Noelia Alonso-Morales

Ammonia capture from the gas phase by encapsulated ionic liquids (ENILs)

Encapsulated ionic liquids (ENILs) based on carbonaceous submicrocapsules were designed, synthesized and applied to the sorption of NH3 from gas streams. The ENILs were prepared using three different task-specific ILs with adequate properties for NH3 capture: 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate (EtOHmimBF4), choline bis(trifluoromethylsulfonyl)imide (CholineNTf2) and tris(2-hydroxyethyl)methylammonium methylsulfate [(EtOH)3MeNMeSO4]. The ENILs synthesized were analyzed by different techniques to assess their morphology, chemical composition, porous structure and thermal stability. The capture of NH3 was tested in fixed-bed experiments under atmospheric pressure. The influence of the type and load of IL, temperature (30, 45 and 60 °C) and NH3 inlet concentration was analyzed. Desorption of NH3 from the exhausted ENILs was also studied at atmospheric pressure and temperatures in the range of 150 to 200 °C. The ENILs prepared with task-specific ILs were found to be suitable for NH3 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 sensitiveness to high temperatures of the gas stream, (iv) fast and complete regeneration of the exhausted ENIL at mild conditions; and (v) recovery of NH3.

Encapsulated Ionic Liquids for CO2 Capture: Using 1-Butyl-methylimidazolium Acetate for Quick and Reversible CO2 Chemical Absorption.

The potential advantages of applying encapsulated ionic liquid (ENIL) to CO2 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 CO2 sorbent was evaluated by gravimetric and fixed-bed sorption experiments at different temperatures and CO2 partial pressures. ENIL maintains the favourable thermodynamic properties of the neat IL regarding CO2 absorption. Remarkably, a drastic increase of CO2 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 CO2 chemical absorbents (low absorption rate and difficulties in solvent regeneration) are overcome by using ENIL systems.

Encapsulation of Ionic Liquids with an Aprotic Heterocyclic Anion (AHA-IL) for CO2 Capture: Preserving the Favorable Thermodynamics and Enhancing the Kinetics of Absorption

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P66614][2-CNPyr]), for CO2 capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO2-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 CO2 solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO2 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 CO2 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 CO2 capture. The newly synthesized AHA-ENIL material was evaluated as a CO2 sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO2 absorption capacity of the AHA-IL but drastically enhance the CO2 absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

Enhancement of the activity of Pd/C catalysts in aqueous phase hydrodechlorination through doping of carbon supports

The enhancement of the activity of Pd catalysts for aqueous phase hydrodechlorination (HDC) was studied using N-doped tailored supports. N-Doped (1–1.7 wt% N) and non-doped mesoporous carbon materials with equivalent pore structures were prepared via templating with MSU-F silica. At 30 °C, doping of the support resulted in a higher catalytic activity (26 vs. 49 mmol g−1 Pd min−1 for non-doped and doped supports, respectively) in the removal of 4-chlorophenol from water. However, the activity of the catalyst with non-doped carbon supports increased more with reaction temperature, even being the most active at 70 °C (131 vs. 102 mmol g−1 Pd min−1 for non-doped and doped supports, respectively). The activation energy of the process was found to decrease from 32 to 16 kJ mol−1 due to nitrogen doping of the support. Nitrogen doping of the carbon support is an interesting strategy to prepare catalysts with high HDC activity under mild temperature conditions, whereas non-doped supports are more convenient for the intensification of the process by increasing the reaction temperature.