Theoretical and Experimental Studies of CO2 and H2 Separation Using the 1-Ethyl-3-methylimidazolium Acetate ([emim][CH3COO]) Ionic Liquid

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• 作者：Wei Shi ; Christina R. Myers ; David R. Luebke ; Janice A. Steckel ; Dan C. Sorescu
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：January 12, 2012
• 年：2012
• 卷：116
• 期：1
• 页码：283-295
• 全文大小：665K
• 年卷期：v.116,no.1(January 12, 2012)
• ISSN：1520-5207

文摘

The performance of [emim][CH₃COO] ionic liquid (IL) to separate mixtures of CO₂ and H₂ is studied using both classical and ab initio simulation methods and experiments. Simulations show that H₂ solubility and permeability in [emim][CH₃COO] are quite low with Henry鈥檚 law constants about 1 脳 10⁴ bar and permeabilities in the range 29鈥?9 barrer at 313鈥?73 K. In the case of CO₂ absorption in [emim][CH₃COO], ab initio molecular dynamics simulations predict two types of CO₂ absorption states. In type I state, CO₂ molecules interact with the [CH₃COO]^{鈭?/sup> anion through strong complexation leading to high CO₂ solubility. The C atom of CO₂ is located close to the O atoms of the [CH₃COO]鈭?/sup> anion with an average distance of about 1.61 脜. The CO₂ bond angle (胃(OCO)) is about 138掳, significantly perturbed from that of an isolated linear CO₂. In type II state, the CO₂ molecule maintains a linear configuration and is located at larger separations (>2.2 脜) from the [CH₃COO]鈭?/sup> anion. The weaker interaction of CO₂ with the [CH₃COO]鈭?/sup> anion in type II state is similar to the one observed when CO₂ absorbs in [bmim][PF₆]. Simulations further demonstrate that the [emim]+ cation competes with CO₂ to interact with the [CH₃COO]鈭?/sup> anion. The predicted high CO₂ permeability and low H₂ permeability in [emim][CH₃COO] are also verified by our experiments. The experimental CO₂ permeability in [emim][CH₃COO] is in the range of 1325鈥?701 barrer, and high experimental CO₂/H₂ permeability selectivities of 21鈥?7 at 313鈥?73 K are observed. We propose that by replacing [emim]+ cation with 1-butyl-1-methylpyrrolidinium ([PY₁₄]+) further enhancement of CO₂ solubility in [PY₁₄][CH₃COO] IL will be obtained as well as good performance to separate CO₂ and H₂.}