Conventionally, as a catalyst purifying exhaust gas from a diesel engine, an oxidation catalyst oxidizing carbon monoxide (CO), hydrocarbon (HC), and nitrogen monoxide (NO) in the exhaust gas is used. The oxidation catalyst is made by applying a carrier including porous oxide such as alumina to a member of ceramic or metal so as to form a catalyst layer. The catalyst layer including precious metal such as platinum (Pt) and palladium (Pd) is known.
In the oxidation catalyst, for exhibiting characteristics of platinum (Pt), palladium (Pd) and the like so as to improve performance of the oxidation catalyst, in consideration of temperature at each part of the catalyst and components of the exhaust gas, the oxidation catalyst in which different materials are arranged in upstream and downstream sides of a substrate is developed. For example, an art described in the Patent Literature 1 is so.
However, in the oxidation catalyst described in the Patent Literature 1, the carrier in which amounts of Pt and Pd are adjusted corresponding to characteristics of the exhaust gas must be applied to a predetermined position. Namely, blending of a plurality of catalysts arranged in each part of the substrate must be performed for the diesel engine connected to the oxidation catalyst, whereby it is disadvantageous because production cost is increased.