Exhaust gas purification system of vehicle

Abstract

An exhaust gas purification system for a vehicle may include a diesel oxidation catalyst (DOC) unit installed at an exhaust pipe, and a composite catalyst unit installed at the exhaust pipe at a rear end of the DOC unit and including a selective catalyst reduction (SCR) catalyst and an oxidation catalyst formed at a diesel particulate matter filter (DPF). The exhaust gas purification system may also include an injector provided between the DOC unit and the composite catalyst unit and configured to inject a reducing agent into the exhaust pipe. The SCR catalyst may be formed at an exhaust gas inlet side of the DPF and the oxidation catalyst may be formed at an exhaust gas outlet side of the DPF.

What is claimed is: 
     
         1 . An exhaust gas purification system for a vehicle, comprising:
 a diesel oxidation catalyst (DOC) unit installed at an exhaust pipe;   a composite catalyst unit installed at the exhaust pipe at a rear end of the DOC unit and including a selective catalyst reduction (SCR) catalyst and an oxidation catalyst formed at a diesel particulate matter filter (DPF); and   an injector provided between the DOC unit and the composite catalyst unit and configured to inject a reducing agent into the exhaust pipe,   wherein the SCR catalyst is formed at an exhaust gas inlet side of the DPF and the oxidation catalyst is formed at an exhaust gas outlet side of the DPF.   
     
     
         2 . The exhaust gas purification system of  claim 1 , wherein a catalyst non-coating region is present between the inlet side and the outlet side of the DPF. 
     
     
         3 . The exhaust gas purification system of  claim 1 , wherein the SCR catalyst comprises a material selected from Cu or Fe based zeolite and/or vanadium based materials. 
     
     
         4 . The exhaust gas purification system of  claim 1 , wherein the oxidation catalyst comprises a noble metal catalyst selected from a group consisting of Pt, Pd, and Rh. 
     
     
         5 . The exhaust gas purification system of  claim 1 , wherein the composite catalyst unit includes a SCR on DPF (SDPF). 
     
     
         6 . An exhaust gas purification system comprising:
 a DOC unit installed at an exhaust pipe; and   a composite catalyst unit installed at the exhaust pipe at a rear end of the DOC unit and including a SCR catalyst and an oxidation catalyst formed at a DPF,   wherein the composite catalyst unit includes a catalyst non-coating region provided between a coating region of the SCR catalyst and a coating region of the oxidation catalyst.   
     
     
         7 . The exhaust gas purification system of  claim 6 , wherein the DPF includes a cell passage having a zigzag form. 
     
     
         8 . The exhaust gas purification system of  claim 7 , wherein the SCR catalyst is coated on an exhaust gas inlet side of the cell passage, and the oxidation catalyst is coated on an exhaust gas outlet side of the cell passage.