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.