Kinetics of CO2 Absorption in Aqueous Hexamethylenediamine Blended N-Methyldiethanolamine

Carbon dioxide (CO2) absorption kinetics in the aqueous blend of hexamethylenediamine (HMDA) and N-methyldiethanolamine (MDEA) is studied at the temperatures varying from 303 to 333 K using the pressure decay technique in a reaction calorimeter setup. For the experimental study, HMDA concentration is varied in the range of 5-15 mass % keeping total amine (HMDA + MDEA) concentration at 30 mass %. Overall rate constant for this reaction system is estimated assuming pseudo-first-order reaction condition. CO2 absorption kinetics are significantly enhanced due to the presence of HMDA as compared to single MDEA solvent. The individual rate contribution of CO2-HMDA and CO2-MDEA reaction systems are combined to represent the overall CO2 absorption rate in this mixed amine solvent. The kinetic models (I and II) developed using the zwitterion and termolecular mechanism for HMDA-CO2 reaction system and base catalyzed hydration mechanism for MDEA-CO2 reaction are able to predict the kinetic data with good accuracy.