Improving the regeneration of CO2-binding organic liquids with a polarity changeElectronic supplementary information (ESI) available: NMR spectra of LLE measurements and let-down turbine configuration. See DOI: 10.1039/c3ee41016a

This paper describes a solvent regeneration method unique to CO 2 -binding organic liquids (CO 2 BOLs) and other switchable ionic liquids: utilizing changes in polarity to shift the free energy of the system. The degree of CO 2 loading in CO 2 BOLs is known to control the polarity of the solvent; conversely, polarity can be exploited as a means to control CO 2 loading. In this process, a chemically inert nonpolar antisolvent (AS) such as hexadecane (C16) is added to aid in de-complexing CO 2 from a CO 2 -rich CO 2 BOL. The addition of this polarity assist reduces the temperature required for regeneration of our most recent CO 2 BOL, 1-((1,3-dimethylimidazolidin-2-ylidene)amino)propan-2-ol by as much as 73 C. The lower regeneration temperatures realized with this polarity change allow reduced solvent attrition and thermal degradation. Furthermore, the polarity assist shows considerable promise for reducing the regeneration energy of CO 2 BOL solvents, and separation of the CO 2 BOL from the AS is as simple as a cooling the mixture to promote phase separation. Based on vaporliquid and liquidliquid equilibrium measurements of a candidate CO 2 BOL with CO 2 , with and without an AS, we present the evidence and impacts of a polarity change on a CO 2 BOL. Equilibrium thermodynamic models and analysis of the system were constructed using Aspen Plus, and forecasts of preliminary process configurations and feasibility are also presented. Lastly, projections of solvent performance for removing CO 2 from a subcritical coal-fired power plant (total net power and parasitic load) are presented with and without this polarity assist and compared to the U.S. Department of Energy's Case 10 monoethanolamine baseline. Unique CO 2 -separating solvent regeneration strategy that alters free energies of solvation of the CO 2 -carrier by means of a polarity change.