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In situ K-edge X-ray absorption spectroscopy of the ligand environment of single-site Au/C catalysts during acetylene hydrochlorination

In situ K-edge X-ray absorption spectroscopy of the ligand environment of single-site Au/C catalysts during acetylene hydrochlorination
In situ K-edge X-ray absorption spectroscopy of the ligand environment of single-site Au/C catalysts during acetylene hydrochlorination

The replacement of HgCl2/C with Au/C as a catalyst for acetylene hydrochlorination represents a significant reduction in the environmental impact of this industrial process. Under reaction conditions atomically dispersed cationic Au species are the catalytic active site, representing a large-scale application of heterogeneous single-site catalysts. While the metal nuclearity and oxidation state under operating conditions has been investigated in catalysts prepared from aqua regia and thiosulphate, limited studies have focused on the ligand environment surrounding the metal centre. We now report K-edge soft X-ray absorption spectroscopy of the Cl and S ligand species used to stabilise these isolated cationic Au centres in the harsh reaction conditions. We demonstrate the presence of three distinct Cl species in the materials; inorganic Cl-, Au-Cl, and C-Cl and how these species evolve during reaction. Direct evidence of Au-S interactions is confirmed in catalysts prepared using thiosulfate precursors which show high stability towards reduction to inactive metal nanoparticles. This stability was clear during gas switching experiments, where exposure to C2H2 alone did not dramatically alter the Au electronic structure and consequently did not deactivate the thiosulfate catalyst.

2041-6520
7040-7052
Malta, Grazia
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Kondrat, Simon A.
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Freakley, Simon J.
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Morgan, David J.
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Gibson, Emma K.
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Wells, Peter P.
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Aramini, Matteo
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Gianolio, Diego
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Thompson, Paul B.J.
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Johnston, Peter
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Hutchings, Graham J.
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Malta, Grazia
f8644878-b7a5-4e78-b099-8ea07b1dd233
Kondrat, Simon A.
8f09c877-8bb6-4c82-8f81-564085479aff
Freakley, Simon J.
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Morgan, David J.
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Gibson, Emma K.
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Wells, Peter P.
bc4fdc2d-a490-41bf-86cc-400edecf2266
Aramini, Matteo
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Gianolio, Diego
5b316f7d-f314-4337-954e-8c0ce8e38223
Thompson, Paul B.J.
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Johnston, Peter
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Hutchings, Graham J.
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Malta, Grazia, Kondrat, Simon A., Freakley, Simon J., Morgan, David J., Gibson, Emma K., Wells, Peter P., Aramini, Matteo, Gianolio, Diego, Thompson, Paul B.J., Johnston, Peter and Hutchings, Graham J. (2020) In situ K-edge X-ray absorption spectroscopy of the ligand environment of single-site Au/C catalysts during acetylene hydrochlorination. Chemical Science, 11 (27), 7040-7052. (doi:10.1039/d0sc02152k).

Record type: Article

Abstract

The replacement of HgCl2/C with Au/C as a catalyst for acetylene hydrochlorination represents a significant reduction in the environmental impact of this industrial process. Under reaction conditions atomically dispersed cationic Au species are the catalytic active site, representing a large-scale application of heterogeneous single-site catalysts. While the metal nuclearity and oxidation state under operating conditions has been investigated in catalysts prepared from aqua regia and thiosulphate, limited studies have focused on the ligand environment surrounding the metal centre. We now report K-edge soft X-ray absorption spectroscopy of the Cl and S ligand species used to stabilise these isolated cationic Au centres in the harsh reaction conditions. We demonstrate the presence of three distinct Cl species in the materials; inorganic Cl-, Au-Cl, and C-Cl and how these species evolve during reaction. Direct evidence of Au-S interactions is confirmed in catalysts prepared using thiosulfate precursors which show high stability towards reduction to inactive metal nanoparticles. This stability was clear during gas switching experiments, where exposure to C2H2 alone did not dramatically alter the Au electronic structure and consequently did not deactivate the thiosulfate catalyst.

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Accepted/In Press date: 23 June 2020
e-pub ahead of print date: 24 June 2020

Identifiers

Local EPrints ID: 442887
URI: http://eprints.soton.ac.uk/id/eprint/442887
ISSN: 2041-6520
PURE UUID: 78fcfa9d-0084-4e9c-ab97-ac95eed7fc43
ORCID for Peter P. Wells: ORCID iD orcid.org/0000-0002-0859-9172

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Date deposited: 30 Jul 2020 16:31
Last modified: 28 Apr 2022 01:55

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Contributors

Author: Grazia Malta
Author: Simon A. Kondrat
Author: Simon J. Freakley
Author: David J. Morgan
Author: Emma K. Gibson
Author: Peter P. Wells ORCID iD
Author: Matteo Aramini
Author: Diego Gianolio
Author: Paul B.J. Thompson
Author: Peter Johnston
Author: Graham J. Hutchings

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