Influence of the pressure and temperature on CO2 adsorption using zeolite

“Several investigations carried out with diverse zeolites (LaM-10, H-ZSM-5, M-ZSM-5 (M = Li+, Na+, K+, Rb+, Cs+), NaX or 13X, 5A, 4A, NaLSX, MCM-48, erionite, mordenite, clinoptilolite) have shown the effect of pressure and temperature on CO2 adsorption [10–1214161819375263–67]. In general, the capacity of CO2 adsorption on the zeolites enhances when the partial CO2 pressure increases and decreases with a rise of temperature (table 3). The results obtained by Yucel and Ruthven [68] and Gardner et al [69] have also shown that the diffusion of CO2 in the zeolite 4A and H-ZSM-5 enhances with the increase of the partial pressure. Moreover, the data obtained by Akten et al [52] have indicated that the Na-4A selectivity for the CO2 in the presence of N2 and H2 decreases slightly when the pressure in the gas phase enhances. This decrease of selectivity is more marked when the molecules of other gas smaller than CO2 are presents in the gas phase. The effect of the pressure on the CO2 adsorption might be attributed to fact that the amounts of CO2 adsorbed are directly proportional to the cationic density in the zeolites pores at low pressures, whereas the volume of pores plays an important role at high pressures [944]. Katoh et al [19] have also attributed this effect of the pressure in the case of the zeolite Li-ZSM-5, to the existence of two types of cations sites species and to the possibility that a rise of the partial pressure might induce a penetration of CO2 deep into the small channels of zeolite, this allowed to interact more strongly with the Li+ cations. In parallel, the decrease of the CO2 adsorption with the increase of the temperature has been associated with a decrease of adsorbent-adsorbate interactions (site–adsorbate) induced by an increase of the mobility of adsorbed molecules into the zeolites cavities that might be caused by a rise of thermal agitation [34].”

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