Patent ID: 6625976
Filing Date: 2003-09-30
Classification: B01D,B01J,Y02T

Abstract:
A method of making a platinum group metal three-way catalyst composition which comprises a high temperature catalytic component, a low temperature catalytic component, and an oxygen storage material wherein each catalytic component is present in the catalyst composition as separate distinct particles in a single layer and the oxygen storage material comprises a particulate support material for the high temperature catalytic component, and wherein the high temperature catalytic component exhibits enhanced catalytic activity at temperatures above 500Â° C. and the low temperature catalytic component exhibits enhanced catalytic activity at temperatures in the range of 200 to 400Â° C., the method comprising:(a) forming on a non-porous substrate a combined washcoat of a high temperature catalyst support material and a low temperature catalyst support material from a slurry in which each of the catalyst support materials is of sufficiently large particle size so as to prevent each catalyst support material from forming a solution or a sol with the liquid medium of the slurry, wherein the high temperature catalyst support material comprises the oxygen storage material which comprises the particulate support material; and (b) impregnating a platinum group metal or metals into each catalyst support material either by adding the platinum group metal or metals to the slurry of the high temperature catalyst support material and the low temperature catalyst support material before forming the combined washcoat on the non-porous substrate or by applying the platinum group metal or metals to the washcoat after formation of the washcoat on the non-porous substrate, wherein the high temperature catalytic component comprises a first platinum group metal or metals that is supported on the oxygen storage material and the low temperature catalytic component comprises a second platinum group metal or metals that is supported on the low temperature catalytic support material, wherein the second platinum group metal or metals is the same as or different from the first platinum group metal or metals and wherein the amounts of high temperature and low temperature catalyst support materials present in the catalyst composition are determined by the amount of platinum group metal or metals required in each support material and the ratio of the high temperature catalyst support material to the low temperature catalyst support material is determined by the respective incipient water absorption capability of each catalyst support material wherein the water absorption capabilities of the high temperature catalyst support material and the low temperature catalyst support material are respectively 0.2 to 1.0 ml/g and 0.5 to 2.5 ml/g.