Exhaust gas purification catalyst device

Abstract

This exhaust gas purification catalyst device includes an upper layer which includes first carrier particles and rhodium, and a lower layer which includes second carrier particles, and the upper layer includes a rhodium enriched area in the range a, from the downstream end in the exhaust gas flow to greater than 50% and up to 80% of the upper layer length, and a range b from the upper layer top surface less than 20 μm in the depth direction. The rhodium enriched area contains at least 50% and less than 100% of all the rhodium in the upper layer.

1 . An exhaust gas purification catalyst, comprising:
 an upper layer containing first carrier particles and rhodium, and   a lower layer containing second carrier particles,   wherein
 the upper layer includes a rhodium-rich portion in a range of greater than 50% to 80% of the length of the upper layer from a downstream side end of an exhaust gas flow and of less than 20 μm in the depth direction from an outermost surface of the upper layer, and 
 the rhodium-rich portion contains rhodium in an amount of 50% to less than 100% of the total rhodium included in the upper layer. 
   
     
     
         2 . The exhaust gas purification catalyst device according to  claim 1 , wherein the range of the rhodium-rich portion in an exhaust gas flow direction is up to 70% of the length from the upper layer exhaust stream flow downstream side end. 
     
     
         3 . The exhaust gas purification catalyst device according to  claim 2 , wherein the range of the rhodium-rich portion in the depth direction is a range of up to 18 μm in the depth direction from the outermost surface of the upper layer. 
     
     
         4 . The exhaust gas purification catalyst device according to  claim 1 , wherein a content of ceria in the upper layer is greater than 5% by mass to 25% by mass or less, when the total mass of the first carrier particles in the upper layer is 100% by mass. 
     
     
         5 . The exhaust gas purification catalyst device according to  claim 4 , wherein the content of ceria in the upper layer is 7% by mass to 15% by mass, when the total mass of the first carrier particles in the upper layer is 100% by mass. 
     
     
         6 . The exhaust gas purification catalyst device according to  claim 1 , wherein a quantity of rhodium included in the range of the rhodium-rich portion up to 50% of the length of the rhodium-rich portion from the downstream side end of the exhaust gas flow is 70% or less of the quantity of rhodium included in the rhodium-rich portion. 
     
     
         7 . The exhaust gas purification catalyst device according to  claim 1 , wherein the lower layer and the upper layer are present on a substrate. 
     
     
         8 . The exhaust gas purification catalyst according to  claim 1 , wherein the lower layer constitutes a part or the entirety of a substrate, and the upper layer is present on the lower layer. 
     
     
         9 . A method for the production of the exhaust gas purification catalyst device according to  claim 1 , comprising the steps of:
 providing a coating liquid including a rhodium precursor to an exhaust gas downstream side end of an exhaust gas purification catalyst device precursor comprising an upper layer containing first carrier particles and rhodium and a lower layer containing second carrier particles, and thereafter suctioning from an exhaust gas upstream side end of the exhaust gas purification catalyst device precursor.