Gas Separation Using Supported Ionic Liquids

Supported Ionic Liquick Fundamentals and Applications, First Edition. 

Edited by Rasmus Fehrmann, Anders Riisager, and Marco Haumann. 

Formation of dibutyldisulfide was found to be the cause for a shghtly decreased extraction performance over time. Besides thaf the potential for these new materials in gas purification is estimated to be high, mainly due to the variety of ILs that can be found for any given separation problem, especially with the help of a priori selection methods such as COSMO-RS (see Chapter 9). 

Because of the extremely high surface area in SILP materials, equilibrium was reached after less than 15 min, while in the pure IL it took 45 min. Interestingly, the SILP material with the lower IL loading resulted in higher capacity of 0.95 g(S02) g(IL) h The authors attributed this effect to the remaining nanopores at this low loading, facilitating pore condensation of SO2. Multiple absorption/desorption 

Wu et al. [8] synthesized amino add-functionaUzed ILs for SILP-faciUtated COj absorption, based on N-(3-aminopropyl)aminoethyl tributylphosphonium bromide dihydrobromide ([apaeP444]Br2HBr). The amino add-ILs were synthesized via ion exchange with water, followed by neutralization with the corresponding amino acid. The different ILs were immobilized onto SiOj and tested in the gas-phase COj absorption. The results suggested an absorption mechanism following a 1 2 stoichiometry, by which first a carbamic acid is formed followed by reaction with 

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Jiang YY, Zhou Z, Jiao Z, Li L, Wu YT, Zhang ZB (2007) SOj gas separation using supported ionic liquid membranes. J Phys Chem B 111 5058-5061... 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Scovazzo P, Kieft J, Finan DA et al (2004) Gas separations using non-hexafluorophosphate [PF6] anion supported ionic liquid membranes. J Membr Sci 238(l-2) 57-63... 

In gas chromatography, a column is coated with a thin layer of a hquid stationary phase and a sample is separated by the relative abilities of its components to dissolve in it from the gas phase. The greater the interactions with the stationary phase, the slower the transit of the sample through the column. Combination of Abraham s solvation parameter model (Eq. (2.1)) [104] with GC measurements has been used to determine the nature of ionic liquid-solute interactions [105-107]. Given the experimental setup, this technique is likely to be particularly appropriate for understanding what ionic liquid-solute interactions could be important in SILP and other related surface-supported ionic liquid applications. 

Membrane processes offer another attractive option to apply ionic liquids in separation processes. Two general approaches have been reported the use of ionic liquids as bulk ionic liquid membranes (BILM) [131,132] or as supported ionic liquid membranes (SILM) [133, 134]. In the former case, the ionic liquid acts as selective separation layer in the latter case, the membrane supports the liquid separation layer and separates two conpartments, resulting in a very efficient ionic liquid use and separation unit. Reported exanples for SILMs include reactions with in situ product removal [135], extraction of bioorganic substances [136,137] and removal of CO2 and SO2 from gas streams [138,139]. SILMs have also been successfully... 

In conventional solid-liquid or solid-gas heterogeneous catalytic systems, the catalyst is conveniently separated from the fluid-phase reaction product. When an ionic liquid is used as a phase to isolate a catalyst, the catalyst is fully dispersed and mobile and may be fully involved in the reaction. When a homogeneous catalyst is isolated by anchoring onto the surface of a solid support (e.g., by reaction with OH groups), the result may be a stable catalyst that is not leached into the reactant... 

Bara JE, Gabriel CJ, Carlisle TK, Camper DE, FinoteUo A, Gin DL, Noble RD (2009) Gas separations in fluoroalkyl-functionalized room-temperature ionic liquids using supported liquid membranes. Chem Eng J 147 43-50... 

The electrolyte constitutes a separator for the gas flows shown in Fig. 3.16, in addition to providing ionic transport. Physically, it consists of a compressed powder behaving as a soft paste at the operating temperatures, thus substantiating the name "molten carbonate" for the liquid Li-Na or Li-K carbonates inhabiting the electrolyte substrate. The LiAlOj material used for the support structure can exist in three different forms (phase a, P and fj, and transitions have been observed (e.g., yto d) after extended fuel cell operation... 

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