Platinum group alumina-supported metal oxidation catalysts and method of making same

摘要

A catalyst construction and method of making is disclosed for treating automotive exhaust gases from a fossil fueled internal combustion engine. The construction comprises: (a) a substrate; (b) a coating on said substrate having comingled first and second phases, said first phase comprising ceria and precious metal in microscale intimacy and said second phase comprising precious metal substantially devoid of ceria and separated from the ceria in said first phase on a macroscale. The phases may be in particle form with (i) the first phase particles resulting from the codeposition of CeO2, precious metal, and Al2O3 from an aqueous solution containing dissolved salts of CeO2 and precious metal and suspended particles of Al2O3; and (ii) the second phase particles resulting from the codeposition of precious metal and Al2O3 from an aqueous solution containing a dissolved salt of the precious metal and suspended particles of Al2O3. Alternatively, the substrate has Al2O3 thereon to increase its surface area, and the two-phase coating is adhered to said Al2O3, said first phase resulting partially from the discontinuous deposition of CeO2 onto said Al2O3 and partially from the continuous deposition of precious metal over said discontinuous CeO2 and over the exposed Al2O3; the precious metal in immediate microscale contact with the CeO2 constitutes the first phase and the precious metal not immediately in microscale contact with the CeO2 constitutes the second phase.