Solid sorbents such as zeolites, MOFs, and finely divided metal oxides are one of the most promising candidates for the implementation of carbon capture (CC), both for direct air capture (DAC) solutions and point sources. Bringing a promising material from the lab to industry requires a realistic screening of its performance in process relevant conditions. The main goal from a materials standpoint is identifying and screening sorbents with the necessary affinity at the relevant CO₂ concentration (from 400 ppm up to 100%), long term usability, and thermal properties¹.

One of the most pertinent challenges relies in the presence of humidity in the process stream, leading to several possible effects on a material’s CO₂ capture potential. Water molecules compete with CO₂ for sorption sites in many materials (zeolites and most MOFs). In others the presence of a certain amount of humidity can increase total amount adsorbed, or speed up the sorption kinetics, as in the case of amine-based materials² and alkali or alkaline earth metal carbonation processes.³ Even in non-interacting scenarios, the coadsorption of water at high humidity levels leads to higher energy requirements during the regeneration since besides CO₂ also water must be desorbed.

Therefore, assessing the influence of moisture on the CO2, and the amount taken up of each from a multicomponent mixture, is of crucial importance. In this work we explore several methods of accomplishing this difficult task – gravimetry and breakthrough analysis – and then walk through several examples on prototypical materials – Zeolite 13X, CALF-20, Lewatit VP OC 1065.

References

[1] M.-Y. (Ashlyn) Low, L. V. Barton, R. Pini, C. Petit, Chem. Eng. Res. Des. 2023, 189, 745–767.

[2] T. Wang, K. S. Lackner, A. Wright, Environ. Sci. Technol. 2011, 45, 6670–6675.

[3] P. López-Arce, L. S. Gómez-Villalba, S. Martínez-Ramírez, M. Álvarez De Buergo, R. Fort, Powder Technol. 2011, 205, 263–269.