期刊
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
卷 52, 期 51, 页码 13553-13557出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.201306620
关键词
heterogeneous catalysis; molybdenum; olefin metathesis; oxidation; supported catalysts
资金
- Alexander von Humboldt Foundation (Germany)
- U.S. DOE [DE-FG02-05ER15688]
- U.S. DOE-Basic Energy Sciences [FG02-93ER14350]
- Mitsubishi Gas Chemical Co. Inc.
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 (0.2-2.5Mo atomsnm(-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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