Abstract: A three-way layered catalyst adapted for use in a system operating at about the stoichiometric air/fuel ratio having significantly improved resistance to poisoning in automotive exhaust comprising an alumina support having a first layer of the catalyst material platinum positioned at the support surface and penetrating the body thereof to a desired depth with an inner second layer of the catalyst material rhodium, the second layer being adjacent to the first layer and penetrating the body of the support, the maximum concentration of platinum being at or near the surface of the support with the minimum concentration of rhodium in the first layer being at or close to the surface and increasing in concentration to a maximum to define the boundary between the first and second layers, the concentrations of platinum and rhodium decreasing inwardly from the boundary with the greater portion of rhodium being in the second layer.

Abstract: This invention relates to oxidation catalysts wherein the catalytically active metallic material has an impregnation depth of at least 90 microns up to about 250 microns on the porous support which has a surface area of at least 100 m.sup.2 /g. up to about 250 m.sup.2 /g. and a pore structure characterized by a macropore volume of at least 0.020 cm.sup.3 /g. and a macropore radius greater than about 10,000 A.degree., the maximum value for macropore volume being that at which the catalyst is unable to sustain the load and vibration forces to which it is subjected in the converter.

Abstract: This invention relates to oxidation catalysts wherein the catalytically active metallic material has an impregnation depth of at least 90 microns up to about 250 microns on the porous support which has a surface area of at least 100 m.sup.2 /g. up to about 250 m.sup.2 /g. and a pore structure characterized by a macropore volume of at least 0.020 cm.sup.3 /g. up to about 0.200 cm.sup.3 /g. and a macropore radius greater than about 10,000 A.