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Possible articles to expand upon
edit- I would like to explore more the characteristics of char and how this is a feasible alternative to slash and burn. I would also include data about how much CO2 it saves from being vented to the atmosphere.
- I think that we could add in the commercial applications for this page and expand upon the chemistry for several sections.
- This page lacks basic structure and is hard to read. We could edit it by adding in different sections and expanding the information where we see fit.
Ionic Liquids in Carbon Capture
editOur group is choosing to edit the Ionic Liquids in Carbon Capture Wikipedia page. We immediately noticed that this page was lacking in a solid introduction, a history section, enough references, there are no drawbacks of the technology (making it seem biased towards favoring ionic liquids over amines), lacked any mention of environmental impacts of use, and doesn’t provide many examples of commercial application. Our group would like to improve this web page by gathering articles in this area and introducing new sections about the history, commercial applications, as well as a drawbacks and benefits section. This will allow the reader to gain a more comprehensive view of ionic liquids as they pertain to carbon capture. I am responsible for writing the drawbacks section.
Drawbacks
editSelectivity
editIn carbon capture an effective absorbent is one which demonstrates a high selectivity, meaning that CO2 will preferentially dissolve in the absorbent compared to other gaseous components. In post-combustion carbon capture the most salient separation is CO2 from N2, whereas in pre-combustion separation CO is primarily separated from H2. Other components and impurities may be present in the flue gas, such as hydrocarbons, SO2, or H2S. Before selecting the appropriate solvent to use for carbon capture it is critical to ensure that at the given process conditions and flue gas composition CO2 maintains a much higher solubility in the solvent than the other species in the flue gas and thus has a high selectivity.
The selectivity of CO2 in ionic liquids has been widely studied by researchers. Generally, polar molecules and molecules with an electric quadrupole moment are highly soluble in liquid ionic substances.[1] It has been found that at high process temperatures the solubility of CO2 decreases, while the solubility of other species, such as CH4 and H2, may increase with increasing temperature, thereby reducing the effectiveness of the solvent. However, the solubility of N2 in ionic liquids is relatively low and does not increase with increasing temperature so the use of ionic liquids in post-combustion carbon capture may be appropriate due to the consistently high CO2/N2 selectivity.[2] The presence of common flue gas impurities such as H2S severely inhibits CO2 solubility in ionic liquids and should be carefully considered by engineers when choosing an appropriate solvent for a particular flue gas.[3]
Viscosity
editA primary concern with the use of ionic liquids for carbon capture is their high viscosity compared with that of commercial solvents. Ionic liquids which employ chemisorption to depend on a chemical reaction between solute and solvent for CO2 separation. The rate of this reaction is dependent on the diffusivity of CO2 in the solvent and is thus inversely proportional to viscosity[1]. The self diffusivity of CO2 in ionic liquids are generally to the order of 10-10 m2/s,[4] approximately an order of magnitude less than similarly performing commercial solvents used on CO2 capture. The viscosity of an ionic liquid can vary significantly according to the type of anion and cation, the alkyl chain length, and the amount of water or other impurities in the solvent[5] [6][7]. Because these solvents can be “designed” and these properties chosen, developing ionic liquids with lowered viscosities is a current topic of research.
- ^ a b Weingartner, H (2008). "Understanding ionic liquids at the molecular level: facts, problems, and controversies". Angew. Chem., Int. Ed. 47: 654–670.
- ^ Anthony, J. L.; Maginn, E. J.; Brennecke, J. F. (2002). "Solubilities and thermodynamic properties of gases in the ionic liquid 1-n-butyl-3- methylimidazolium hexafluorophosphate". J. Phys. Chem. B. 106: 7315−7320.
- ^ Ramdin, M; de Loos, T. W.; Vlugt, T. J. H (2012). "State-of-the-Art of CO2 Capture with Ionic Liquids". Ind. Eng. Chem. Res. 51: 8149−8177.
- ^ Maginn, E. J. (2009). "Molecular simulation of ionic liquids: current status and future opportunities". J. Phys.: Condens. Matter. 21: 1−17.
- ^ Jacquemin, J; Husson, P.; Padua, A. A. H; Majer, V. (2006). "Density and viscosity of several pure and water-saturated ionic liquids". Green Chemistry. 8: 172−180.
- ^ Gardas, R. L.; Coutinho, J. A. P. (2008). "A group contribution method for viscosity estimation of ionic liquids". Fluid Phase Equilib. 266: 195−201.
- ^ Gardas, R. L.; Coutinho, J. A. P. (2009). "Group contribution methods for the prediction of thermophysical and transport properties of ionic liquids". AIChE J. 55: 1274−1290.