Patent ID: 8105561
Filing Date: 2012-01-31
Classification: B01D,B01J,F01N,Y02T

Abstract:
1. A catalyst for purification of exhaust gas in which a noble metal is supported on a metal-oxide support, wherein the support contains a composite oxide of zirconia and/or alumina, and at least one element selected from the group consisting of alkaline earth metal elements, rare earth elements and 3A group elements, an addition component supported on the support, and containing at least one element selected from the group consisting of alkaline earth metal elements, rare earth elements and 3A group elements, an amount of the noble metal supported on the support ranges from 0.05% to 2% by mass to the mass of the catalyst, and a molar ratio (amount of addition component/amount of noble metal) of an amount of the addition component supported on the support to the amount of the noble metal ranges from 0.5 to 20 in terms of metal, in an oxidation atmosphere, the noble metal exists on the surface of the support in high oxidation state, and the noble metal binds with a cation of the support via an oxygen atom on the surface of the support to form a surface oxide layer, and in a reduction atmosphere, the noble metal exists on the surface of the support in a metal state, and an amount of noble metal exposed at the surface of the support, measured by CO chemisorption, is 10% or more in atomic ratio to a whole amount of the noble metal supported on the support.