The effective diffusivities in single catalyst pellets with bidisperse pore structure were estimated for the first time from an unsteady state diffusion model, and were compared with the experimental results of nonadsorbable and adsorbable gas pairs. The helium-nitrogen and ethylene-helium gas pairs were used in each nonadsorbable and adsorbable dynamic pulse response experiments. The estimated diffusivities were also compared with the previously reported experimental results.
The unsteady state diffusion model necessitated simple experiments for physical characteristics of pellets and was based on random pore model which represents the bidisperse pore structure of a single pellet satisfactorily. The bidisperse pore structure of a single pellet made the model have three independent diffusion paths. Through these three paths, the first absolute moment of a response resulted in the sum of the multiplications between each path's retention time and zeroth moment fraction.
The errors which the model had for various pellets ranged from 3 to 20 percentage.
