Search

It was a big surprise to see crystals of an ionic liquid (IL) forming by sublimation at room temperature. ILs are generally accepted to have negligible vapour pressures at elevated temperatures, making their sublimation or distillation very difficult. ILs that sublime easily contain silylimidazolium-based cations. In order to establish the details of the unusual behaviour of this subclass of ILs, a combined spectroscopic, X-ray crystallographic, physicochemical and theoretical characterization was performed. The results are compared with those of other easily vaporizable compounds, like ammonium chloride and naphthalene. The single-crystal X-ray structure analysis of one of these compounds, N-methyl- N′-dimethyl(phenyl)silylimidazolium chloride (monoclinic, C2/ c), clearly shows the existence of isolated ions, demonstrating that the compound is an ionic liquid. [ABSTRACT FROM AUTHOR]

Abstract: The use of ionic liquid–polymer in supported ultrafiltration membrane in vacuum pervaporation has been verified. The ultrafiltration membranes were impregnated by two ionic liquids (1-ethenyl-3-ethyl-imidazolium hexafluorophosphate and tetrapropylammonium tetracyano-borate) and polydimethylsiloxane. These new and very stable supported ionic liquid–polymer membranes were used for separation of ternary mixtures butan-1-ol–acetone–water by vacuum pervaporation. In comparison with polydimethylsiloxane membranes, the average enrichment factor of butan-1-ol increased in both cases. This higher selectivity shows a good potential for improving pervaporation separation process. [Copyright &y& Elsevier]

Pervaporation proved to be one of the best methods to remove solvents out of a solvent producing Clostridium acetobutylicum culture. By using an ionic liquid (IL)-polydimethylsiloxane (PDMS) ultrafiltration membrane (pore size 60 nm), we could guarantee high stability and selectivity during all measurements carried out at 37°C. Overall solvent productivity of fermentation connected with continuous product removal by pervaporation was 2.34 g l−1 h−1. The supported ionic liquid membrane (SILM) was impregnated with 15 wt% of a novel ionic liquid (tetrapropylammonium tetracyano-borate) and 85 wt% of polydimethylsiloxane. Pervaporation, accomplished with the optimized SILM, led to stable and efficient removal of the solvents butan-1-ol and acetone out of a C. acetobutylicum culture. By pervaporation through SILM, we removed more butan-1-ol than C. acetobutylicum was able to produce. Therefore, we added an extra dose of butan-1-ol to run fermentation on limiting values where the bacteria would still be able to survive its lethal concentration (15.82 g/l). After pervaporation was switched off, the bacteria died from high concentration of butan-1-ol, which they produced. [ABSTRACT FROM AUTHOR]

A fundamental electrochemical study of several highly diluted ionic liquids (ILs) at the interface between two immiscible electrolyte solutions (ITIES) is reported to evaluate the electrochemical and the solvation properties of [BMIM]Cl, [BMIM]BF 4 , [BMIM]OTf, [EMIM]Br and [AMIM]Cl. The interface is formed between a hydrophilic electrolyte dissolved in water and a hydrophobic electrolyte dissolved in an organic solvent, here 1,2-dichloroethane (DCE). The transfer of the highly diluted ionic species from the water phase into the organic phase occurs when an electrical potential difference is applied across the interface. Standard Gibbs energy of transfer, the relative hydrophilicity/hydrophobicity and transfer coefficients across the interface of the selected ILs are determined by cyclic voltammetry at large ITIES. [ABSTRACT FROM AUTHOR]