Continuous direct air capture and conversion tandem system applicable to a wide range of CO2 concentrations

Abstract

The concentrations of CO₂ emitted from different CO₂ sources vary significantly. Thus, processes capable of accommodating a broad range of CO₂ concentrations, from 0.04% (air) to 10% (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.

Keywords: Direct air capture (DAC); Zeolite sorbent; Temperature swing adsorption (TSA); Methanation; Reverse water-gas shift (RWGS).