期刊
CATALYSIS TODAY
卷 160, 期 1, 页码 116-130出版社
ELSEVIER
DOI: 10.1016/j.cattod.2010.08.022
关键词
Silver clusters; Propene; Propylene; Propylene oxide; Acrolein; Density-functional calculations; Oxametallacycle complex; Cluster reshaping
资金
- Ministerio de Ciencia e Innovacion [MAT2008-06483-C03-01]
- Junta de Castilla y Leon [VA017A08, GR23]
- EC [ERC-2008-AdG-227457]
- CASPUR Supercomputing Center (Rome, Italy)
- Deutsche Forschungsgemeinschaft [Schwerpunktprogramm 1153]
- American Chemical Society
- US Department of Energy, BES-Materials Sciences and BES-Chemical Sciences, and BES-Scientific User Facilities [DE-AC-02-06CH11357]
- UChicago Argonne, LLC
- Air Force Office of Scientific Research
Model silver nanocatalysts between 9 and 23 nm in size were prepared by size-selected cluster deposition from a free cluster beam on amorphous alumina films and their size-dependent catalytic performance studied in the partial oxidation of propylene under realistic reaction conditions. Smaller clusters preferentially produced acrolein, while the 23 nm particles were considerably more selective towards the formation of propylene oxide, at reaction rates far exceeding those previously reported for larger silver particles. The activity of clusters dropped significantly with increasing particle size. First-principle calculations, of the activation energies for oxygen adsorption and its dissociation, at variable surface coverage yielded surface energies which resulted in particle shapes resembling the experimentally observed shapes of partially oxidized silver clusters. The calculated activation barriers for propylene oxide and acrolein formation on various facets and on the edges of the nanoparticles provided detailed information about the energetics of the competing reaction pathways. The size-and corresponding morphology dependent theoretical activity and selectivity are in good accord with experimental observations. (C) 2010 Elsevier B.V. All rights reserved.
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