Ionic Liquid Mixtures for Direct Air Capture: High CO₂ Permeation Driven by Superior CO₂ Absorption with Lower Absolute Enthalpy

Abstract

This paper reports a series of liquid materials suitable for use as high-performance separation membranes in direct air capture. Upon mixing two ionic liquids (ILs), namely N-(2-aminoethyl)ethanolamine-based IL ([AEEA][X]) and 1-ethyl-3-methylimidazolium acetate ([emim][AcO]), the resulting mixtures with a specific range of their composition showed higher CO2 absorption rates, larger CO2 solubilities, and lower absolute enthalpies of CO2 absorption compared to those of single ILs. NMR spectroscopy of the IL mixture after exposure to 13CO2 allowed elucidation of the chemisorbed species, wherein [AEEA][X] reacts with CO2 to form CO2–[AEEA]+ complexes stabilized by hydrogen bonding with acetate anions. Supported IL membranes composed of [AEEA][X]/[emim][AcO] mixtures were then fabricated, and the membrane with a suitable mixing ratio showed a CO2 permeability of 25,983 Barrer and a CO2/N2 selectivity of 10,059 at 313.2 K and an applied CO2 partial pressure of 40 Pa without water vapor. These values are higher than those reported for known facilitated transport membranes.

Accelerated Oxidative Degradation of Phosphonium-Type Ionic Liquid with l-Prolinate Anion: Degradation Mechanism and CO2 Separation Performance

“…A schematic illustration of the CO 2 /N 2 mixed gas permeation measurement is shown in Figure S5. Supported IL membranes using non-degraded and degraded [P 4444 ]­[Pro] were fabricated according to our previous report . The filling rate of each IL in the membrane support (PTFE filter) was calculated to be 98∼99%, which is determined as a volume of IL loaded in a void of the PTFE filter.…”

Co-electrolysis SOEC and internal reforming SOFC for achieving a carbon-neutral society

“…CO 2 is captured from the exhaust gas of plants and directly from the air (DAC). [9][10][11] Renewable energy sources such as solar and wind power are supplied to consumers such as houses, buildings, and plants. The excess electric power is converted into chemical energy.…”

“…10 Mixed ionic liquid membranes exhibit a high CO 2 permeability of 2.5983 × 10 −6 cm 3 (STP)$cm cm −2 s −1 cm Hg −1 and a high CO 2 /N 2 selectivity of 1.0059 × 10 4 at 400 ppm CO 2 . 11 SOECs can simultaneously perform steam and CO 2 electrolysis, known as co-electrolysis. [12][13][14][15][16] Syngas, a mixture of H 2 and CO, is produced via the co-electrolysis SOECs.…”

“…10 Mixed ionic liquid membranes exhibit a high CO 2 permeability of 2.5983 × 10 −6 cm 3 (STP)·cm cm −2 s −1 cm Hg −1 and a high CO 2 /N 2 selectivity of 1.0059 × 10 4 at 400 ppm CO 2 . 11…”

Plasma–ionic liquid-assisted CO2 capture and conversion: A novel technology

“…[1][2][3] Ionic liquids (ILs) have recently gained considerable interest in CO 2 capture. [3][4][5] The absorption of CO 2 by ILs results from physical interactions between the anions and cations of the ILs and CO 2 molecules. 6) An alternative approach to reducing the CO 2 concentration in the atmosphere involves the conversion of CO 2 into valuable products.…”