| 摘要 |
PURPOSE:To improve purification performance for CO and NOx at a wide air-to- fuel ratio range by making Pt and Rh, which are active components, carried on a carrier at specific concentrations in a monolith type 3-element type catalyst for purification of waste gas of automobiles. CONSTITUTION:A monolith type 3-element catalyst A is disposed in a catalyst device 2 provided in the exhaust pipe 1 of the engine of an automobile. This catalyst A is prepd. by impregnating Pt and Rh on a catalyst carrier 3 of cordierite composition, and changing the amount of impregnation of Pt so as to be made rich on the waste gas inlet 3a side of the catalyst carrier 3 and lean on the waste gas outlet side 3b. Also, that of Rh is so changed and carried as to be made conversely lean or nil on the waste gas inlet side 3a and be rich on the waste gas outlet side 3b. As a 3-element catalyst for HC, CO and NOx, this catalyst excells particularly in purification performance for CO and NOx and permits the expansion of the air-to-fuel ratio to be used. |
