A series of hydrophilic and hydrophobic 1-alkyl-3-methylimidazolium room temperature ionic liquids (RTILs) have been prepared and characterized to determine how water content, density, viscosity, surface tension, melting point, and thermal stability are affected by changes in alkyl chain length and anion. In the series of RTILs studied here, the choice of anion determines water miscibility and has the most dramatic effect on the properties. Hydrophilic anions (e.g., chloride and iodide) produce ionic liquids that are miscible in any proportion with water but, upon the removal of some water from the solution, illustrate how sensitive the physical properties are to a change in water content. In comparison, for ionic liquids containing more hydrophobic anions (e.g., PF 6 2 and N(SO 2 CF 3 ) 2 2 ), the removal of water has a smaller affect on the resulting properties. For a series of 1-alkyl-3-methylimidazolium cations, increasing the alkyl chain length from butyl to hexyl to octyl increases the hydrophobicity and the viscosities of the ionic liquids increase, whereas densities and surface tension values decrease. Thermal analyses indicate high temperatures are attainable prior to decomposition and DSC studies reveal a glass transition for several samples. ILs incorporating PF 6 2 have been used in liquid/liquid partitioning of organic molecules from water and the results for two of these are also discussed here. On a cautionary note, the chemistry of the individual cations and anions of the ILs should not be overlooked as, in the case of certain conditions for PF 6 2 ILs, contact with an aqueous phase may result in slow hydrolysis of the PF 6 2 with the concomitant release of HF and other species.

The partitioning of simple, substituted-benzene derivatives between water and the room temperature ionic liquid, butylmethylimidazolium hexafluorophosphate, is based on the solutes' charged state or relative hydrophobicity; room temperature ionic liquids thus may be suitable candidates for replacement of volatile organic solvents in liquid-liquid extraction processes.

Hydrophilic ionic liquids can be salted-out and concentrated from aqueous solution upon addition of kosmotropic salts forming aqueous biphasic systems as illustrated by the phase behavior of mixtures of 1-butyl-3-methylimidazolium chloride ([C4mim]Cl) and K3PO4.

The impact that anthropogenic CO 2 is having on the environment has been thoroughly documented over the last 20 years. Many different technologies have been proposed to reduce its impact on global warming such as geological sequestration. However, an interesting and attractive alternative would be the recycling of the gas into energy-rich molecules. Iron rather than cobalt catalysts, based on the Fischer-Tropsch technology, have shown the greatest promise in converting CO 2 to value-added hydrocarbons. The addition of co-catalysts is, however, essential to fine tune the product distribution to the more desired alkene products. The role that both the promoter and support play on the catalyst's activity is reviewed.

Aqueous biphasic systems (ABSs) represent wholly aqueous systems that are safe, nontoxic, and nonflammable, and thus, they represent relatively environmentally benign extraction media. Such systems could be employed as alternatives to traditional aqueous-organic systems for the separation of, inter alia, small organic molecules, thus it is important to develop a fundamental understanding of these systems and the variables that govern solute partitioning within them. The partitioning of a series of neutral, substituted benzene compounds and neutral, aliphatic compounds in ABSs composed of different molecular weights of poly(ethylene glycol) (PEG-1000, 2000, and 3400) and formed as a result of the addition of different salt types [K 3 PO 4 , K 2 CO 3 , (NH 4 ) 2 SO 4 , Li 2 SO 4 , MnSO 4 , ZnSO 4 , and NaOH] has been examined. The results show that the distribution of organic solutes is a function only of the degree of phase divergence of the biphasic system as expressed by the difference in polymer concentration between the phases: ∆[poly-(ethylene glycol)], ∆[ethylene oxide monomers], or tie line length (∆PEG, ∆EO, or TLL, respectively). Solute partitioning depends only on the composition of the phase-forming components, PEG and salt. Using ideas taken from the study of critical phenomena, it can be shown that the composition of the phases is the result of the salting-out ability of the salt and the number of ethylene oxide monomers comprising the PEG. The salting-out strength of the salt (measured by its lyotropic number or position in the Hofmeister series) is related to its ability to lower the cloud point of the PEG solution. Hence, cosmotropic salts salt-out PEG, producing a series of nearly identical ABSs that, although differing in their overall concentrations of PEG and salt, are identical in terms of their lyotropic properties. This is an extraordinary simplification of a complex array of different ABSs to a single series of ABSs of graded lyotropy. Further comparison of solute partitioning in PEG/salt ABSs to partitioning in 1-octanol/water systems is discussed, and a greater similarity of solute distribution was found between different PEG/salt ABSs than between PEG/salt ABSs and 1-octanol/water.

Partition coefficients, as values of log P, between water and two room-temperature ionic liquids and between water and an aqueous biphasic system have been correlated with Abraham's solute descriptors to yield linear free energy relationships that can be used to predict further values of log P, to ascertain the solute properties that lead to increased or decreased log P values, and to characterize the partition systems. It is shown that, in all three of the systems, an increase in solute hydrogen-bond basicity leads to a decrease in log P and an increase in solute volume leads to an increase in log P. For the two ionic liquid systems, an increase in solute hydrogenbond acidity similarly decreases log P, but for the aqueous biphasic system, solute hydrogenbond acidity has no effect on log P. These effects are rather smaller than those observed in traditional water-solvent systems. However, the ionic liquids appear to have an increased affinity for polyaromatic hydrocarbons as compared to traditional organic solvents. Principal component analysis and nonlinear mapping show that the three unconventional partition systems are considerably different from conventional water-organic solvent systems. IntroductionA major contemporary industrial challenge is to continued manufacturing beneficial chemical products while eliminating or substantially reducing the detrimental environmental consequences of the processes adopted. The Montreal Protocol 1 identified the need to reevaluate chemical processes to take account of their environmental impact, especially with regard to the use of volatile organic solvents. In addition, some 90% of hazardous waste is aqueous in nature, 2 and thus, industry is reliant upon efficient separations from liquid media. To this end, liquid-liquid separations are widely applied in the chemical process industry. Typically, because of their immiscibility with water, volatile organic solvents are often employed in such processes. 3 Taken together, these issues suggest that the elimination of the use of flammable toxic and volatile organic solvents in separations processing represents a significant step in the creation of a sustainable industrial technology. 4 A number of different approaches to this problem have been identified, including solvent-free synthesis, the use of water as a solvent, 5 the use of supercritical fluids, 6 and the use of ionic liquids. Recently, roomtemperature ionic liquids (RTILs) have received worldwide attention 7,8 as replacements for organic solvents in catalysis, 9 synthesis, 10,11 and separations processes. 12,13 Room-temperature ionic liquids, in contrast to conventional ionic liquids such as molten sodium chloride, which are only liquids at temperatures above 800°C, represent ionic salts that are liquid at room temperature. Many RTILs are liquids over a wide temperature range, and RTILs with melting points as low as -96°C are known. The constituents of many RTILs (being ionic) are constrained by high Coulombic forces and thus exert practically no vapor pressure abo...

Aqueous biphasic systems (ABSs) composed of poly(ethylene glycol) (PEG) and salt have been examined as potential environmentally benign solvents for liquid/liquid extraction. These systems might also represent an alternative to traditional solvent/water systems used in quantitative structure-activity relationships (QSARs). For the application and design of these systems, it is important to have a thorough understanding of the nature of the solvent and its interactions with the solute, and thus, PEG/salt ABSs have been characterized to this end by a variety of methods. The relative hydrophobicities of several PEG/salt ABSs composed of different molecular weights of PEG (1000, 2000, and 3400) and a variety of inorganic salts [K 3 PO 4 , K 2 CO 3 , (NH 4 ) 2 -SO 4 , Li 2 SO 4 , MnSO 4 , ZnSO 4 , and NaOH] were measured by the free energy of transfer of a methylene group ∆G CH 2 . These results indicate that the relative hydrophobicity of a PEG/salt ABS is a function of only the degree of phase divergence of the biphasic system as expressed by the difference in polymer concentration between the phases [delta poly(ethylene glycol) (∆PEG), delta ethylene oxide monomer (∆EO)] or the tie line length (TLL). The distributions of a wide range of solutes differing in structure and functionality were also measured in PEG/salt ABSs, and the results were compared to the corresponding 1-octanol/water partition coefficients. These data were used to develop a linear free energy relationship (LFER) based on Abraham's generalized solvation equation, enabling a direct comparison to be made between the solvent properties of PEG/salt ABSs and those of traditional solvent/water systems used, for example, in the determination of log P. Similar comparisons are also enabled with the properties of certain aqueous micellar systems.

Phase diagrams determined by the cloud point method at 25 °C, including tie lines assigned from mass phase ratios according to the lever arm rule, are presented for several poly(ethylene glycol) (PEG) + salt aqueous biphasic systems (ABS). The systems include PEG-1000 + K3PO4, PEG-2000 + K3PO4, PEG-3400 + K3PO4, and PEG-2000 in combination with the following salts K2CO3, (NH4)2SO4, Li2SO4, ZnSO4, MnSO4, and NaOH.