Comparative study on low-temperature CO2 adsorption performance of metal oxide-supported, graphite-casted K2CO3 pellets

Abstract

K2CO3-based adsorbent pellets produced by graphite-casting method are promising alkali metal-based solid CO2 adsorbents. The incorporation of porous metal oxide supports is an effective to enhance CO2 adsorption capacity of K2CO3-based adsorbent pellets. In this work, graphite-casted K2CO3-based adsorbent pellets incorporated with different porous supports (i.e., TiO2, ZrO2, and SiO2) were prepared for CO2 capture. Comparatively, the ZrO2-supported, K2CO3 pellets loaded with 30 wt% of K2CO3 exhibit the highest CO2 adsorption capacity, approximately 0.93 mmol/g. For the SiO2-supported K2CO3 adsorbent pellets, the high calcination temperature (>700 °C) required to remove the graphite layer covering the pellet surface will cause the formation of new eutectics (i.e., K2Si2O5 and K2Si4O9), which leads to the collapse of the adsorbent pellets. Low calcination temperature of 500 °C can avoid the collapse of the SiO2-supported K2CO3 adsorbent pellets and remove most of the graphite on the surface. Moreover, the CO2 adsorption capacity can be further increased to 1.30 mmol/g by adding 20 wt% of microcrystalline cellulose to the SiO2-supported K2CO3 adsorbent pellet. Although the adsorption capacity of structurally improved, SiO2-supported K2CO3 pellets is still inferior to that of structurally improved, ZrO2-supported K2CO3 pellets, they exhibit great cost advantage. Therefore, SiO2-supported K2CO3 pellets with 20 wt% of microcrystalline cellulose have industrial application prospects.