An interesting innovative concept for the removal of CO2 from sour gas using immobilised amines (IA) in the CO2 absorption process with methyldiethanolamine (MDEA) has been evaluated in our previous work [2]. The positive effect of IA on the absorption behaviour has been demonstrated by means of preliminary batch experiments in an aerated stirred tank reactor. In order to identify the rate-limiting steps in the three-phase system, experiments with a liquid medium in a fixed-bed reactor have been carried out to establish the absorption kinetics of dissolved CO2 onto IA and the desorption (regeneration) kinetics of CO2-loaded IA with MDEA solution. The breakthrough profiles of CO2 at the outlet of the reactor are measured using a newly developed analytical method. Based on the experimentally determined adsorption and packing parameters, a mathematical model has been developed to describe the experiments and found to yield an accurate prediction of the dynamic CO2 concentration profiles. It could be shown experimentally that the adsorption rate of dissolved CO2 with IA (k(liquid-solid) 1.54 x 10(-7) m/s, 298 K) and the desorption rate of CO2-loaded IA (k(solid-liquid) = 5.64 x 10(-8) m/s, 298 K) are the same order of magnitude and both constitute rate-limiting processes. On the basis of observations and results, two possible mechanisms for this novel three-phase gas-liquid-solid system are proposed and compared with one another. (c) 2004 Elsevier B.V. All rights reserved.