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Chromium and Lanthanum on Transition Alumina Surfaces: The Role of Bulk Point-Defect Distributions on Catalytic Activity

Published online by Cambridge University Press:  11 February 2011

S. N. Rashkeev
Affiliation:
Dept. Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, U.S.A.
K. Sohlberg
Affiliation:
Dept. Chemistry, Drexel University, Philadelphia, PA 19104, U.S.A.
M. V. Glazoff
Affiliation:
Alcoa Technical Center, Alcoa Center, PA 15069, U.S.A.
J. Novak
Affiliation:
Alcoa Technical Center, Alcoa Center, PA 15069, U.S.A.
S. J. Pennycook
Affiliation:
Dept. Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, U.S.A. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.A.
S. T. Pantelides
Affiliation:
Dept. Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, U.S.A. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, U.S.A.
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Abstract

We employ a combination of Z-contrast scanning transmission electron microscopy (Z-STEM) and first-principles density-functional calculations to investigate the interaction between metal atoms and cubic alumina catalytic supports. We show that there are two observed La sites at the porous γ- alumina surface, and that single La atoms do not exhibit a tendency to cluster. Cr behaves very differently from La - it has a tendency to cover the alumina surface in ordered, periodic raft-like patches. The degradation of the chromia/alumina catalyst is related to the possibility for the chromium to move away from the surface into the bulk, and the activation barrier for such a process is higher in η- alumina than in γ- alumina, i.e., η- alumina is a more durable support for chromium catalyst.

Type
Research Article
Copyright
Copyright © Materials Research Society 2003

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References

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