High pressure phase behavior of carbon dioxide in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-butyl-3-methylimidazolium dicyanamide ionic liquids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The acidity/basicity of the reaction media has a substantial influence on the efficiency of many reactive processes: therefore, a new class of acidic or basic ionic liquids is gaining special attention due to the possibility of increasing the efficiency of many processes by a wise manipulation of their properties. The absorption of sour gases is one of the processes that can be enhanced by the basic character of the ionic liquid. The fluorination of the cation or anion can also contribute to the gas solubility enhancement. In this work, these two characteristics are evaluated and compared through the study of gas-liquid equilibrium of two ionic liquids, 1-butyl-3-methylimidazolium dicyanamide ([C(4)mim][DCA]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(4)mim]][Tf(2)N]), with carbon dioxide (CO(2)) at temperatures up to 363 K and pressures up to 74 MPa. A thermodynamic model based on the Peng-Robinson equation of state with the Wong-Sandler mixing rule, using the UNIQUAC model for the activity coefficients, was used to describe the experimental data and for the estimation of the Henry's constants. The solubility of CO(2) in 1-butyl-3-methylimidazolium dicyanamide is much lower than anticipated on the basis of the reported pK(a) of the anion when compared with the acetate anion. No chemisorption is observed and the solvation enthalpy is quite low, ruling out any Lewis acid/base interaction between the anion and the CO(2). The 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid, known to present one of the highest solubilities towards CO(2) due to the presence of fluoroalkyl groups, showed a much larger solubility for CO(2) than 1-butyl-3-methylimidazolium dicyanamide. (C) 2009 Elsevier B.V. All rights reserved.502105111Fundacao para a Ciencia e a Tecnologia [PTDC/EQU/65252/2006]Pedro J. Carvalho [SFRH/BD/41562/2007]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundacao para a Ciencia e a Tecnologia [PTDC/EQU/65252/2006]Pedro J. Carvalho [SFRH/BD/41562/2007]FAPESP [2006/03711-1

High carbon dioxide solubilities in trihexyltetradecylphosphonium-based ionic liquids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Due to the potential of ionic liquids for industrial application in CO(2) capture and gas separation processes, solubility of near or supercritical CO(2) in ionic liquids has been object of extensive research during the last few years. This work studies the solubility of CO(2) in phosphonium-based ionic liquids that, unlike imidazolium-based ILs, have received little attention in spite of their interesting characteristics. This work addresses the study of the gas-liquid equilibrium of two ionic liquids, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium chloride, in a wide range of temperatures, pressures, showing that phosphonium ionic liquids can dissolve even larger amounts of CO(2) (on a molar fraction basis) than the corresponding imidazolium-based ILs. In particular trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide seems to be the IL with the largest CO(2) sorption capacity reported up to present, revealing the potential of phosphonium-based ILs for CO(2) capture. A thermodynamic model based on the Peng-Robinson equation of state with the Wong-Sandler mixing rule, using the UNIQUAC model for the activity coefficients, was here adopted to describe the experimental data and for the estimation of the Henry's constants. A universal correlation, for the description of the solubility of CO(2) in ILs previously proposed by us was also applied to the description of the data here measured showing a good agreement with the experimental data. (C) 2010 Elsevier B.V. All rights reserved.523258265Fundacao para a Ciencia e a Tecnologia [PTDC/EQU-FTT/102166/2008]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)[SFRH/BD/41562/2007]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundacao para a Ciencia e a Tecnologia [PTDC/EQU-FTT/102166/2008]FAPESP [2006/037111][SFRH/BD/41562/2007

A closer look into deep eutectic solvents: exploring intermolecular interactions using solvatochromic probes.

Deep eutectic solvents (DESs) constitute a new class of ionic solvents that has been developing at a fast pace in recent years. Since these solvents are commonly suggested as green alternatives to organic solvents, it is important to understand their physical properties. In particular, polarity plays an important role in solvation phenomena. In this work, the polarity of different families of DESs was studied through solvatochromic responses of UV-vis absorption probes. Kamlet-Taft α, β, π* and ETN parameters were evaluated using different solvatochromic probes, as 2,6-dichloro-4-(2,4,6-triphenyl-N-pyridino)-phenolate (Reichardt's betaine dye 33), 4-nitroaniline, and N,N-diethyl-4-nitroaniline for several families of DESs based on cholinium chloride, dl-menthol and a quaternary ammonium salt ([N4444]Cl). In addition, a study to understand the difference in polarity properties between DESs and the corresponding ILs, namely ILs based on cholinium cation and carboxylic acids as anions ([Ch][Lev], [Ch][Gly] and [Ch][Mal]), was carried out. The chemical structure of the hydrogen bond acceptor (HBA) in a DES clearly controls the dipolarity/polarizability afforded by the DES. Moreover, Kamlet-Taft parameters do not vary much within the family, but they differ among families based on different HBA, either for DESs containing salts ([Ch]Cl or [N4444]Cl) or neutral compounds (dl-menthol). A substitution of the HBD was also found to play an important role in solvatochromic probe behaviour for all the studied systems

High pressure phase behavior of carbon dioxide in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)New standards concerning environmental and safety issues are creating an increasing interest on ionic liquids as alternative solvents for a wide range of industrial applications. In this work, a new apparatus developed to measure vapor-liquid phase equilibrium in a wide range of pressures and temperatures was used to measure the phase behavior of the binary systems of carbon dioxide (CO(2))+1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C(2) mim][Tf(2)N]) and CO(2)+1-methyl-3-pentyl-imidazolium bis(trifluoromethylsulfonyl)imide ([C(5) mim][Tf(2)N]) at temperatures up to 363 K and pressures up to 50 MPa. A thermodynamic consistency test, developed for systems with incomplete PTxy data and based on the Gibbs-Duhem equation, was applied to the experimental data measured in this work and the Peng-Robinson EoS using the Wong-Sandler mixing rule was used to describe the experimental data with excellent results. (C) 2008 Elsevier B.V. All rights reserved.48299107Fundacao para a Ciencia e a Tecnologia [POCI/EQU/58152/2004]Pedroj. Carvalho [SFRH/BD/41562/2007]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundacao para a Ciencia e a Tecnologia [POCI/EQU/58152/2004]Pedroj. Carvalho [SFRH/BD/41562/2007]FAPESP [2006/03711-1

Specific Solvation Interactions of CO2 on Acetate and Trifluoroacetate Imidazolium Based Ionic Liquids at High Pressures

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)New classes of acidic or basic ionic liquids (ILs) are gaining special attention, since the efficiency of many processes can be enhanced by the judicious manipulation of these properties. The absorption of sour gases can be enhanced by the basic character of the IL. The fluorination of the cation or the anion can also contribute to enhance the gas solubility. In this work these two characteristics are evaluated through the study of the gas-liquid equilibrium of two ionic liquids based on similar anions, 1-butyl-3-methylimidazolium acetate ([C(4)mim] [Ac]) and 1-butyl-3-methylimidazolium trifluoroacetate ([C(4)mim] [TFA]), with carbon dioxide (CO2) at temperatures up to 363 K and pressures up to 76 MPa. The data reported are shown to be thermodynamically consistent. Henry's constants estimated from the experimental data show the solubility of CO2 on the [C(4)mim][Ac] to be spontaneous unlike in [C(4)mim][TFA] due to the differences in solvation enthalpies in these systems. Ab initio calculations were performed on simple intermolecular complexes of CO2 with acetate and trifluoroacetate using MP2/6-31G(d) and the G3 and G3MP2 theoretical procedures to understand the interactions between CO2 and the anions. The theoretical study indicates that although both anions exhibit a simultaneous interaction of the two oxygen of the carboxylate group with the CO2, the acetate acts as a stronger Lewis base than the trifluoroacetate. C-13 high-resolution and magic angle spinning (HRMAS) NMR spectra provide further evidence for the acid/base solvation mechanism and the stability of the acetate ion on these systems. Further similarities and differences observed between the two anions in what concerns the solvation of CO2 are discussed.1131968036812Fundacao para a Ciencia e a Tecnologia [POCI/EQU/58152/2004]Funda do para a Ci ncia e a Tecnologia [SFRH/BD/41562/2007]postdoctoral scholarships [SFRH/BPD/38637/2007]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundacao para a Ciencia e a Tecnologia [POCI/EQU/58152/2004]Funda do para a Ci ncia e a Tecnologia [SFRH/BD/41562/2007]postdoctoral scholarships [SFRH/BPD/38637/2007]FAPESP [2006/03711-1