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

摘要

A catalyst system to be used in an automobile exhaust gas purification apparatus which exerts excellent purification capability to a nitrogen oxide, even when hydrocarbon concentration varies, by subjecting exhaust gas discharged from an automotive internal engine to contacting with a catalyst, an exhaust gas purification apparatus using the same, and an exhaust gas purification method. A catalyst system etc. to be used in an automobile exhaust gas purification apparatus, composed by using two or more exhaust gas purification catalysts, containing a first catalyst supported on an inorganic structural carrier and a second catalyst other than this, characterized by having the first catalyst supported on apart of the inorganic structural carrier positioned at the upstream side, when arranged in an exhaust gas passage; on the other hand having the second catalyst supported on a part of the inorganic structural carrier, positioned at the downstream side, when arranged in an exhaust gas passage; and containing a cerium-zirconium-type composite oxide (A) having a pyrochlore phase in the crystal structure.