Patent ID: 7157405

Claim:
An exhaust emission control system for an internal combustion engine, the system comprising a monolith catalyst (MC) that comprises an oxygen storage agent and a noble metal-based three-way catalyst comprising Pd, Rh, and Pt disposed at an upstream location in the exhaust gas flow in the internal combustion engine ( 2 ), and a catalyst comprising a perovskite-type double oxide having a three-way catalytic function disposed at a downstream location in the exhaust gas flow, an amount C1 of said Pd being 0.97 g/L≦C1≦1.68 g/L, an amount C2 of said Rh being 0.11 g/L≦C2≦0.2 g/L, an amount C3 of said Pt being 0.06 g/L≦C3≦0.11 g/L, an amount C4 of said oxygen storage agent being 25 g/L≦C4≦75 g/L, and an amount C5 of said perovskite-type double oxide being 5 g/L≦C5≦15 g/L.