FIGURE 1 - uploaded by Ana B Pereiro
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Mapping of azeotropes in the matrix of ILs anions and cations used as separating agents. The colors refer to the number of different studied azeotropes from literature per ion combination; the length of the bars gives the count per ion.
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![FIGURE 5. Comparison of the relative volatility for [BMIM][Cl] [29] and...](profile/Ana-Pereiro/publication/221905811/figure/fig4/AS:393970757718044@1470941356827/Comparison-of-the-relative-volatility-for-BMIMCl-29-and-other-proposed-entrainers_Q320.jpg)
Efforts to make existing separation methods more efficient and eco-friendly may get a boost from the use of a relatively new class of compounds known as ionic liquids (ILs). The separation of azeotropic mixtures has conventionally been one of the most challenging tasks in industrial processes due to the fact that their separation by simple distilla...
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... the physical and corrosion properties of ILs are generally more Azeotropes studied using ionic liquids as separating agent (azeotrope data from reference [1] adequate for separation processes than those of inorganic molten salts, opening the door to their use in azeotropic separation processes. Figure 1 maps the large number of publications already avail- able on this subject showing the distinct azeotropes studied with different IL anions and cations used as separating agents. Table 2 lists the nomenclature used for all IL cations and anions mentioned herein. ...
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... of the nature of the anion. The effect of the ionic li- quid's anion nature on the relative volatility of the system at two ethanol concentrations was studied at x Ethanol = 0.1 (supporting information figure S1) and 0.95 (figure 2). Imidazolium cation was chosen due to the wealth of available data. ...
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... Figure 10 depicts the effect of the IL concentration on the rela- tive volatility of the (THF + water) system at azeotropic point (x THF = 0.817). An increase in IL concentration leads to a higher THF concentration in the vapor phase and, therefore, to greater rel- ative volatility due to strong selective interactions between the IL and water molecules. ...
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... increase in IL concentration leads to a higher THF concentration in the vapor phase and, therefore, to greater rel- ative volatility due to strong selective interactions between the IL and water molecules. Figure 10 clearly shows that [EMIM] [BF 4 ] is the most suitable entrainer for the THF + water separation. ...
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... effect of the ionic liquid's anion nature on the relative vol- atility of the (THF + water) system at the azeotropic point (x THF = 0.817) is plotted in figure 11 ...
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... pioneering work of Sada et al. [91], containing VLE data, analyzes the effect of adding inorganic chlorides salts on the (va- por + liquid) equilibria of the (THF + water) azeotropic system at fixed solvent composition and atmospheric pressure. Figure 12 compares chloride inorganic salt versus IL regarding their effects on the relative volatility of the (THF + water) system at azeotropic point (x THF = 0.817). The relative volatility for THF in the binary (THF + water) azeotropic system is also shown. ...
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... a comparison between the influence of hyperbranched polymers and ILs on the VLE of (THF + water) aze- otropic system is required to access which additive performs better in breaking the azeotrope. Figure 13 compares the effect of all investigated ILs, at a constant mole fraction of 0.30, on the relative volatility of THF in the (THF + water) system at azeotropic point (x THF = 0.817) to that obtained for hyperbranched polyesteramide Hydrane S1200. The relative volatility for THF in the system (THF + water + hyperbranched polyesteramide Hydrane S1200) (mole fraction of 0.40) is 1.87 [92], and is represented as a straight horizontal line. ...
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... can be concluded that the hyperbranched poly- mer only performed better than two ILs, [EMIM] The results, interestingly, also suggest the feasibility of specific tailoring of the extraction solvent. Figure 15 plots the contrast be- tween IL and polymer behavior. While ILs are miscible in the water and immiscible in THF, the polymers are miscible in THF and immiscible in water. ...
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... ethanol + ethyl acetate is the most frequently studied system of this type. Figure 16 shows the influence of ILs on the rel- ative volatility of ethyl acetate to ethanol. The separation ability of the four ILs at x IL = 0.30 is in the following order: [OMIM] [BF 4 ] and is mainly due to the difference in polarity of the ILs and the demixing effect [102]. ...
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... + ethyl acetate azeotrope was also the most studied system for liquid-liquid extraction. Figure 17 illustrates the influ- ence on the selectivity values of alkyl or hydroxyl substituent in the imidazolium cation of the ILs. These data show that [(EtOH)- MIM] [BF 4 ] has greater extraction capacity than the other ILs and that a hydroxyl group on the cation and a methyl group at the 2-position can obviously affect the IL ethanol interaction. ...
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... data show that [(EtOH)- MIM] [BF 4 ] has greater extraction capacity than the other ILs and that a hydroxyl group on the cation and a methyl group at the 2-position can obviously affect the IL ethanol interaction. Figure 18 illustrates how the immiscibility region decreases with the increase in the length of the alkyl chain in the imidazoli- um ring when the [C n MIM] [PF 6 ] is used as solvent in liquid-liquid extraction. The analysis of the LLE data [108] indicates that the al- kyl chain length of the imidazolium ring plays a negative role in the extraction solvent capability of [C n MIM][PF 6 ], due, perhaps, to the hydrophobic steric effect of the alkyl group reducing the po- lar character of 2-propanol. ...
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... systems present small immiscibility regions, increasing with temperature at the highest chloroform compositions. The highest alkanol/chloroform selectiv- ities for [EMIM][OTf] were obtained at low concentration of alcohol in organic phase (supporting information figure S10). ...
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... IL selec- tion criteria were those for where the benzene distribution coeffi- cient is greater then 0.46 mol/mol and benzene/hexane selectivity greater than 22.2, at T % 298.15 K and at w Benzene = 0.10 in organic phase (comparison between ILs and sulfolane in supporting infor- mation figure S11). Room temperature was considered as the refer- ence due to the research tendency to determine the (liquid + liquid) equilibria of ternary systems at this temperature, given that all compounds and their mixtures are liquid at such temperature. ...
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... temperature was considered as the refer- ence due to the research tendency to determine the (liquid + liquid) equilibria of ternary systems at this temperature, given that all compounds and their mixtures are liquid at such temperature. figure S11), but this IL is not suitable for industrial processes due to its reaction with water 4 ] À has been commonly investigated and con- sidered historically to be one of the most important anion families. However, this anion can undergo hydrolysis producing hydroflu- oric acid when in contact with water and at high temperatures [182,183]. ...
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... et al. [189][190][191] demonstrate the ability of the ILs based on imidazolium cations to act as extraction solvents for liquid-liquid extraction and as azeotrope breakers for extractive distillation (ta- ble 14) in order to separate azeotrope ETBE + ethanol, thus purify- ing the tertiary ether, which is the most common additive for improving gasoline octane indexes. A comparison between etha- nol/ETBE selectivity values for all the ILs used as solvents in li- quid-liquid extraction (supporting information figure S12) shows that the use of [EMIM] [MeSO 3 ] as the leads to the highest selectiv- ity values. Moreover, the data depicted in figure S12 indicates that the fluorination of the anion plays a negative role in the capability of the IL to purify the ether by liquid extraction. ...
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... comparison between etha- nol/ETBE selectivity values for all the ILs used as solvents in li- quid-liquid extraction (supporting information figure S12) shows that the use of [EMIM] [MeSO 3 ] as the leads to the highest selectiv- ity values. Moreover, the data depicted in figure S12 indicates that the fluorination of the anion plays a negative role in the capability of the IL to purify the ether by liquid extraction. ...
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... LLE data for the ternary systems (cyclohexane + 2-buta- none + [HMIM] [PF 6 ] or [OMIM][PF 6 ]), the experimental tie-lines (supporting information, figure S13) show a positive slope where the solute goes preferentially to the solvent-rich phase. Another significant aspect is the fact that the IL does not enter in the organ- ic-rich phase, e.g., the presence of [HMIM][PF 6 ] and [OMIM][PF 6 ] was not detected in the upper phase. ...
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... significant aspect is the fact that the IL does not enter in the organ- ic-rich phase, e.g., the presence of [HMIM][PF 6 ] and [OMIM][PF 6 ] was not detected in the upper phase. The selectivity values for the studied ternary systems (supporting information, figure S14) are higher for the [HMIM][PF 6 ] than for the [OMIM][PF 6 ], indicating that the former is a better choice as solvent for these azeotropic separations. Also, the increase of alkyl chain length of the imidazolium decreases the IL's capacity to separate the two azeotropes with hexafluorophosphate. ...
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... azeotropes as a function of the ILs used as separation agents depicted in figure 1, identified the three most utilized as azeotrope breakers: [EMIM] 4 ] À anions have received the most research attention. Nevertheless, in the last decade, the use of these ILs has slowed down since they hydrolise in water and at high tempera- ture [182,183] leading to the formation of HF; their use has conse- quently been restricted to those systems under water-free conditions and moderate temperatures. ...
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Citations
... Currently, there are five types of entrainers used in extractive distillation, that is, solid salts, 1-4 liquid solvents, 5-8 the mixture of liquid solvents and solid salts, [9][10][11][12] hyperbranched polymers, 13 and ionic liquids (ILs). [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Due to their unique advantages, such as nonvolatility, salt effect, high separation ability, regeneration, being present in the liquid state around room temperature, and thermal and chemical stabilities, ILs have received considerable attention in recent years for their use in extractive distillation for the separation of olefins and alkanes, alcohols and aliphatics, alcohols and water, and many other systems. [22][23][24][25][26][27][28][29] In principle, the salting effect of solid inorganic salts could be stronger than ILs due to their small molecular volumes. ...
This work proposes the use of the mixture of ionic liquid (IL) and solid inorganic salt in place of the single IL as entrainers for extractive distillation, which integrates the advantages of a liquid solvent, i.e., IL (easy operation and nonvolatility) and a solid salt (high separation ability). The vapor-liquid equilibrium (VLE) experiments indicated that the combination of [EMIM]+[Ac]- and KAc is the most promising for the separation of ethanol and water among all of the entrainers investigated. Based on the thermodynamic study, the conceptual process design was developed to evaluate the competitiveness of the suggested entrainers for the separation of ethanol and water. It was determined that the overall heat duty on reboilers in the extractive distillation process using the new mixed entrainers decreases 19.04% compared with the benchmark entrainer [EMIM]+[Ac]-. Moreover, the density functional theory and COSMO-RS model were used to achieve theoretical insights at the molecular level. © 2014 American Institute of Chemical Engineers AIChE J, 2014
... Based on the analysis of the ILs extraction capacities for ethanol + alkanes (hexane or heptane) systems, ILs with the methyl sulfate anion ([MMIM][MeSO 4 ] and [BMIM][MeSO 4 ]) were included in a lab-scale extraction process incorporating a solvent recycling stage [123,124,126,127,129]. These selectivities are the highest reported in the literature for azeotropic separation in general using liquid-liquid extraction. ...
... Extraction efficiencies (from equation (6)) for the separation of the azeotrope ethanol + alkanes in the packed column [123,124,126,127,129]. The ILs reported in table 12 [134,135] were used as azeotrope breakers for the (alcohols + chloroform) systems using extractive distillation and liquid-liquid extraction. ...
... Figure 30 compares [EMIM][EtSO 4 ] selectivities for different azeotropes separated by FIGURE 29. Selectivity (S VLE ) for the ILs [27,34,37,62,63,69,71] used as entrainers in the aqueous azeotropes separated by extractive distillation at THF or alcohol molar fraction % 0. 95 [123,124,126,127,129]. These papers confirm the assumption that the IL regeneration and recycling are indeed simple for this process, which is a great advantage relative to traditional extraction solvents. ...
In order to reduce the environmental of the separation of 1-propanol from water in a residual industry stream for its reuse, the capability as solvents of two different trihexyl(tetradecyl)phosphonium ionic liquids (ILs) - trihexyl(tetradecyl)phosphonium chloride ([TDTHP][Cl]) and trihexyl(tetradecyl)phosphonium bromide ([TDTHP][Br])-, was studied. The liquid-liquid equilibria data for both ternary systems, {water + 1-propanol + [TDTHP][Cl]} and {water + 1-propanol + [TDTHP][Br]} at different mild work temperatures, (283.2, 303.2 and 323.2) K, and atmospheric pressure were measured. The thermodynamic parameters for both ternary systems at different work conditions were obtained by the non-random two-liquid activity coefficient model (NRTL) in order to achieve a posterior correct equipment design. Finally, the selectivity and distribution coefficient of [TDTHP][Cl] and [TDTHP][Br] were bibliographically benchmarked with different ILs, trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate ([TDTHP][Phosph]) and 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([dmim][Tf2N]), achieving a solubility of 1-propanol in the IL around 20 times greater than in water and a capability of [TDTHP][Br] to incorporate 1-propanol in its phase instead of in water rich phase around 40, which means, a great selectivity and values of the distribution coefficient close to the double in respect to the ILs researched. It could be concluded that both ILs, [TDTHP][Cl] and [TDTHP][Br], are capable to purify 1-propanol from water with great technical, environmental and economic advantages, in respect of the classical solvents and other ILs researched.
Four different glycerol-based deep eutectic solvents (DESs) were tested as extracting agents for the separation of the azeotropic mixture {methyl ethyl ketone + ethanol} via liquid-liquid extraction. The selected DESs for this work were: glycerol/choline chloride with molar ratios (4:1) and (2:1), and glycerol/tetramethylammonium chloride with molar ratios (4:1) and (2:1). The selected DESs have been characterized by measuring the density and the viscosity at different temperatures. The liquid-liquid equilibria data of the ternary systems {methyl ethyl ketone + ethanol + DES} were experimentally determined at T/K = 298.15 and atmospheric pressure. The extraction efficiencies of the selected DESs were analyzed by determining the solute distribution coefficients and the selectivity values, which were calculated from the experimental results. The extraction performance of the DESs was compared to the extraction data of pure glycerol. The integrity of the DESs after recovery was also studied. Finally, the experimental LLE data were regressed using the nonrandom two liquid (NRTL) model. It was found that the addition of a hydrogen bond acceptor to glycerol, and therefore, the formation of a deep eutectic solvent, improves the extraction efficiency of this mixture via liquid-liquid extraction.
Halogenated hydrocarbons are members of priority water contaminants because of their negative health and environmental impacts. In this study, the solubility of three halogenated hydrocarbons, namely, carbon tetrachloride, chloroform, and bromoform was measured in 12 hydrophobic ionic liquids (ILs) for temperature ranging between 25 and 45 °C. We investigated the chemical structure and alkyl chain length effect of three different cations (piperidinium, pyrrolidinium, and ammonium-based) paired with bis(trifluoromethylsulfonyl)imide anion. It was found that carbon tetrachloride and bromoform are partially miscible in all tested ILs while chloroform exhibits full miscibility. For ammonium based ionic liquids, the solubility increases with the increase of the cation molecular weight and alkyl chain length. The results indicate that the solubility of the studied halogenated hydrocarbons in methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, octyltriethylammonium bis(trifluoromethylsulfonyl)imide, and 1-octyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-imide is substantial. These results confirm the potential use of ionic liquids as powerful alternative solvents for wastewater treatment. Finally, the predictive capability of COSMO-RS model provided excellent qualitative agreement with experimental data both for temperature dependence and for cations structure effect.
