One-step synthesis of structurally improved, Al2O3-supported K2CO3 pellets via graphite-casting method for low-temperature CO2 capture

The desirable CO 2 adsorption capacity and mechanical property are both important for the large-scale industrial applications of K 2 CO 3 -based CO 2 adsorbents. In this work, graphite-casted, Al 2 O 3 -supported, K 2 CO 3 -based pellets were prepared for CO 2 adsorption. The prepared K 2 CO 3 -based pellets containing 30 wt% of K 2 CO 3 calcinated at 900 °C exhibit CO 2 adsorption capacity of 1.4 mmol/g, which is over 2.5 times that of the pellets calcinated at 300 °C. It is mainly attributed to the residual graphite coating on the surface of the K 2 CO 3 -based pellets calcinated at 300 °C, which inhibits the diffusion of H 2 O due to the hydrophobicity of graphite and further causes the poor carbonation performance. Moreover, the addition of 40 wt% of microcrystalline cellulose can further enhance the adsorption capacity of the graphite-casted K 2 CO 3 -based pellets to ∼1.95 mmol/g due to the improved pore structure. However, excessive addition of microcrystalline cellulose (50–60 wt%) will lead to poor CO 2 adsorption performance (1.07–1.16 mmol/g) because of the active sites within the pellets being covered by molten K 2 CO 3 . Additionally, the structurally improved K 2 CO 3 -based pellets also exhibit desirable mechanical property with a compression strength of 69.45 MPa. Comprehensively considering the simple and easily scaled-up preparation route of graphite-casting method, the structurally improved, graphite-casted, Al 2 O 3 -supported, K 2 CO 3 -based pellets possess potential practical application prospect.