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Deactivation of PT / Zeolite-L Catalysts Studied by Z-Contrast

Published online by Cambridge University Press:  02 July 2020

M. M. J. Treacy
M. M. J. Treacy*
Affiliation:
NEC Research Institute, Inc., 4 Independence Way, Princeton, NJ08540
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Extract

When Pt particles of sub-nanometer dimensions are inserted into the linear channels of the potassium ion form of zeolite L, the resultant Pt/KL catalyst converts linear n-C6 hexane into cyclic C6 benzene with remarkable efficiency [1,2].

However, a drawback to Pt/KL catalysts is that they are exquisitely sensitive to sulfur contamination in the n-hexane feed. The catalyst deactivates rapidly when there are trace amounts (> 50 parts per billion) of sulfur in the feed. Bright field TEM studies show that the Pt particles remain finely dispersed within the channels after sulfur poisoning, with typical particle widths < 1.5 nm, implying that a large percentage of the Pt atoms still reside on the surfaces of the particles. For heterogeneous catalysts such as Pt/γ-alumina, where the Pt particles are always readily accessible on the external surface of the alumina support, such sulfur concentrations are tolerated.

Type
Sir John Meurig Thomas Symposium: Microscopy and Microanalysis in the Chemical Sciences
Information
Microscopy and Microanalysis , Volume 6 , Issue S2: Proceedings: Microscopy & Microanalysis 2000, Microscopy Society of America 58th Annual Meeting, Microbeam Analysis Society 34th Annual Meeting, Microscopical Society of Canada/Societe de Microscopie de Canada 27th Annual Meeting, Philadelphia, Pennsylvania August 13-17, 2000 , August 2000 , pp. 20 - 21
Copyright
Copyright © Microscopy Society of America

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References

1.Bernard, J.R., in Proceedings of the 5th International Zeolite Conference, Napoli, L.V.C. Rees (Ed.) Heyden, London, 686, (1980).Google Scholar
2.Besoukhanova, C., Guidot, J., Barthomeuf, D., Breysse, M., and Bernard, J.R., J. Chem. Soc, Faraday Trans. 1 1595 (1981).CrossRefGoogle Scholar
3.Treacy, M. M. J., Microporous and Mesoporous Materials, 28 271 (1999).CrossRefGoogle Scholar