Water-ionic liquid system

Figure 33 Simulation snapshots of the phase transfer process of the PNIPAM-PEO micellar shuttle in a water-ionic liquid system at different temperatures. Figure taken from Cesar et a I (2012).

Rodriguez, O., Madeira, P.P. Macedo, E.A. (2007). Amino-acid recovery using ionic liquids Partitioning in water+ionic liquid systems. Proceedings of European Congress of Chemical Engineering (ECCE-6) Copenhagen, 16-20 September 2007. 

An ionic liquid can be used as a pure solvent or as a co-solvent. An enzyme-ionic liquid system can be operated in a single phase or in multiple phases. Although most research has focused on enzymatic catalysis in ionic liquids, application to whole cell systems has also been reported (272). Besides searches for an alternative non-volatile and polar media with reduced water and orgamc solvents for biocatalysis, significant attention has been paid to the dispersion of enzymes and microorganisms in ionic liquids so that repeated use of the expensive biocatalysts can be realized. Another incentive for biocatalysis in ionic liquid media is to take advantage of the tunability of the solvent properties of the ionic liquids to achieve improved catalytic performance. Because biocatalysts are applied predominantly at lower temperatures (occasionally exceeding 100°C), thermal stability limitations of ionic liquids are typically not a concern. Instead, the solvent properties are most critical to the performance of biocatalysts. 

The presence of small amounts of water was found to be essential even for hydrophobic ionic liquids (284). When a-chymotrypsin (in the form of salt-free lyophilized powder) was applied for the transesterification of Ai-acetyl-L-phenyl-alanine ethyl ester with 1-propanol in the dry ionic liquids [BMIM]PFg and [OMIMJPFg, little enzymatic activity was observed. The maximum activity was observed when 0.5 vol% water was added to the ionic liquids. Supercritical CO2 was also sufficient to activate the enzyme in dry ionic liquids. The addition of water to the supercritical C02-ionic liquid system further enhanced the enzymatic activity. 

Pina, F. et al.. Thermal and photochemical properties of 4, 7-dihydroxyflavylium in water-ionic liquid biphasic systems a write-read-erase molecular switch, Angew. Chem. Int. Ed., 43,1525,2004. 

Abraham, M.H., Zissimos, A.M., Huddleston, J.G., Willauer, H.D., Rogers, R.D., Acree, W.E., Some novel liquid partitioning systems Water-ionic liquids and aqueous biphasic systems, Ind. Eng. Chem. Res., 42, 413-418,2003. 

The Tsuji-Trost ally lie substitution catalyzed by Pd complexes using CH-acidic nucleophiles can be performed in an ionic liquid of type 1 alone [30] as well as in a biphasic system [31]. In the latter case the use of trisulfonated triphenylphosphine (TPPTS) prevents the catalyst from leaching into the organic phase. In comparison with water as the catalyst-supporting phase, the ionic liquid system exhibits higher activity and selectivity. The enantio-selective version of the allylic substitution with dimethyl malonate can also be performed in ionic liquids with a homochiral ferrocenylphosphine as the ligand [32]. 

As evident from Fig. 8.4, an increase in the selectivity has been observed in IL/ scCOj biphasic systems media (>99.5%) with respect to scCO assayed alone (95%). These results could be explained by the use of water-immiscible ILs which have a specific ability to reduce water activity in the enzyme microenvironment. The synthetic activity of the immobilized lipase in IL/scCO biphasic systems is lower than that in scCO assayed alone. Similar results were found by Mori et al. [40] in IL/ hexane biphasic systems. These authors reported that the enzymatic membranes prepared by simple adsorption of CaLB onto the surface were more reactive than membranes prepared with ILs. As can be observed in Fig. 8.4, the initial reaction rate in the assayed IL/scCO biphasic systems increased in the following sequence [bdimim ][PF ]<[bmim ][PFg ]<[bmim ][NTfj ]<[omim ] [PF ], which was practically in agreement with flie activity sequence reported by these authors using free Candida antarctica lipase B in homogeneous ionic liquid systems ([bmim ] [PF ]<[bdmim+][PFg ]<[bmim+][NTfj ]<[omim ][PF ]), with the exception of [bmim [PF ] and [bdimim+][PFg ]. These results were explained taking into account that biotransformation occurs within the ionic liquid phase, so substrates have to be transported from scCOj to the ionic liquid phase. The mechanism of substrate transport between the ionic liquid and the supercritical carbon dioxide could be by three consecutive steps diffusion of the substrates through the diffusion... 

Water and the ionic liquid bmimPF act as powerful reaction media not only for rate acceleration (for adduct 80, in water, conversion = 92-99%, yield = 83-97%, and in bmimPF, conversion = 81-99%, yield = 71-96%) and chemoelectivity enhancement but also for facilitating catalyst recycling in the [0=P(2-py)3W(CO)(NO)2](BF4)2-catalyzed Diels-Alder reaction systems. A key feature of this catalyst-water or catalyst-ionic liquid system is that the catalyst was recycled many times. In addition, the authors illustrated the development of the catalyst by conventional heating or under the action of microwave irradiation, the results of which are summarized in Scheme 11.21. 

The nitration of aromatic compounds with nitric acid in an ionic liquid was shown by Earle et al. [96,97]. It was found that triflate and triflimide ionic liquids catalyze nitration reactions with nitric acid. This methodology has the advantage that water is the only by-product (Scheme 5.2-44). This process could also be carried out in phosphonium ionic liquids [46]. Acidic ionic liquids such as [EMIM][HS04] or the Davis-type ionic liquids [41] could also be used but gave lower reaction rates and selectivities [98]. The effect of metal triflates such as Yb(OTf)3 or Cu(OTf)2 dissolved in [N-butyl-N-methylpyrrolidium][triflimide] was investigated by Handy and Egrie [99]. These gave similar yields and selectivities to ionic liquids systems... 

For ligands, see Refs, for water (59-62), fluorous (52,63), SCCO2 (47,64 -67), and ionic liquid systems (68). The biphasic hydroformylation systems could be achieved by the proper combination of these solvents (69). 

Soto-Figueroa C, del Rosario Rodriguez-Hidalgo M, Vicente L Dissipative particle dynamics simulation of the miceHization-demicellization process and micellar shuttle of a diblock copolymer in a biphasic system (water/ionic-liquid). Soft Matter 8 1871-1877, 2012. 

The phase behaviour of binary ionic liquid systems can roughly be divided into three classes (i) ionic liquids with dissolved gases, (ii) ionic liquids with water and (hi) ionic liquids with organic solvents. The first class involves vapour-liquid equilibrium (VLE) data, whereas the last two classes mainly involve liquid-liquid equilibrium (LLE) data. 

Molecular simulations have been used to obtain thermodynamic properties and phase equilibria data of ionic liquid systems (i) Monte Carlo simulation techniques were employed to predict the solubility of gases and water in ionic liquids and (ii) molecular dynamics simulations were used to investigate the solvation dynamics of water and various organics in ionic liquids. ... 

The phase behaviours of binary and ternary ionic liquid mixtures with carbon dioxide,organics " and water " have been determined using COSMO-RS. In the COSMO-RS framework, ionic liquids are considered to be completely dissociated into cations and anions. Ionic liquids are thus taken as an equimolar mixture of two distinct ions, which contribute as two different compounds. Because ionic liquids only dissociate in the presence of strongly polar substances, the COSMO-RS prediction of the phase behaviour of ionic liquid systems with polar compounds (water and alcohols) is more accurate than that of ionic liquid systems with nonpolar compounds (carbon dioxide and organics). Especially the COSMO-RS prediciton of the solubility of (relatively nonpolar) carbon dioxide in ionic liquids shows considerable deviations ( 15 %) from experimental values. lUPAC Technical Reports document the measurements of the thermodynamic and thermophysical properties of l-hexyl-3-methylimidazolium bis [(trifluoromethyl)sulfonyl]amide and the recommended values. ... 

Electrocatalytic ORR carries out in three pathways the 1-electron transfer pathway, producing superoxide ion the 2-electron transfer pathway, producing hydrogen peroxide and the 4-electron transfer pathway, producing water. In a non-aqueous aprotic solvent system, a room-temperature ionic liquid system, and on specific transition-metal, macrocyclic-compounds-coated graphite electrodes in alkaline solutions, 1-electron reduction can be observed. Carbon materials, quinone and derivatives, mono-nuclear cobalt macrocyclic compounds, and some chalcogenides can only catalyze 2-electron ORR. Noble metal, noble metal alloy materials, iron-macrocyclic complexes, di-nuclear cobalt macrocyclic complexes, some chalcogenides, and transition-metal carbide-promoted Pt catalysts can catalyze 4-electron reduction. 

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