1992-02-01

Optimisation of Metallic TWC Behaviour and Precious Metal Costs 920395

Two different catalyst series were investigated to optimize metallic 3-way catalyst behaviour and precious metal costs. In the dual bed catalyst formulations the inlet and the outlet halves had different Pt/Rh, Pd/Rh, Pt or Pd loadings. The effects of relative cerium loading were also evaluated. All catalysts were tested in the laboratory as thermally aged. Also some catalysts were tested and aged on an engine bench.
The behaviour and the durability of 3-way catalysts was not proportional to their precious metal costs. The results of different aging and test procedures (from both laboratory and engine environments) must be combined in order to get the whole picture of the catalyst characteristics and of its suitability for the TWC-purpose.
Separate, thermally resistant catalyst combinations with low cost could be found for rich (Pd20+Pt/Rh40), stoichiometric (Pt/Rh20+Pt/Rh40) or lean (Pt/Rh40+Pd20) conditions. The performance of Pt/Rh, Pt and Rh catalysts improved with increasing cerium loading. The amount of cerium had no effect in the case of Pd/Rh or Pd catalysts.

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