A Computational Study of Dicationic Ionic Liquids/CO₂ Interfaces

Journal Article · Mon Feb 09 00:00:00 EST 2015 · Langmuir

DOI:https://doi.org/10.1021/la5048563· OSTI ID:1265425

Li, Song ^[1]; Zhao, Wei ^[1]; Feng, Guang ^[1]; Cummings, Peter T. ^[2]

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1. Huazhong Univ. of Science and Technology, Wuhan (China). School of Energy and Power Engineering
2. Vanderbilt Univ., Nashville, TN (United States)

Our recent studies on CO₂ capture using dicationic ionic liquids (DILs) demonstrated that DILs are promising absorbents for CO₂ uptake especially compared with monocationic ionic liquids (MILs) analogues, in which each cation carries single positive charge in contrast to two unit charges of a dication. However, DILs/CO₂ interfacial properties at the molecular level are still unknown. This work investigated the CO₂ absorption properties of representative DILs, 1-alkyl-3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide, [C_n(mim)₂](Tf₂N)₂ (n = 3, 6, 12), using molecular dynamics (MD) simulations. The higher interfacial CO₂ density at DIL than that at MIL interfaces suggests the increased CO₂ interaction sites in DILs. The interfacial CO₂ density also exhibits an alkyl chain length dependence which decreases with the elongation of alkyl chain and proportionally correlates with the content of fluorine atoms at interfaces. Different alkyl chain orientations in DILs were illustrated in contrast to those of MILs; both DILs and CO2 inside DILs exhibit lower diffusivity than MILs, in agreement with the stronger cation–anion binding energy of DILs. Moreover, DILs show a lower H2O and N2 uptake from flue gas compared with MILs, implicating the higher CO₂/H₂O and CO₂/N₂ selectivity.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Energy Frontier Research Centers (EFRC) (United States). Fluid Interface Reactions, Structures and Transport Center (FIRST)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC05-00OR22725; AC02- 05CH11231; 2014CFA089; 51406060
• OSTI ID: 1265425
• Journal Information: Langmuir, Vol. 31, Issue 8; ISSN 0743-7463
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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