Design of an optimized DRIFT cell/microreactor for spectrokinetic investigations of surface reaction mechanisms

Abstract

A cell/microreactor is develop and fully characterized to perform diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments to investigate heterogeneously catalyzed surface reactions. The experimental setup allows the simultaneous acquisition of time-resolved infrared spectra at high quality and the gas phase quantification by a mass spectrometer connected at the outlet of the cell. The cell behaves as a true plug-flow microreactor while allows the infrared radiation to sense the lateral part of the catalyst bed. The selected geometry allows a better correlation between the evolution of infrared signals from surface species and the gas concentration at the exit of the cell, that is, for strict Operando experimentation. The mass and heat transport phenomena were characterized using well established criteria to determine the operative limitations under steady state and fast transient experiments, e.g. during concentration-modulation excitation spectroscopy (c-MES). The performance of the cell is validated by studying the CO oxidation on a Au/CeO2 catalyst. Identification and quantification of active surface species under reaction conditions are obtained combining modulation approach with phase sensitive detection (PSD) analysis and step experiments.