Design, modelling, and application of a low void-volume in situ diffuse reflectance spectroscopic reaction cell for transient catalytic studies

Abstract

This paper describes a new low void-volume in situ reaction cell for use in diffuse reflectance spectroscopic studies. It was demonstrated by means of a residence time distribution analysis that the cell's average gas residence time was relatively small (∼1.3 s) and within the time scale of rapid scan spectra sampling. Such combination enabled the rigorous implementation of transient periodic techniques such as modulation excitation-phase sensitive detection-diffuse reflectance Fourier infrared spectroscopy (ME-PSD-DRIFTS), which allowed unique access to surface reaction intermediates in gas–solid reactions. Application of the new cell and ME-PSD-DRIFTS to the conversion of ethanol on γ-Al₂O₃ at 200 °C demonstrated the presence of likely surface intermediate species that conform with ethanol conversion to diethyl ether via a SN2 mechanism and the involvement of several alumina hydroxyl types as possible active sites.