Optimal design of complex reactive separations is inconceivable unless reliable process models are available. Such models have to be both rigorous enough in order to reflect the process complexity and simple enough in order to ensure feasibility of process simulations. In this respect, an optimal model should represent a kind of a consensus between the rigour and simplicity, and its development requires a comparison of both detailed and simplified process models with experimental data. From this viewpoint, reactive absorption operations with their pronounced kinetic character and complex non-ideal behaviour provide one of the best objects for studying. This work gives a detailed analysis of the problem supplemented by the examples of industrial importance.