Patent ID: 7785545

Claim:
An exhaust gas catalytic conversion system comprising: a first catalytic converter disposed in an upstream side of an exhaust passage of an engine in the direction of exhaust gas flow and including a first catalyst in which at least one catalyst layer for converting exhaust gas is formed on a honeycomb support; and a second catalytic converter disposed in the exhaust passage downstream of the first catalytic converter in the direction of exhaust gas flow and including a second catalyst in which at least one catalyst layer for converting exhaust gas is formed on a honeycomb support; the at least one catalyst layer of the first catalyst containing oxygen storage component particles, active alumina particles and a catalytic precious metal supported on at least either the oxygen storage component particles or the active alumina particles; the at least one catalyst layer of the second catalyst containing active alumina particles, mixed oxide particles containing Ce cations, cations of a rare earth element other than Ce, Zr cations and Rh cations and having an oxygen storage/release capacity, Rh supported as a catalytic precious metal on the surfaces of the mixed oxide particles, and Pt supported as a catalytic precious metal on the surfaces of the active alumina particles; the oxygen storage component particles in the first catalyst having a lower oxygen storage/release capacity than the mixed oxide particles in the second catalyst.