Nanocomposite MFI-alumina and FAU-alumina Membranes: Synthesis, Characterization and Application to Paraffin Separation and CO2 Capture

In this work, we report the preparation of thermally and mechanically resistant high-surface (24-cm2 ) nanocomposite MFI-alumina and FAUalumina membranes by pore-plugging synthesis inside the macropores of α -alumina multilayered tubular supports. The MFI membranes were prepared from a clear solution precursor mixture being able to easily penetrate into the pores of the support. The MFI membranes were evaluated in the separation of n-/i-butane mixtures. The synthesis reliability was improved by mild stirring. The most selective MFI membranes were obtained for supports with mean pore sizes of 0.2 and 0.8 μ m. The MFI effective thickness could be reduced to less than 10 μ m by impregnating the support with water prior to synthesis and by diluting the synthesis mixture. The best MFI membrane offered an excellent tradeoff between selectivity and permeance at 448 K, with separation factors for equimolar n-butane/i-butane mixtures up to 18 and n-butane mixture permeances as high as 0.7 μ mols-1 m-2 Pa-1 . Furthermore, a novel nanocomposite FAU membrane architecture has been obtained by an original synthesis route including in situ seeding using a cold gel-like precursor mixture, followed by growth of the FAU material by hydrothermal synthesis in two steps using a clear solution of low viscosity. This new membrane showed interesting performance in the separation of an equimolar CO2 /N2 mixture at 323 K, with CO2 /N2 separation factors and mixture CO2 permeances up to 12 and 0.4 μ mols-1 m-2 Pa-1 , respectively.