In situ UV/Vis/near-IR diffuse reflection measurement of catalysts at temperatures up to 673 K

In situ UV/VIS/near-IR diffuse reflectance spectroscopy can be carried out on catalysts with a suitable microreactor at temperatures up to 673 K. The experimental difficulties in the application of such a reactor at higher temperatures could be solved as follows. Integrating sphere and reactor are connected by a ceramic part of high reflectivity and low thermal conductivity, i.e., the integrating sphere is enlarged. The signal/noise ratio increases by a factor of 2. The standard IR detector was replaced by a temperature-stabilized version. In addition watercooling jackets were mounted at the integrating sphere. The signal/noise ratio in the near-IR region was thus improved by a factor of 2–3 with a very good reproducibility of measurements. To overcome an alteration of catalyst spectra by thermal radiation, a series of reference spectra of quartz powder (SiO₂) were recorded at several temperatures. These spectra are used to correct the catalyst spectra by dividing catalyst and SiO₂ spectra. © 2002 American Institute of Physics.