464674 Process and Material Design for Micro-Encapsulated Ionic Liquids in Post-Combustion CO2 Capture

Friday, November 18, 2016: 10:25 AM
Continental 3 (Hilton San Francisco Union Square)
Bo Hong, Mark J. McCready, Joan F. Brennecke and Mark A. Stadtherr, Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN

Aprotic Heterocyclic Anion (AHA) Ionic Liquids (ILs) have been identified as promising new solvents for post-combustion carbon capture due to their high CO2 uptake and the high tunability1,2 of their binding energy with CO2. Some of these compounds change phase (solid to liquid) on absorption of CO2; these Phase Change ILs (PCILs)3 offer the additional advantage that part of the heat needed to desorb the CO2 from the absorbent is provided by the heat of fusion as the PCIL solidifies upon release of CO2. However, the relatively high viscosity of AHA ILs and the occurrence of a phase change in PCILs present challenges for conventional absorption equipment. To overcome these challenges we are pursuing the use of new technology to micro-encapsulate the AHA ILs and PCILs. Our partners at Lawrence Livermore National Laboratory have successfully demonstrated this technology in the application of post-combustion carbon capture with sodium and potassium carbonate solutions,4 and have recently shown the feasibility of micro-encapsulation of an AHA IL for carbon capture.5 The large effective surface area and high CO2 permeability of the micro-capsules is expected to offset the drawback of the high IL viscosity and to provide for a more efficient and cost-effective mass transfer operation involving AHA ILs and PCILs.

These opportunities, however, present us with both process and materials design questions. For example, what is the target CO2 absorption strength (enthalpy of chemical absorption) for the tunable AHA IL? What is the target for micro-capsule diameter in order to obtain a high mass transfer rate and good fluidization performance? What are the appropriate temperatures and pressures for the absorber and stripper? In order to address these and other questions, we have developed a rate-based model of a post-combustion CO2 capture process using micro-encapsulated ILs. As a performance baseline, we have also developed a rate-based model of a standard packed bed absorber using an un-encapsulated AHA IL absorbent. Using such models we can determine optimal CO2 capture performance and investigate the sensitivity of the optimum with respect to the key thermo-physical and transport properties of the IL (e.g., CO2 binding energy, viscosity, etc.) and the micro-capsules (e.g. diameter, CO2 permeability, etc.). Results of these process and material design studies will be presented, and the performance of this novel micro-encapsulation technology will be assessed.


(1) Gurkan, B.; Goodrich, B. F.; Mindrup, E. M.; Ficke, L. E.; Massel, M.; Seo, S.; Senftle, T. P.; Wu, H.; Glaser, M. F.; Shah, J. K.; Maginn, E. J.; Brennecke, J. F.; Schneider, W. F. Molecular Design of High Capacity, Low Viscosity, Chemically Tunable Ionic Liquids for CO2 Capture. J. Phys. Chem. Lett. 2010, 1, 3494-3499.

(2) Seo, S.; Quiroz-Guzman, M.; DeSilva, M. A.; Lee, T. B.; Huang, Y.; Goodrich, B. F.; Schneider, W. F.; Brennecke, J. F. Chemically Tunable Ionic Liquids with Aprotic Heterocyclic Anion (AHA) for CO2 Capture. J. Phys. Chem. B 2014, 118, 5740-5751.

(3) Seo, S.; Simoni, L. D.; Ma, M.; DeSilva, M. A.; Huang Y.; Stadtherr, M. A.; Brennecke, J. F. Phase-Change Ionic Liquids for Postcombustion CO2 Capture. Energy Fuels, 2014, 28, 5968-5977.

(4) Vericella, J. J.; Baker, S. E.; Stolaroff, J. K.; Duoss, E. B.; Hardin, J. O.; Lewicki, J.; Glogowski, E.; Floyd, W. C.; Valdez, C. A.; Smith, W. L.; Satcher, J. H.; Bourcier, W. L.; Spadaccini, C. M.; Lewis, J. A.; Aines, R. D. Encapsulated Liquid Sorbents for Carbon Dioxide Capture, Nature Commun., 2015, 6, 6124.

(5) Stolaroff, J. K.; Ye, C.; Oakdale, J. O.; Baker, S. E.; Smith, W. L.; Nguyen, D. T.; Spadaccini, C. M.; Aines, R. D. Microencapsulation of Advanced Solvents for CO2 Capture. Faraday Discuss., 2016, in press, DOI: 10.1039/C6FD00049E.

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