A route to MFI zeolite-α-alumina composite membranes for separation of light paraffins

Zeolites are microporous crystalline materials used as catalysts, ion-exchangers, adsorbents and molecular sieves. Several industrial separation processes, e.g. dehydration of alcohols, have been developed based on zeolite membranes. It is also of great interest the separation of light paraffins. Silicalite-1 crystal layers were synthesised on the surface of asymmetric α-alumina planar supports. A molar ratio of synthesis mixture was 100 SiO2:42.9 TPAOH: 2229 H2O with Aerosil 380 (Degussa) used as a silica source. Permeation and separation characteristics of the membranes were measured using steady state apparatus MEMFIS. Separation factor of ceramic silicalite-1 composite membrane, which was synthesised for 24 h using a synthesis mixture aged for 7 days, was studied by an equimolar mixture of butane isomers as a function of temperature. High separation factor for n-butane (>10) in the mixture with isobutane showed good quality of the composite membrane. The results showed that the separation performance of the membrane could be tailored to find suitable compromise between permeation and separation.