EXHAUST GAS CLEANING CATALYST DEVICE

PROBLEM TO BE SOLVED: To effectively suppress a fall in cleaning performance due to a Pt-Rh solid solution by effectively suppressing the interlayer migration of Pt or Rh due to the change of an atmosphere of exhaust gas. SOLUTION: This exhaust gas cleaning catalyst device 1 includes: first and second diversion passages 11, 12 which are disposed in an exhaust route of an internal combustion engine (engine 2) for exhausting the exhaust gas in a lean atmosphere, stoichiometric atmosphere, and a rich atmosphere, and through which the exhaust gas exhausted from the internal combustion engine branches and flows; a first two-layer coat catalyst RP which is disposed in the first diversion passages 11 and has a first surface layer containing Rh and a first inner layer containing Pt as a first catalyst layer; a second two-layer coat catalyst PR which is disposed in the second diversion passages 12 and has a second surface layer containing Pt and a second inner layer containing Rh as a second catalyst layer; and a switching means 40 for switching the passage so that the exhaust gas in the stoichiometric atmosphere and the rich atmosphere circulates through the first diversion passage 11, and the exhaust gas in the lean atmosphere circulates through the second diversion passage 12. COPYRIGHT: (C)2008,JPO&INPIT