New DRIFTS cell design for the simultaneous acquisition of IR spectra and kinetic data using on-line product analysis

A new design for a DRIFTS (diffuse reflectance infrared Fourier transform s pectrometry) cell for in situ studies in heterogeneous catalysis is present ed, 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-2 oxidati on makes it possible to study the preferential CO oxidation in H-2-rich gas es (PROX) at relevant reaction temperatures (150-350 degreesC) and reactant concentrations (less than or equal to1 kPa CO and O-2). Comparison with re sults 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 o n the PROX reaction over a Au/ Fe2O3 catalyst. The addition of CO2 to ideal ized reformate (varying CO and O-2 partial pressures, 75 kPa H-2, balance N -2) significantly reduces both the CO oxidation rate and the selectivity of the PROX reaction on Au/alpha -Fe2O3 and strongly affects the frequency of the C-O stretch vibration of adsorbed CO due to CO2 coadsorption.