (B) selected from platinum, palladium, or rhodium wherein platinum and palladium are in the lower layer and rhodium is in the upper layer.