US EPA

7423977 

Journal Article 

High CO2 absorption capacity by chemisorption at cations and anions in choline-based ionic liquids 

Bhattacharyya, S; Filippov, A; Shah, FU; , 

2017 

1 

Physical Chemistry Chemical Physics
ISSN: 1463-9076
EISSN: 1463-9084 

ROYAL SOC CHEMISTRY 

CAMBRIDGE 

19 

46 

31216-31226 

English 

29143022 

10.1039/c7cp07059d 

WOS:000416425400023 

http://xlink.rsc.org/?DOI=C7CP07059D
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The effect of CO2 absorption on the aromaticity and hydrogen bonding in ionic liquids is investigated. Five different ionic liquids with choline based cations and aprotic N-heterocyclic anions were synthesized. Purity and structures of the synthesized ionic liquids were characterized by 1H and 13C NMR spectroscopy. CO2 capture performance was studied at 20 °C and 40 °C under three different pressures (1, 3, 6 bar). The IL [N1,1,6,2OH][4-Triz] showed the highest CO2 capture capacity (28.6 wt%, 1.57 mol of CO2 per mol of the IL, 6.48 mol of CO2 per kg of the ionic liquid) at 20 °C and 1 bar. The high CO2 capture capacity of the [N1,1,6,2OH][4-Triz] IL is due to the formation of carbonic acid (-OCO2H) together with carbamate by participation of the -OH group of the [N1,1,6,2OH]+ cation in the CO2 capture process. The structure of the adduct formed by CO2 reaction with the IL [N1,1,6,2OH][4-Triz] was probed by using IR, 13C NMR and 1H-13C HMBC NMR experiments utilizing 13C labeled CO2 gas. 1H and 13C PFG NMR studies were performed before and after CO2 absorption to explore the effect of cation-anion structures on the microscopic ion dynamics in ILs. The ionic mobility was significantly increased after CO2 reaction due to lowering of aromaticity in the case of ILs with aromatic N-heterocyclic anions.