CO2 capture and selective hydrogenation to CO over Ag-K co-loaded Al2O3 under simulated realistic conditions

CO₂ capture and reduction with H₂ (CCR) to CO over dual-functional materials (DFMs) with CO₂ chemisorption and hydrogenation abilities have attracted attention as a promising approach to utilize low-concentration CO₂ in exhaust gases. However, the reported DFMs suffer from the requirement of high reaction temperatures, deactivation by O₂ in simulated exhaust gases, and the use of platinum group metal elements. Recently, we found that Ag-K-based DFMs exhibited low-temperature activity in the CCR for selective CO formation and good compatibility with O₂ in the CO₂ capture step. In this study, the screening of metal oxide supports and metal loading amounts of Ag-K-based DFMs were investigated during CCR in the presence of O₂ at 350 °C. The Al₂O₃-supported Ag-K DFMs with 1 and 8 wt% loading of Ag and K (Ag(1)K(8)/Al₂O₃), respectively, were the best among the tested DFMs. Using the optimized Ag-K/Al₂O₃, CCR operation under scaled-up conditions was also performed. Notably, the amount of CO formed was maintained even in the presence of water vapor, which is advantageous for practical applications under realistic conditions. The effect of the co-loaded K species on the CO₂ hydrogenation catalysis is also discussed.