Ionic liquids in carbon capture: Difference between revisions
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== Separations == |
== Separations == |
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=== Carbon capture === |
=== Carbon capture === |
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[[Amine]]s are the most prevalent absorbent in postcombustion carbon capture technology today. In particular, [[monoethanolamine]] (MEA) has been used in industrial scales in [[Amine gas treating|postcombustion carbon capture]], as well as other CO<sub>2</sub> separations, such as "sweetening" of natural gas.<ref name=Kohl>{{cite book|author=Arthur Kohl and Richard Nielson|title=Gas Purification|edition=5th|publisher=Gulf Publishing|year=1997|isbn=0-88415-220-0}}</ref> However, amines are corrosive, degrade over time, and require large industrial facilities. Ionic liquids on the other hand, have is low [[vapor pressure]]s . This property results from ionic liquids' strong Coulombic attractive force and vapor pressure remains low through the substance's [[thermal decomposition]] point (typically >300 °C).<ref name = "Bates">Bates |
[[Amine]]s are the most prevalent absorbent in postcombustion carbon capture technology today. In particular, [[monoethanolamine]] (MEA) has been used in industrial scales in [[Amine gas treating|postcombustion carbon capture]], as well as other CO<sub>2</sub> separations, such as "sweetening" of natural gas.<ref name=Kohl>{{cite book|author=Arthur Kohl and Richard Nielson|title=Gas Purification|edition=5th|publisher=Gulf Publishing|year=1997|isbn=0-88415-220-0}}</ref> However, amines are corrosive, degrade over time, and require large industrial facilities. Ionic liquids on the other hand, have is low [[vapor pressure]]s . This property results from ionic liquids' strong Coulombic attractive force and vapor pressure remains low through the substance's [[thermal decomposition]] point (typically >300 °C).<ref name = "Bates">{{cite journal|last1=Bates|first1=Eleanor D.|last2=Mayton|first2=Rebecca D.|last3=Ntai|first3=Ioanna|last4=Davis|first4=James H.|title=CO<sub>2</sub> Capture by a Task-Specific Ionic Liquid|journal=Journal of the American Chemical Society|volume=124|issue=6|year=2002|pages=926–927|issn=0002-7863|doi=10.1021/ja017593d}}</ref> In principle, this low vapor pressure simplifies their use and makes them "[[green chemistry|green]]" alternatives. Additionally, it reduces risk of contamination of the CO<sub>2</sub> gas stream and of leakage into the environment.<ref name = "Zhang">{{cite journal|last1=Zhang|first1=Xiangping|last2=Zhang|first2=Xiaochun|last3=Dong|first3=Haifeng|last4=Zhao|first4=Zhijun|last5=Zhang|first5=Suojiang|last6=Huang|first6=Ying|title=Carbon capture with ionic liquids: overview and progress|journal=Energy & Environmental Science|volume=5|issue=5|year=2012|pages=6668|issn=1754-5692|doi=10.1039/c2ee21152a}}</ref> |
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The solubility of CO<sub>2</sub> in ionic liquids is governed primarily by the anion, less so by the cation.<ref name = "Ramdin">Ramdin |
The solubility of CO<sub>2</sub> in ionic liquids is governed primarily by the anion, less so by the cation.<ref name = "Ramdin">{{cite journal|last1=Ramdin|first1=Mahinder|last2=de Loos|first2=Theo W.|last3=Vlugt|first3=Thijs J.H.|title=State-of-the-Art of CO<sub>2</sub> Capture with Ionic Liquids|journal=Industrial & Engineering Chemistry Research|volume=51|issue=24|year=2012|pages=8149–8177|issn=0888-5885|doi=10.1021/ie3003705}}</ref> The [[hexafluorophosphate]] (PF<sub>6</sub><sup>–</sup>) and [[tetrafluoroborate]] (BF<sub>4</sub><sup>–</sup>) anions have been shown to be especially amenable to CO<sub>2</sub> capture.<ref name = "Ramdin" /> |
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Ionic liquids have been considered as solvents in a variety of [[liquid-liquid extraction]] processes.<ref name = "Rodriguez" /> Beside that, ionic liquids have replaced the conventional volatile solvents in industry such as absorption of gases or extractive distillation. Additionally, ionic liquid is also used as co-solutes for the gener |
Ionic liquids have been considered as solvents in a variety of [[liquid-liquid extraction]] processes.<ref name = "Rodriguez" /> Beside that, ionic liquids have replaced the conventional volatile solvents in industry such as absorption of gases or extractive distillation. Additionally, ionic liquid is also used as co-solutes for the gener |
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== Tunability == |
== Tunability == |
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[[File:1-butyl-3-propylamineimidazolium-tetrafluoroborate-balls.png|300px|thumb|right|1-butyl-3-propylamineimidazolium tetrafluoroborate is a task-specific ionic liquid for use in CO<sub>2</sub> separation.]] |
[[File:1-butyl-3-propylamineimidazolium-tetrafluoroborate-balls.png|300px|thumb|right|1-butyl-3-propylamineimidazolium tetrafluoroborate is a task-specific ionic liquid for use in CO<sub>2</sub> separation.]] |
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As required for all separation techniques, ionic liquids exhibit selectivity towards one or more of the phases of a mixture. [[1-Butyl-3-methylimidazolium hexafluorophosphate]] (BMIM-PF<sub>6</sub>) is a room-temperature ionic liquid that was identified early on as a viable substitute for volatile organic solvents in liquid-liquid separations.<ref name = "Huddleston" /> Other [PF<sub>6</sub>]- and [BF<sub>4</sub>]- containing ionic liquids have been studied for their CO<sub>2</sub> absorption properties, as well as 1-ethyl-3-methylimidazolium (EMIM) and unconventional cations like trihexyl(tetradecyl) phosphonium ([P<sub>66614</sub>]).<ref name = "Zhang" /> Selection of different anion and cation combinations in ionic liquids affects their selectivity and physical properties. Additionally, the organic cations in ionic liquids can be "tuned" by changing chain lengths or by substituting radicals.<ref name = "Rodriguez" /> Finally, ionic liquids can be mixed with other ionic liquids, water, or amines to achieve different properties in terms of absorption capacity and heat of absorption. This tunability has led some to call ionic liquids "designer solvents."<ref>Freemantle |
As required for all separation techniques, ionic liquids exhibit selectivity towards one or more of the phases of a mixture. [[1-Butyl-3-methylimidazolium hexafluorophosphate]] (BMIM-PF<sub>6</sub>) is a room-temperature ionic liquid that was identified early on as a viable substitute for volatile organic solvents in liquid-liquid separations.<ref name = "Huddleston" /> Other [PF<sub>6</sub>]- and [BF<sub>4</sub>]- containing ionic liquids have been studied for their CO<sub>2</sub> absorption properties, as well as 1-ethyl-3-methylimidazolium (EMIM) and unconventional cations like trihexyl(tetradecyl) phosphonium ([P<sub>66614</sub>]).<ref name = "Zhang" /> Selection of different anion and cation combinations in ionic liquids affects their selectivity and physical properties. Additionally, the organic cations in ionic liquids can be "tuned" by changing chain lengths or by substituting radicals.<ref name = "Rodriguez" /> Finally, ionic liquids can be mixed with other ionic liquids, water, or amines to achieve different properties in terms of absorption capacity and heat of absorption. This tunability has led some to call ionic liquids "designer solvents."<ref>{{cite journal|last1=Freemantle|first1=Michael|title=Designer Solvents|journal=Chemical & Engineering News|volume=76|issue=13|year=1998|pages=32–37|issn=0009-2347|doi=10.1021/cen-v076n013.p032}}</ref> 1-butyl-3-propylamineimidazolium tetrafluoroborate was specifically developed for CO<sub>2</sub> capture; it is designed to employ chemisorption to absorb CO<sub>2</sub> and maintain efficiency under repeated absorption/regeneration cycles.<ref name = "Bates" /> Other ionic liquids have been simulated or experimentally tested for potential use as CO<sub>2</sub> absorbents. |
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== Industrial applications == |
== Industrial applications == |
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Industrial operations require an energy efficient and environmentally friendly process for CO<sub>2</sub> capture. Currently, CO<sub>2</sub> capture uses mostly [[amine]]-based absorption technologies, which are energy intensive and solvent intensive. [[Volatile organic compound]]s alone in chemical processes represent a multi-billion dollar industry.<ref name = "Huddleston">Huddleston |
Industrial operations require an energy efficient and environmentally friendly process for CO<sub>2</sub> capture. Currently, CO<sub>2</sub> capture uses mostly [[amine]]-based absorption technologies, which are energy intensive and solvent intensive. [[Volatile organic compound]]s alone in chemical processes represent a multi-billion dollar industry.<ref name = "Huddleston">{{cite journal|last1=Huddleston|first1=Jonathan G.|last2=Willauer|first2=Heather D.|last3=Swatloski|first3=Richard P.|last4=Visser|first4=Ann E.|last5=Rogers|first5=Robin D.|title=Room temperature ionic liquids as novel media for ‘clean’ liquid–liquid extraction|journal=Chem. Commun.|issue=16|year=1998|pages=1765–1766|issn=1359-7345|doi=10.1039/A803999B}} </ref> Therefore, ionic liquids offer an alternative that requires less energy. Due to the properties of ionic liquids, they have potential for large-scale implementation of post-combustion CO<sub>2</sub> capture. |
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During the capture process, the anion and cation play a crucial role in the dissolution of CO<sub>2</sub>. Spectroscopic results suggest a favorable interaction between the anion and CO<sub>2</sub>, wherein CO<sub>2</sub> molecules preferentially attach to the anion. Furthermore, [[intermolecular force]]s, such as [[hydrogen bond]]s, [[van der Waals bond]]s, and [[Electrostatic force|electrostatic]] attraction, contributes to the solubility of CO<sub>2</sub> in ionic liquids. This makes ionic liquids promising candidates for CO<sub>2</sub> capture because the solubility of CO<sub>2</sub> can be modeled accurately by the regular solubility theory (RST), which reduces operational costs in developing more sophisticated model to monitor the capture process. |
During the capture process, the anion and cation play a crucial role in the dissolution of CO<sub>2</sub>. Spectroscopic results suggest a favorable interaction between the anion and CO<sub>2</sub>, wherein CO<sub>2</sub> molecules preferentially attach to the anion. Furthermore, [[intermolecular force]]s, such as [[hydrogen bond]]s, [[van der Waals bond]]s, and [[Electrostatic force|electrostatic]] attraction, contributes to the solubility of CO<sub>2</sub> in ionic liquids. This makes ionic liquids promising candidates for CO<sub>2</sub> capture because the solubility of CO<sub>2</sub> can be modeled accurately by the regular solubility theory (RST), which reduces operational costs in developing more sophisticated model to monitor the capture process. |
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For example, due to their practical properties, ionic liquids have been shifting more from academic labs into industrial applications. Ionic liquids have been marketed as Gasguard Subatmospheric System by Air Products. This application was specifically for gas absorption, where it has proven to be twice as effective in performance as normal absorption techniques. |
For example, due to their practical properties, ionic liquids have been shifting more from academic labs into industrial applications. Ionic liquids have been marketed as Gasguard Subatmospheric System by Air Products. This application was specifically for gas absorption, where it has proven to be twice as effective in performance as normal absorption techniques. |
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One of the main drawbacks of ionic liquids is their high viscosity, which complicates their use in industrial operations. Supported ionic liquid phases (SILPs) are one proposed solution to this problem.<ref name = "Rodriguez">Rodríguez |
One of the main drawbacks of ionic liquids is their high viscosity, which complicates their use in industrial operations. Supported ionic liquid phases (SILPs) are one proposed solution to this problem.<ref name = "Rodriguez">{{cite journal|last1=Rodríguez|first1=Héctor|year=2016|issn=2196-6982|doi=10.1007/978-3-662-48520-0 | title = Ionic Liquids for Better Separation Processes }}</ref> |
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== References == |
== References == |
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== Further reading == |
== Further reading == |
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# {{cite journal|last1=Blanchard|first1=Lynnette A.|last2=Hancu|first2=Dan|last3=Beckman|first3=Eric J.|last4=Brennecke|first4=Joan F.|journal=Nature|volume=399|issue=6731|year=1999|pages=28–29|issn=00280836|doi=10.1038/19887| title = Green processing using ionic liquids and CO<sub>2</sub>}} |
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# Blanchard, L. A. et al., ''[http://www.nature.com/nature/journal/v399/n6731/abs/399028b0.html Green processing using ionic liquids and CO<sub>2</sub>]'', ''Nature'' '''399''', 28-29 (6 May 1999). doi: 10.1038/19887 |
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# Camper |
# {{cite journal|last1=Camper|first1=Dean|last2=Bara|first2=Jason E.|last3=Gin|first3=Douglas L.|last4=Noble|first4=Richard D.|title=Room-Temperature Ionic Liquid−Amine Solutions: Tunable Solvents for Efficient and Reversible Capture of CO<sub>2</sub>|journal=Industrial & Engineering Chemistry Research|volume=47|issue=21|year=2008|pages=8496–8498|issn=0888-5885|doi=10.1021/ie801002m}} |
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[[Category:Carbon dioxide]] |
[[Category:Carbon dioxide]] |
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Revision as of 20:31, 7 May 2016
Ionic liquids in carbon capture describes a potential application of ionic liquids as absorbents for use in carbon capture and sequestration. Ionic liquids, which are salts that exist as liquids near room temperature, are polar, nonvolatile materials that have been considered for many applications. The urgency of climate change has spurred research into their use in this energy-related applications such as carbon capture and storage.
Separations
Carbon capture
Amines are the most prevalent absorbent in postcombustion carbon capture technology today. In particular, monoethanolamine (MEA) has been used in industrial scales in postcombustion carbon capture, as well as other CO2 separations, such as "sweetening" of natural gas.[1] However, amines are corrosive, degrade over time, and require large industrial facilities. Ionic liquids on the other hand, have is low vapor pressures . This property results from ionic liquids' strong Coulombic attractive force and vapor pressure remains low through the substance's thermal decomposition point (typically >300 °C).[2] In principle, this low vapor pressure simplifies their use and makes them "green" alternatives. Additionally, it reduces risk of contamination of the CO2 gas stream and of leakage into the environment.[3]
The solubility of CO2 in ionic liquids is governed primarily by the anion, less so by the cation.[4] The hexafluorophosphate (PF6–) and tetrafluoroborate (BF4–) anions have been shown to be especially amenable to CO2 capture.[4]
Ionic liquids have been considered as solvents in a variety of liquid-liquid extraction processes.[5] Beside that, ionic liquids have replaced the conventional volatile solvents in industry such as absorption of gases or extractive distillation. Additionally, ionic liquid is also used as co-solutes for the gener
Process
A typical CO2 absorption process consists of a feed gas, an absorption column, a stripper column, and output streams of CO2-rich gas to be sequestered, and CO2-poor gas to be released to the atmosphere. Ionic liquids could follow a similar process to amine gas treating, where the CO2 is regenerated in the stripper using higher temperature. However, ionic liquids can also be stripped using pressure swings or inert gases, reducing their energy requirement.[3] A current issue with ionic liquids for carbon capture is that they have a lower working capacity than amines. Task-specific ionic liquids which employ chemisorption and physisorption are being developed in an attempt to increase the working capacity. 1-butyl-3-propylamineimidazolium tetrafluoroborate is one example of a TSIL.[2]
Tunability
As required for all separation techniques, ionic liquids exhibit selectivity towards one or more of the phases of a mixture. 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6) is a room-temperature ionic liquid that was identified early on as a viable substitute for volatile organic solvents in liquid-liquid separations.[6] Other [PF6]- and [BF4]- containing ionic liquids have been studied for their CO2 absorption properties, as well as 1-ethyl-3-methylimidazolium (EMIM) and unconventional cations like trihexyl(tetradecyl) phosphonium ([P66614]).[3] Selection of different anion and cation combinations in ionic liquids affects their selectivity and physical properties. Additionally, the organic cations in ionic liquids can be "tuned" by changing chain lengths or by substituting radicals.[5] Finally, ionic liquids can be mixed with other ionic liquids, water, or amines to achieve different properties in terms of absorption capacity and heat of absorption. This tunability has led some to call ionic liquids "designer solvents."[7] 1-butyl-3-propylamineimidazolium tetrafluoroborate was specifically developed for CO2 capture; it is designed to employ chemisorption to absorb CO2 and maintain efficiency under repeated absorption/regeneration cycles.[2] Other ionic liquids have been simulated or experimentally tested for potential use as CO2 absorbents.
Industrial applications
Industrial operations require an energy efficient and environmentally friendly process for CO2 capture. Currently, CO2 capture uses mostly amine-based absorption technologies, which are energy intensive and solvent intensive. Volatile organic compounds alone in chemical processes represent a multi-billion dollar industry.[6] Therefore, ionic liquids offer an alternative that requires less energy. Due to the properties of ionic liquids, they have potential for large-scale implementation of post-combustion CO2 capture.
During the capture process, the anion and cation play a crucial role in the dissolution of CO2. Spectroscopic results suggest a favorable interaction between the anion and CO2, wherein CO2 molecules preferentially attach to the anion. Furthermore, intermolecular forces, such as hydrogen bonds, van der Waals bonds, and electrostatic attraction, contributes to the solubility of CO2 in ionic liquids. This makes ionic liquids promising candidates for CO2 capture because the solubility of CO2 can be modeled accurately by the regular solubility theory (RST), which reduces operational costs in developing more sophisticated model to monitor the capture process.
For example, due to their practical properties, ionic liquids have been shifting more from academic labs into industrial applications. Ionic liquids have been marketed as Gasguard Subatmospheric System by Air Products. This application was specifically for gas absorption, where it has proven to be twice as effective in performance as normal absorption techniques.
One of the main drawbacks of ionic liquids is their high viscosity, which complicates their use in industrial operations. Supported ionic liquid phases (SILPs) are one proposed solution to this problem.[5]
References
- ^ Arthur Kohl and Richard Nielson (1997). Gas Purification (5th ed.). Gulf Publishing. ISBN 0-88415-220-0.
- ^ a b c Bates, Eleanor D.; Mayton, Rebecca D.; Ntai, Ioanna; Davis, James H. (2002). "CO2 Capture by a Task-Specific Ionic Liquid". Journal of the American Chemical Society. 124 (6): 926–927. doi:10.1021/ja017593d. ISSN 0002-7863.
- ^ a b c Zhang, Xiangping; Zhang, Xiaochun; Dong, Haifeng; Zhao, Zhijun; Zhang, Suojiang; Huang, Ying (2012). "Carbon capture with ionic liquids: overview and progress". Energy & Environmental Science. 5 (5): 6668. doi:10.1039/c2ee21152a. ISSN 1754-5692.
- ^ a b Ramdin, Mahinder; de Loos, Theo W.; Vlugt, Thijs J.H. (2012). "State-of-the-Art of CO2 Capture with Ionic Liquids". Industrial & Engineering Chemistry Research. 51 (24): 8149–8177. doi:10.1021/ie3003705. ISSN 0888-5885.
- ^ a b c Rodríguez, Héctor (2016). "Ionic Liquids for Better Separation Processes". doi:10.1007/978-3-662-48520-0. ISSN 2196-6982.
{{cite journal}}: Cite journal requires|journal=(help) - ^ a b Huddleston, Jonathan G.; Willauer, Heather D.; Swatloski, Richard P.; Visser, Ann E.; Rogers, Robin D. (1998). "Room temperature ionic liquids as novel media for 'clean' liquid–liquid extraction". Chem. Commun. (16): 1765–1766. doi:10.1039/A803999B. ISSN 1359-7345.
- ^ Freemantle, Michael (1998). "Designer Solvents". Chemical & Engineering News. 76 (13): 32–37. doi:10.1021/cen-v076n013.p032. ISSN 0009-2347.
Further reading
- Blanchard, Lynnette A.; Hancu, Dan; Beckman, Eric J.; Brennecke, Joan F. (1999). "Green processing using ionic liquids and CO2". Nature. 399 (6731): 28–29. doi:10.1038/19887. ISSN 0028-0836.
- Camper, Dean; Bara, Jason E.; Gin, Douglas L.; Noble, Richard D. (2008). "Room-Temperature Ionic Liquid−Amine Solutions: Tunable Solvents for Efficient and Reversible Capture of CO2". Industrial & Engineering Chemistry Research. 47 (21): 8496–8498. doi:10.1021/ie801002m. ISSN 0888-5885.