Exhaust gas purifier

An exhaust gas purification apparatus, comprising:

• a first oxidation catalyst (DOC) comprising a noble metal component for oxidizing, in particular, nitrogen monoxide, among carbon monoxide, hydrocarbons, nitrogen oxides, and for combusting light oil,
• a catalyzed soot filter (CSF) comprising a noble metal component for collecting a particulate component such as soot and removing by combustion (oxidation),
• a second oxidation catalyst (DOC),
• a reducing agent spraying means for supplying a reducing agent selected from a urea component or an ammonia component, and
• a selective reduction catalyst (SCR) for removing by reduction of nitrogen oxides by contacting with the reducing agent,
• wherein the first oxidation catalyst (DOC), the catalyzed soot filter (CSF), the second oxidation catalyst (DOC), the reducing agent spraying means, and the selective reduction catalyst (SCR) are arranged in this order from the upstream side of an exhaust gas passage, in order to purify carbon monoxide, hydrocarbons, nitrogen oxides, and particulate components such as soot, in exhaust gas discharged from a diesel engine,
• the first oxidation catalyst (DOC) and the second oxidation catalyst (DOC) have a catalyst layer where platinum (Pt) and palladium (Pd) are supported on alumina (Al2O3) having a pore size of 12 to 120 nm, and ratio of platinum and palladium is 1:1 to 11:2 in weight equivalent, and
• the catalyzed combustion filter (CSF) has a catalyst layer, where platinum (Pt) and palladium (Pd) are supported on alumina having a pore size of 12 to 120 nm, or a mixture of two or more kinds of alumina having different pore size within its range, and ratio of platinum and palladium is 1:1 to 11:4 in weight equivalent.