Patent ID: 6887443

Claim:
A method for purifying exhaust gas with an exhaust gas purifying catalyst, comprising: contacting an exhaust gas from a diesel engine with a carbon monoxide reduction catalyst positioned upstream of the exhaust gas purifying catalyst; and contacting the exhaust gas with an exhaust gas purifying catalyst for absorbing NOx in a lean condition and reducing NOx to N 2 in a stoichiometric condition and a rich condition, the exhaust gas catalyst, comprising: a catalytic ingredient comprising rhodium, at least one of platinum and palladium, at least one of absorption materials for absorbing NOx, the absorption materials being selected from the group consisting of Mg, Ca, Sr, Ba, Na, K and Cs, and a porous carrier; and a monolithic support for supporting the catalytic ingredient, wherein the exhaust gas purifying catalyst includes a plurality of catalytic layers containing at least a part of the catalytic ingredient, and rhodium is contained at least in an outermost layer of the catalytic layers, a rhodium amount in the catalytic ingredient is 0.5 g or more for each liter of the catalyst, and a rhodium amount contained in the outermost layer accounts for 80 wt % or more of a total rhodium amount, and a weight of the catalytic layer at the outermost layer accounts for 40 wt % or below of a total weight of the catalytic layers, wherein the exhaust gas is maintained at a temperature at an inlet of the exhaust gas purifying catalyst in the lean condition of at least about 200Â° C.