This work involves the joining of two new technologies: supercritical fluid
s (SCF) and inorganic microporous materials. The objective of this study is
the determination and description of transfer mechanisms of supercritical
fluids through inorganic microporous membranes whose selective layer is con
stituted of MFI zeolite, a material with particular properties of porosity,
crystalline structure and adsorption. To describe the evolution that exper
iences the supercritical fluid inside the microporous medium as a function
of pressure and temperature, models based on the formulation of Stefan-Maxw
ell and ordinarily used for gas phase transfer were selected. A statistical
analysis of permeation data allow to distinguish between the convective (o
r Poiseuille viscous) and diffusive (Knudsen flow) contributions, as well a
s to highlight the effect of adsorption at wall. As a whole it appears that
the transfer of SCF results from a combination of diffusive mechanism and
interaction with the membrane surface, well in agreement with what the prox
imity of sizes of pores and gas molecules enables to foresee. Under the ass
umption that adsorption is characterised by a low occupation rate of availa
ble places inside the micropores, the Stefan-Maxwell equations give a good
description of the general system behavior. (C) 2001 Elsevier Science Ltd.
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