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The adsorption of CO 2 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 CO 2 surface species identified in the current work include physisorbed CO 2 , bidentate carbonate, bridged bidentate carbonate, monodentate carbonate, and carboxylate. Both pretreatment temperature and CO 2 adsorption temperature affected the type and amount of adsorbed CO 2 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 CO 2 was the most abundant species observed. Bridged bidentate carbonate was found to be more stable than bidentate carbonate. Tests involving both CO 2 and H 2 O showed that the two species competed for the same adsorption sites on the zeolite surface.

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