Combined surface and gas phase diffusion through plugs of porous adsorbent in transition diffusion region.

Experimental studies of combined counter diffusion in gaseous and adsorbed phases (propylenehelium, propylene-argon and ethylene-helium systems) through plugs of fine particles of activated carbon were performed in the transition diffusion region to obtain relatively large surface diffusion rates comparable to those of gas-phase diffusion in the pore space and also relatively large total pressure gradient in the plug in spite of being isobaric at both ends of the plug. The observed results were compared with the theoretical ones obtained by assuming negligible adsorption resistance on the inner surface of the porous plug to obtain good agreement between them. The results confirm the existence of intimate interactions between diffusion in gas phase and adsorbed phase. The transfer mechanisms of combined diffusion are discussed in detail.