Among a number of techniques used for the research of heterogeneous (gas-solid) catalysis, transmission infrared spectroscopy is one of the most widely used techniques for the characterization of surface species adsorbed on the catalyst. It offers useful information, particularly when the spectroscopy is carried out under reaction conditions. Various types of infrared cell have been designed so that the spectra of adsorbed species can be obtained during reactions at high temperatures. Most of them, however, have been used at atmospheric or reduced pressure, and less attention has been paid to high-pressure operations. Also one usually requires an efficient flow of gas in the cell in order to follow the kinetic behavior of the surface species.
T. Tagawa and Y. Amenomiya, "An Infrared Spectroscopy System for Catalytic Reaction at Elevated Pressure and Temperature," Appl. Spectrosc. 39, 358-360 (1985)