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 N-2. 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. (C) 2010 Elsevier Inc. All rights reserved.