Kinetics study of carbon dioxide absorption into aqueous solutions containing N-methyldiethanolamine + diethanolamine

Abstract

Kinetics of the absorption of CO 2 into N-methyldiethanolamine (MDEA) + diethanolamine (DEA) + water were investigated at 30, 35, and 40 °C using a wetted wall column apparatus. Eight systems of which 1.0 and 1.5 kmol/m 3 MDEA mixed with various DEA concentrations (0.1, 0.2, 0.3, and 0.4) kmol/m 3 were studied. Densities and viscosities of eight blended amine systems were measured. The solubilities and diffusivities of N 2O in the studied amine systems were also measured. The N 2O analogy was applied to estimate the solubilities and diffusivities of CO 2 in the investigated amine systems. Based on the pseudo first-order for the CO 2 absorption, the overall pseudo first-order reaction rate constants were determined from the measured kinetic data. The addition of small amounts of DEA to MDEA results in a significant enhancement of CO 2 absorption rates. A hybrid reaction rate model, a zwitterion mechanism for DEA and a first-order reaction for MDEA was used to model the kinetic data. The model satisfactory represented the CO 2 absorption rates in MDEA + DEA aqueous systems.