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

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• 作者：Brett F. Goodrich ; Juan C. de la Fuente ; Burcu E. Gurkan ; Zulema K. Lopez ; Erica A. Price ; Yong Huang ; Joan F. Brennecke
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：July 28, 2011
• 年：2011
• 卷：115
• 期：29
• 页码：9140-9150
• 全文大小：1007K
• 年卷期：v.115,no.29(July 28, 2011)
• ISSN：1520-5207

文摘

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 鈭?3 kJ/mol of CO₂ for the 1:1 reaction of CO₂ with [P₆₆₆₁₄][Pro], when we use the two-reaction model.