Issue 6, 2016

Adsorption and transformations of ethene on hydrogenated rhodium clusters in faujasite-type zeolite. A computational study

Abstract

Regarding the heterogeneous catalytic hydrogenation of ethene on small rhodium clusters, anchored in faujasite, we computationally studied C2Hx (x = 2–5) intermediates on zeolite-supported Rh3 and Rh4 clusters with pre-loaded hydrogen. According to the calculated Gibbs free energies, at temperatures and hydrogen pressure values representing pertinent experiments, the favored stable species on hydrogen-loaded Rh3 is ethylidyne which apparently prevents further hydrogenation due to its strong CH3–C[triple bond, length as m-dash]Rhn interaction. In contrast, on bare and hydrogenated Rh4 clusters, the partially hydrogenated species C2H5, a locally stable intermediate, is among the most stable adsorption complexes examined. These “pseudo ethyl” C2H5 ligands exhibit a very specific structure, where both carbon atoms and a hydrogen atom of the organic moiety interact with the apical Rh center of Rh4; previously, such ligand structures have been identified only computationally as transition states in homogeneous catalysis of ethene hydrogenation. According to our analysis based on the thermodynamic phase diagrams, one is led to conclude that only Rh clusters of such specific topology may be appropriate for the catalytic hydrogenation of ethene, in contrast to the zeolite-supported Rh3 clusters. Suggestions are made for further probing this size-specific catalytic activity of Rh clusters.

Graphical abstract: Adsorption and transformations of ethene on hydrogenated rhodium clusters in faujasite-type zeolite. A computational study

Supplementary files

Article information

Article type
Paper
Submitted
21 Sep 2015
Accepted
12 Oct 2015
First published
15 Oct 2015

Catal. Sci. Technol., 2016,6, 1726-1736

Author version available

Adsorption and transformations of ethene on hydrogenated rhodium clusters in faujasite-type zeolite. A computational study

V. K. Markova, G. N. Vayssilov, A. Genest and N. Rösch, Catal. Sci. Technol., 2016, 6, 1726 DOI: 10.1039/C5CY01589H

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