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A SAPO-34 membrane was prepared on an alumina tubular support. This membrane appears to exhibit molecular sieving properties with permeances that decrease as the kinetic diameter increases. The room-temperature permeances of H2 and n-C4H10 were 2.4 × 10-8 and 1.9 × 10-10 mol/(m2 s Pa), respectively, and the permeances were in the order H2 > CO2 > N2 > CH4 > n-C4H10. As the temperature increased, the single gas permeances of H2 and N2 exhibited minima, whereas the permeance of CO2 decreased and that of CH4 increased. As the pressure increased with a constant pressure drop across the membrane, the permeances of H2, CO2, N2, and CH4 decreased. The H2/CH4, CO2/CH4, H2/N2, and CO2/N2 ideal selectivities at 300 K and 270 kPa feed pressure with a 138 kPa pressure drop were 25, 19, 7.4, and 5.7, respectively, and these selectivities decreased with increasing temperature and increased with increasing pressure. The ideal selectivity of N2/CH4 was 3.4 at the same conditions and decreased with increasing temperature and increasing pressure. The H2/CO2 ideal selectivity was 1.3 at the same conditions and increased with increasing temperature and pressure. At 270 kPa feed pressure and 138 kPa pressure drop, the CO2/CH4 mixture selectivity was 30 at 300 K and 3.4 at 470 K.

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Alkali-free, H−ZSM-5 membranes were synthesized by in-situ crystallization on porous α-alumina, γ-alumina, and stainless steel tubular supports. Membranes prepared from different Si sources were characterized by X-ray diffraction, scanning electron microscopy, and electron probe microanalysis. Membranes prepared under different conditions were also characterized by single-gas permeances of H2, N2, n-C4H10, i-C4H10, and SF6 and by separation selectivities of n-C4H10/i-C4H10 mixtures from 300 to 473 K. The effects of preparation procedure, crystallization time and temperature, number of synthesis layers, gel dilution, Si source, and type of support were studied. The permeation and separation properties of the membranes depend strongly on the preparation procedure. Permeating synthesis solution into the pores of the support before hydrothermal treatment allows zeolites crystal growth within those pores. Increasing the crystallization time and temperature increases the n-C4H10/i-C4H10 separation selectivities, whereas increasing the number of synthesis layers and gel dilution decreases the selectivities. Membranes were prepared with high ideal and separation selectivities for n-C4H10/i-C4H10. The highest separation selectivity for n-C4H10/i-C4H10 is 111, which was obtained at 429 K, and the highest separation selectivity at 473 K is 36. Ideal selectivities do not correlate with mixture selectivities for n-butane/i-butanes at low temperature, but they correlate at 473 K.

ZSM‐5 zeolite membranes with boron substituted into the framework for silicon were prepared on porous stainless‐steel and α‐alumina tubular supports. These membranes had higher n‐C4H10/i‐C4H10 separation selectivities, and effectively separated these isomer mixtures to higher temperatures than membranes with aluminum substituted into the framework. Membranes were prepared with Si/B ratios as low as 12, and the best membranes were prepared from alkali‐free gels. The highest n‐C4H10/i‐C4H10 permselectivity at 473 K was 60, and the highest at 527 K was 24. For most alkali‐free membranes, the n‐C4H10/i‐C4H10 permselectivities and separation selectivities increased with boron content, and membranes on α‐alumina supports had both higher permeances and separation selectivities. Membranes with the same permeances and selectivities can be reproducibly prepared, and they are stable at elevated temperatures.