283242 Vibrational Spectroscopy Characterization of CO2-Ionic Liquid Systems for Pre-Combustion CO2

Thursday, November 1, 2012: 5:35 PM
301 (Convention Center )
Anita S. Lee and John R. Kitchin, Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA

Ionic liquids are attractive for pre-combustion CO2 capture applications due to their low volatility, thermal stability, and non-aqueous environment.1,2  Studies have shown that CO2 solubility in ionic liquids can be modified through molecular changes in the anion and cation.3–5  This is promising for the development of new ionic liquids.  However, the larger number of possible cation and anion combinations suggest that a better understanding of molecular structure and CO2 solubility is necessary guide the development of new ionic liquid CO2 solvents.  Vibrational spectroscopy techniques can provide a picture at the molecular level of CO2-ionic liquid interactions, aiding in understanding the mechanism of CO2 capture and relationships of solubility to properties of the ionic liquid.  In this work, we use Raman spectroscopy to study the interaction of CO2 with a class of imidazolium ionic liquids a high pressure optical cell, we are able to study the vibrational spectra of solvated CO2 from 1 to 40 bar, pressures relevant to pre-combustion capture condition.  We observe peaks in the CO2-IL spectra that correspond to the upper and lower band of the fermi-diad split of the CO2 symmetric stretch vibration, suggesting that solvated CO2 maintains a linear geometry.  The bands are slightly shifted from the gas phase spectra of CO2, indicating impact of the solvent environment.  Additionally, we observe a pressure dependence on spectral intensity of the solvated CO2 peaks that correlate with CO2concentration.  

1.        Hasib-ur-Rahman, M., Siaj, M. & Larachi, F. Ionic liquids for CO2 capture—Development and progress. Chemical Engineering and Processing: Process Intensification 49, 313-322 (2010).

2.        Brennecke, J.F. & Gurkan, B.E. Ionic Liquids for CO 2 Capture and Emission Reduction. Society3459-3464 (2010).doi:10.1021/jz1014828

3.        Bates, E.D., Mayton, R.D., Ntai, I. & Davis, J.H. CO 2 Capture by a Task-Specific Ionic Liquid. 2001-2002 (2002).

4.        Wang, C. et al. Tuning the Basicity of Ionic Liquids for Equimolar CO 2 Capture **. Communications4918-4922 (2011).doi:10.1002/anie.201008151

5.        Anthony, J.L., Anderson, J.L., Maginn, E.J. & Brennecke, J.F. Anion effects on gas solubility in ionic liquids. The journal of physical chemistry. B 109, 6366-74 (2005).

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