Long-term stability of composite zeolite MFI membranes

Zeolite MFI layers were grown on asymmetric alpha-alumina supports developed in cooperation with an industrial partner. The layers were prepared by direct hydrothermal synthesis procedure using aged synthesis solutions composed of silica source, structure directing agent and deionized water. Selected zeolite MFI composite membranes were tested during long-term permeation and separation experiments to determine flux and separation factor as a function of total molar amount fed to zeolite membrane surface area. The flux of permeating components (n-butane, isobutane) was reduced by an average factor of 1.6 and 2 for n-butane and isobutane, respectively after 30 mol of butane isomers passed the selected membranes. The separation factor towards n-butane showed the maximum or decreased with increasing feeding amount of butane isomers.