IR Spectroscopic Study of Adsorption of Binary Gases over Ion-Exchanged ZSM-5 Zeolites.

Adsorption of binary gases (CH4/CO, CO/NO, and CO/CO2) on alkali metal (Li, Na, K, Rb, and Cs) ion-exchanged ZSM-5 zeolites were studied using IR spectroscopy. IR absorption bands of preadsorbed CH4, particularly that of nu1 (induced band), decreased with the increase in the partial pressure of CO, indicating the preferential adsorption of CO on the cation site of zeolite. In addition, IR band profiles of adsorbed CO changed in a different manner when CH4, NO, or CO2 was added to the system, suggesting that the selectivity of adsorption was governed not only by the polarity of adsorbates but also by the nature of sites present in the ZSM-5 pore bearing different electric field strengths. Copyright 1998 Academic Press.