TEMPERATURE-PROGRAMMED DESORPTION AND INFRARED SPECTROSCOPIC STUDIES OF NITROGEN MONOXIDE ADSORBED ON ION-EXCHANGED COPPER MORDENITE CATALYSTS

The natures of the surface species formed upon adsorption of NO on cop per-ion exchanged mordenite catalysts were investigated by means of te mperature programmed desorption (TPD) and diffuse reflectance infrared spectroscopy. When nitrogen monoxide (NO) was contacted with Cu/morde nite at room temperature, the evolution of dinitrogen monoxide (N2O) a nd nitrogen occurred, accompanied by the formation of the adsorbed oxy gen species (Os). In the TPD runs, three NO desorption peaks appeared, with maxima at 383 K (alpha-NO peak), 523 K (delta-NO peak), and 673 K (gamma-NO peak). The desorptions of oxygen and nitrogen dioxide (NO2 ) were observed together with the desorption of NO at 673 K. These alp ha-NO and beta-NO peaks correspond to the desorptions of nitrogen oxid e species which adsorbed as NO-type species. The desorptions of gamma- NO, gamma-NO2 and gamma-O-2 at 673 K arose from the decomposition of N O3-type adsorbed species. The NO3-type species may have formed by the reaction between NO and the adsorbed oxygen species (Os). By compariso n of the :ate of the NO decomposition with that of the decomposition o f NO3-type adsorbed species, it was shown that the NO3-type adsorbed s pecies plays a pivotal role in the decomposition of NO as intermediate of the reaction. (C) 1998 Elsevier Science B.V.