Direct formation of hierarchically porous MgO-based sorbent bead for enhanced CO2 capture at intermediate temperatures

Abstract

Solid CO2 sorbents operating at elevated temperatures have been extensively studied for pre-combustion CO2 capture and sorption-enhanced H2 production. The sorbent must be prepared as a structured one for integration in a process, retaining high and stable working capacity, though this remains the most overlooked challenge. Herein, a novel combustion-assisted method was used to develop MgO-CeO2 beads with dimensions of several hundred micrometers, featuring homogeneous metal oxide composites and hierarchical pore structure. With the coordination complex of cerium, the controlled release of water and volatile gases by the temperature allows the ground gel to grow into a sphere-like structure for minimizing the interfacial surface. The sorption capacity of the beads impregnated with alkali metal salts was 45 wt% at 325 °C and 240 min., and 43 wt% at the 30th cycle during repeated sorption (under 100% CO2 for 60 min at 325 °C) and regeneration (with 100% N2 for 15 min at 425 °C). In addition, compared to the corresponding power and pressed-pellet sorbents, the beads impregnated with alkali metal salts showed significantly enhanced stability with high working capacity for CO2 capture. The results indicate that the MgO-CeO2 beads developed via environmentally benign and industrially feasible route provide a promising platform not only for CO2 capture, but also for sorption-enhanced H2 production.