Carbon dioxide (C16O2 and C18O2) adsorption in zeolite Y materials: effect of cation, adsorbed water and particle size

Abstract

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 ν₃ 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 ¹⁸O-labeled carbon dioxide and theoretical quantum chemical calculations confirm these assignments and conclusions.