Adsorption characteristics of ion-exchanged ZSM-5 zeolites for CO2/N2 mixtures

Adsorption characteristics of alkali metal ion-exchanged ZSM-5 zeolites, M-ZSM-5 (M = Li, Na, K, Rb, and Cs), for CO2/N-2 mixtures were investigated by a column method and IR study. It was shown that CO2 was adsorbed from CO2/N-2 mixtures on M-ZSM-5 zeolites by two types of adsorbtion at temperatures below 333 K. One was a weak adsorption due to interaction with the wall of ZSM-5, and the other was a strong adsorption caused by interactions with the cation of ZSM-5. IR-spectra of gases adsorbed at various temperatures revealed that the CO2 were strongly adsorbed on M-ZSM-5 in several ways, which seemed to be caused by different adsorption sites. At temperatures above 373 K, almost all CO2 adsorbed were on cation sites, while Nz coadsorbed with CO2 was shown to interact with the wall of ZSM-5 under all experimental conditions. (C) 2000 Academic Press.