Modeling of CO₂ solubility of an aqueous polyamine solvent for CO₂ capture

Development of absorbents with large absorption capacities is important for improvements in the CO₂ capture technology. Polyamines include more than two amine groups in their molecular structures and may exhibit great potential as candidate solvents. In this study, CO₂ solubility and speciation in aqueous 3,3′-iminobis(N,N-dimethylpropylamine) (IBDMPA) was experimentally investigated and a chemical equilibrium reaction model was proposed. Solubility measurements were conducted at four different IBDMPA contents (9.37, 18.7, 31.6 and 37.5 mass%) in the temperature range from 40 to 120 °C and CO₂ partial pressure in the range of from 2 kPa to 480 kPa. In addition, both proton and carbon nuclear magnetic resonance (NMR) spectroscopic techniques were employed for the quantitative and qualitative analyses of various species in CO₂-loaded solutions. Using these experimental results, a chemical equilibrium reaction model was developed for the IBDMPA-H₂O-CO₂ system based on the electrolyte NRTL model.