Thermal aging of Pd/Pt/Rh automotive catalysts under a cycled oxidizing–reducing environment

Abstract Mono- and multi-metallic (bi- and tri-) Pt, Pd and Rh supported on cerium-promoted alumina (La Roche, SAS-1/16) catalysts were tested for activity as TWC, both fresh [G.C. Koltsakis, and A.M. Stamatelos, Progr. Energy Combust. Sci. 23 (1997) 1] and after accelerated aging. Aging consisted of a treatment at 900°C for 5 h during which an oxidizing (2.5% O2, 10% H2O, in N2) and a reducing (5.0% CO, 10% H2O, in N2) feedstream were cycled at 0.017 Hz through the catalyst. Activity tests were carried out by increasing temperature from 100 to 600°C at 3°C min−1, while two oxidizing and reducing (±0.5 A/F) feedstreams were alternately (1 Hz) fed through the reactor at 125 000 h−1 (STP). Conversion was continuously analyzed. Light-off temperature, T50, conversion at 500°C (normal running temperature), X500, and the stoichiometric window (A/F from 14.13 to 15.13) for stationary feedstreams, were determined.

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