Jump to main content
Jump to site search

Can the tricyanomethanide anion improve CO2 absorption by acetate-based ionic liquids?


Carbon dioxide absorption by mixtures of two ionic liquids with a common cation — 1-butyl-3-methylimidazolium acetate, [C4C1Im][OAc], and 1-butyl-3-methylimidazolium tricyanomethanide, [C4C1Im][C(CN)3] — was determined experimentally at pressures below atmospheric as a function of temperature between 303 K and 343 K, and at 303 K as a function of pressure up to 10 bar. It is observed that the absorption of carbon dioxide decreases with increasing tricyanomethanide anion concentration and with increasing temperature, showing a maximum of 0.4 mole fraction of carbon dioxide in pure [C4C1Im][OAc] at 303 K. At this temperature, the CO2 absorption in the mixtures [C4C1Im][OAc](1−x)[C(CN)3]x is approximately the mole-fraction average of that in the pure ionic liquids. By applying an appropriate thermodynamic treatment, after identification of the species in solution, it was possible to calculate both the equilibrium constant, Keq, and the Henry’s law constant, KH, in the different mixtures studied thus obtaining an insight about the relative contribution of chemical and physical absorption of the gas. It is shown that chemical sorption proceeds through a 1:2 stoichiometry between CO2 and acetate-based ionic liquid. The presence of the C(CN)3− anion does not significantly affect the chemical reaction of gas with the solvent (Keq = 75 ± 2 at 303 K) but leads to lower Henry’s law constants (from KH = 77.8 ± 0.6 bar to KH = 49.5 ± 0.5 bar at 303 K), thus pointing towards larger physical absorptions of the gas. The tricyanomethanide anion considerably improves the mass transfer by increasing the fluidity of the absorbent as proven by the larger diffusivities of all the ions when the concentration of the C(CN)3− anion increases in the mixtures.

Back to tab navigation
Please wait while Download options loads

Supplementary files

Publication details

The article was received on 10 Mar 2017, accepted on 18 Apr 2017 and first published on 19 Apr 2017

Article type: Paper
DOI: 10.1039/C7CP01559C
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
  •   Request permissions

    Can the tricyanomethanide anion improve CO2 absorption by acetate-based ionic liquids?

    L. F. Lepre, J. Szala-Bilnik, L. Pison, M. Traikia, A. A.H. Padua, R. A. Ando and M. C. Costa Gomes, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP01559C

Search articles by author