Fabrication of b-oriented MFI membranes from MFI nanosheet layers by ammonium sulfate modifier for the separation of butane isomers

Fabrication of thin and oriented zeolite membrane is highly preferable and challenging, providing the advantage of less resistance and high permeation for efficient molecular separation. MFI zeolite nanosheets serve as the desirable building block for fabricating thin and preferably b-oriented MFI membranes. However, the secondary growth of deposited MFI zeolite nanosheet layer is an indispensable aspect that comes with the challenges of sealing the nanoscale/interlayer gaps while preserving the orientation and controlling the thickness of fabricated zeolite membrane for efficient gas separation. Herein, ammonium sulfate assisted hydrothermal secondary growth of MFI nanosheet slip coated on the γ-Al2O3 disc was carried out to seal the nanoscale and interlayer gaps for the separation of butane isomers. The addition of ammonium sulfate helps to preserve the b-orientation of the deposited nanosheet layer and plays a critical role in tuning the thickness of the MFI membrane. Ammonium sulfate assisted thin MFI membrane was obtained with preserved b-orientation having a thickness of about 630 nm while exhibiting a separation factor and n-butane permeance of 41 and 1.10 × 10−7 mol m−2 s−1.Pa−1, respectively for the separation of butane isomers.