AN EXPERIMENTAL-STUDY OF DIFFUSION AND CONVECTION OF MULTICOMPONENT GASES THROUGH CATALYTIC AND NONCATALYTIC MEMBRANES

Diffusion of binary and ternary gases through catalytic and non-cataly tic membranes has been studied experimentally at atmospheric pressure. These experiments were conducted in a modified Wicke-Kallenbach diffu sion cell consisting of two continuously stirred gas volumes separated by a membrane. The equipment was suitable to measure fluxes of compon ents through the membrane in the absence of gas-to-membrane mass trans fer limitations. Transport through a porous membrane has been measured and compared with the results of the dusty-gas model, which has been used to predict transport through a membrane. With independently deter mined input parameters this model turned out to be able to predict the transport of a multicomponent gas mixture through a membrane within a few percent ( < 5%). The Fick model extended with a convective transp ort contribution was not able to produce similar results as obtained f rom the dusty-gas model, especially when an overall pressure gradient was present over the membrane. In order to demonstrate the occurrence of surface effects, dynamic transport of a binary ps was studied in a similar experimental setup as described by Novak et al. In this setup the transport of gas mixtures containing helium, argon and nitrogen wa s in good agreement with the model simulations. For transport of carbo n dioxide and propane through a gamma-Al2O3 coated membrane, adsorptio n phenomena were observed, but no substantial surface mobility was det ected at temperatures ranging from 293 to 433 K.