Properties and Performance of Ether-Functionalized Imidazoles as Physical Solvents for CO2 Separations

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• 作者：Matthew S. Shannon ; Jason M. Tedstone ; Scott P. O. Danielsen ; Michelle S. Hindman ; Jason E. Bara
• 刊名：Energy & Fuels
• 出版年：2013
• 出版时间：June 20, 2013
• 年：2013
• 卷：27
• 期：6
• 页码：3349-3357
• 全文大小：329K
• 年卷期：v.27,no.6(June 20, 2013)
• ISSN：1520-5029

文摘

Previously, we investigated 1-n-alkylimidazoles as low viscosity, low vapor pressure physical solvents for CO₂/CH₄ separation and noted a decrease in performance as the length of the n-alkyl chain was extended. Here, we examine imidazoles featuring oligo(ethylene glycol) substituents (鈥淧EG_n-imidazoles鈥? as an opportunity to improve upon the separation performance of this class of molecules. In the current work, we have characterized the density and the viscosity of PEG_n-imidazoles over the temperature range 20鈥?0 掳C. PEG_n-imidazoles are slightly more viscous than 1-n-alkylimidazoles but still fall below 20 cP. Ideal gas solubilities of CO₂ and CH₄ were measured in PEG_n-imidazoles at gas partial pressures of 5 bar and temperatures of 25鈥?0 掳C. Solubilities of CO₂ and CH₄ were both found to decrease with increasing temperature, with a stronger dependence for CO₂. However, better CO₂/CH₄ selectivity was achieved in PEG_n-imidazoles at lower operating temperatures than was observed for 1-n-alkylimidazoles. Physical properties and gas separation performances were correlated with fractional free volume calculated via COSMOtherm, as well as solubility parameters. The results show trends of decreased FFV when polar ether groups comprise the substituent, and that CO₂ solubility and solubility selectivity for CO₂/CH₄ are improved compared to their nonpolar, hydrocarbon-based analogues.