In situ Fourier transform infrared (FTIR) investigation of CO2 adsorption onto zeolite materials

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 degrees C) and adsorption temperature (30 and 120 degrees 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 degrees C, as opposed to 120 degrees 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.