Dynamic separation of CO2 from N2 in humid streams using nano-sized zeolites

Water is constantly encountered in untreated CO 2 -containing gas streams, making their separation between CO 2 and the other components challenging. Here, the CO₂ adsorption capability of nano-sized potassium-exchanged chabazite (K-CHA45) was evaluated and compared to the industrial benchmark for CO 2 and water capture, zeolite 13X used as a reference, using equilibrium adsorption measurements and breakthrough curve analysis in the presence of humidity. K-CHA45, with its smaller crystalline domains (∼45 nm), exhibited a lower isosteric heat of adsorption, indicative of more facile regeneration, compared to sodium-form 13X (∼5 μm). Breakthrough experiments revealed that both adsorbents effectively adsorb CO 2 and H 2 O, but purging the adsorbent bed with He alone was insufficient to regenerate the adsorbents after several cycles, necessitating additional energy input. By leveraging the different diffusion kinetics of CO 2 and H 2 O, the different molecules were separated. Single-step dynamic cycling experiments demonstrated that K-CHA45 significantly outperforms 13X, achieving CO 2 removal efficiencies up to 2.2 times higher. Specifically, K-CHA45 removed 1842 and 1756 mmol g −1 of CO 2 per month from gas streams containing 1.5 vol% and 3.0 vol% H 2 O, respectively. These findings suggest that K-CHA45 zeolite is a highly efficient and promising adsorbent for CO 2 capture in the presence of humidity, suitable for industrial applications. • Single-step dynamic cycling separates CO 2 from humid N 2 streams. • Nano-K-CHA45 outperforms zeolite 13X: 2.2 times higher CO 2 capture in humid gas. • Differential diffusion of CO 2 vs. H 2 O enables single-cycle separation. • High CO 2 separation for K-CHA45 (1842 mmol g −1 month −1 at 1.5 % H 2 O) demonstrated. • K-CHA45: lower adsorption heat equals to easier regeneration and reduced energy use.