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The Contribution of Alumina Phase Transformations to the Sintering of Pd Automotive Catalysts

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Abstract

High temperature aging of supported Pd/alumina causes a phase transformation of the transitional (γ, θ or δ) alumina support into alpha (α) alumina. This phase transformation is accompanied by a loss in surface area. This raises the question: how much is the drop in Pd dispersion caused by support sintering? We answer this question by a comparison of chemically similar Pd/alumina catalysts that differ only in one aspect, their physical treatment. The physical treatment is the milling of the support which is often used during wash coating of monolithic automotive catalysts. We show that milling of transitional alumina supports can accelerate their phase transformation into alpha alumina. By comparing catalysts that were milled with those that were not milled, we conclude that the sintering of the catalyst support does not contribute significantly to the sintering of the metal phase. Our results apply specifically to isothermal aging of the catalysts at 900 °C in 10% H2O in N2 for periods of up to 200 h.

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Acknowledgments

The authors KCK and AKD would like to thank Prof. Harold Kung (Nothwestern University), to whom this volume is dedicated, for numerous discussions on the subject of catalysis. The research reported here was supported by the National Science Foundation, CBET division and the GOALI program, and by Delphi Catalysts, Tulsa, OK. We thank Sasol for providing us with the alumina support. The electron microscopy was performed in the microscopy facility within the Earth and Planetary Sciences Department using the TEM which was acquired via NSF grant CTS 9871292.

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Author notes

  1. Qing Xu

    Present address: Nanostructured & Amorphous Materials Inc, Houston, TX, 77084, USA

  2. Karl C. Kharas

    Present address: Rentech, Commerce City, CO, 80022, USA

Authors and Affiliations

  1. Department of Chemical & Nuclear Engineering and Center for Microengineered Materials, University of New Mexico, Albuquerque, NM, 87131, USA

    Qing Xu & Abhaya K. Datye

  2. Delphi Catalyst, Tulsa, OK, 74158, USA

    Karl C. Kharas & Brandon J. Croley

Authors
  1. Qing Xu
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  2. Karl C. Kharas
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  3. Brandon J. Croley
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  4. Abhaya K. Datye
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Corresponding author

Correspondence to Abhaya K. Datye.

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Xu, Q., Kharas, K.C., Croley, B.J. et al. The Contribution of Alumina Phase Transformations to the Sintering of Pd Automotive Catalysts. Top Catal 55, 78–83 (2012). https://doi.org/10.1007/s11244-012-9770-x

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