The adsorption of NO on Co/ZSM-5 zeolites with different Co content is studied by FTIR spectroscopy. The dominant NO species absorbed on Co/ZSM-5 is found to be in a dinitrosyl form, as demonstrated by the IR bands at 1813 and 1896 cm" . The mononitrosyl form occurs in the region of 1939-1941 cm" as a minor species. Based on the integrated intensities of IR bands at 1813 and 1896 cm"1, an experimental equation, i.e., C-NO = I-NO/ (ε-NO· m/3.14), has been proposed for estimating the amount of adsorbed NO molecules ( CNO), from which the values of C-NO on both Co/ZSM-5 and [Co+ Mg(Sr)]/ZSM-5 have been calculated. In addition, the OH stretching region on Co/ZSM-5 and [Co+ Mg(Sr)]/ZSM-5 is studied by FTIR. These studies may provide useful information for SCR catalysts of NO

Key words: FT, IR, NITROGEN OXIDE, COBALT, ZSM-5, ADSORPTION, REDUCTION, MOLECULAR SIEVE, CATALYST