Carbon dioxide ((CO2)-O-16 and (CO2)-O-18) adsorption in zeolite Y materials: effect of cation, adsorbed water and particle size

In this study, CO2 adsorption in the presence and absence of co-adsorbed H2O was investigated in zeolite Y. Several different zeolite Y materials were investigated including commercial NaY, commercial NaY ion-exchanged with Ba2+ and nanocrystalline NaY; herein referred to as NaY, BaY and nano-NaY. Following heating of these zeolites to 573 K and cooling to room temperature, CO2 was adsorbed as a function of pressure. FTIR spectra show that a majority of CO2 adsorbs in the pores of these three zeolites (NaY, BaY and nano-NaY) in a linear complex with the exchangeable cation, as indicated by the intense absorption band near 2350 cm(-1), assigned to the nu(3) asymmetric stretch of adsorbed CO2. Most interestingly is the formation of carbonate and bicarbonate on the external surface of nano-NaY zeolites as indicated by the presence of several broad absorption bands in the 1200-1800 cm(-1) region, suggesting unique sites for CO2 adsorption on the surface of the nanomaterial. For the other two zeolite materials investigated, bicarbonate formation is only evident in BaY zeolite in the presence of co-adsorbed water. Adsorption of O-18-labeled carbon dioxide and theoretical quantum chemical calculations confirm these assignments and conclusions.