(321b) Solubilities of CO2 in Aqueous Solutions of Ionic Liquid and Monoethanolamine

With the deterioration of climate change, CO₂ capture and sequestration have been paid much attention to reduce greenhouse gas emissions. Currently aqueous solutions of alkanolamines or their mixtures are commonly used in many industrial processes to capture CO₂. However, drawbacks such as solvent loss and high regeneration costs due to the high water content drive researchers for new superior technologies [1]. Ionic liquids (ILs), due to their wide liquid range, low point, tunable properties, negligible vapor pressure, high CO₂ solubility and reasonable thermal stability, are emerging as promising candidates to capture CO₂, but it is difficult to realize industrialization owing to its high viscous and high cost. Recently, the idea of mixing ILs and alkanolamines has been received great attention from the industries, since its advantages and capabilities in reducing the problem caused by the usage of conventional alkanolamines solutions are promising [2-4]. In this work, a low viscous IL ([C₂OHmim][N(CN)₂]) has been synthesized and the solubilities of CO₂ in aqueous mixture of IL-MEA were measured by instruments with high accuracy at temperature 313.15K and 333.15K, over CO₂ partial pressure ranging from 100 to 1000kPa and IL concentration varying from 5% to 30%. Then the corrected PVT equation has been used to calculate the absorption of CO₂. The results indicate that 0.583 mol CO₂/mol MEA could be reached under the condition of 40°C and 100.66 kPa when appropriate amount of IL has been added, which only dropped by 1.7% when compared with 30% MEA aqueous at the same condition. The results sufficiently demonstrated that the addition of the IL can reduce regeneration energy consumption to 27% with little affecting their absorption performance.

 

References

[1] Chinn, D.; Vu, D. Q.; Driver, M. S.; Boudreau, L. C. CO₂ removal from gas using ionic liquid absorbents. US Patent, 7,527,775 B2, 2009

[2] Camper, D.; Bara, J. E.; Gin, D. L.; Noble, R. D. Room-temperature ionic liquid − amine solutions: Tunable solvents for efficient and reversible capture of CO₂. Ind. Eng. Chem. Res., 2008, 47, 8496-8498.

[3] Zhao, Y.; Zhang, X.; Zeng, S.; Zhou, Q.; Dong, H.; Tian, X.; Zhang, S., Density,

Viscosity, and Performances of Carbon Dioxide Capture in 16 Absorbents of Amine+ Ionic Liquid+ H₂O, Ionic Liquid+ H₂O, and Amine+ H₂O Systems. J. Chem. Eng., Data, 2010, 55, 3513-3519.

[4] Ahmady, A.; Hashim, M. A.; Aroua, M. K., Absorption of carbon dioxide in the aqueous mixtures of methyldiethanolamine with three types of imidazolium-based ionic liquids. Fluid Phase Equilibria, 2011, 309, 76-82.