COADSORPTION OF NITROGEN MONOXIDE AND NITROGEN-DIOXIDE IN ZEOLITIC DE-NOX CATALYSTS

Room temperature adsorption and temperature programmed desorption (TPD ) of NO, NO with O2, and NO after NO2 saturation were investigated for Na/Y, Na/ZSM5, Cu/ZSM5 and SiO2 gel. The adsorbates were characterize d by TPD, using mass spectrometry to identify the desorbed molecules. In the presence of O2, the adsorption of NO and NO2 is non-additive; c o-desorption of nearly equal amounts of NO and NO2 takes place suggest ing the formation of a complex with an overall composition N2O3 within the zeolite. Since SiO2 gel does not adsorb NO nor NO2, the adsorptio n capacity of the zeolites is a function of their specific structure. The oxidation of NO to NO2 is catalyzed by Na/Y and Na/ZSM5.