Theoretical studies on carbon dioxide adsorption in cation-exchanged molecular sieves

摘要

The capture and storage of the greenhouse gas, CO _(2) , has attracted much interest from scientists in recent years. In this work, density functional theory (DFT) was used to study the adsorption of CO _(2) in different cation-exchanged molecular sieves. The results show that for the monovalent metal (Li, Na, K, Cu) ion-exchanged molecular sieves (zeolite Y, ZSM-5, CHA and A), the adsorption capacities for CO _(2) decrease in the order of Li ~(+) > Na ~(+) > K ~(+) > Cu ~(+) . Cu ~(+) -exchanged zeolites are not suitable as adsorbents for CO _(2) . For the CO _(2) adsorption capacities in different zeolites with the same exchanged cation, the adsorption energy decreases in the order of Y > A > ZSM-5 ≈ CHA for Li-exchanged zeolites, and ZSM-5 still has the lowest CO _(2) adsorption energy for both Na- and K-exchanged zeolites. In the cation-exchanged Y zeolites with divalent metals (Be, Mg, Ca and Zn), the CO _(2) adsorption performance increases in the order of Zn ~(2+) < Be ~(2+) < Ca ~(2+) < Mg ~(2+) . Thus, Zn ~(2+) -exchanged zeolites are not suitable as adsorbents for CO _(2) .