Reaction Kinetics of CO₂ in Aqueous 1-Amino-2-Propanol, 3-Amino-1-Propanol, and Dimethylmonoethanolamine Solutions in the Temperature Range of 298−313 K Using the Stopped-Flow Technique

The observed pseudo-first-order rate constants ( k o ) for the reactions between CO 2 and 1-amino-2-propanol (1-AP), 3-amino-1-propanol (3-AP), and dimethylmonoethanolamine (DMMEA) have been measured using the stopped-flow technique in aqueous solutions at 298, 303, 308, and 313 K. The alkanolamine concentrations ranged from 25.3 to 82.0 mol·m -3 for 1-AP, 27.0 to 60.7 mol·m -3 for 3-AP, and 304.0 to 984.8 mol·m -3 for DMMEA. The zwitterion mechanism was used to correlate the experimentally obtained rate constants. Both the zwitterion formation step and the proton-removal step played a significant role for 1-AP and 3-AP. The reaction rate of CO 2 in the aqueous-3-AP solution was found to be faster than that in aqueous monoethanolamine (MEA). The absorption rate of CO 2 in the latter was faster than that in aqueous 1-AP solution under the conditions studied. The reaction rate of CO 2 in DMMEA was higher than that in methyldiethanolamine (MDEA) but not in diethyl-monoethanolamine (DEMEA). The base catalysis of the CO 2 hydration mechanism could explain the reaction between CO 2 and DMMEA, a tertiary amine.