INFRARED-SPECTROSCOPY AT HIGH-PRESSURE - ADSORPTION OF DINITROGEN ON SUPPORTED RHODIUM IN THE ABSENCE OF CARBON-MONOXIDE

A primary limitation in using FTIR to study adsorbed species on supported catalysts in the presence of high pressures of reactant gases is the possible presence of small amounts of impurity gases that bind strongly to the active metal sites and/or that have high extinction coefficients for their IR-active vibrational modes. A catalytic converter containing Rh/Al2O3 has been employed to remove traces of CO from high-purity N2 so as to produce the IR spectrum of N2/Rh/Al2O3 without interference from CO surface species. The spectra obtained for 8000 Torr of pure N2 at 298 K verified the assignments of Wang and Yates for their low-temperature, low-pressure studies of the same system and showed that impurity CO does influence the nature of the N2/Rh/Al2O3 surface species.