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Measurement of the ceria surface area of a three-way commercial catalyst after laboratory and engine bench aging

Elsevier Science & Technology
DOI: 10.1016/s0167-2991(98)80871-9
  • Earth Science
  • Geography


Abstract The ceria surface area of a commercial Pt-Rh three-way catalyst was determined after laboratory hydrothermal aging at 1173-1373 K and after 200 h on engine bench. It was measured by X-ray diffraction (XRD) line broadening analysis and by a method based on the exploitation of the hydrogen temperature programmed reduction (TPR) profiles. In this case, the hydrogen uptakes below about 900 K include the ceria surface reduction and that of the oxidized noble metals. They are analyzed and discussed, assuming two possibities for the metals oxidation state. Compared to the fresh catalyst, the TPR profiles are deeply modified by the aging treatments. The ceria seems to sinter more than alumina, particularly between 1173 K and 1273 K. After aging at 1273-1373 K, the calculated ceria surface area is only 15-10 m2g−1 washcoat, which represents 20% of the BET area, instead of 40% initially. A stabilization treatment at 823 K under reactants leads to an additional ceria sintering even for the more aged system. Finally, the measurements on the engine bench aged catalysts seem to indicate a better resistance of ceria to sintering in working conditions. The presence of a pollutant layer, containing phosphorus, zinc and calcium, did not modify the accessible ceria surface area measured by TPR.

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