Recent Advances in CO2 Adsorption from Air: a Review

Carbon dioxide (CO2) adsorption from air and storage is a developing technology that can achieve negative carbon emissions, therefore easing climate deterioration. However, adsorbing CO2 from air is still a challenge when compared to the high CO2 concentration sources such as flue gas and syngas because it is hard to separate the steady and dilute target gas accurately with a moderate approach. Most related literatures focus on the development of adsorbents for higher adsorption capacity and lower regeneration energy consumption. However, studies on practical factors and adsorption processes are also necessary for engineering applications. Based on research of the CO2 adsorption, an introduction to recent advances in dilute CO2 adsorption using physical or chemical adsorbents is presented, and practical factors are emphasized. From the aspect of structure-property relationships, porous structure optimization of adsorbents is discussed for better equilibrium capacity and adsorption kinetics. Effects of practical parameters (such as moisture, fluctuating temperature, and oxygen) on working performance, especially stability of adsorbents, are revealed. Moisture influences are complex and multifaceted, so possible mechanisms of the moisture influences are summarized to help readers understand. Adsorption processes of capturing CO2 from air are also discussed and compared, distinguishing from the adsorption processes with other feeds. Energy supply and gas-solid contactors which are vital in practical adsorption process are discussed separately.