Gas and organic vapor permeation through b-oriented MFI membranes

Siliceous ZSM-5 zeolite membranes oriented with their straight 0.55-nm pores perpendicular to the support and exhibiting high separation factors for p-xylene over o-xylene were reported recently using secondary growth of an oriented seed monolayer and employing organic structure-directing agents as crystal shape modifiers (Lai et al., Science 2003, 300, 456). Here, we report additional permeation results for this type of membrane. High separation factors, as well as high permeances, were observed for benzene/cyclohexane and benzene/2,2-dimethylbutane, although the separation factors for n-/i-butane and N₂/SF₆ were small. The membrane stability is satisfactory. Reproducibility of the permeation properties at 220 °C is demonstrated.