Characterization of AlPO4-type molecular sieving membranes formed on a porous α-alumina tube

AlPO4-type membranes were prepared on porous α-alumina tubes by a hydrothermal synthesis method in the presence of HF, using tetraethylammonium hydroxide (TEAOH) as the organic template. The gas permeation properties of the membranes were determined at permeation temperatures in the range of 308–423 K, using H2, CO2, O2, N2 and iso-C4H10. For the membrane prepared by a two-step hydrothermal synthesis (membrane M3), the ideal separation factors for single-component H2/N2, H2/CO2, and H2/iso-C4H10 systems at 310 K reached 13.3, 23.9 and 40.1, respectively. With increasing permeation temperature, permeances of the membrane increased, and separation factors of H2 to the other gases decreased. The separation factors for the binary H2/N2, H2/CO2, H2/iso-C4H10 systems were lower than the corresponding ideal separation factors. The presence of humidity in the feed led to a decrease in permeance, and the separation factors of membrane M3 for the equimolar binary H2/N2, H2/CO2, H2/iso-C4H10 systems at 310 K were 12.0, 31.7 and 28.2, respectively.