Thin oriented AFI zeolite membranes for molecular sieving separation

• SAPO-5 crystal plates of about 1 μm in side length and 200 nm in thickness were prepared.
• C-oriented SAPO-5 crystal monolayer was deposited on α-Al2O3 coated with a PVA film.
• SAPO-5 seed layer was grown to continuous 1.5 μm thick, c-oriented membrane.
• SAPO-5 membranes show high permeability and excellent separation characteristics.

Oriented AFI zeolite membranes are difficult to prepare in spite of their many potential applications. This paper reports reproducible synthesis of c-oriented, thin SAPO-5 zeolite membrane on macroporous ceramic support by a seeded-secondary growth method. A c-oriented SAPO-5 crystal monolayer was deposited on a macroporous alumina support precoated with a polyvinyl alcohol film. The c-oriented SAPO-5 seed layer was deposited by spray-blowing of powder of well-defined hexagonal SAPO-5 crystal plates of about 1 μm in side length and 200 nm in thickness. The SAPO-5 seed layer on the alumina support was then gown to a continuous, 1.5 μm thick, c-oriented SAPO-5 membrane in a secondary growth step. The SAPO-5 membranes prepared in this work show molecule-sieving separation characteristics for hydrocarbons with molecular size close to the intracrystalline pore size of SAPO-5. The synthesis method reported in this work is simple and quite reproducible, and it produces c-oriented SAPO-5 membranes with higher organic permeability and permeance, and better separation characteristics than other methods reported in the literature.

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