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The effect of metal composition on the performance of Ir–Au/TiO2 catalysts for citral hydrogenation.

Paper ID Volume ID Publish Year Pages File Format Full-Text
39261 45815 2015 7 PDF Available
Title
The effect of metal composition on the performance of Ir–Au/TiO2 catalysts for citral hydrogenation.
Abstract

•Bimetallic Ir–Au catalysts are active in hydrogenation reactions.•Different bimetallic composition Ir–Au/TiO2 catalysts were investigated in the citral hydrogenation.•A partial coverage of iridium sites by gold atoms takes place as the gold amount increases.•The presence of gold modifies the Irδ+/Ir0 ratio.•The most active sample is Ir–Au (1) where was evidenced the Irδ+/Ir0 ratio.

The effect of gold addition to iridium catalysts and the nature of active sites for citral hydrogenation were investigated over Ir–Au/TiO2 catalysts. All samples (Au/TiO2, Ir/TiO2 and Ir–Au/TiO2) were prepared by deposition-precipitation with urea (DPU). Bimetallic catalysts were synthetized by co-deposition at different Ir/Au atomic ratios (3, 1, 0.3). The catalysts were characterized by ICP, BET, H2–TPR, H2-Chemisorption, TEM, DRIFTS and XPS techniques. A partial coverage of iridium sites by gold atoms takes place as the gold amount in the catalyst increases as shown by chemisorption and XPS measurements. The latter also evidenced a trend consistent with modification of the electronic environment of iridium due to interaction with gold atoms. Also, compared to Ir/TiO2, the amount of Irδ+ species was higher in the bimetallic catalysts reaching a maximum in Ir–Au (1) sample. Characterization of the catalytic surface using DRIFTS of adsorbed CO evidenced a shift towards higher wavenumbers as a function of the gold content indicating, as the XPS results, a modification of the adsorption site. The catalytic activity for citral hydrogenation increased as a function of the gold content. The selectivity to unsaturated alcohol is related to the amount of Irδ+ species which in turns depends on the catalyst composition. For the most active sample Ir–Au (1), a suitable Irδ+/Ir0 ratio is already obtained when the catalyst is reduced at 573 K and does not vary with reduction temperature.

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Keywords
Ir–Au; TiO2; Citral; Hydrogenation; Irδ+/Ir0 ratio
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The effect of metal composition on the performance of Ir–Au/TiO2 catalysts for citral hydrogenation.
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 503, 25 August 2015, Pages 196–202
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