CO2 adsorption over ion-exchanged zeolite beta with alkali and alkaline earth metal ions

Zeolite beta with high aluminum content (BEA, Si/Al = 7.4) was synthesized and evaluated as a CO2 capturing agent after conducting ion-exchange with various alkali and alkaline earth metal ions (Li+, K+, Cs+, Mg2+, Ca2+, and Ba2+). The extent of ion-exchange was confirmed by ICP-AES, and textural properties of the samples were measured by XRD, SEM, and BET surface area measurement. CO2 adsorption isotherms of the ion-exchanged beta samples up to 101.3 kPa were obtained at 273 and 298 K, and the corresponding heats of adsorption were estimated by the Clausius–Clapeyron equation. CO2 adsorption capacity increased in the sequence of K+>Na+>Li+>Ba2+>Ca2+≒Cs+>Mg2+, and all of the evaluated metal ions showed high adsorption selectivity to CO2 over N2. The best performance of K+-exchanged beta was also confirmed by a breakthrough curve analysis. Cyclic CO2 adsorption–desorption performance of the sample was also studied by TGA in a flow system, exhibiting stable cyclic runs accompanied by complete CO2 desorption at 473 K.