Carbon dioxide in Y and ZSM-20 zeolites: Adsorption and infrared studies

Abstract Adsorption of carbon dioxide was performed on sodic and protonic forms of Y and ZSM-20 zeolites. The adsorption isotherms of carbon dioxide were determined in the temperature range of 293—318 K by the volumetric method. Isosteric heats were obtained by the Clausius-Clapeyron equation. In order to obtain information on the adsorbed molecules at low coverages, the infrared technique was used. It is shown that, in spite of having closely related structures, the Y and ZSM-20 zeolites present structures with different polar sites. This difference in textural properties can influence the adsorption of molecules capable of having specific interactions with surface polar groups.