LEAN NOX TRAP TYPE EXHAUST GAS PURIFICATION CATALYST AND EXHAUST GAS PURIFICATION SYSTEM

摘要

Provided is a lean NOx trap type exhaust gas purification catalyst having excellent durability, and an exhaust gas purification system provided with same. The lean NOx trap type exhaust gas purification catalyst contains platinum, palladium and rhodium, which are catalytic noble metals, inorganic oxides that support the catalytic noble metals, and at least one type of NOx adsorbent selected from among the group comprising magnesium, barium, sodium, potassium and cesium. Among the inorganic oxides, an inorganic oxide that supports palladium contains cerium and aluminum and/or zirconium. The inorganic oxide that supports palladium contains 1 to 20 mass %, in terms of CeO2, of cerium. The exhaust gas purification system is provided with the lean NOx trap type exhaust gas purification catalyst and another catalyst which contains a catalytic noble metal and which is positioned on the upstream side of the lean NOx trap type exhaust gas purification catalyst relative to the exhaust gas flow direction.