Application of Nonlinear Frequency Response to Adsorption Systems with Complex Kinetic Mechanisms

The paper is a contribution to formation of a library of sets of frequency response functions of different orders, for complex kinetic mechanisms typical for adsorption on bidispersed sorbents. The first and second order frequency response functions have been derived starting from a general model, taking into account macro-pore diffusion, micro-pore diffusion, adsorption/desorption kinetics at the micropore mouth and film mass transfer at the particle surface. Simplified models, which neglect one or more mass transfer resistances, were also considered. The frequency response functions were derived for isothermal case, constant diffusion coefficients and planar geometry. The first and second order functions were simulated for the general and for some special cases. Based on these simulation results, some characteristic patterns of the amplitude and phase functions, corresponding to different cases, have been recognized. These patterns can serve as a basis for model and mechanism identification.