| 摘要 |
PURPOSE:To provide an exhaust gas purifying catalyst efficiently purifying NOx in oxygen excessive exhaust gas and to still more enhance NOx purifying capacity. CONSTITUTION:A first catalyst 1 wherein a noble metal catalyst 2 is supported on a porous acidic carrier, a second catalyst 2 wherein at least one kind of a metal 22 selected from alkali metal, alkaline earth metal and rare earth metal is supported on a porous carrier and a third catalyst 3 wherein a noble metal catalyst 32 is supported on a porous carrier are successively arranged in a row from the upstream side of an exhaust gas stream to the downstream side thereof. Since SO2 is not adsorbed on the first catalyst 1 to be not oxidized, exhaust gas flows to the downstream side without forming sulfate in the second catalyst. Since the second catalyst 2 is not deteriorated by poisoning, the second catalyst 2 keeps high NOx absorbing action on a lean side and the third catalyst 3 reduces and removes NOx discharged from the second catalyst 2 on a rich- stoichiometric side. |
