Effect of Water on CO2 Adsorption on CaNaY Zeolite: Formation of Ca2+(H2O)(CO2), Ca2+(H2O)(CO2)2 and Ca2+(H2O)2(CO2) Complexes

Efficient CO2 capture materials must possess a high adsorption capacity, suitable CO2 adsorption enthalpy and resistance to water vapor. We have recently reported that Ca2+ cations exchanged in FAU zeolite can attach up to three CO2 molecules. Here we report the effect of water on the adsorption of CO2. Formation of Ca2+(H2O)(CO2), Ca2+(H2O)(CO2)(2) and Ca2+(H2O)(2)(CO2) mixed ligand complexes were established. The Ca2+(H2O)(CO2) species are readily formed even at ambient temperature and are characterized by ?((CO2)-C-12) and ?((CO2)-C-13) infrared bands at 2358 and 2293 cm(-1), respectively. The Ca2+(H2O)(CO2)(2) species are produced at low temperature and are identified by a ?((CO2)-C-13) band at 2291 cm(-1). In the presence of large amounts of water, Ca2+(H2O)(2)(CO2) complexes were also evidenced by ?((CO2)-C-12) and ?((CO2)-C-13) bands at 2348 and 2283 cm(-1), respectively. The results demonstrate that, although it has a negative effect on CO2 adsorption uptake, water in moderate amounts does not block CO2 adsorption sites.