| 摘要 |
PROBLEM TO BE SOLVED: To remove hydrocarbon, carbon monoxide or the like along with nitrogen oxide by the catalytic treatment of exhaust gas containing hydrocarbon, carbon monoxide or the like along with nitrogen oxide and to prevent the lowering of the exhaust gas cleaning capacity of a catalyst even if the exhaust gas contains sulfur oxide and to stably clean the exhaust gas over a long period of time. SOLUTION: In an exhaust gas cleaning catalyst for cleaning three components of nitrogen oxide, hydrocarbon and carbon monoxide by alternately swinging an exhaust gas treating atmosphere between an oxygen excessive atomosphere and a reducing atmosphere, the exhaust gas is brought into contact with (1) a first catalyst comprising at least one platinum element selected from a group consisting of Rh and Ir and subsequently brought into contact with (2) a second catalyst consisting of (a) oxide of at least one metal selected from alkali metal, alkaline earth metal, aluminum silver, titanium and a rare element or composite oxide of those metals and (b) at least one element selected from a group selected from Pt, Rh, Pd and Ir. |
