Effect of Water on CO 2 Adsorption on CaNaY Zeolite: Formation of Ca 2+ (H 2 O)(CO 2 ), Ca 2+ (H 2 O)(CO 2 ) 2 and Ca 2+ (H 2 O) 2 (CO 2 ) Complexes.

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