TITLE: Recent Advances on CO2 capture based on zeolites

AUTHOR: Fernando Rey, Instituto de Tecnología Química (CSIC-UPV)

WHEN: September, 12 - 12 PM (Coffee at 11.30AM)

WHERE: Salón de Actos, ICMM-CSIC - C/ Sor Juana Inés de la Cruz, 3, Madrid.

ABSTRACT: There is no doubt that one of the most major societal concerns today is global warming, which is directly linked to the rising concentration of CO₂ in the atmosphere. In response, both industrial companies and public funding agencies have launched research initiatives aimed at reducing CO₂ emissions, as well as capturing CO₂ at emission sources or directly from the atmosphere, and converting it into valuable products. These efforts are key steps toward achieving a near-zero emissions society (NZE) in the near future.
Among all CO₂ capture scenarios, Direct Air Capture (DAC) is the most challenging one, due to the extremely low CO₂ concentration in the atmosphere (approximately 400 ppm). To efficiently adsorb CO₂ from the air on a solid porous material, the heat of adsorption must be relatively high, which in turn makes the regeneration of the adsorbent energetically demanding. Despite these challenges, a growing number of research publications and patents have appeared focusing on DAC technologies. 
In this work, our main objective was to optimize the CO₂ adsorption capacity of zeolites while ensuring that the adsorbent remains easily regenerable, meaning that the heat of adsorption is kept at moderate levels. At the beginning of this project, the highest CO₂ uptake reported in the literature was obtained on Zn-exchanged chabazite, which exhibited an adsorption capacity of 0.67 mmol/g at 400 ppm CO₂ (equivalent to 0.4 mbar of absolute CO₂ pressure) and 25°C [1]. Later studies of the same research group showed that Zn-exchanged mordenite surpassed the performance of Zn-chabazite, achieving an adsorption capacity of 1.15 mmol/g under DAC conditions [2]. This value was very similar to that observed for Li-exchange low silica X zeolite (Li-LSX) that provided an adsorption capacity of 1.34 mmol/g, the highest uptake reported on zeolite adsorbents to our best knowledge [3].
To achieve this objective, a comprehensive study was conducted to evaluate the influence of chemical composition and zeolitic topology on the CO₂ adsorption capacity of microporous adsorbents under DAC conditions. We have found that an optimized Ca-exchanged Chabazite is a promising candidate for CO₂ capture under DAC conditions, achieving a record adsorption capacity of 2.14 mmol/g [4], which is the highest ever reported for zeolite-based adsorbent. However, further stability assessments and a detailed investigation of water competition during the DAC process are required to fully evaluate its practical applicability.
[1] D. Fu, Y. Park, M.E. Davis, Angew. Chem.; Inter. Ed., 2022, 61, e202112916.
[2] D. Fu, Y. Park, M.E. Davis, Proc. Natl. Acad. Sci., 2022, 119, e2211544119.
[3] N.R. Stuckert, R.T. Yang, Environ. Sci. Technol., 2011, 45, 10257-10264.
[4] M. Taborga, F. Rey, S. Valencia, M. Palomino, M.T. Navarro, WO2024/256367 A1 (2024).