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Title: Equimolar CO(2) capture by imidazolium-based ionic liquids and superbase systems

Abstract

Imidazolium-based ionic liquids continue to attract interest in many areas of chemistry because of their low melting points, relatively low viscosities, ease of synthesis, and good stabilities against oxidative and reductive conditions. However, they are not totally inert under many conditions due to the intrinsic acidity of hydrogen at the C-2 position in the imidazolium cation. In this work, this intrinsic acidity was exploited in combination with an organic superbase for the capture of CO{sub 2} under atmospheric pressure. During the absorption of CO{sub 2}, the imidazolium-based ionic liquid containing an equimolar superbase reacted with CO{sub 2} to form a liquid carboxylate salt so that the equimolar capture of CO{sub 2} with respect to the base was achieved. The effects of ionic liquid structures, types of organic superbases, absorption times, and reaction temperatures on the capture of CO{sub 2} were investigated. Our results show that this integrated ionic liquid-superbase system is capable of rapid and reversible capture of about 1 mol CO{sub 2} per mole of ionic liquid. Furthermore, the captured CO{sub 2} can be readily released by either heating or bubbling N{sub 2}, and recycled with little loss of its capture capability. This efficient and reversible catch-and-release process usingmore » the weak acidity of the C-2 proton in nonvolatile imidazolium-based ionic liquids provides a good alternative to the current CO{sub 2} capture methods that use volatile alkanols, amines, or water.« less

Authors:
 [1];  [2];  [1];  [3];  [1];  [3]
  1. ORNL
  2. Pacific Northwest National Laboratory (PNNL)
  3. Zhejiang University
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1044699
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Green Chemistry; Journal Volume: 12; Journal Issue: 11
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ABSORPTION; AMINES; ATMOSPHERIC PRESSURE; CHEMISTRY; HEATING; HYDROGEN; MELTING POINTS; MOLTEN SALTS; PH VALUE; PROTONS; SYNTHESIS; WATER

Citation Formats

Dai, Sheng, Wang, Chongmin, Luo, Huimin, Luo, Xiaoyan, Li, Qing, and Li, Haoran. Equimolar CO(2) capture by imidazolium-based ionic liquids and superbase systems. United States: N. p., 2010. Web.
Dai, Sheng, Wang, Chongmin, Luo, Huimin, Luo, Xiaoyan, Li, Qing, & Li, Haoran. Equimolar CO(2) capture by imidazolium-based ionic liquids and superbase systems. United States.
Dai, Sheng, Wang, Chongmin, Luo, Huimin, Luo, Xiaoyan, Li, Qing, and Li, Haoran. 2010. "Equimolar CO(2) capture by imidazolium-based ionic liquids and superbase systems". United States. doi:.
@article{osti_1044699,
title = {Equimolar CO(2) capture by imidazolium-based ionic liquids and superbase systems},
author = {Dai, Sheng and Wang, Chongmin and Luo, Huimin and Luo, Xiaoyan and Li, Qing and Li, Haoran},
abstractNote = {Imidazolium-based ionic liquids continue to attract interest in many areas of chemistry because of their low melting points, relatively low viscosities, ease of synthesis, and good stabilities against oxidative and reductive conditions. However, they are not totally inert under many conditions due to the intrinsic acidity of hydrogen at the C-2 position in the imidazolium cation. In this work, this intrinsic acidity was exploited in combination with an organic superbase for the capture of CO{sub 2} under atmospheric pressure. During the absorption of CO{sub 2}, the imidazolium-based ionic liquid containing an equimolar superbase reacted with CO{sub 2} to form a liquid carboxylate salt so that the equimolar capture of CO{sub 2} with respect to the base was achieved. The effects of ionic liquid structures, types of organic superbases, absorption times, and reaction temperatures on the capture of CO{sub 2} were investigated. Our results show that this integrated ionic liquid-superbase system is capable of rapid and reversible capture of about 1 mol CO{sub 2} per mole of ionic liquid. Furthermore, the captured CO{sub 2} can be readily released by either heating or bubbling N{sub 2}, and recycled with little loss of its capture capability. This efficient and reversible catch-and-release process using the weak acidity of the C-2 proton in nonvolatile imidazolium-based ionic liquids provides a good alternative to the current CO{sub 2} capture methods that use volatile alkanols, amines, or water.},
doi = {},
journal = {Green Chemistry},
number = 11,
volume = 12,
place = {United States},
year = 2010,
month = 1
}
  • Protic ionic liquids (PILs) from a superbase and fluorinated alcohol, imidazole, pyrrolinone, or phenol were designed to capture CO{sub 2} based on the reactivity of their anions to CO{sub 2}. These PILs are capable of rapid and reversible capture of about one equivalent of CO{sub 2}, which is superior to those sorption systems based on traditional aprotic ILs.
  • Protic ionic liquids (PILs) from a superbase and fluorinated alcohol, imidazole, pyrrolinone, or phenol were designed to capture CO{sub 2} based on the reactivity of their anions to CO{sub 2}. These PILs are capable of rapid and reversible capture of about one equivalent of CO{sub 2}, which is superior to those sorption systems based on traditional aprotic ILs.
  • Phenolic ionic liquids for the efficient and reversible capture of CO{sub 2} were designed and prepared from phosphonium hydroxide and substituted phenols. The electron-withdrawing or electron-donating ability, position, and number of the substituents on the anion of these ionic liquids were correlated with the physicochemical properties of the ionic liquids. The results show that the stability, viscosity, and CO{sub 2}-capturing ability of these ionic liquids were significantly affected by the substituents. Furthermore, the relationship between the decomposition temperature, the CO{sub 2}-absorption capacity, and the basicity of these ionic liquids was quantitatively correlated and further rationalized by theoretical calculation. Indeed, thesemore » ionic liquids showed good stability, high absorption capacity, and low absorption enthalpy for CO{sub 2} capture. This method, which tunes the physicochemical properties by making use of substituent effects in the anion of the ionic liquid, is important for the design of highly efficient and reversible methods for CO{sub 2}-capture. This CO{sub 2} capture process using diverse phenolic ionic liquids is a promising potential method for CO{sub 2} absorption with both high absorption capacity and good reversibility.« less
  • Basic ionic liquids (ILs) based on a phosphonium hydroxide derivative can be tuned for CO{sub 2} capture by varying the weak proton donors, which have different pK{sub a} values. The stability, absorption capacity, and absorption enthalpy of the ILs could be easily tuned: the best IL for CO{sub 2} capture has good stability (>300 C), energy saving (ca. 56 kJ mol{sup -1}), and equimolar absorption capability.