2007年6月
Thermal activation of molecular tungsten halide clusters with the retention of an octahedral metal framework and the catalytic dehydration of alcohols to olefins as a solid acid catalyst
JOURNAL OF CLUSTER SCIENCE
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- 巻
- 18
- 号
- 2
- 開始ページ
- 414
- 終了ページ
- 430
- 記述言語
- 英語
- 掲載種別
- DOI
- 10.1007/s10876-006-0083-8
- 出版者・発行元
- SPRINGER/PLENUM PUBLISHERS
When the molecular tungsten halide cluster (H3O)(2)[(W6Cl8)Cl-6]center dot 6H(2)O, with an octahedral metal framework, is heated to 50 and 150 degrees C in flowing helium gas, it changes into (H3O)(2)[(W6Cl8)Cl-6] and [(W6Cl8)Cl-4(H2O)(2)], respectively. Activation at 250 degrees C yields a poorly crystallized solid state cluster, [W6Cl8]Cl2Cl4/2, which exhibits catalytic activity for the dehydration of ethanol to yield ethylene and a small amount of ethyl ether and acetal. The activity is attributed to the Bronsted acidity of the hydroxo ligand that is produced by elimination of hydrogen chloride from the chloro and aqua ligands. The catalytic activity increases with increasing temperature, and reaches a maximum at 300 degrees C. The catalytic activity then disappears above 350 degrees C, at which temperature the crystallinity of the cluster improves and the active sites are included in the crystal. In the case of primary alcohols, the reactivity decreases with increasing length of the carbon chain, and secondary alcohols are more reactive than the corresponding primary alcohols. Halide clusters of niobium, molybdenum, and tantalum having the same metal framework are also active catalysts for these reactions.
- リンク情報
- ID情報
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- DOI : 10.1007/s10876-006-0083-8
- ISSN : 1040-7278
- Web of Science ID : WOS:000248171500008