Coating dispersion for exhaust gas catalysts

A catalyst for treating exhaust gas of an internal combustion engine, comprising:

• an inert ceramic or metal element having a honeycomb structure;
• a coating on the inert ceramic or metal element, wherein the coating includes at least one temperature-resistant support material and active components in an amount of 0.01 to 10% by weight, the active components being platinum, palladium, and optionally rhodium or iridium, with a ratio by weight of platinum to palladium of 1:10 to 10:1, wherein the catalyst is obtained by coating the inert ceramic or metal element with a coating dispersion to form a coated ceramic or metal element, drying the element in air at 250.degree. C., and treating the element at temperatures of 250.degree. to 650.degree. C., optionally in a hydrogen-containing gas stream, wherein the coating dispersion is an aqueous dispersion of the temperature-resistant support material and the active components, wherein the active components optionally include at least one promoter, wherein at least one of the members selected from the group consisting of the temperature-resistant support material, the active components, and the promoter has a multimodal particle size distribution including a fine-particle solids fraction and a coarse-particle solids fraction, wherein the coarsest particle solids fraction has an average particle diameter in the range of 20 to 100 .mu.m, wherein the coating dispersion is applied to the inert ceramic or metal element in a quantity of 30 to 400 grams dry matter per liter catalyst volume.

A catalyst for treating exhaust gas of an internal combustion engine, comprising:

• an inert ceramic or metal element having a honeycomb structure;
• a catalyst coating on the inert ceramic or metal element, wherein the catalyst coating includes at Least one temperature resistant support material and active components in an amount of 0.01 to 10% by weight, the active components being platinum, palladium, and optionally rhodium or iridium, with a ratio by weight of platinum to palladium of 1:10 to 10:1, wherein the catalyst is obtained by coating the inert ceramic or metal element with a coating dispersion including the temperature-resistant support material, to thereby provide a coated element, and impregnating the coated element, after drying in air at 250.degree. C., with an aqueous solution of a salt or a mixture of salts of the active components to thereby provide an impregnated coating on the element, drying and treating the impregnated coating at temperatures of 250.degree. to 650.degree. C., optionally in a hydrogen-containing gas stream, to thereby provide the catalyst coating on the inert ceramic or metal element, wherein the active components optionally include at least one promoter, and wherein at least one member selected from the group consisting of the temperature-resistant support material, the active components, and the promoter has a multi-modal particle size distribution including a fine-particle solids fraction and a coarse-particle solids fraction, wherein the coarsest particle solids fraction has an average particle diameter in the range of 20 to 100 .mu.m, wherein the coating is present on the inert ceramic or metal element in a quantity of 30 to 400 grams dry matter per liter catalyst volume.