The Solubility of Carbon Dioxide and Density for Binary Mixtures of 1-Butyl-3-methylimidazolium Acetate and 1-Butyl-3-methylimidazolium Tetrafluoroborate

Abstract

The gas sweetening process requires an efficient solvent with strong absorption capability to capture acid gases from flue gas. Absorption can be strong by a chemical formation (as "chemical" absorption) or simple with no chemical reactions (as "physical" absorption). The purpose of the present study was to compare the CO 2 solubility of the chemically absorbing ionic liquid, 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]), with the physically absorbing ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4 ]), as a function of temperature at (298.15 to 318.15) K for pressure up to 50 bar. In addition, the CO 2 solubility for binary mixtures containing 75% [BF 4 ] are measured over the same temperature range. Henry's law constants are reported for the solubility of CO 2 in the studied pure and mixed ionic liquids. Furthermore, the density of mixed ionic liquids is experimentally measured in T = 298.15 K, 308.15 K, and 318.15 K. Finally, the partial molar thermodynamic functions of solvation containing Gibbs free energy, enthalpy, and entropy are evaluated based on the variation of Henry's law constants (as a representative of solubility) with temperature.

Temperature and Pressure Dependence of the Viscosity of the Ionic Liquid 1-Butyl-3-methylimidazolium Acetate

“…As mentioned above, the Na-dried sample values are also close to these results, as are the literature data for other IoLiTec sourced samples, namely, those of Zorębski et al [10 6 × w (H 2 O) = 1512], Lepre et al [10 6 × w (H 2 O) = 1600] (excellent agreement), Almeida et al [10 6 × w (H 2 O) = 850], and Hiraga et al [10 6 × w (H 2 O) = 250]. The literature data for Sigma-Aldrich, BASF, and Fluka samples tend to lie slightly higher, though the difference is small: Kanakubo et al [10 6 × w (H 2 O) = 3500], Haghtalab and Shojaeian [10 6 × w (H 2 O) = 15 000, not vacuum dried, so the apparent agreement may have been fortuitous, though again the water content may be overestimated], Safarov et al [10 6 × w (H 2 O) = 300], Shaahmadi et al [10 6 × w (H 2 O) < 100], Araújo et al [10 6 × w (H 2 O) < 4700], and Tariq et al [10 6 × w (H 2 O) < 70]. The results for the laboratory synthesized sample of Xu et al [10 6 × w (H 2 O) = 99] are scattered above and below our results.…”

“…The water content was remeasured on withdrawal of samples from the densimeter after the measurements: there was slight absorption during filling and handling (see Table 2). As mentioned above, the Na-dried sample values are also close to these results, as are the literature data for other IoLiTec sourced samples, namely, those of Zorebski et al 14 [10 6 × w(H 2 O) = 15 000, not vacuum dried, so the apparent agreement may have been fortuitous, though again the water content may be overestimated], Safarov et al 35 [10 6 × w(H 2 O) = 300], Shaahmadi et al 38 [10 6 × w(H 2 O) < 100], Araujo et al 10 [10 6 × w(H 2 O) < 4700], and Tariq et al 39 Manufacturers' specifications do not always distinguish between mole fraction and mass fraction concentration scales. This table cites the information given in the literature references.…”

“…Deviations of experimental and literature densities from values predicted by eq as a function of temperature, T . Symbols: IoLiTec sample, this work, blue filled inverted triangle, sample 1 as received [10 6 × w (H 2 O) = 2300]; blue filled diamond, sample 2 as received [10 6 × w (H 2 O) = 3700]; blue filled triangle, sample 1 dried isopiestically over Na [10 6 × w (H 2 O) = 1457]; blue filled circle, sample 1 dried under vacuum [10 6 × w (H 2 O) = 1180]; blue filled box, sample 2 dried under vacuum [10 6 × w (H 2 O) = 1100]; literatureother IoLiTec samples: solid triangle, Almeida et al [10 6 × w (H 2 O) = 850]; solid diamond, Hiraga et al [10 6 × w (H 2 O) = 250]; solid inverted triangle, Zorębski et al [10 6 × w (H 2 O) = 1512); solid circle, Lepre et al [10 6 × w (H 2 O) = 1600]; literatureFluka sample: open diamond, Tariq et al [10 6 × w (H 2 O) < 70]; literatureBASF sample: asterisk, Araújo et al [10 6 × w (H 2 O) < 4700]; literatureSigma-Aldrich samples: open triangle, Kanakubo et al [10 6 × w (H 2 O) = 3500]; open box, Haghtalab and Shojaeian [10 6 × w (H 2 O) = 15 000]; open circle, Safarov et al [10 6 × w (H 2 O) = 300]; open inverted triangle, Shaahmadi et al [10 6 × w (H 2 O) < 100]; literaturelaboratory-synthesized samples: Pandit et al [10 6 × w (H 2 O) < 50], off scale, 37 mg·cm –3 ; cross, Xu et al [10 6 × w (H 2 O) = 99).…”

The Role of Binary Mixtures of Ionic Liquids in ZIF-8 for Selective Gas Storage and Separation: A Perspective from Computational Approaches

“…For convenience, here, we have named them based on components, that is, as binary IL mixtures. The binary/ternary component/constituent of ILs can enhance CO 2 adsorption …”

“…Our study will deliver the effect of various anions in simple ILs and the binary mixture of ILs with the combination of ZIF-8 nanopores. Only a few studies have reported the physical and chemical adsorption of gases in IL mixtures, − but there are no clear reports on the microscopic picture of ILs at the interface and how these IL mixtures can behave in the confined environment. The structure and composite stability of the resulting complexes were studied using DFT-based periodic calculations, and gas selectivity and adsorption isotherms were identified from force-field-based simulations.…”