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 H<sub>2</sub> oxidation makes it possible to study the preferential CO oxidation in H<sub>2</sub>-rich gases (PROX) at relevant reaction temperatures (150-350 °C) and reactant concentrations (≤1 kPa CO and O<sub>2</sub>). 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 CO<sub>2</sub> on the PROX reaction over a Au/Fe<sub>2</sub>O<sub>3</sub> catalyst. The addition of CO<sub>2</sub> to idealized reformate (varying CO and O<sub>2</sub> partial pressures, 75 kPa H<sub>2</sub>, balance N<sub>2</sub>) significantly reduces both the CO oxidation rate and the selectivity of the PROX reaction on Au/α-Fe<sub>2</sub>O<sub>3</sub> and strongly affects the frequency of the C-O stretch vibration of adsorbed CO due to CO<sub>2</sub> coadsorption.
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