Activated DEEA solutions for CO2 capture—A study of equilibrium and kinetic characteristics

N,N-Diethylethanolamine (DEEA) can be considered as a promising absorbent producible from renewable resources. In this study, the reactions between CO2 and aqueous solutions containing blends of DEEA and promoter mixtures were investigated using a stirred-cell reactor. Three diamines, viz. piperazine (PZ), N-(2-aminoethyl) ethanolamine (AEEA) and 1,6-hexamethyl diamine (HMDA) were used as promoters. The molarities of the blend (DEEA+promoter) in the aqueous solution were (2.5+0.1), (2.5+0.3) and (2.5+0.5). The CO2 absorption rates in the blend (DEEA+promoter) were much higher than those in DEEA, whereas the increase in promoter concentration resulted in the expected increase in the absorption rates. Kinetics of the CO2 reaction with the blend (DEEA+HMDA) was studied at 303 K. The overall reaction can be regarded as a reaction between CO2 and DEEA in parallel with the reaction of CO2 with HMDA. The rate constant for the blended amine (DEEA+HMDA) was determined. Besides, the solubility of CO2 in DEEA and in the blend (DEEA+PZ) was measured at 303 K for equilibrium CO2 partial pressures up to 5.8 kPa. The molarities of the blend (DEEA+PZ) in the aqueous solution were (2+0.5). Based on these measurements, the dependence of the CO2 partial pressure on the loading could be determined using simple mathematical correlations.

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► PZ, AEEA and HMDA promote CO2 reaction with DEEA.
► Kinetics of the CO2 reaction with the blend (DEEA+HMDA) was studied.
► Equilibrium solubility of CO2 in DEEA and in the blend (DEEA+PZ) was measured.