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Artigo Produção Nacional Revisado por pares
BIBTEX RIS

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

2006; Elsevier BV; Volume: 318; Linguagem: Inglês

10.1016/j.apcata.2006.10.045

ISSN

1873-3875

Autores

B.A. Riguetto, Christianne Elisabete da Costa Rodrigues, Marco A. Morales, E. Baggio‐Saitovitch, L. Gengembre, E. Payen, C.M.P. Marques, J.M.C. Bueno,

Tópico(s)

Catalysts for Methane Reforming

Resumo

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 structures such Ru3Sn7 I, Ru3Sn7 II, and oxide species (RuOSn). The contents of the various species depended on Sn loading. The reaction data showed that the Ru/SiO2 catalyst was active only for hydrogenation of the CC bond, while the addition of a small amount of Sn (1 wt.% of Sn) made the catalyst active for hydrogenation of both the CC and CO bonds. Upon increasing the Sn loading from 1 to around 3.6 wt.%, the specific rate for CC hydrogenation is greatly reduced whereas the specific rate for CO hydrogenation decreases more gradually. The activity for CC hydrogenation remains unvarying for Sn loading higher than 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 CO 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 CO bond, but has the opposite effect on hydrogenation of the CC bond. The geometric effect of formation of Sn-Ru intermetallic and SnOx compounds on the Ru particle surface may play a part in the suppression of CC bond hydrogenation.

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