In situ crystallization of b-oriented MFI films on plane and curved substrates coated with a mesoporous silica layer

A simple and reproducible method is presented for preparing b-oriented MFI films on plane (disc) and curved (hollow fiber) supports by in situ hydrothermal synthesis. A mesoporous silica (sub-)layer was pre-coated on the supports by dip coating followed by a rapid thermal calcination step (973 K during 1 min) to reduce the number of grain boundaries while keeping the hydrophilic behavior of silica. The role of the silica sub-layer is not only to smoothen the substrate surface, but also to provide a silica source to promote the nucleation and growth of zeolite crystals via a heterogeneous nucleation mechanism (zeolitization), and adsorb zeolite moieties generated in the synthesis solution via a homogeneous nucleation mechanism. A monolayer of b-oriented MFI crystals was obtained on both supports after 3 h synthesis time with a moderate degree of twinning on the surface.

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► We have prepared b-oriented MFI films on alumina discs and YSZ hollow fibers.
► The substrates were covered with a silica layer by sol–gel dip coating.
► A rapid calcination treatment allows a significant reduction of grain boundaries.
► A monolayer of b-oriented MFI crystals was obtained after 3 h synthesis.
► We discuss the interplay between heterogeneous/homogeneous nucleation mechanisms.