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

• Ca modified ZnO was assessed for its effectiveness in CO 2 capture. • Ca loading on ZnO resulted in enhancement in CO 2 capture. • Temperature of CO 2 adsorption/desorption is dependent on Ca loading on ZnO Intermediate-high temperature adsorbents are of interest as they can be used in process intensification and integrated CO 2 capture and conversion processes to couple gas separation with a chemical reaction. Herein we develop CaO-modified ZnO as a new intermediate-high temperature CO 2 adsorbent and show that the extent of CaO doping allows tuning of the CO 2 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 CO 2 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.