Method for purifying exhaust gases with two layer catalyst in oxygen-rich atmosphere

A method for purifying exhaust gas comprising bringing exhaust gas into contact with a catalyst in oxygen-rich atmospheres in which oxygen concentrations of the exhaust gas are at or above the stoichiometric point required for oxidizing components of the exhaust gas to be oxidized, said catalyst comprising:

• a porous support,
• a lower layer loaded on said porous support, said lower layer comprising a noble metal catalyst ingredient and at least one NO.sub.x absorber selected from the group consisting of alkaline metals, alkaline-earth metals and rare earth metals, and
• an upper layer formed on said lower layer, said upper layer comprising oxides of at least one metal selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) and manganese (Mn),
• wherein under said oxygen-rich atmospheres, nitrogen oxides and sulfur oxides in said exhaust gas react with said oxides of at least one metal to form nitrogen oxide salts and sulfur oxide salts, said nitrogen oxide salts decompose to restore said nitrogen oxides and said oxides of at least one metal, said restored nitrogen oxides are absorbed by said NO.sub.x absorber, said restored oxides of at least one metal react with sulfur oxides to form sulfur oxide salts, and said sulfur oxide salts decompose at a temperature higher than said nitrogen oxide salts to restore said oxides of at least one metal.