Patent attributes
Provided is an exhaust cleaning catalyst that exhibits higher NOX-reducing activities at the time of engine restart while maintaining its catalytic activities during normal traveling. This invention provides an exhaust cleaning catalyst including a substrate and a catalyst coating layer including CeO2. Catalyst coating layer is constituted in its thickness direction with multiple coating layers. In a top coating layer located at the outermost surface, the CeO2 content in a top coating layer's upstream portion is less than the CeO2 content in a top coating layer's downstream portion. In a bottom coating layer near substrate, the CeO2 content in a bottom layer's downstream portion is less than the CeO2 content in a bottom coating layer's upstream portion.
