Effect of Water and Temperature on Absorption of CO₂ by Amine-Functionalized Anion-Tethered Ionic Liquids

Citations Over TimeTop 10% of 2011 papers

Abstract

Amine-functionalized anion-tethered ionic liquids (ILs) trihexyl(tetradecyl)phosphonium asparaginate [P66614][Asn], glutaminate [P66614][Gln], lysinate [P66614][Lys], methioninate [P66614][Met], prolinate [P66614][Pro], taurinate [P66614][Tau], and threoninate [P66614][Thr] were synthesized and investigated as potential absorbents for CO2 capture from postcombustion flue gas. Their physical properties, including density, viscosity, glass transition temperature, and thermal decomposition temperature were determined. Furthermore, the CO2 absorption isotherms of [P66614][Lys], [P66614][Tau], [P66614][Pro], and [P66614][Met] were measured using a volumetric method, and the results were modeled with two different Langmuir-type absorption models. The most important result of this study is that the viscosity of [P66614][Pro] only increased by a factor of 2 when fully complexed with 1 bar of CO2 at room temperature. This is in stark contrast to the other chemically reacted ILs investigated here and all other amino acid-based ILs reported in the literature, which dramatically increase in viscosity, typically by 2 orders of magnitude, when complexed with CO2. The unique behavior of [P66614][Pro] is likely due to its ring structure, which limits the number and availability of hydrogen atoms that can participate in a hydrogen bonding network. We found that water can be used to further reduce the viscosity of the CO2-complexed IL, while only slightly decreasing the CO2 capacity. Finally, from temperature-dependent isotherms, we estimate a heat of absorption of −63 kJ/mol of CO2 for the 1:1 reaction of CO2 with [P66614][Pro], when we use the two-reaction model.

Related Papers

• → Competing Reactions of CO₂ with Cations and Anions in Azolide Ionic Liquids(2014)72 cited
• → Thermal and Transport Properties of Ionic Liquids Based on Benzyl-Substituted Phosphonium Cations(2009)68 cited
• → Biodegradable Ionic Liquids: Selected Synthetic Applications(2007)36 cited
• Phosphonium salts, ylides and phosphoranes(1994)
• → Physicochemical and Electrochemical Properties of Room-Temperature Ionic Liquids Based on Quaternary Phosphonium Cations and Tetracyanoborate Anion(2016)4 cited