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Abstract

An emissions treatment catalyst formed using pH-compatible ingredients is disclosed. Engine exhaust treatment systems including such catalysts are also provided. Methods of making and using these catalysts are also provided. Methods include creating precious metal-support composites where the precious metal precursor has a solution pH that is compatible an aqueous slurry pH of the support. In one example, a basic precious metal solution having a pH of 7 or greater is mixed with a promoted refractory metal oxide support having an aqueous slurry pH of 7 or greater. On the other hand, an acidic precious metal solution having a pH of less than 7 is mixed with a promoted refractory metal oxide support having an aqueous slurry pH of less than 7. The mixture of the salt and the promoted refractory metal oxide support can be thermally treated at a temperature of at least 180° C. to thermally fix the well-dispersed precious metal on the support. Complex ions of basic solutions and include tetraamine nitrate, tetraamine hydroxide, tetraamine acetate, a primary amine nitrate, a primary amine hydroxide, a primary amine acetate, or combinations thereof. The refractory metal oxide support can be promoted by oxides of lanthanum, barium, zirconium, neodymium, yttrium, praseodymium, somarium, ceria, or combinations thereof.

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First Claim