Kinetic approach to modelling CO₂ adsorption from humid air using amine-functionalized resin: Equilibrium isotherms and column dynamics

Humidity can up to double the adsorption capacity of CO₂ in conditions relevant to direct air capture (DAC) on amine-functionalized adsorbents, but the treatment of this phenomenon in isotherm or kinetic models has been all but neglected in the literature. In this work, a kinetic model based on reaction mechanisms of CO₂ adsorption on supported amines in dry and humid conditions is proposed. The kinetic model was used in modelling of humid CO₂ adsorption isotherms and dynamics of fixed-bed CO₂ adsorption from air. The improvement of equilibrium CO₂ capacity by humidity was captured well by the kinetic model, leading to good fits of CO₂ isotherms. At best, the dynamic model closely represented the whole shape of CO₂ adsorption breakthrough curves in several-hour fixed-bed adsorption experiments. Therefore, the proposed kinetic model is expected to be useful in simulation of the DAC process based on supported amine-adsorbents.