Wilde, C.A., Ryabenkova, Y., Firth, I.M. et al. (8 more authors) (2019) Novel rhodium on carbon catalysts for the oxidation of benzyl alcohol to benzaldehyde: A study of the modification of metal/support interactions by acid pre-treatments. Applied Catalysis A: General, 570. pp. 271-282. ISSN 0926-860X
Abstract
Rhodium nanoparticles or rhodium organometallic complexes are mainly used in catalysis for reduction or hydroformylation reactions. In this work instead, we explored the capabilities of Rh nanoparticles as an oxidation catalyst, applied to the oxidation of benzyl alcohol to benzaldehyde under very mild conditions (100 °C, and atmospheric pressure) as a model reaction. Here we report the preparation of novel Rh/C catalysts by using an impregnation protocol, with particular emphasis on the pre-treatment of the carbon supports by using HNO3 and HCl, as well as the characterization of these materials by using an array of methods involving TEM, XPS and XRPD. Our preparation method led to a wide Rh particle size distribution ranging from 20 to 100 nm, and we estimate an upper limit diameter of Rh nanoparticles for their activity towards benzyl alcohol oxidation to be ca. 30 nm. Furthermore, a HNO3 pre-treatment of the activated carbon support was able to induce a smaller and narrower particle size distribution of Rh nanoparticles, whereas a HCl pre-treatment had no effect or sintered the Rh nanoparticles. We rationalise these results by HNO3 as an acid able to create new nucleation sites for Rh on the carbon surface, with the final effect of smaller nanoparticles, whereas for HCl the effect of sintering was most likely due to site blocking of the nucleation sites over the carbon surface. The roles of acid centres on the carbon surfaces for the oxidation reaction was also investigated, and the larger their amounts the larger the amounts of by-products. However, by treatment with HNO3 we were able to convert neutral or basic carbons into supports capable to enhance the catalytic activity of Rh, and yet minimised detrimental effects on the selectivity of the oxidation to benzaldehyde.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). |
Keywords: | Rhodium; Nanoparticles; Activated carbons; Acid pre-treatment; Alcohol oxidation |
Dates: |
|
Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Chemistry (Sheffield) |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 18 Feb 2019 14:24 |
Last Modified: | 18 Feb 2019 14:25 |
Published Version: | https://doi.org/10.1016/j.apcata.2018.11.006 |
Status: | Published |
Publisher: | Elsevier |
Refereed: | Yes |
Identification Number: | 10.1016/j.apcata.2018.11.006 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:141461 |