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Selective liquid-phase hydrogenation of citral over supported bimetallic Pt–Co catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
42924 45947 2009 10 PDF Available
Title
Selective liquid-phase hydrogenation of citral over supported bimetallic Pt–Co catalysts
Abstract

The liquid-phase hydrogenation of citral was studied at 393 K and 10 bar on Pt–Co/C catalysts, having different Pt/(Pt + Co) ratios and containing a total metal load of about 2%. The monometallic and bimetallic Pt–Co/C catalysts were prepared by impregnation and co-impregnation, respectively, with cobalt tris(acetylacetonate) and platinum bis(acetylacetonate). Monometallic Pt/C and Co/C catalysts showed very low activity and selectivity to the desired products. Undesirable reactions, such as citral decarbonylation and hydrogenolysis, were observed with these monometallic catalysts. Instead, bimetallic Pt–Co/C proved very active and selective to geraniol/nerol and the main products detected were geraniol/nerol, citronellal and citronellol. Hydrogenation kinetic constants were determined by modeling catalytic data and using a pseudo-homogeneous kinetics. From the analysis of the kinetic parameters, an optimum Pt/(Pt + Co) ratio was found for both the catalytic activity and selectivity towards geraniol/nerol. Furthermore, it was determined that this optimum ratio depends on the activation conditions. Temperature-programmed reduction (TPR) experiments and X-ray absorption spectroscopy (XAS) demonstrated the existence of Pt–Co bimetallic compounds on the carbon support. On the basis of these results, it was proposed that cobalt improves the catalytic performance of platinum by electron transfer. This electron transfer is favored by the high interaction of both metals existing in these types of bimetallic compounds.

Graphical abstractBimetallic Pt–Co/C catalysts proved more active and selective than monometallic Pt/C and Co/C samples in the liquid-phase hydrogenation of citral. The improved catalytic performance of Pt–Co/C samples was attributed to (1) the formation of a bimetallic Pt–Co phase; (2) electron transfer from Co to Pt; (3) a highly activated citral adsorption in the on-top, di-σCO and πCO modes over Pt–Co phase.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Citral hydrogenation; Aldehydes (α,β-unsaturated); Platinum-based catalysts; Cobalt-based catalysts; Bimetallic compounds
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Selective liquid-phase hydrogenation of citral over supported bimetallic Pt–Co catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 358, Issue 1, 30 April 2009, Pages 32–41
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
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us