Abstract

A new design for a DRIFTS (diffuse reflectance infrared Fourier transform spectrometry) cell for <i>in situ</i> studies in heterogeneous catalysis is presented, which allows for improved reaction control (i.e., gas flow, temperature, minimized background conversion) and for precise kinetic measurements via on-line gas analysis by a tandem-arranged gas chromatograph. Specifically, the very low background activity of the cell itself for CO and H₂ oxidation makes it possible to study the preferential CO oxidation in H₂-rich gases (PROX) at relevant reaction temperatures (150-350 °C) and reactant concentrations (≤1 kPa CO and O₂). Comparison with results obtained in a quartz tube reactor shows excellent agreement with the reaction rates obtained in the DRIFTS cell. The improved performance of the new DRIFTS cell design is demonstrated by examining the influence of CO₂ on the PROX reaction over a Au/Fe₂O₃ catalyst. The addition of CO₂ to idealized reformate (varying CO and O₂ partial pressures, 75 kPa H₂, balance N₂) significantly reduces both the CO oxidation rate and the selectivity of the PROX reaction on Au/α-Fe₂O₃ and strongly affects the frequency of the C-O stretch vibration of adsorbed CO due to CO₂ coadsorption.

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