EXPERIMENTAL CONCENTRATION-DEPENDENCE OF SURFACE DIFFUSIVITY OF HYDROCARBONS IN ACTIVATED CARBON

A new procedure is introduced to a differential adsorption bed (DAB) t o determine the intrinsic concentration dependence of the surface diff usivity of hydrocarbons in activated carbon. The DAB is operated under a small change in bulk concentration that the adsorbed concentration is nearly constant during the adsorption process. The intrinsic surfac e diffusivity is then determined by analysing the experimental data us ing a pore and surface diffusion model. Experimental results show a mu ch stronger concentration dependence of the surface diffusivity than t hat predicted by a Darken relationship in the studies of ethane and pr opane adsorption in Ajax-activated carbon. The effect of adsorption eq uilibrium equations on the prediction of the intrinsic surface diffusi vity is also studied.