The kinetics of CO 2 absorption by aqueous solutions of methyl diethanol amine (MDEA) were measured in the temperature range (296-343) K and MDEA concentration range (830-4380) mol‚m -3 (10-50 mass %). A thermoregulated constant interfacial area Lewis-type cell was operated by recording the pressure drop during batch absorption. The kinetic results are in agreement with a fast regime of absorption according to film theory. MDEA depletion at the interface has a significant effect on the kinetics at the CO 2 pressures (100 to 200 kPa) studied in this work, especially at low temperatures and low MDEA concentrations. Considering only the reaction between CO 2 and MDEA, the CO 2 absorption appears as a first-order reaction with respect to MDEA. The activation energy found for the reaction between CO 2 and MDEA is 45 kJ‚mol -1 , but this value depends significantly (by about 10% in the worst case) on the vapor-liquid equilibrium data used.

An apparatus developed to measure absorption kinetics of acid gases by amine solutions is described as well as the experimental procedures dealing with either the initial kinetics or kinetics for loaded solutions. Data obtained for H 2 S absorption into a 50 mass % methyldiethanolamine (MDEA) aqueous solution with various initial H 2 S loadings are reported for the following conditions: H 2 S loadings from 0 to 0.44 mol H 2 S per mol MDEA and two temperatures, 296 and 343 K. The H 2 S experimental absorption rates have been used together with a model, based on mass transfer and involving an instantaneous reversible reaction, to determine the MDEA diffusion coefficient.