(384g) Role of the Diffusion in the Transport of Gas Species through Polymer Membranes

Membrane-based gas separation is becoming a significant unit operation in chemical process industry; the productivity is determined by the permeation rate of the species while the purity level is mainly established by the separation factor. Specifically the separation of gaseous mixtures by means of polymeric non-porous membranes is based on differences in gas diffusivity and solubility through the membrane material and the evaluation of the role of the two factors is an important aspect. Diffusion coefficient of different permanent gases was measured by the time-lag method in a temperature range of 15-60 °C and at a low feed pressure through homogeneous dense membrane samples, prepared according to the phase inversion technique. Both glassy (polysulfone and a modified poly-ehter-ether-ketone) and rubbery (poly-styrene-butadiene-styrene with two different styrene contents) polymers were investigated and for all materials the contribution of the diffusive term to the permeability coefficient was experimentally determined. Furthermore the apparent activation energy for permeation and diffusion processes was calculated in order to evaluate as a temperature change affects the gas transport through these membranes.