Zwitterionic "Solutions" for Reversible CO 2 Capture

• Published in: ChemSusChem Vol. 16; no. 23; p. e202300971
• Main Authors: Aydos, Guilherme L P, Marin, Graciane, Ebeling, Günter, Dos Santos, Francisco P, Leal, Bárbara C, Zink, Rafael D, Vargas, Brenda A, Migowski, Pedro, Stieler, Rafael, de Araújo, Bruno B, Gonçalves, Paulo, Stassen, Hubert K, Dos Santos Pereira, Leonardo, Musse, Ana Paula, Dupont, Jairton
• Format: Journal Article
• Language: English
• Published: Germany 07.12.2023
• Subjects: carbon dioxide capture; bicarbonate; ionic liquids; zwitterion; organic base
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300971

The zwitterions resulting from the covalent attachment of 3- or 4-hydroxy benzene to the 1,3-dimethylimidazolium cation represent basic compounds (pKa of 8.68 and 8.99 in aqueous solutions, respectively) that chemisorb in aqueous solutions 0.58 mol/mol of carbon dioxide at 1.3 bar (absolute) and 40 °C. Equimolar amounts of chemisorbed CO in these solutions are obtained at 10 bar and 40 °C. Chemisorption takes place through the formation of bicarbonate in the aqueous solution using imidazolium-containing phenolate. CO is liberated by simple pressure relief and heating, regenerating the base. The enthalpy of absorption was estimated to be -38 kJ/mol, which is about 30 % lower than the enthalpy of industrially employed aqueous solutions of MDEA (estimated at -53 kJ/mol using the same experimental apparatus). The physisorption of CO becomes relevant at higher pressures (>10 bar) in these aqueous solutions. Combined physio- and chemisorption of up to 1.3 mol/mol at 40 bar and 40 °C can be attained with these aqueous zwitterionic solutions that are thermally stable and can be recycled at least 20 times.