Tuning Nanoscale Molecular Heterogeneity to Improve CO2 Transport and Binding in CO2 Capture Solvents
Aqueous amine-based technology has been considered the most promising carbon capture solution for post-combustion gas from fossil fuel plants. However, solvent degradation and the high energy cost associated with removing CO2 from the solvent, known as regeneration, have hindered its widespread implementation. It has been proposed that utilizing a water lean solvent, in contrast to aqueous amines, can decrease the required heat to regenerate the solvent. Additionally, Malhotra et al. proposed that controlling the viscosity can help increase the mass transport properties of CO2 in the solvent. A recent study on CO2 binding organic liquids (CO2BOLs) found them to exist in dynamic equilibrium between two species: (1) a carbamate ion pair and (2) a zwitterion and carbamic acid. In the same study, molecular dynamics simulation showed that intermolecular hydrogen bonds between zwitterions result in higher viscosity, and alternatively, intramolecular hydrogen bonds within the molecule result in lower viscosity. To test the hypothesis that changes in isomer structure can shift the balance of intra- and intermolecular bonding and result in molecular arrangements that control CO2 transport properties, we use three solvents, each with an identical aliphatic chain, and differing in the position of the nitrogen within the planar aromatic pyridine ring (n-MPMEA, n=2,3,4). We use Wide-Angle X-ray Scattering to analyze how the different positions of the nitrogen in the pyridine ring impact the mesoscopic structure of MPMEA at different CO2 concentrations, temperatures, and pressures. Wide-angle X-ray scattering analysis demonstrates that intermediate-range domains of high or low polarity arise with increased CO2 loading. The nanoscale domain separations increase in all liquids with CO2 loading, with increasing temperature, and remain constant at high pressure.
Chemistry|Nanoscience|Molecular chemistry|Chemical engineering|Organic chemistry
Aviña, Omar, "Tuning Nanoscale Molecular Heterogeneity to Improve CO2 Transport and Binding in CO2 Capture Solvents" (2022). ETD Collection for University of Texas, El Paso. AAI29208643.