Abstract
Visualizing and measuring the gas distribution in close proximity to a working catalyst is crucial for understanding how the catalytic activity depends on the structure of the catalyst. However, existing methods are not able to fully determine the gas distribution during a catalytic process. Here we report on how the distribution of a gas during a catalytic reaction can be imaged in situ with high spatial (400 μm) and temporal (15 μs) resolution using infrared planar laser-induced fluorescence. The technique is demonstrated by monitoring, in real-time, the distribution of carbon dioxide during catalytic oxidation of carbon monoxide above powder catalysts. Furthermore, we demonstrate the versatility and potential of the technique in catalysis research by providing a proof-of-principle demonstration of how the activity of several catalysts can be measured simultaneously, either in the same reactor chamber, or in parallel, in different reactor tubes.
Highlights
Visualizing and measuring the gas distribution in close proximity to a working catalyst is crucial for understanding how the catalytic activity depends on the structure of the catalyst
In the case of industrial catalyst development, the efficiency of a material to catalyse a particular reaction is evaluated by analysing the end products, after the reactants have passed the catalyst containing the active material, using appropriate characterization techniques, such as mass spectrometry (MS), gas chromatography (GC), Fourier transform infrared spectrometry (FTIR) or specific analysers depending on the reaction
In our experiments we used infrared planar laser-induced fluorescence (PLIF) to image the temperature-dependent dynamics of CO2 close to the surface of catalytic discs during ignition and extinction of catalytic carbon monoxide (CO) oxidation
Summary
Visualizing and measuring the gas distribution in close proximity to a working catalyst is crucial for understanding how the catalytic activity depends on the structure of the catalyst. At more realistic and industrial-like operating conditions in the mbar pressure region and above, the gas-phase situation becomes more complicated This is because in such investigations the reactants pass over the catalyst, causing gas-phase phenomena such as mass-transfer limitation and convection, which changes the conditions near the catalyst. The difficulty with Raman scattering is the low cross-section, limiting the measurements to one-dimension (1D) and most often with long collection times because of averaging, ranging from several minutes to an hour ( in other fields, and with a very sophisticated experimental set-up, single shot Raman has been achieved[18]) This makes it mostly suitable for stationary situations where changes in the gas-phase conditions are minimal or very slow. The mentioned techniques have the capability for multispecies detection, but are all limited either in the temporal or the spatial domain and are less suitable for measurements of the 2D gas distributions above catalytically active surfaces in a changing environment
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