Analysis and modeling of hydrogen permeation through alumina membranes with finely dispersed palladium

The alpha-alumina disk with 0.85 mu m-thickness finely dispersed palladium was prepared by spin dipping. The fluxes of pure hydrogen and nitrogen thro ugh this membrane were measured at temperatures of 423-573 K and pressures difference up to 225 kPa. In the case of the pressure difference of 80 kPa, the ideal separation factor of H-2/N-2 increased from 3.4 at 423 K to 4.4 at 573 K. Furthermore, the effects of operating temperature and pressure on the transport behaviors of hydrogen through the membrane were analyzed bas ed on the resistance model. The results demonstrated that the hydrogen perm eation through this membrane was categorized into two regimes. About 41-58% of hydrogen flux was contributed by Knudsen diffusion in the temperature r ange of 423-473 K. Within the temperature ranging from 523 K to 573 K, the hydrogen permeance increased with increasing temperature. This is about 52- 73% of the overall permeance and is attributed to the solution-diffusion me chanism in this regime.