| 摘要 |
PROBLEM TO BE SOLVED: To resolve a problem that partial HC desorbed is discharged without being oxidized in a catalyst activating process because a desorption temperature of HC is lower than an activating starting temperature of a catalyst layer, in a catalytic converter of a multiplayer structure provided with an oxidation catalytic layer on a surface of an HC adsorptive layer (zeolite layer). SOLUTION: Catalytic noble metal content or density of a three-way catalyst layer A on a surface layer side of two layers of three-way catalytic layers A, B formed on a surface side of a zeolite layer C is set to be larger than that of the three-way catalyst layer B on a lower layer side. Since surface layer parts of a plurality of the three-way catalyst layers become high temperatures comparatively earlier in an engine warming process, HC desorbed from the zeolite layer C within the catalytic converter can be treated with high efficiency in an activating process by making content or density of catalytic noble metal of the three-way catalyst layer A on the surface layer comparatively higher. By making catalytic noble metal partially exist on the three-way catalyst layer on the surface layer in this way, the whole amount of catalytic noble metal used is suppressed and an increase in cost can be suppressed. |
