(681d) Dispersible Exfoliated Zeolite Nanosheets and Their Application As Membrane

High
aspect ratio zeolite particles with thickness in the 2-3 nanometer range
(zeolite nanosheets) can be derived from exfoliation of their lamellar
precursors (layered zeolites) and can be used as catalysts and building blocks
for fabrication of thin films. Thin zeolite films made using exfoliated zeolite
nanosheets could show improved performance and processing advantages as
membranes for separations, low dielectric coatings, corrosion protection,
chemical sensors, membrane reactors, etc. Here we report exfoliation of a
multilamellar zeolite (silicalite-1) and subsequent processing to obtain a
dispersible coating suspension of exfoliated silicalite-1 sheets followed by
demonstration of its utility as a gas separation membrane. Exfoliation and structure
preservation of multilamellar silicalite-1 was confirmed by Transmission
electron microscopy (TEM). Scanning probe microscopy (SPM) was used to
characterize the thickness of the exfoliated silicalite-1 nanosheets. A thin
b-oriented film of exfoliated nanosheets was coated on top of a porous
α-alumina support. The coating morphology and cross section was
characterized by scanning electron microscopy (SEM) and TEM respectively. The
defects in the coating were removed by hydrothermal treatment of the silicalite-1
in presence of a growth solution. The silicalite-1 membrane was characterized
by xylene isomer vapor permeance in Wicke-Kallenbach mode at 150°C, where a
separation factor of 67 was obtained between p-xylene and o-xylene. The
permeance of p-xylene through the membrane (3.1E-07 mol/m²/s/Pa) was
close to that of the alumina support (4.2E-07 mol/m²/s/Pa).