(381f) Comparing the Adsorptive CO2 Capture Performance of Zeolite 13X and Calf-20 Under Humid Conditions

Zeolite 13X is the adsorbent of choice in adsorptive CO₂ capture processes due to its high CO₂ adsorption capacity and selectivity over other gases like N2. However, its CO₂ capture performance in the presence of even small quantities of moisture is compromised due to the competitive nature of H₂O/CO₂ adsorption equilibria¹. Thus, necessitating the complete removal of H₂O upstream of the adsorptive CO₂ capture unit using drying processes which are believed to impose a high energetic penalty. Despite its excellent adsorptive separation capabilities, its use for CO₂ capture from a realistic flue gas stream containing significant amounts of water vapour is challenging. It is thus imperative to explore and evaluate alternative adsorbents that are resilient to water vapour. Experimental competitive CO₂/H₂O adsorption equilibrium studies on CALF-20 suggest that it can sustain its CO₂ adsorption capacity in the presence of water vapour to a considerable extent². This indicates it could potentially be more suitable for adsorptive CO₂ capture processes such as pressure/vacuum/temperature swing adsorption (P/V/TSA).

This study aims to compare the adsorptive CO₂ capture performance of Zeolite 13X and CALF-20 under humid conditions using detailed process simulation models. A four-step light product pressurization (LPP) adsorption process is simulated and run for a large number of cycles using the gPROMS Process software. The competitive adsorption equilibrium loading for H₂O in the presence of CO₂ on CALF-20 is modelled by fitting multi-component experimental data to a custom isotherm model, and that for CO₂ in the presence of H₂O on CALF-20 using the Langmuir-Freundlich isotherm model. As for Zeolite 13X, the extended form of the dual-site Langmuir isotherm model is used to predict competitive adsorption both for CO₂ and H₂O. The key process performance indicators, mainly CO₂ purity and recovery, obtained from the process model are compared against experimentally obtained CO₂ purity and recovery for a set of varying moisture content in the feed.

References:

1. Wilkins, Nicholas Stiles, James A. Sawada, and Arvind Rajendran. "Measurement of competitive CO₂ and H₂O adsorption on zeolite 13X for post-combustion CO₂" Adsorption 26, no. 5 (2020): 765-779.
2. Lin, Jian-Bin, Tai TT Nguyen, Ramanathan Vaidhyanathan, Jake Burner, Jared M. Taylor, Hana Durekova, Farid Akhtar et al. "A scalable metal-organic framework as a durable physisorbent for carbon dioxide capture." Science 374, no. 6574 (2021): 1464-1469.