Spatial profiling of a Pd/Al2O3 catalyst during selective ammonia oxidation

Decarolis, D., Clark, A. H., Pellegrinelli, T., Nachtegaal, M., Lynch, E. W., Catlow, C. R. A., Gibson, E. K. , Goguet, A. and Wells, P. P. (2021) Spatial profiling of a Pd/Al2O3 catalyst during selective ammonia oxidation. ACS Catalysis, 11(4), pp. 2141-2149. (doi: 10.1021/acscatal.0c05356) (PMID:33643682) (PMCID:PMC7901671)

Abstract

The utilization of operando spectroscopy has allowed us to watch the dynamic nature of supported metal nanoparticles. However, the realization that subtle changes to environmental conditions affect the form of the catalyst necessitates that we assess the structure of the catalyst across the reactant/product gradient that exists across a fixed bed reactor. In this study, we have performed spatial profiling of a Pd/Al2O3 catalyst during NH3 oxidation, simultaneously collecting mass spectrometry and X-ray absorption spectroscopy data at discrete axial positions along the length of the catalyst bed. The spatial analysis has provided unique insights into the structure–activity relationships that govern selective NH3 oxidation—(i) our data is consistent with the presence of PdNx after the spectroscopic signatures for bulk PdNx disappear and that there is a direct correlation to the presence of this structure and the selectivity toward N2; (ii) at high temperatures, ≥400 °C, we propose that there are two simultaneous reaction pathways—the oxidation of NH3 to NOx by PdO and the subsequent catalytic reduction of NOx by NH3 to produce N2. The results in this study confirm the structural and catalytic diversity that exists during catalysis and the need for such an understanding if improvements to important emission control technologies, such as the selective catalytic oxidation of NH3, are to be made.

• Item Type: Articles
• Additional Information: UK Catalysis Hub is kindly thanked for resources and support provided via our membership of the UK Catalysis Hub Consortium and funded by EPSRC grant: EP/R026939/1, EP/R026815/1, EP/R026645/1, EP/R027129/1, or EP/ M013219/1 (biocatalysis).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Gibson, Dr Emma
• Authors: Decarolis, D., Clark, A. H., Pellegrinelli, T., Nachtegaal, M., Lynch, E. W., Catlow, C. R. A., Gibson, E. K., Goguet, A., and Wells, P. P.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: ACS Catalysis
• Publisher: American Chemical Society
• ISSN: 2155-5435
• ISSN (Online): 2155-5435
• Published Online: 03 February 2021
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in ACS Catalysis 11(4): 2141-2149
• Publisher Policy: Reproduced under a Creative Commons License
• Data DOI: 10. 5258/SOTON/D1723