(734a) Intrinsic Adsorption Properties of CO2 On 5A and 13X Zeolite

ABSTRACT

Literature data for the adsorption of CO₂ on 5A (CaA) and 13X (NaA) zeolite are critically analyzed. In addition, new data for the adsorption of CO₂ on 13X zeolite is presented. The intrinsic properties examined are q_max, the saturation loading, K_H the Henry constant and (-ΔH)_q, the isosteric heat of sorption. The q_max values for both 5A and 13X zeolites are similar to theoretical values that may be derived using zeolitic crystallographic properties and the sorbate density calculated using the Rackett equation below a reduced temperature (T_r) of 0.8. However, above a T_r of 0.8, the q_max values exceed the theoretical values similarly calculated, indicating that the molecules have a smaller molar volume than in a similar liquid phase. This is a similar result to that observed in ionic liquids. The Henry constant values for 5A are remarkably consistent for the five studies examined, with a correlation coefficient, R, of 0.9990. The result for K_H for the seven studies examined in 13X is not as good as the correlation coefficient, R, is 0.8989. The values of (-ΔH)_q, the isosteric heat of sorption are in agreement with the literature. An explanation is advanced for the discrepancy between the higher heat of sorption values obtained calorimetrically from those obtained from adsorption studies. Finally, the new data is observed to fit the Toth model. The parameters obtained by regression for the Toth equation are significantly different compared to the intrinsic properties derived above.