Thermodynamic research on zeolites can not only evaluate their stability with respect to various frameworks, Si/Al ratios, and charge-compensating cations, but also reveal the interactions between guest gas molecules and zeolites. By combining high temperature oxide melt solution calorimetry and water absorption calorimetry, formation enthalpies of ion-exchanged zeolites ZK-5 (KFI frameworks) were determined at different hydration levels. Extra-framework cations are found to have great impacts on thermodynamic stability of zeolites, which also affect water absorption processes and lead to differing formation enthalpies for different hydration statuses. Besides water absorption, CO2 and CH4 adsorption on ion-exchanged zeolites ZK-5 were also investigated by gas adsorption calorimetry. The obtained gas adsorption enthalpies contribute to recognize the interactions between zeolites and CO2/CH4 molecules and the role of extra-framework cations in these confinement effects, which are instructive to applications of zeolites in selective gas adsorption and separation.

Experimental thermodynamic studies of stabilities and gas adsorption of ion-exchanged zeolites ZK-5 (KFI frameworks)

ACS Spring 2022

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