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

Paper ID Volume ID Publish Year Pages File Format Full-Text
44069 46002 2007 9 PDF Available
Title
Ru-Sn catalysts for selective hydrogenation of crotonaldehyde: Effect of the Sn/(Ru + Sn) ratio
Abstract

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.

Graphical abstractOne series of Ru-Sn/SiO2 catalysts with various Sn loading was studied in the hydrogenation of crotonaldehyde. The addition of a small amount of Sn (1 wt.% Sn) made the catalyst active for hydrogenation of both the CC and CO bonds. The enhancement of the surface electron density of the Ru particle is crucial to improving the adsorption and reactivity of the CO bond.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Ruthenium tin catalysts; SiO2; Crotonaldehyde hydrogenation; XPS; Mössbauer spectroscopy
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Ru-Sn catalysts for selective hydrogenation of crotonaldehyde: Effect of the Sn/(Ru + Sn) ratio
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 318, 20 February 2007, Pages 70–78
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
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Full-text PDF Download
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