Encapsulated Protic Ionic Liquids as Sustainable Materials for CO(2)Separation


Protic ionic liquids (PILs) have been suggested as promising solvents forCO2capture; however, their high viscosity and consequent poor mass transfercoefficients hinder their large-scale industrial application. To overcome this limitation,PILs (neat or encapsulated) can be incorporated into polymers coated on hollowfibermembranes, to be implemented in gas-liquid contactor units. However, before theimmobilization of PIL-based solvents on membranes, fundamental studies on the CO2sorption process in PILs are still mandatory. Here, the carboxylate-based PILs'ability forCO2absorption was evaluated using an isochoric solubility cell in a wide range oftemperatures (303-343 K) and CO2partial pressures (0-0.8 MPa). The experimentaldata revealed the existence of a distinct sorption mechanism than that typically observedin other low-volatile physical solvents, where the solubility was mainly affected byentropic effects. The soft-SAFT equation of state was further applied for modeling of thesolubility data, which allowed us to infer the influence of the anion's structure on thesystem's interactions. Aiming to improve the process kinetics, the PILs wereencapsulated in carbonaceous submicrocapsules, herein proposed as an efficient material for CO2separation. To characterize thecomposition, morphology, porous structure, and thermal stability of the solvents used, SEM, TEM, TGA, BET, and elementalanalyses were performed. The adsorption of CO2on these materials showed that these materials retained the same sorption capacityas their neat counterparts and with considerably increased sorption rates. These materials also retained their performance aftervarious sorption-desorption cycles and showed fast and complete regeneration and high sorption capacity, thus indicating theirpotential for CO(2 )capture.



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Silva, LP; Crespo, EA; Martins, MAR; Barbosa, PC; Gardas, RL; Vega, LF; Coutinho, JAP; Carvalho, PJ

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This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020, and LA/P/0006/2020, financed by national funds through the FCT/MEC (PIDDAC). This work was also developed within the scope of the IndoPortuguese Program for Cooperation in Science & Technology DST/INT/Portugal/P-01/2017, financed by FCT and the Government of India. L. P. Silva and E. A. Crespo acknowledge FCT for their Ph.D. Grants SFRH/BD/135976/2018 and SFRH/BD/130870/2017, respectively. P. J. Carvalho acknowledges FCT for his contract under the Investigator FCT 2015 contract number IF/00758/2015. L.F. Vega acknowledges partial financial support from Khalifa University of Science and Technology under project RC2-2019-007. The research contract of P. B. is funded by national funds (OE), through FCT.Fundacao para a Ciencia e a Tecnologia, I.P., in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of article 23, of the DecreeLaw 57/2016, of August 29, changed by Law 57/2017, of July 19.

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