Characterization of the superior CO2-capturing absorbent blend AMP/PZ/EGMEE/Water

Abstract

Together, 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ), ethylene glycol monoethyl ether (EGMEE or 2-ethoxyethanol) and water form a capable, non-traditional CO2-separation solvent. Detailed characterization and scrutiny of the CO2 absorption capacity and reactivity of this solvent is hitherto missing. In this work, we investigated equilibrium and reaction kinetic features of the AMP/PZ/EGMEE/H2O blend for the first time. We worked at different molarities of AMP (2–3 M), PZ (0.2-0.6 M) and EGMEE (0.8–2.5 M) to look at their specific roles in the absorption process. In a stirred cell reactor, we measured CO2 absorption rates in the 30–45 °C range and reported the fast pseudo-first order rate constant. The prevalent reaction pathway was elucidated using zwitterion mechanism. Additional useful information was also extracted from the kinetic data of pure CO2 absorption. For example, it was found that PZ reacts with CO2 according to a second-order reaction (rate constant k2,PZ = 5.6 × 104 M−1 s−1 at T = 35 °C) with activation energy value of 43 kJ mol−1. In an ambient-pressure vapor-liquid-equilibrium (VLE) apparatus, we reported the dependence of equilibrium CO2 pressure on absorption capacity of the chosen blend at T = 30 °C; loading capacity was markedly higher than that in AMP/H2O and AMP/PZ/H2O mixtures. This progress in knowledge will stimulate further interest into this promising solvent.