Unveiling the potential of CaO-modified ZnO adsorbents for CO2 capture

Intermediate-high temperature adsorbents are of interest as they can be used in process intensification and integrated CO₂ capture and conversion processes to couple gas separation with a chemical reaction. Herein we develop CaO-modified ZnO as a new intermediate-high temperature CO₂ adsorbent and show that the extent of CaO doping allows tuning of the CO₂ adsorption/desorption temperature as well as capture capacity. Five different adsorbents were synthesized with Ca loadings of 0 %, 1 %, 5 %, 10 %, and 15 % by weight on ZnO and tested via fixed bed reactor experiments and TGA-DSC. The highest adsorption capacity was found to be 0.73 mmol/g_cat for 5 %Ca/ZnO. The desorption temperatures for CO₂ was found to also be influenced by Ca loading. Adsorbents were characterised by XRD, SEM, TGA, BET and ICP-MS, to understand their structure it was determined that CaO deposits on ZnO pores as separate domains. Herein we develop CaO-modified ZnO as a novel intermediate-high temperature CO₂ adsorbent, demonstrating tuneable adsorption/desorption characteristics through CaO dispersion on a ZnO scaffold.