Abstract
To discuss the effects of intraparticle diffusion on the gas adsorption process in the pellet, the processes were simulated on thethree cases of adsorption by mass transfers for ( I ) volume diffusion only, (II) surface diffusion only and (III) these two diffusions together. At the same time concentration changes of gas flow were measured for benzene adsorption on alumina pellets at 50°C to obtain the adsorption curves. The volume diffusion coefficient DKe was calculated by the pore radius (38 Å) of pellet, the adsorption rate constant kads by the adsorption curve for the small particles of the adsorbent and the surface diffusion coefficient Ds by the adsorption curve for the large pellet (Fig.4 and Table 1). The experimental adsorption curves are in good agreement with the theoretical results for both of the cases II and III equivalently as shown in Fig.4. Therefore, it indicates that the volume diffusion can be neglected when the surface diffusion is predominant. This fact might explain well that the adsorption from gas phase by the volume diffusion is very little, because the adsorption concentration becomes high by the surface diffusion and easily reaches the equilibrium state between surface and gas phases in the pore, with the surface diffusion being predominant (Fig.6).
