Exhaust gas purification device

Abstract

An exhaust gas purification device has an injector and a wall-flow type honeycomb support. The injector supplies fuel to the honeycomb support. The honeycomb support has a plurality of porous walls separating a plurality of inlet cells and a plurality of outlet cells. The exhaust gas flowing into the inlet cells flows through the porous walls into the outlet cells. Each porous wall has an upstream surface facing the inlet cell and a downstream surface facing the outlet cell. An upstream catalytic layer is formed on the upstream surface and a downstream catalytic layer is formed on the downstream surface. One of the upstream catalytic layer and the downstream catalytic layer is composed of a fuel reforming catalyst whose function is to reform the fuel to generate a reducing agent, and the other of the upstream catalytic layer and the downstream catalytic layer has a catalytic function which is different from the function of the fuel reforming catalyst.

1 . An exhaust gas purification device comprising:
 an injector; and   a wall-flow type honeycomb support to which the injector supplies fuel, the honeycomb support having a plurality of porous walls separating a plurality of inlet cells and a plurality of outlet cells, wherein the exhaust gas flowing into the inlet cells flows through the porous walls into the outlet cells, wherein each porous wall has an upstream surface facing the inlet cell and a downstream surface facing the outlet cell, wherein an upstream catalytic layer is formed on the upstream surface and a downstream catalytic layer is formed on the downstream surface, wherein one of the upstream catalytic layer and the downstream catalytic layer is composed of a fuel reforming catalyst whose function is to reform the fuel to generate a reducing agent, and the other of the upstream catalytic layer and the downstream catalytic layer has a catalytic function which is different from the function of the fuel reforming catalyst.   
   
   
       2 . The exhaust gas purification device according to  claim 1 , wherein the upstream catalytic layer is composed of the fuel reforming catalyst, wherein the downstream catalytic layer is composed of a nitrogen oxide storage-reduction catalyst reducing nitrogen oxide contained in the exhaust gas to generate nitrogen by the reducing agent which is generated by the fuel reforming catalyst. 
   
   
       3 . The exhaust gas purification device according to  claim 2 , further comprising a selective catalytic reduction catalyst at downstream of the honeycomb support. 
   
   
       4 . The exhaust gas purification device according to  claim 1 , wherein the upstream catalytic layer is composed of an oxidizing catalyst burning particulate matter contained in the exhaust gas, wherein the downstream catalytic layer is composed of the fuel reforming catalyst. 
   
   
       5 . The exhaust gas purification device according to  claim 4 , further comprising a selective catalytic reduction catalyst at downstream of the honeycomb support. 
   
   
       6 . The exhaust gas purification device according to  claim 1 , wherein the fuel reforming catalyst is to reform diesel fuel to generate at least one of carbon monoxide, hydrogen or hydrocarbon as a reducing agent. 
   
   
       7 . A honeycomb support comprising:
 a plurality of porous walls separating a plurality of inlet cells and a plurality of outlet cells, wherein exhaust gas flowing into the inlet cells flows through the porous walls into the outlet cells, wherein each porous wall has an upstream surface facing the inlet cell and a downstream surface facing the outlet cell, wherein an upstream catalytic layer is formed on the upstream surface and a downstream catalytic layer is formed on the downstream surface, wherein one of the upstream catalytic layer and the downstream catalytic layer is composed of a fuel reforming catalyst whose function is to reform fuel to generate a reducing agent, and the other of the upstream catalytic layer and the downstream catalytic layer has a catalytic function which is different from the function of the fuel reforming catalyst.