Exhaust gas purification apparatus for diesel engine

Abstract

A DPF disposed in an exhaust passage of a diesel engine is coated with a selective reducing catalyst, for selectively reducing and purifying NOx by using a reducing agent, and a thin film, having fine pores of size for allowing passage of the NOx and preventing passage of PM, in this order. In regeneration treatment of a DPF, the thin film prevents direct transmission of combustion heat of the PM to the selective reducing catalyst and suppresses a temperature rise of the selective reducing catalyst to thereby suppress deterioration of an active component.

1 . An exhaust gas purification apparatus for a diesel engine, comprising:
 a diesel particulate filter disposed in an exhaust passage of the diesel engine;   a selective reducing catalyst for selectively reducing and purifying nitrogen oxides by using a reducing agent; and   a thin film, having fine pores of size for allowing passage of the nitrogen oxides and preventing passage of particulate matter,   wherein the diesel particulate filter is coated with the selective reducing catalyst and the thin film in this order.   
     
     
         2 . An exhaust gas purification apparatus for a diesel engine according to  claim 1 , wherein the thin film is applied only on an exhaust inflow face of the diesel particulate filter. 
     
     
         3 . An exhaust gas purification apparatus for a diesel engine according to  claim 1 , wherein the thin film is made of alumina or zeolite.