| 摘要 |
PURPOSE: To produce a catalyst for purifying exhaust gas by which NOx purification performance is increased in the lean atmosphere and a function as a ternary catalyst is fully revealed. CONSTITUTION: At least one kind of noble metal selected from a group consisting of platinum, palladium and rhodium, at least one kind of transition metal selected from a group consisting of iron, cobalt, nickel, and manganese, lanthanum, barium and potassium are incorporated on a refractory inorganic carrier. A part or the whole of the transition metal and lanthanum forms a multiple oxide. This catalyst consists of a catalytic layer A and a catalytic layer B which contains at least one kind of noble metal selected from a group consisting of platinum, palladium and rhodium and does not contain potassium. At least two pieces of catalysts are provided in the exhaust gas current of an engine. The catalyst containing zeolite carrying copper is arranged on the upstream side for an exhaust gas current and either of the two kinds of catalysts is arranged on the downstream side therefor. |
