Effect of number of amine groups in aqueous polyamine solution on carbon dioxide (CO2) capture activities

The absorption and desorption of aqueous polyamine solutions with different number of amine groups (ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA)) were determined for their equilibrium CO2 loading, initial absorption and desorption rates, heat duty for solvent regeneration, heat of CO2 absorption and pKa. The absorption was carried out at 313 K using 15% CO2 in N2 balance while desorption was performed at 363 K. The results showed that the equilibrium CO2 loading and the initial absorption rate were increased with increasing the number of amine groups because of the increase in the amine reactive sites for CO2 to form various species such as carbamate and dicarbamate at the equilibrium condition. The regeneration efficiency also increased with increasing number of amine groups because these caused an increase in the initial desorption rate and the decrease of heat duty. TEPA solution (2 mol/L) showed the best performance for all CO2 capture activities which are 2.12 molCO2/mol amine for the equilibrium CO2 loading, 0.74 × 10−2 molCO2/min for the initial absorption rate, 4.14 × 10−2 molCO2/min for the initial desorption rate, 41.13 kJ/mol for heat duty for solvent regeneration, and −70.18 kJ/mol for heat of absorption.