Structurally improved, urea-templated, K2CO3-based sorbent pellets for CO2 capture

The development of K2CO3-based sorbents with desirable CO2 capture capacity and mechanical property is highly necessary for its large-scale application. In this work, a range of extruded-spheronized K2CO3-based pellets containing different K2CO3 loading (30-70 wt%) and Al2O3-based supports (i.e., activated alumina, Bayer aluminum hydroxide, kaolinite clay and calcium aluminate cement) were prepared for CO2 capture. It is found that the distinct textural properties of different supports result in the obvious diversities in CO2 uptake and mechanical property of K2CO3-based pellets. The activated alumina-supported sorbent pellets loaded with 50 wt % of K2CO3 possess the highest CO2 adsorption capacity of 2.29 mmol/g. It is mainly attributed to the moderate amounts of active component contributing to good textural properties and abundant CO2-philic sites, whereas excessive K2CO3 loading will cause the destruction of porous structure, consequently the inferior CO2 uptake. Moreover, the addition of 15 wt% of urea can furher enhace CO2 uptake of the activated alumina-supported sorbent pellets loaded with 50 wt% of K2CO3, similar to 3.10 mmol CO2/g. The improved CO2 uptake is due to the significantly enhanced porosity of sorbent pellets as a result of urea decomposition. In addition, the urea-templated sorbent pellets still maintain the high compressive strength (18.96 MPa) and good attrition resistance (a weight loss of 0.59% after 4000 rotations).