CO2 capture is an energy intensive process due to the energy loss associated with the boiling and condensing copious amounts of water. As a consequence, many formulations of water-lean CO2 capture solvents have been developed to alleviate these energy requirements. CO2-Binding Organic Liquids (CO2BOLs) are one such solvent platform deriving from Jessop’s switchable ionic liquids. We have shown that these organic liquids have distinctive ‘heterogeneous’ molecular structure that can transition between two states as a function of CO2 loading and temperature. This inherent heterogeneity differs substantially from water-based and other water-lean CO2-capture solvents. It has been linked to unique observations such as the non-linear viscosity increase with binding CO2 and an inverse temperature dependence on CO2 mass transport. Recent viscosity measurements of these fluids have shown that solvent viscosities are intrinsically low when the residence time of the solvent is kept below 15 minutes, yet viscosity increases substantially over time with no associated change in CO2 loading of the solvent. Molecular dynamics simulations show evidence of both the low-viscosity metastable solvent structure and the more viscous glassy state. This transformation is only observed at temperatures near 40C, leading us to believe that this phenomenon is akin to a glass transition temperature, where long-range order increases as zwitterionic clusters begin to aggregate. Although there is a slight energy difference between the two states the impacts of solvent viscosity are substantial. This talk presents experimentally measured and calculated from simulation viscosity data for multiple CO2BOL solvents, in both their metastable and glassy states. Simulations of extended solvent structures in both fluid states are discussed. We conclude by assessing how this knowledge could impact water-lean solvents for CO2 capture.

Dual nature of extended solvent structure in CO2-binding organic liquids: Thermodynamic vs kinetic stability

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.