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Structure and Reactivity of RH in the SMSI State

Published online by Cambridge University Press:  28 February 2011

Ehrich J. Braunschweig ,
A. David Logan  and
Abhaya K. Datye
Ehrich J. Braunschweig
Affiliation:
Department of Chemical & Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131, U.S.A.
A. David Logan
Affiliation:
Department of Chemical & Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131, U.S.A.
Abhaya K. Datye
Affiliation:
Department of Chemical & Nuclear Engineering, University of New Mexico, Albuquerque, NM 87131, U.S.A.
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Abstract

Hydrogenolysis of n-butane and CO hydrogenation were used to charac-terize the behavior of TiO2 supported Rh in the SMSI state. The Rh was supported on a model support consisting of nonporous spherical particles of TiO2. The simple geometry of the support permits the metal crystallites to be imaged ‘edge-on’ in a transmission electron microscope. This allows detailed examination of the metal surface and the metal-oxide interface as a function of pretreatment. After high temperature reduction in H2, there is no significant change in the morphology of the Rh crystallites. However, the presence of amorphous overlayers 0.2–0.4 nm thick is clearly evident on the Rh surface. These overlayers can only be partially removed after oxidation at 473 K. The presence of these overlayers is well correlated with the drop in hydrogen chemisorption and altered reactivity. While the butane hydrogenolysis activity of Rh is considerably suppressed in the SMSI state, the CO hydrogenation activity is increased by a factor of 3. The H2 uptake and the butane hydrogenolysis activity can be only partially restored after oxidation at 473 K. Treatment at 773 K in oxygen is necessary for restoring the pre-SMSI behavior.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 111: Symposium O – Microstructure and Properties of Catalysts , 1987 , 35
Copyright
Copyright © Materials Research Society 1988

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