Improving the regeneration of CO sub(2)-binding organic liquids with a polarity change

• Published in: Energy & environmental science Vol. 6; no. 7; pp. 2233 - 2242
• Main Authors: Mathias, PaulM, Afshar, Kash, Zheng, Feng, Bearden, Mark D, Freeman, Charles J, Andrea, Tamer, Koech, Phillip K, Kutnyakov, Igor, Zwoster, Andy, Smith, Arnold R, Jessop, Philip G, Nik, Omid Ghaffari, Heldebrant, David J
• Format: Journal Article
• Language: English
• Published: 01.06.2013
• Subjects: Carbon dioxide; Cooling; Organic liquids; Phase separation; Polarity; Regeneration; Solvents; Thermodynamic models; USA
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/c3ee41016a

This paper describes a solvent regeneration method unique to CO sub(2)-binding organic liquids (CO sub(2)BOLs) and other switchable ionic liquids: utilizing changes in polarity to shift the free energy of the system. The degree of CO sub(2) loading in CO sub(2)BOLs is known to control the polarity of the solvent; conversely, polarity can be exploited as a means to control CO sub(2) loading. In this process, a chemically inert nonpolar "antisolvent" (AS) such as hexadecane (C16) is added to aid in de-complexing CO sub(2) from a CO sub(2)-rich CO sub(2)BOL. The addition of this polarity assist reduces the temperature required for regeneration of our most recent CO sub(2)BOL, 1-((1,3-dimethylimidazolidin-2-ylidene)amino)propan-2-ol by as much as 73 degree 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 sub(2)BOL solvents, and separation of the CO sub(2)BOL from the AS is as simple as a cooling the mixture to promote phase separation. Based on vapor-liquid and liquid-liquid equilibrium measurements of a candidate CO sub(2)BOL with CO sub(2), with and without an AS, we present the evidence and impacts of a polarity change on a CO sub(2)BOL. Equilibrium thermodynamic models and analysis of the system were constructed using Aspen Plus registered , and forecasts of preliminary process configurations and feasibility are also presented. Lastly, projections of solvent performance for removing CO sub(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.