How Strain Affects the Reactivity of Surface Metal Oxide Catalysts |
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Authors: | Dr. Kazuhiko Amakawa Dr. Lili Sun Dr. Chunsheng Guo Dr. Michael Hävecker Pierre Kube Prof. Dr. Israel E. Wachs Soe Lwin Prof. Dr. Anatoly I. Frenkel Dr. Anitha Patlolla Prof. Dr. Klaus Hermann Prof. Dr. Robert Schlögl Dr. Annette Trunschke |
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Affiliation: | 1. Department of Inorganic Chemistry, Fritz‐Haber‐Institut der Max‐Planck‐Gesellschaft, Faradayweg 4‐6, 14195 Berlin (Deutschland) http://www.fhi‐berlin.mpg.de/;2. Department of Solar Energy Research, Helmholtz‐Zentrum Berlin/BESSY II, Albert‐Einstein‐Strasse 15, 12489 Berlin (Deutschland);3. Operando Molecular Spectroscopy & Catalysis Laboratory, Department of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (USA);4. Department of Physics, Yeshiva University, 245 Lexington Avenue, New York, NY 10016 (USA) |
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Abstract: | Highly dispersed molybdenum oxide supported on mesoporous silica SBA‐15 has been prepared by anion exchange resulting in a series of catalysts with changing Mo densities (0.2–2.5 Mo atoms nm?2). X‐ray absorption, UV/Vis, Raman, and IR spectroscopy indicate that doubly anchored tetrahedral dioxo MoO4 units are the major surface species at all loadings. Higher reducibility at loadings close to the monolayer measured by temperature‐programmed reduction and a steep increase in the catalytic activity observed in metathesis of propene and oxidative dehydrogenation of propane at 8 % of Mo loading are attributed to frustration of Mo oxide surface species and lateral interactions. Based on DFT calculations, NEXAFS spectra at the O‐K‐edge at high Mo loadings are explained by distorted MoO4 complexes. Limited availability of anchor silanol groups at high loadings forces the MoO4 groups to form more strained configurations. The occurrence of strain is linked to the increase in reactivity. |
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Keywords: | heterogeneous catalysis molybdenum olefin metathesis oxidation supported catalysts |
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