Apparatus for after-treatment of exhaust from diesel engine

Abstract

An apparatus for after-treatment of exhaust gas from a diesel engine may include a Diesel Particulate Filter (DPF) located upstream of an exhaust pipe connected to an engine exhaust manifold, a Diesel Oxidation Catalyst (DOC) located downstream of the diesel particulate filter, and an ammonia Selective Catalyst Reduction (SCR) catalyst located downstream of the diesel oxidation catalyst, wherein the ammonia SCR catalyst is made of zeolite. The DOC has a carrier containing a single active material of Ru or a composite active material of Pt and Ru, and the weight ratio of Pt to Ru is 2:1 or less. The apparatus can efficiently remove pollutants such as hydrocarbons and CO in the exhaust, naturally regenerate the DPF by burning off particulate matter, and maximize the ability of the ammonia SCR catalyst to remove NOx by increasing the amount of NO 2 among NOx in the exhaust entering the ammonia SCR catalyst.

1 . An apparatus for after-treatment of exhaust gas from a diesel engine, comprising:
 a diesel particulate filter (DPF) located upstream of an exhaust pipe connected to an engine exhaust manifold;   a diesel oxidation catalyst (DOC) located downstream of the diesel particulate filter (DPF); and   an ammonia-selective catalyst reduction (SCR) catalyst located downstream of the diesel oxidation catalyst (DOC),   wherein the ammonia SCR catalyst is made of zeolite, and   wherein the diesel oxidation catalyst (DOC) includes a carrier containing a single active material of Ru or a composite active material of Pt and Ru, wherein a weight ratio of Pt to Ru is approximately 2:1 or less.   
     
     
         2 . The apparatus in accordance with  claim 1 , wherein the diesel particulate filter (DPF) is provided adjacent to the engine exhaust manifold. 
     
     
         3 . The apparatus in accordance with  claim 1 , wherein the diesel particulate filter (DPF) has an oxidation catalyst coated on a surface thereof. 
     
     
         4 . The apparatus in accordance with  claim 3 , wherein the oxidation catalyst coated on the surface of the diesel particulate filter includes Pt and Pd, wherein a weight ratio of Pt to Pd is in a range from approximately 2:1 to approximately 6:1. 
     
     
         5 . The apparatus in accordance with  claim 1 , wherein the diesel particulate filter (DPF) has an oxidation catalyst coated on entire surfaces thereof. 
     
     
         6 . The apparatus in accordance with  claim 5 , wherein the oxidation catalyst coated on the entire surfaces of the diesel particulate filter includes Pt and Pd, wherein a weight ratio of Pt to Pd is in a range from approximately 2:1 to approximately 6:1. 
     
     
         7 . The apparatus in accordance with  claim 1 , wherein the ammonia SCR catalyst is made of zeolite, which is ion exchanged with transition metal. 
     
     
         8 . The apparatus in accordance with  claim 7 , wherein weight of transition metal is approximately 1 to approximately 4 percent of weight of the zeolite. 
     
     
         9 . The apparatus in accordance with  claim 7 , wherein the zeolite includes mordenite zeolite, MFI-type zeolite (e.g., ZSM5), BEA zeolite, or Y-type zeolite. 
     
     
         10 . The apparatus in accordance with  claim 7 , wherein the zeolite is ion exchanged with at least one of Fe and Cu. 
     
     
         11 . The apparatus in accordance with  claim 7 , wherein the zeolite is ion exchanged with at least one of Fe, Ni, Co, and Cu. 
     
     
         12 . The apparatus in accordance with  claim 1 , wherein the carrier of the diesel oxidation catalyst (DOC) includes Al 2 O 3 , and the active material is approximately 0.5 to approximately 5 percent by weight of the diesel oxidation catalyst (DOC). 
     
     
         13 . The apparatus in accordance with  claim 12 , wherein the carrier of the diesel oxidation catalyst (DOC) is porous. 
     
     
         14 . The apparatus in accordance with  claim 1 , wherein a content of NO 2  in the exhaust gas from the diesel engine is approximately 30 percent more by volume of entire NOx.