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Article Dans Une Revue Applied Catalysis A : General Année : 2007

Ru-Sn catalysts for selective hydrogenation of crotonaldehyde:Effect of the Sn/(Sn+Ru) ratio

Résumé

The effects of the Sn/(Ru+Sn) ratio and Ru loading on the properties of silica-supported RuSn catalysts were investigated. Ru-Sn/SiO2 bimetallic catalysts were prepared by the impregnation method and characterized in situ by XPS and Mössbauer Spectroscopy. The XPS results indicated the presence of two Sn species on the surface of the catalysts, in different oxidation states, Sn0 and Snn+, and 119Sn Mössbauer spectra revealed Sn(II), Sn(IV), and intermetallic particles with structure like Ru3Sn7 I, Ru3Sn7 II and oxidic species (RuOSn). The contents of the different species depended on Sn loading. The reaction data show that the Ru/SiO2 catalyst is active only for hydrogenation of the C=C bond, while upon addition of a small amount of Sn (1wt.% Sn), the catalyst becomes active for hydrogenation of the C=O bond. Upon increasing the Sn loading from 1 to around 3.6 wt. %, the specific rate for C=C hydrogenation is strongly hindered whereas the specific rate for C=O hydrogenation decrease. The activity for C=C hydrogenation remains unvarying for Sn loading higher then around 3.6 wt. %. This results in an optimum selectivity to crotyl alcohol at Sn/(Ru+Sn) molar ratio around 0.2-0.3. The abrupt change of activity toward C=O hydrogenation is observed as a lower binding energy than expected is observed for the Ru0. This enhancement of the surface electron density of the Ru particle is crucial to improving the adsorption and reactivity of the C=O bond, but has the opposite effect on hydrogenation of the C=C bond. The geometric effect by formation of Sn-Ru intermetallic and SnOx compounds on the Ru particle surface may have a part in the suppression of C=C bond hydrogenation.

Dates et versions

hal-00115564 , version 1 (21-11-2006)

Identifiants

Citer

Leon Gengembre, B.A Riguetto, C.E.C Rodrigues, M.A Morales, E. Baggio-Saitovitch, et al.. Ru-Sn catalysts for selective hydrogenation of crotonaldehyde:Effect of the Sn/(Sn+Ru) ratio. Applied Catalysis A : General, 2007, pp.318 (70-78). ⟨10.1016/j.apcata.2006.10.045⟩. ⟨hal-00115564⟩
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