Development of highly stable zeolite-based CO₂ adsorbent under a temperature swing process

Amine-grafted zeolites are synthesized via a simple acid-base reaction, which adsorbs CO₂ effectively and is highly regenerable under a realistic temperature swing CO₂ adsorption process.

Article  |  Fall 2016

Solid adsorbents, including amine-functionalized materials and zeolites, have been extensively investigated for CO₂ capture. Amine-functionalized materials have shown promising CO₂ uptake in wet flue gas, but suffer from significant amine deactivation due to urea formation under the desorption conditions (e.g., desorption under 100% CO₂ at 130^oC) of a temperature swing process.

In contrast, zeolites are thermochemically stable but cannot adsorb CO₂ from wet flue gas because of the preferential H₂O adsorption, which restricts their application in post-combustion CO₂ capture.

To overcome these limitations, Prof. Minkee Choi’s group in the Department of Chemical and Biomolecular Engineering at KAIST has developed an amine-grafted Y zeolite, which can synergistically combine the strengths of both adsorbent systems. The amine-zeolite hybrid material was synthesized via gas-phase titration of the acid sites in commercial zeolite with ethylenediamine vapor. The amine groups can effectively capture CO₂ in wet flue gas, while the strongly co-adsorbed H₂O within the hydrophilic zeolite micropores suppresses urea formation (dehydration reaction between amines and CO₂) under desorption conditions according to Le Chatelier’s principle. The amine–zeolite hybrid adsorbent retains working capacities higher than 1.1 mmol g1 over 20 TSA cycles.

The new organic-zeolite hybrid adsorbent has a benefit of H₂O tolerance during the adsorption of CO₂ under wet flue gas compared with purely inorganic zeolites (e.g., molecular sieve 13X). On the other hand, the hybrid material has the benefit of remarkable resistance against urea formation compared with conventional amine-modified materials. Because the adsorbent is synthesized with commercially-available Y zeolite, the material can be economically produced on a large scale. The crystalline zeolite is also more hydrothermally stable than conventional amine supports such as amorphous silica, which can suffer from pore structural collapse under a CO₂ stream containing H₂O vapor.

An article on this research (entitled “An ethylenediamine-grafted Y zeolite: a highly regenerable carbon dioxide adsorbent via temperature swing adsorption without urea formation”) was published in March 2016 in Energy & Environmental Science.
Reference: C. Kim, H. S. Cho, S. Chang, S. J. Cho, and M. Choi, Energy & Environmental Science, 9, 1803 – 1811 (2016).

Additional link for more information:
http://pubs.rsc.org/en/content/articlelanding/2016/ee/c6ee00601a#!divAbstract (Article)
http://egcl.kaist.ac.kr/