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Impact of nanoparticle–support interactions in Co3O4/Al2O3 catalysts for the preferential oxidation of carbon monoxide

Impact of nanoparticle–support interactions in Co3O4/Al2O3 catalysts for the preferential oxidation of carbon monoxide
Impact of nanoparticle–support interactions in Co3O4/Al2O3 catalysts for the preferential oxidation of carbon monoxide
Different supporting procedures were followed to alter the nanoparticle–support interactions (NPSI) in two Co3O4/Al2O3 catalysts, prepared using the reverse micelle technique. The catalysts were tested in the dry preferential oxidation of carbon monoxide (CO-PrOx) while their phase stability was monitored using four complementary in situ techniques, viz., magnet-based characterization, PXRD, and combined XAS/DRIFTS, as well as quasi in situ XPS, respectively. The catalyst with weak NPSI achieved higher CO2 yields and selectivities at temperatures below 225 °C compared to the sample with strong NPSI. However, relatively high degrees of reduction of Co3O4 to metallic Co were reached between 250 and 350 °C for the same catalyst. The presence of metallic Co led to the undesired formation of CH4, reaching a yield of over 90% above 300 °C. The catalyst with strong NPSI formed very low amounts of metallic Co (less than 1%) and CH4 (yield of up to 20%) even at 350 °C. When the temperature was decreased from 350 to 50 °C under the reaction gas, both catalysts were slightly reoxidized and gradually regained their CO oxidation activity, while the formation of CH4 diminished. The present study shows a strong relationship between catalyst performance (i.e., activity and selectivity) and phase stability, both of which are affected by the strength of the NPSI. When using a metal oxide as the active CO-PrOx catalyst, it is important for it to have significant reduction resistance to avoid the formation of undesired products, e.g., CH4. However, the metal oxide should also be reducible (especially on the surface) to allow for a complete conversion of CO to CO2 via the Mars–van Krevelen mechanism.
2155-5435
7166-7178
Nyathi, Thulani M.
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Fischer, Nico
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York, Andrew P. E.
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Morgan, David J.
a54eaa5b-09bc-4185-8f18-dfc1eeeb310e
Hutchings, Graham J.
efab6909-c2f0-4992-a188-10b761075311
Gibson, Emma K.
738c74e4-ab68-42fe-bda8-9d4a43669b31
Wells, Peter P.
bc4fdc2d-a490-41bf-86cc-400edecf2266
Catlow, C. Richard A.
50b88125-9415-4b37-9146-af6783e42510
Claeys, Michael
19cb6adb-b243-4dba-b0a8-94fd2c1f9658
Nyathi, Thulani M.
e5a3f8fb-63de-4b2c-a7d2-3b6be6f8107e
Fischer, Nico
35b81bb7-173c-4a45-a2fd-0a99910b1e5f
York, Andrew P. E.
fbd1bacf-79f8-4e88-842e-af3e4ab7dd3d
Morgan, David J.
a54eaa5b-09bc-4185-8f18-dfc1eeeb310e
Hutchings, Graham J.
efab6909-c2f0-4992-a188-10b761075311
Gibson, Emma K.
738c74e4-ab68-42fe-bda8-9d4a43669b31
Wells, Peter P.
bc4fdc2d-a490-41bf-86cc-400edecf2266
Catlow, C. Richard A.
50b88125-9415-4b37-9146-af6783e42510
Claeys, Michael
19cb6adb-b243-4dba-b0a8-94fd2c1f9658

Nyathi, Thulani M., Fischer, Nico, York, Andrew P. E., Morgan, David J., Hutchings, Graham J., Gibson, Emma K., Wells, Peter P., Catlow, C. Richard A. and Claeys, Michael (2019) Impact of nanoparticle–support interactions in Co3O4/Al2O3 catalysts for the preferential oxidation of carbon monoxide. ACS Catalysis, 9, 7166-7178. (doi:10.1021/acscatal.9b00685).

Record type: Article

Abstract

Different supporting procedures were followed to alter the nanoparticle–support interactions (NPSI) in two Co3O4/Al2O3 catalysts, prepared using the reverse micelle technique. The catalysts were tested in the dry preferential oxidation of carbon monoxide (CO-PrOx) while their phase stability was monitored using four complementary in situ techniques, viz., magnet-based characterization, PXRD, and combined XAS/DRIFTS, as well as quasi in situ XPS, respectively. The catalyst with weak NPSI achieved higher CO2 yields and selectivities at temperatures below 225 °C compared to the sample with strong NPSI. However, relatively high degrees of reduction of Co3O4 to metallic Co were reached between 250 and 350 °C for the same catalyst. The presence of metallic Co led to the undesired formation of CH4, reaching a yield of over 90% above 300 °C. The catalyst with strong NPSI formed very low amounts of metallic Co (less than 1%) and CH4 (yield of up to 20%) even at 350 °C. When the temperature was decreased from 350 to 50 °C under the reaction gas, both catalysts were slightly reoxidized and gradually regained their CO oxidation activity, while the formation of CH4 diminished. The present study shows a strong relationship between catalyst performance (i.e., activity and selectivity) and phase stability, both of which are affected by the strength of the NPSI. When using a metal oxide as the active CO-PrOx catalyst, it is important for it to have significant reduction resistance to avoid the formation of undesired products, e.g., CH4. However, the metal oxide should also be reducible (especially on the surface) to allow for a complete conversion of CO to CO2 via the Mars–van Krevelen mechanism.

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Nyathi et al_2019_ACS Catal_final version - Accepted Manuscript
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e-pub ahead of print date: 28 June 2019

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Local EPrints ID: 432652
URI: http://eprints.soton.ac.uk/id/eprint/432652
ISSN: 2155-5435
PURE UUID: 0a0db5c2-c26d-4d8f-a61a-e893984d7fc3
ORCID for Peter P. Wells: ORCID iD orcid.org/0000-0002-0859-9172

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Date deposited: 23 Jul 2019 16:30
Last modified: 16 Mar 2024 08:01

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Contributors

Author: Thulani M. Nyathi
Author: Nico Fischer
Author: Andrew P. E. York
Author: David J. Morgan
Author: Graham J. Hutchings
Author: Emma K. Gibson
Author: Peter P. Wells ORCID iD
Author: C. Richard A. Catlow
Author: Michael Claeys

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