Abstract
Efforts to limit rising concentrations of CO2 have motivated the development of negative emission technologies. Direct air capture (DAC) of CO2 is one of the negative emissions technologies that has been proposed for the direct removal of CO2 from the atmosphere. Phase-changing bis(iminonoguanidine) (BIG) sorbents have been developed for the direct air capture of CO2. These phase changing sorbents, specifically glyoxal-bis(iminoguanidine) (GBIG), involve (1) CO2 absorption with aqueous amino acid salts, such as K-or Na-glycinate to yield bicarbonate-rich solutions, (2) crystallization of the bicarbonate anions with a BIG solid, which regenerates the amino acid, and (3) solid-state CO2 release from the carbonate crystals and BIG regeneration. Despite the promising potential of these materials, their structural evolution during the thermal regeneration of the BIG solids, chemical regeneration of the sodium or potassium glycinate solvents, and the crystallization behavior of CO2-loaded BIG bicarbonate remain to be evaluated and understood in detail. The aim of this study is to probe these knowledge gaps. In situ wide-angle X-ray Scattering (WAXS) results show that CO2 and water molecules in GBIG bicarbonate are simultaneously released in a single step during the thermal regeneration of the sorbent at 97-134 °C. In situ ATR-FTIR measurements showed that sodium glycinate and GBIG bicarbonate are simultaneously generated when GBIG, glycine, and sodium bicarbonate are reacted. The crystallization of GBIG bicarbonate from GBIG and CO2-loaded monoethanolamine (MEA) occurs rapidly in the first 10 min of the reaction, as determined using in situ GI-SAXS measurements. The insights from these studies are essential for the scalable implementation of CO2 capture technologies using these phase-changing sorbents.
Original language | English |
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Pages (from-to) | 20953-20959 |
Number of pages | 7 |
Journal | Industrial and Engineering Chemistry Research |
Volume | 59 |
Issue number | 47 |
DOIs | |
State | Published - Nov 25 2020 |
Funding
The authors gratefully acknowledge the support of Dr. Jan Ilavsky, X-ray Science Division, Argonne National Laboratory, for providing experimental support for the combined USAXS/SAXS/WAXS measurements and GI-SAXS measurement at the Advanced Photon Source. The authors gratefully acknowledge the support of Cornell Atkinson Center for Sustainability. The authors gratefully acknowledge Hassnain Asgar, Xun Gao, and Tianhe Yin for their help with the experiments at the Advanced Photon Source. The use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, is supported by the U.S. DOE under Contract DE-AC02-06CH11357. The synthesis and analysis of GBIG and the design of the DAC system were performed at the Oak Ridge National Laboratory with support from the US Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.