Abstract
Non-aqueous amine systems have been suggested as energy-efficient alternatives to conventional aqueous amine systems in post-combustion carbon capture, as low regeneration temperatures can be achieved. The solubility of CO2 and heat of absorption in non-aqueous systems were studied using the sterically hindered amine 2-amino-2-methyl-1-propnaol (AMP) in the organic solvent dimethyl sulfoxide (DMSO). 13C NMR was used to study the product species in solution as CO2 reacts with AMP in either DMSO or N-methyl-2-pyrrolidone (NMP). The solubility of CO2 in AMP/DMSO showed that low loadings could be achieved at 80–88 °C, indicating that regeneration can be carried out at lower temperatures than in conventional aqueous systems. Precipitation occurred at 25 wt% AMP in DMSO, increasing the overall capacity of the system. The heat of absorption decreased with increasing temperature, and was explained by physical absorption dominating the absorption mechanism at higher temperatures. This was also confirmed by the results of NMR, as less chemically absorbed species were observed at higher temperatures. The reaction products observed in AMP/DMSO and AMP/NMP were identified as the AMP carbamate, bicarbonate from water impurities, and the AMP carbonate from CO2 reacting with the hydroxyl group of AMP.
Highlights
Due to the increasing concentration of CO2 in the atmosphere, extensive research in recent years has focused on technologies to control and reduce the emission of anthropogenic CO2
If regeneration is performed without stripping gas for 10 wt% AMP/dimethyl sulfoxide (DMSO), this can be represented by the solubility data at 88 ◦C and 100 kPa, resulting in a lean loading of approximately 0.09 mol CO2/mol AMP
The CO2 partial pressures needed in the incoming gas (20–50 kPa) indicate that the 10 wt% AMP/DMSO system could be suitable for carbon capture in biogas upgrading and industrial carbon capture and storage (CCS)
Summary
Due to the increasing concentration of CO2 in the atmosphere, extensive research in recent years has focused on technologies to control and reduce the emission of anthropogenic CO2. Due to the maturity of such techniques, and the possibility of retro-fitting existing industrial plants, post-combustion capture is considered the most promising alternative for carbon capture and storage (CCS) applications [1] Drawbacks such as high operating cost, mostly associated with the high amount of energy needed to regenerate the aqueous absorption systems, must be addressed in order to increase their suitability for future large-scale industrial implementation [2]. The energy required for regeneration is partly dependent on the absorption system used, and includes the sensible heat, i.e., the heat needed to raise the temperature of the solvent to the appropriate regeneration temperature, and the heat of reaction between the amine and CO2 [3] Aqueous systems, such as aqueous monoethanolamine (MEA), are associated with regeneration temperatures above the boiling point of water (120 ◦C), leading to the requirement of energy to vaporize water in the absorption solution. This CO2rich phase could be separated before regeneration of the solution, reducing the total amount of solvent that has to be heated in regeneration
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