CATALYST MECHANISM FOR PURIFYING EXHAUST GAS AND PURIFICATION OF EXHAUST GAS

摘要

PROBLEM TO BE SOLVED: To provide a catalyst system effectively removing nitrogen oxide in exhaust gas under an oxygen excessive condition over a wide temp. range and having excellent durability even at high temp. and a method for purifying the exhaust gas by utilizing the catalyst system. SOLUTION: In the exhaust gas purifying catalyst system arranged to an exhaust gas passage, a catalyst obtained by supporting iridium and alkali metal on a carrier composed of at least one kind of a component selected from a group consisting of metal carbide and metal nitride is contained and has at least two-stage catalyst containing beds consisting of a catalyst-containing bed (A) arranged to the exhaust gas passage and the catalyst-containing bed (B) containing a catalyst wherein a silver-containing component is supported on activated alumina and arranged on the downstream side of the catalyst- containing bed (A) of the exhaust gas passage.