In Situ Fourier Transform Infrared (FTIR) Investigation of CO2 Adsorption onto Zeolite Materials

The adsorption of CO2 onto five zeolite materials (13X, WEG, AGP, 4A, and 5A) was studied by in situ infrared spectroscopy at 1 atm as a function of the pretreatment temperature (120 and 350 °C) and adsorption temperature (30 and 120 °C). Adsorbed CO2 surface species identified in the current work include physisorbed CO2, bidentate carbonate, bridged bidentate carbonate, monodentate carbonate, and carboxylate. Both pretreatment temperature and CO2 adsorption temperature affected the type and amount of adsorbed CO2 species formed. Materials pretreated at 350 °C, as opposed to 120 °C, had more surface adsorption sites available as evidenced from the resulting more intense IR bands. Physisorbed CO2 was the most abundant species observed. Bridged bidentate carbonate was found to be more stable than bidentate carbonate. Tests involving both CO2 and H2O showed that the two species competed for the same adsorption sites on the zeolite surface.