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Encapsulated ionic liquid (ENIL) material was developed, consisting of ionic liquid (IL) introduced into carbon submicrocapsules. ENILs contain >85% w/w of IL but discretized in submicroscopic encapsulated drops, drastically increasing the surface contact area with respect to the neat fluid. ENIL materials were here tested for gas separation processes, obtaining a drastic increase in mass transfer rate.

The potential advantages of applying encapsulated ionic liquid (ENIL) to CO capture by chemical absorption with 1-butyl-3-methylimidazolium acetate [bmim][acetate] are evaluated. The [bmim][acetate]-ENIL is a particle material with solid appearance and 70 % w/w in ionic liquid (IL). The performance of this material as CO sorbent was evaluated by gravimetric and fixed-bed sorption experiments at different temperatures and CO partial pressures. ENIL maintains the favourable thermodynamic properties of the neat IL regarding CO absorption. Remarkably, a drastic increase of CO sorption rates was achieved using ENIL, related to much higher contact area after discretization. In addition, experiments demonstrate reversibility of the chemical reaction and the efficient ENIL regeneration, mainly hindered by the unfavourable transport properties. The common drawback of ILs as CO chemical absorbents (low absorption rate and difficulties in solvent regeneration) are overcome by using ENIL systems.

Encapsulated ionic liquids (ENILs) based on carbonaceous submicrocapsuleswere designed, synthesized and applied to the sorption of NH 3 from gas stream. The ENILs were prepared using three different task-specific ILs with adequate properties for NH 3 capture: 1-2(-hydroxyethyl)-3-methylimadazolium tetrafluoroborate (EtOHmimBF 4 ), choline bis(trifluoromethylsulfonyl)imide (CholineNTf 2 ) and tris(2hydroxyethyl)-methylammoniummethylsulfate [(EtOH) 3 MeNMeSO 4 ]. The ENILs synthesized were analyzed by different techniques to assess their morphology, chemical composition, porous structure and thermal stability. The capture of NH 3 was tested in fixed-bed experiments under atmospheric pressure. The influence of the type and load of IL, temperature (30, 45 and 60 ºC) and NH 3 inlet concentration was analyzed.Desorption of NH 3 from the exhausted ENILs was also studied at atmospheric pressure and temperatures in the range of 150 to 200 ºC. The ENILs prepared with task-specific ILs were found to be suitable for NH 3 capture in the fixed-bed operation. These systems can be a promising alternative to conventional absorption or adsorption due to: i) high sorption capacity controlled by IL selection, ii) remarkable mass transfer rate, iii) low 2 sensitiveness to high temperatures of the gas stream, iv) fast and complete regeneration of the exhausted ENIL at mild conditions; and v) recovery of NH 3 .

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P][2-CNPyr]), for CO capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO-AHA-IL systems were carried out from 298 to 333 K and at pressures up to 15 bar, analyzing the role of both chemical and physical absorption phenomena in the overall CO solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO chemical absorption process was evaluated by in situ Fourier transform infrared spectroscopy-attenuated total reflection, following the characteristic vibrational signals of the reactants and products over the reaction time. A chemical absorption model was used to describe the time-dependent concentration of species involved in the reactive absorption, obtaining kinetic parameters (such as chemical reaction kinetic constants and diffusion coefficients) as a function of temperatures and pressures. As expected, the results demonstrate that the CO absorption rate is mass-transfer-controlled because of the relatively high viscosity of AHA-IL. The AHA-IL was encapsulated in a porous carbon sphere (Encapsulated Ionic Liquid, ENIL) to improve the kinetic performance of the AHA-IL for CO capture. The newly synthesized AHA-ENIL material was evaluated as a CO sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO absorption capacity of the AHA-IL but drastically enhance the CO absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

The performance of three amino-acid-based ionic liquids (aa-ILs) has been evaluated in CO 2 capture by means of gravimetric measurements. The tested aa-ILs were 1-butyl-3methylimidazolium prolinate, [Bmim][PRO]; 1-butyl-3-methylimidazolium methioninate, [Bmim][MET]; and 1-butyl-3-methylimidazolium glycinate, [Bmim][GLY]. First, the CO 2 chemical absorption process was analyzed by in situ Fourier transform infrared spectroscopy−attenuated total reflection (FTIR-ATR), following the characteristic vibrational signals of the reactants and products, and comparing them with theoretical measurements obtained by quantum chemical calculations. This study let us confirm a mechanism of CO 2 chemical absorption on amino-acid-based ILs. Then, gravimetric experiments were carried out to characterize the CO 2 capture by aa-ILs. It was found that CO 2 absorption quantification of these ILs was rather slow, because of their high viscosities, so alternative methodologies had to be employed to use them as absorbents in CO 2 capture. In this sense, aa-ILs were encapsulated in porous carbon capsules (aa-ENIL), since it has been previously reported as material that defeats the kinetic limitations and preserves the favorable CO 2 capture capacity of the neat ILs, promoting efficient chemical absorption. These aa-ENIL materials permit evaluation of CO 2 capture at equilibrium and experimentally characterize the thermodynamics absorption phenomena, in terms of reaction enthalpy and the contribution of physical (H) and chemical (K eq ) CO 2 absorption for each IL. ENIL materials allow a fast CO 2 capture with high sorption capacity and easy regeneration due to the favorable thermodynamics and kinetics of the process.

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