Helium permeation through a silicalite-1 tubular membrane

A silicalite-1 tubular membrane was prepared on the inner surface of a porous α-alumina support. Helium permeation at different feed volumetric flows (11–41 mL/min) with different sweep flow rates (9–90 mL/min) at STP conditions was measured. The molar fraction was obtained as a function of the residence time ratio. The influences of the geometric parameters of the tubular system and the feed flow rates on the permeation through the membrane were investigated. The dependence of the permeances with the residence time ratio was experimentally obtained and we propose that this dependence is a useful design criterion for tubular membrane permeation systems. The best results in this work were obtained for Q_He,in/Q_N2,in = 0.22 for V^SS/V^TS = 7.3. Also, the data showed that an appropriate combination of the flows and the area sections of the system resulted in an optimum value for the Péclet number of 0.3. The experimental data were reproduced by numerically solving the Maxwell–Stefan equations under the assumption that transport across the membrane can be modeled in terms of a Robin-type boundary condition.