Oxidation characteristics of Ru/CeO2 catalyst

Hosokawa, Saburo; Nogawa, Satoshi; Taniguchi, Makoto; Utani, Kazunori; Kanai, Hiroyoshi; Imamura, Seiichiro

doi:10.1016/j.apcata.2005.04.026

Cited by 48 publications

(54 citation statements)

References 23 publications

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“…The reduction of ruthenium species on other supports such as titania occurred at a temperature higher than 200 8C, and a temperature higher than 100 8C was required for the reduction of bulk RuO 2 . [26,32] These results indicate that the surface ruthenium species on ceria is easily reduced. The used catalyst after the calcination showed a profile similar to that of the fresh catalyst, suggesting that the original surface ruthenium species are regenerated by calcination of the used catalyst.…”

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confidence: 88%

“…The spectrum of the fresh catalyst showed a distinct band at 984 cm À1 that could be assigned to a ruthenium oxo (Ru=O) species. [32] Although such a distinct peak was not recognized for Ru/ZrO 2 , the formation of similar ruthenium-oxygen species has also been proposed for the zirconia-supported catalyst. [33] There were no signs of oxo species for ruthenium catalysts supported on As demonstrated above, the catalytic activity of Ru/CeO 2 gradually decreased during repeated uses.…”

mentioning

confidence: 96%

“…A previous XANES study showed the formation of five-coordinate Ru(IV) species on the surface of Ru/ CeO 2 prepared by a similar method. [32] Based on the results of DRIFTS and an H 2 -TPR study, these oxo species are thought to be transformed to reduced active ruthenium species during the catalytic runs. The absence of distinct induction periods (see Figure 1) suggests that the generation of active species might occur at the very initial stage of the reaction.…”

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Recyclable Solid Ruthenium Catalysts Supported on Metal Oxides for the Addition of Carboxylic Acids to Terminal Alkynes

et al. 2010

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Ceria-supported ruthenium catalysts (Ru/ CeO 2 ) were found to be quite effective for the addition of various carboxylic acids to terminal alkynes, which gave the corresponding enol esters in moderate to high yields. The major products of the reaction were E-isomers of anti-Markovnikov adducts. Among the ceria-supported ruthenium catalysts examined, those prepared using ruthenium precursors with chloride ligands showed high activities. The zirconia-supported ruthenium catalyst (Ru/ZrO 2 )showed activity comparable to that of the ceria-supported catalyst. These catalysts were recyclable without a significant loss of activity, and the leaching of ruthenium species into the liquid phase was negligible after cooling the reaction mixture, which indicates marked superiority of the present solid oxide catalysts to conventional homogeneous catalysts.

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Recyclable Solid Ruthenium Catalysts Supported on Metal Oxides for the Addition of Carboxylic Acids to Terminal Alkynes

et al. 2010

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“…1(a), the X-ray absorption near-edge structure (XANES) spectra of ruthenium on SiO2, Al2O3 and TiO2 are quite similar to that of rutiletype crystalline RuO2. On the other hand, the spectrum of Ru/CeO2 is very different: a pre-edge peak appears at 22,110 eV, which is characteristic of ruthenium(IV) species in a distorted coordination environment 48) . Figure 1(b) shows Fourier transforms of Ru K-edge extended X-ray absorption fine structure (EXAFS) spectra.…”

Section: Reactions Catalyzed By Low-valent Rutheniummentioning

confidence: 99%

“…Whereas the spectra of Ru/SiO2, Ru/Al2O3 and Ru/TiO2 are very close to that of crystalline RuO2, the shape of FT of Ru/CeO2 is very different: peaks due to a second coordination sphere are very weak, which suggests the presence of highly dispersed ruthenium species. The FTIR spectrum of fresh Ru/ CeO2 shows a characteristic peak at 980 cm -1 that could be assigned to the Ru O vibration mode (data not shown) 48) , which disappeared just after the reaction started. These results suggest the presence of highly dispersed ruthenium(IV) oxo species with a distorted coordination environment on the surface of the fresh Ru/CeO2 catalyst (Scheme 1), which would be reduced at the initial stage of the reaction yielding a low-valent Ru species that plays an important role in the catalysis.…”

Section: Reactions Catalyzed By Low-valent Rutheniummentioning

confidence: 99%

グリーン有機分子変換プロセスを指向したセリア担持ルテニウム触媒の開発

Wada

Miura

Hosokawa

et al. 2013

J. Jpn. Petrol. Inst.

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Solid Ru/CeO2 catalysts, which are effective for the catalysis of various highly atom-efficient organic transformations such as dehydrogenative synthesis of indole, regio-and stereo-selective coupling of unsaturated hydrocarbons, C _ C bond-forming reactions via the activation of aromatic C _ H bonds, and selective addition of carboxylic acids to alkynes, have been developed. For these reactions, CeO2-supported and, in some cases, ZrO2-supported catalysts show excellent activities, whereas ruthenium catalysts on other oxide supports are not effective. Spectroscopic studies have revealed that various types of catalytically active, low-valent ruthenium species are generated from ruthenium(IV) oxo species that are exclusively formed on the surface of CeO2 under appropriate conditions. These solid ruthenium catalysts can be recycled without loss of activity or significant leaching of ruthenium species into the solution, and these features, as well as the wide range of applicable reactions, make the present catalytic system quite attractive from both practical and environmental perspectives.

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