Kinetics of nonisothermal sorption: Systems with bed diffusion control



A theoretical model is presented to describe the kinetics of nonisothermal sorption for a system in which the main resistance to mass transfer is the macrodiffusional resistance of the absorbent particle bed while the main resistance to heat transfer is the resistance at the external surface of the adsorbent sample. The model is used to interpret experimental kinetic data for the sorption of several hydrocarbons in 10X and 13X zeolite crystals. By varying the configuration of the sample bed and the size of the zeolite crystals it is shown that, for n-heptane and iso-octane in 13X, the intracrystalline diffusional resistance is negligible even in 40-μm crystals. The assumption of intracrystalline diffusion control which has been made in earlier kinetic studies of similar systems is therefore incorrect.