Equilibrium solubility and kinetics of CO2 absorption in hexamethylenediamine activated aqueous sodium glycinate solvent

Equilibrium solubility and absorption kinetics of CO2 in hexamethylenediamine (HMDA) activated aqueous sodium glycinate (SG) solvent are measured in the temperature range of 313-333 K. For the experimental investigation, HMDA concentration in the solvent is varied in the range of 5-15 mass% keeping total amine concentration at 30 mass%. Solubility data is presented in the form CO2 loading (mole CO2 absorbed per mole of total amine). Kinetics of CO2 absorption is evaluated assuming pseudo first order reaction condition. Both solubility and kinetics of CO2 absorption are found to enhance significantly due to addition of small amount of HMDA in the aqueous SG solvent. CO2 loading data is correlated using modified Kent-Eisenberg model. For developing kinetic model, overall rate is assumed to be the combined rate contribution of CO2-HMDA and CO2-SG reaction system. Based on this concept, a kinetic model is proposed using zwitterion mechanism for both the component reaction system. Kinetic and solubility models developed in this work are in good agreement with the experimental data with average absolute deviation of 7.4% and 4.5% respectively.