Continuous direct air capture and conversion tandem system applicable to a wide range of CO 2 concentrations

Abstract

A two-step CO 2 capture and hydrogenation system using Rb-oxide zeolites and Ni/CeO 2 or Cu/ZnO/Al 2 O 3 achieved high-efficiency conversion under low-temperature conditions. The concentrations of CO 2 emitted from different CO 2 sources vary significantly. Thus, processes capable of accommodating a broad range of CO 2 concentrations, from 0.04% (air) to 10% (power plants), must be developed to achieve carbon neutrality. In this study, we developed a two-step CO 2 capture and hydrogenation system by employing Rb-oxide-incorporated zeolites as CO 2 adsorbents and Ni/CeO 2 or Cu/ZnO/Al 2 O 3 as catalysts for CO 2 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 O 2 . Compared with more than 100 previously reported systems that can convert CO 2 including O 2 to green fuels such as CO or CH 4 , the proposed system achieved the best CO 2 conversions to CH 4 and CO.