Temperature-dependent kinetic analysis of direct air capture using a gravimetric approach in porous environments

Abstract Adsorption kinetics has been regarded as one of the most critical factors determining the productivity and economic feasibility of direct air capture (DAC) of CO 2 , but has received relatively little attention compared with adsorption thermodynamics. One commonly used method for kinetics investigation is thermogravimetric analysis (TGA) which suffers from gas diffusion limitations and often underestimates adsorption rates. Here, a modified TGA system equipped with a porous self-made crucible was employed to address the gas diffusion challenges and analyze the kinetic behaviors of three polymeric chemisorbents, including Lewatit VP OC 1065, for DAC. The obtained adsorption kinetics were successfully applied to simulate and describe the breakthrough behaviors in a fixed-bed column. The CO 2 adsorption/desorption kinetics of chemisorbents with different amine structures or loadings were measured at various temperatures and described through the linear driving force model. The present work offers a reliable and fast kinetics analysis approach for DAC, paving the way for accurately collecting the kinetics parameters used for guiding further adsorbent and process design. Graphic abstract