Optimization and Characterization of an Amino Acid Ionic Liquid and Polyethylene Glycol Blend Solvent for Precombustion CO₂ Capture: Experiments and Model Fitting

Abstract

Amino acid ionic liquids are green solvents with low toxicities and properties suitable for precombustion CO 2 capture, such as high CO 2 absorption, good thermal stability, and negligible vapor pressure. However, their high viscosities and relatively high costs have hampered their industrial applications. In this work, we systematically studied the amino acid ionic liquid tetrabutylphosphonium glycinate ([P 4444 ][Gly]) and its blends with the low-cost and less viscous cosolvent poly(ethylene glycol) (PEG400). The concentration of the blend solvent was optimized with respect to CO 2 solubility, regeneration efficiency, and cyclic capacity. The solubilities of CO 2 in [P 4444 ][Gly], PEG400, and their blends of four different concentrations were measured experimentally in the temperature range of 60−140 °C and up to a pressure of 17 bar. The results showed that the CO 2 solubility increased with increasing ionic liquid concentration in the blend and decreased with increasing temperature. The optimum CO 2 absorption was determined to occur at 30 wt % of [P 4444 ][Gly] in the blend. The regeneration study of the 30 wt % [P 4444 ][Gly]−70 wt % PEG400 blend for three cycles verified its reusability in the process and confirmed that the reaction between [P 4444 ][Gly] and CO 2 can be reversed at 140 °C. The CO 2 absorption capacity of the blend absorbent was found to be up to a loading of 1.23 mol of CO 2 /mol of absorbent. The parameter fitting of the experimental data using empirical correlations was evaluated, and these correlations were developed in particular to predict the blend solvent of an amino acid ionic liquid−PEG400 system based on the ionic liquid concentration and temperature.

Chemical solvent in chemical solvent: A class of hybrid materials for effective capture of CO2

“…The viscosities of [emim][Gly]+[emim][Ac] are lower than those of [emim][Gly] but higher than those of [emim][Ac], meanwhile, the viscosities of [emim][Ala]+[emim][Ac] are lower than those of [emim][Ala] but higher than those of [emim][Ac]. The viscosities of [emim][Gly+[emim][Ac] and [emim][Ala]+[emim][Ac] are determined to be 79.1 and 74.4 cP, respectively, at 298.2 K, being higher than those of AAILs + H 2 O hybrids but lower than those of AAILs + PEG hybrids …”

“…Diluting AAILs with low‐viscous physical solvents or immobilizing AAILs in porous supports, represent two commonly referred strategies to promote the absorption of CO 2 in AAILs. For example, Han et al and Deng et al blended choline prolinate ([Ch][Pro]) and tetrabutylphosphonium glycinate ([P 4444 ][Gly]) respectively, with polyethylene glycol (PEG) for reversible absorption of CO 2 ; Wu et al, Zhou et al, Li et al and Luo et al investigated the absorption of CO 2 in aqueous solutions of AAILs, such as tetramethylammonium glycinate ([N 1111 ][Gly]), 1‐(2‐hydroxlethyl)‐3‐methylimidazolium glycinate ([C 2 OHmim][Gly], 1‐ethyl‐3‐methylimidazolium glycinate ([emim][Gly]), etc. ; Li et al immobilized 1‐ethyl‐3‐methylimidazolium glycinate ([emim][Gly]) and 1‐ethyl‐3‐methylimidazolium lysinate ([emim][Lys]) in porous poly(methyl methacrylate) (PMMA) microspheres for facilitated adsorption of CO 2 .…”

Mathematical modeling and validation of CO2 mass transfer in a membrane contactor using ionic liquids for pre-combustion CO2 capture

“…Liquid side mass transfer coefficient is also inversely dependent on its viscosity. To reduce the liquid phase viscosity, blend IL absorbent with low viscous co-solvent, such as low molecular weight PEG (Li et al, 2016;Usman et al, 2016), can be used.…”

Effects of Poly(glycidyl ether) Structure and Ether Oxygen Placement on CO2 Solubility

“…Poly­(ethylene oxide) (PEO) has been used for CO 2 separations as a liquid absorbent since the 1960s and was first applied in membrane applications in the late 1980s. , Favorable quadrupolar interactions between the ether oxygens in the polymer backbone and dissolved CO 2 result in high solubility and permeability. − Currently, PEO is used in two major industrial separations: (1) as the main component of Selexol, an industrial acid gas absorbent, and (2) the Polaris membrane, which is the first commercial membrane used for CO 2 separation. , In the 50 years of the Selexol process, research interest in PEO for CO 2 separation has not declined. PEO has been cross-linked to make free-standing membranes ,, and has been incorporated as a membrane additive , or the soft-segment of block copolymer membranes to increase solubility. , PEO has also been used as a nonaqueous cosolvent for amine and ionic liquid (IL) solutions to increase regeneration efficiency and reduce corrosion, energy consumption, and viscosity. − …”