The Kinetic Effect of Adding Piperazine Activator to Aqueous Tertiary and Sterically-hindered Amines Using Stopped-flow Technique

AbstractAqueous amines as the solvents for CO2 removal in low concentration streams have been exhaustively studied. This work focuses on the blending of piperazine (PZ) activator with aqueous tertiary amines (Methyldiethanolamine, MDEA) across concentration range of 200-900mol/m3 for MDEA and 5-41mol/m3 for PZ and sterically-hindered amines (2-amino-methyl-1-propanol, AMP) across concentration range of 6-24mol/m3 for AMP and 7-48mol/m3 for PZ at temperature range of 298-313K using stopped-flow technique to determine the direct pseudo first-order reaction kinetics of the blends. The different proposed reaction mechanisms such as base-catalyzed hydration, zwitterion and termolecular reaction mechanisms for the reaction of CO2 with aqueous solutions of amines were used to calculate the second-order reaction rate constants k2, (m3·mol-1s-1). Zwitterion mechanism correlated the stand-alone AMP perfectly while base catalysis mechanism correlated the stand-alone MDEA successfully. Hybrid of zwitterion mechanism correlated the blend of AMP/PZ while a hybrid of zwitterion and base catalysis mechanisms correlated the experimental data of MDEA/PZ system