The effective intraparticle diffusivities for nonadsorbable and adsorbable gas pairs of helium-nitrogen and ethylene-helium were measured in single catalyst pellets of $\gamma$-alumina with bidisperse pore size distribution. Measurements were made using both the steady-state technique and the dynamic pulse-response technique, and their results were compared with each other.
In the nonadsorbable gas pair of helium-nitrogen, the effective diffusivities by the steady-state measurements were larger than those by the dynamic pulse-response method, and these of differences increased as the size and volume fraction of the macropore increased. In the adsorbable gas pair of ethylene-helium the effective diffusivities by the steady-state measurements were also larger than those by the dynamic method. It was believed that the micropores are playing more important roles in the dynamic experiment by delaying the diffusion rate but they do minor contributions in the steady-state diffusion. The diffusional fluxes and effective diffusivities predicted by the random pore model, in the nonadsorbable system, were shown to be strongly correlated with those by the steady-state measurement. Through the same random pore model, the contributions by the surface diffusion, in the adsorbable system, were estimated to range from 15 to 20 percent of the total diffusional flux.
