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.