Continuous Direct Air Capture and Conversion Tandem System Applicable to a Wide Range of CO2 Concentrations

Abstract The concentrations of CO2 emitting from different CO2 sources vary significantly. Thus, processes capable of accommodating a broad range of CO2 concentrations, from 0.04% (air) to tens of percent (power plants), must be developed to achieve carbon neutrality. In this study, we developed a two-step CO2 capture and hydrogenation system by employing Rb-oxide-incorporated zeolites as CO2 adsorbents and Ni/CeO2 or Cu/ZnO/Al2O3 as catalysts for CO2 hydrogenation. This process is suitable for continuous operation over a temperature swing of 40–200°C. Notably, this system can operate at low temperatures (below 200°C) using a simple temperature-swing process in the presence of O2. Compared with more than 100 previously reported systems that can convert CO2 including O2 to green fuels such as CO or CH4, the proposed system achieved the best CO2 conversions to CH4 and CO.