Kinetics of absorption of carbon dioxide into aqueous solutions of monoethanolamine+ N-methyldiethanolamine

Abstract

Kinetics of the absorption of CO 2 into monoethanolamine ( MEA)+N - methyldiethanolamine ( MDEA)+ water were investigated at 30° C, 35° C , and 40°C using a laboratory wetted wall column. Ten systems with various MEA concentrations (0.1, 0.2, 0.3, 0.4, and 0.5 kmol m −3) mixed with aqueous MDEA (1.0 and 1.5 kmol m −3 ) solutions were studied. Densities and viscosities of the solutions and the solubilities and diffusivities of N 2O in the aqueous blended amine systems were also measured. The N 2O analogy was applied to estimate the solubilities and diffusivities of CO 2 in amine systems. Based on the pseudo-first order for the CO 2 absorption, the overall pseudo first-order reaction rate constants were determined. The addition of small amounts of MEA to aqueous MDEA results in a significant enhancement of CO 2 absorption rates. A hybrid reaction rate model, a zwitterion mechanism for MEA and a pseudo first-order reaction model for MDEA was used to model the kinetic data. The overall average absolute percentage deviation for the calculation of the apparent reaction rate constant by this model is about 3.0%. The model is satisfactory to represent the CO 2 absorption in MEA+MDEA+H 2O systems.