Effects of the Adsorbent Preparation Method for CO2 Capture from Flue Gas Using K2CO3/Al2O3 Adsorbents

The effect of the preparation method on the CO 2 adsorption capacity of K 2 CO 3 /Al 2 O 3 adsorbents is examined. The multi-step impregnation (MI) method enables uniform dispersion of active species (K 2 CO 3 ) in the broad macropores without blocking narrower mesopores. This facilitates higher loading of accessible K 2 CO 3 for CO 2 adsorption and, hence, higher adsorption capacity. The single-step impregnation (SI) method suffers from blockage of narrower mesopores by excessive growth of K 2 CO 3 . This limits the CO 2 accessibility toward active species in the porous structure because of the formation of larger active species aggregates. For 50 wt % K 2 CO 3 /Al 2 O 3 prepared by MI and SI methods, the maximum CO 2 adsorption capacity at CO 2 partial pressure of 8 kPa is found to be 3.12 and 2.1 mmol/g, respectively. The regeneration efficiency of 50MI and 50SI are observed to be nearly 65 and 56%, respectively, at 130 °C in multi-cycle testing. The experimental data for CO 2 adsorption were described by the Langmuir isotherm, and the isosteric heat as a function of fractional coverage of the adsorbent was evaluated by means of the van’t Hoff equation. The isosteric heat showed a decreasing trend with an increase in the surface coverage of the adsorbent. From the results, it is concluded that the adsorbent prepared by the MI method shows better performance because of its tunable textural and morphological properties to achieve higher CO 2 adsorption capacity.