CHEMISORPTION AND PHYSISORPTION OF CO2 ON CATION EXCHANGED ZEOLITES A, X AND MOR

Calorimetric measurements of the heat of adsorption of CO2 on zeolites with variable content of mono- and divalent cations lead to common conclusions. High initial heats (up to 120 kJ.mol-1 for NaA), generally associated with a slow and activated rate of adsorption, are found for high contents of Na+, Li+ or Ca2+. They are attributed to a limited number of chemisorption sites (0.3 per alpha-cage in NaA). Physisorption results in lower heats (25-50 kJ.mol-1). The lowest values are obtained with partially or totally decationized zeolites. Transition metal cations induce frequently weaker interactions than IA or IIA. Finally the stron er the energy of adsorption is, the larger the adsorbed amount is.