Operando spatially and time-resolved X-ray absorption spectroscopy and infrared thermography during oscillatory CO oxidation

[Display omitted] •A supported Pt/Al2O3 catalyst was studied during stable CO oxidation oscillations.•Operando IR thermography was used to identify active catalyst in fixed bed reactor.•Dynamics of Pt oxidation state and atomic coordination was probed by operando XAS.•Correlation of structure and ac...

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Bibliographic Details
Published in:Journal of catalysis 2015-08, Vol.328, p.216-224
Main Authors: Gänzler, Andreas M., Casapu, Maria, Boubnov, Alexey, Müller, Oliver, Conrad, Sabrina, Lichtenberg, Henning, Frahm, Ronald, Grunwaldt, Jan-Dierk
Format: Article
Language:English
Subjects:
Catalysts
Catalytic oxidation
CO oxidation
Cobalt
Heterogeneous catalysis
Oscillations
Platinum
Spectrum analysis
Structure–activity relationships
Thermography
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Summary:[Display omitted] •A supported Pt/Al2O3 catalyst was studied during stable CO oxidation oscillations.•Operando IR thermography was used to identify active catalyst in fixed bed reactor.•Dynamics of Pt oxidation state and atomic coordination was probed by operando XAS.•Correlation of structure and activity ascribed high activity to metallic Pt.•A schematic mechanism is proposed to explain the observed CO oscillations. A comprehensive approach was applied to investigate oscillatory CO oxidation over a Pt/Al2O3-based diesel oxidation catalyst with small Pt particles (about 1.5nm diameter) in a fixed-bed microreactor under relevant reaction conditions by combining spatially and time-resolved operando X-ray absorption spectroscopy, infrared thermography, and online mass spectrometry. The catalyst-bed zone responsible for the oscillatory behavior and the emerging hot spot was identified by means of IR thermography. Oscillations of the Pt oxidation state and the hot spot region evolved simultaneously and moved from the end toward the beginning of the catalyst bed with increasing reaction temperature. The changes in CO oxidation activity during oscillations can be unambiguously correlated with dynamic structural changes of the Pt particles. The applied operando approach is complementary to surface science studies and also studies on model Pt particles. Surface oxidation of small Pt nanoparticles leads to a fast deactivation of the catalyst, which is regenerated in a slow reduction step. The presence of metallic Pt is required for high activity of the catalyst.
ISSN:0021-9517
1090-2694
DOI:10.1016/j.jcat.2015.01.002