| 摘要 |
To provide a lean NOx trap type exhaust gas purifying catalyst with excellent durability and an exhaust gas cleaning system having this exhaust gas purifying catalyst. The lean NOx trap type exhaust gas purifying catalyst contains platinum, palladium and rhodium as the catalyst noble metals, an inorganic oxide that carries the catalyst noble metals, and a NOx adsorbent made of at least one type selected from the group of magnesium, barium, sodium, potassium, and cerium; among the inorganic oxides, the inorganic oxide carrying palladium contains cerium and aluminum and/or zirconium. The inorganic oxide carrying palladium contains cerium in the CeO 2 -equivalent quantity in the range of 1 to 20 wt%. The exhaust gas cleaning system has the lean NOx trap type exhaust gas purifying catalyst and another catalyst containing a catalyst noble metal and located on the upstream side from the lean NOx trap type exhaust gas purifying catalyst with respect to the exhaust gas flow direction. |
