Core-shell structured CaO-based pellets with enhanced cyclic CO2 capture performance

Calcium looping (CaL) has being considered a CO2 capture technology with great promise because of its wide suitability and low-cost. In this work, the Ca(OH)2 core was coated with porous alumina coverings via a dip-coating approach to produce CaO-based sorbent pellet with core-shell structure. The coating shell was prepared by evaporation-induced self-assembly sol-gel strategy using P123 as the pore-forming agent with different acidic conditions (i.e., acid-alcohol ratio varied from 0.05 to 3). It reveals that the cyclic CO2 capture performance of core-shell structured CaO-based sorbent pellets decreases with the increase of acidity of sol-gel using for covering spherical cores. When coating gel with excessive acidity, the formation of dense alumina shell and the irreversible chlorination inactivation, which together lead to the low cyclic CO2 capture performance. Particularly, the CO2 capture capability of core-shell structured CaO-based sorbent pellets whose shell gel used for coating in low acid-alcohol ratio of 0.05 is as high as 1.4 times that of non-shell CaO-based pellets after 17 cycles. Meanwhile, the core-shell structured CaO-based sorbent holds good potentials to inhibit the adverse impact of in-situ coal combustion compared with conventional non-shell pellets in practical CaL system.