Infrared spectroscopic studies on carbon dioxide adsorption in alkali-metal and alkaline-earth-metal ion-exchanged A-type zeolites. Part 1.—General features of CO2 interaction with A-type zeolites

Abstract

The influence of different alkali-metal and alkaline-earth-metal ions on the formation of physisorbed and chemisorbed carbon dioxide in A-type zeolites has been studied by F.t.i.r. spectroscopy. Various species of both kinds can be distinguished, the mutual correlations of which are determined by the exchange cation. In the case of physisorbed CO₂ the ν₂ band and the 2ν₂/ν₁ Fermi diads, which become i.r. active upon adsorption, can be observed, and possible sites and geometries of the sorption complex are discussed. Compared to X- and Y-type zeolites the ν₃ frequency shift shows a poorer correlation with the charge:radius ratio of the cation, so rendering the detection of sorption sites difficult. The general loss of rotational fine structure points to a strong hindrance to rotation. Satellite bands of the ν₃ fundamental band are tentatively assigned to external motions.